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Stylianakis I, Shalev A, Scheiner S, Sigalas MP, Arkin IT, Glykos N, Kolocouris A. The balance between side-chain and backbone-driven association in folding of the α-helical influenza A transmembrane peptide. J Comput Chem 2020; 41:2177-2188. [PMID: 32735736 DOI: 10.1002/jcc.26381] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2020] [Revised: 06/17/2020] [Accepted: 06/18/2020] [Indexed: 11/07/2022]
Abstract
The correct balance between attractive, repulsive and peptide hydrogen bonding interactions must be attained for proteins to fold correctly. To investigate these important contributors, we sought a comparison of the folding between two 25-residues peptides, the influenza A M2 protein transmembrane domain (M2TM) and the 25-Ala (Ala25 ). M2TM forms a stable α-helix as is shown by circular dichroism (CD) experiments. Molecular dynamics (MD) simulations with adaptive tempering show that M2TM monomer is more dynamic in nature and quickly interconverts between an ensemble of various α-helical structures, and less frequently turns and coils, compared to one α-helix for Ala25 . DFT calculations suggest that folding from the extended structure to the α-helical structure is favored for M2TM compared with Ala25 . This is due to CH⋯O attractive interactions which favor folding to the M2TM α-helix, and cannot be described accurately with a force field. Using natural bond orbital (NBO) analysis and quantum theory atoms in molecules (QTAIM) calculations, 26 CH⋯O interactions and 22 NH⋯O hydrogen bonds are calculated for M2TM. The calculations show that CH⋯O hydrogen bonds, although individually weaker, have a cumulative effect that cannot be ignored and may contribute as much as half of the total hydrogen bonding energy, when compared to NH⋯O, to the stabilization of the α-helix in M2TM. Further, a strengthening of NH⋯O hydrogen bonding interactions is calculated for M2TM compared to Ala25 . Additionally, these weak CH⋯O interactions can dissociate and associate easily leading to the ensemble of folded structures for M2TM observed in folding MD simulations.
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Affiliation(s)
- Ioannis Stylianakis
- Section of Pharmaceutical Chemistry, Department of Pharmacy, National and Kapodistrian University of Athens, Athens, Greece
| | - Ariella Shalev
- Department of Biological Chemistry, The Alexander Silberman Institute of Life Sciences, The Hebrew University of Jerusalem, Edmond J. Safra Campus Givat-Ram, Jerusalem, Israel
| | - Steve Scheiner
- Department of Chemistry and Biochemistry, Utah State University, Logan, Utah, USA
| | - Michael P Sigalas
- Department of Chemistry, Laboratory of Applied Quantum Chemistry, Aristotle University of Thessaloniki, Thessaloniki, Greece
| | - Isaiah T Arkin
- Department of Biological Chemistry, The Alexander Silberman Institute of Life Sciences, The Hebrew University of Jerusalem, Edmond J. Safra Campus Givat-Ram, Jerusalem, Israel
| | - Nikolas Glykos
- Department of Molecular Biology and Genetics, Democritus University of Thrace, Alexandroupolis, Greece
| | - Antonios Kolocouris
- Section of Pharmaceutical Chemistry, Department of Pharmacy, National and Kapodistrian University of Athens, Athens, Greece
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Charistos ND, Muñoz-Castro A, Sigalas MP. The pseudo-π model of the induced magnetic field: fast and accurate visualization of shielding and deshielding cones in planar conjugated hydrocarbons and spherical fullerenes. Phys Chem Chem Phys 2019; 21:6150-6159. [DOI: 10.1039/c9cp00836e] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Hydrogen skeletal models accurately reproduce the π-induced magnetic field of planar PAHs and spherical fullerenes.
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Affiliation(s)
- Nickolas D. Charistos
- Laboratory of Quantum and Computational Chemistry
- Department of Chemistry
- Aristotle University of Thessaloniki
- Thessaloniki
- Greece
| | - Alvaro Muñoz-Castro
- Laboratorio de Química Inorgánica y Materiales Moleculares
- Facultad de Ingeniería
- Universidad Autonoma de Chile
- Santiago
- Chile
| | - Michael P. Sigalas
- Laboratory of Quantum and Computational Chemistry
- Department of Chemistry
- Aristotle University of Thessaloniki
- Thessaloniki
- Greece
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3
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Charistos ND, Papadopoulos AG, Nikopoulos TA, Muñoz-Castro A, Sigalas MP. Canonical orbital contributions to the magnetic fields induced by global and local diatropic and paratropic ring currents. J Comput Chem 2017; 38:2594-2604. [DOI: 10.1002/jcc.24917] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2017] [Revised: 08/02/2017] [Accepted: 08/03/2017] [Indexed: 12/25/2022]
Affiliation(s)
- Nickolas D. Charistos
- Department of Chemistry, Laboratory of Quantum and Computational Chemistry; Aristotle University of Thessaloniki; Thessaloniki 54 124 Greece
| | - Anastasios G. Papadopoulos
- Department of Chemistry, Laboratory of Quantum and Computational Chemistry; Aristotle University of Thessaloniki; Thessaloniki 54 124 Greece
| | - Thomas A. Nikopoulos
- Department of Chemistry, Laboratory of Quantum and Computational Chemistry; Aristotle University of Thessaloniki; Thessaloniki 54 124 Greece
| | - Alvaro Muñoz-Castro
- Laboratorio de Química Inorgánica y Materiales Moleculares; Universidad Autonoma de Chile; El Llano Subercaseaux Santiago 2801 Chile
- Doctorado en FisicoQuimica Molecular; Universidad Andres Bello, Av. Republica 275; Santiago Chile
| | - Michael P. Sigalas
- Department of Chemistry, Laboratory of Quantum and Computational Chemistry; Aristotle University of Thessaloniki; Thessaloniki 54 124 Greece
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Papadopoulos AG, Nenadis N, Sigalas MP. DFT study of radical scavenging activity of sesame oil lignans and selected in vivo metabolites of sesamin. COMPUT THEOR CHEM 2016. [DOI: 10.1016/j.comptc.2015.11.016] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
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Papadopoulos AG, Charistos ND, Kyriakidou K, Sigalas MP. Study of Electron Delocalization in 1,2-, 1,3-, and 1,4-Azaborines Based on the Canonical Molecular Orbital Contributions to the Induced Magnetic Field and Polyelectron Population Analysis. J Phys Chem A 2015; 119:10091-100. [PMID: 26348255 DOI: 10.1021/acs.jpca.5b06027] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The electron delocalization in 1,2-azaborine, 1,3-azaborine, and 1,4-azaborine is studied using canonical molecular orbital contributions to the induced magnetic field (CMO-IMF) method and polyelectron population analysis (PEPA). Contour maps of the out-of-plane component of the induced magnetic field (Bz(ind)) of the π system show that the three azaborines, in contrast with borazine, sustain much of benzene's π-aromatic character. Among them, 1,3-azaborine exhibits the strongest π delocalization, while 1,4-azaborine is the weakest. Contour maps of Bz(ind) for individual π orbitals reveal that the differentiation of the magnetic response among the three isomers originates from the π-HOMO orbitals, whose magnetic response is governed by rotational allowed transitions to unoccupied orbitals. The low symmetry of azaborines enables a paratropic response from HOMO to unoccupied orbitals excitations, with their magnitude depending on the shape of interacting orbitals. 1,3-Azaborine presents negligible paratropic contributions to Bz(ind) from HOMO to unoccupied orbitals transitions, where 1,2- and 1,4-azaborine present substantial paratropic contributions, which lead to reduced diatropic response. Natural bond orbital (NBO) analysis employing PEPA shows that only the 1,3-azaborine contains π-electron fully delocalized resonance structures.
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Affiliation(s)
- Anastasios G Papadopoulos
- Aristotle University of Thessaloniki , Department of Chemistry, Laboratory of Applied Quantum Chemistry, Thessaloniki 54124, Greece
| | - Nickolas D Charistos
- Aristotle University of Thessaloniki , Department of Chemistry, Laboratory of Applied Quantum Chemistry, Thessaloniki 54124, Greece
| | - Katerina Kyriakidou
- Aristotle University of Thessaloniki , Department of Chemistry, Laboratory of Applied Quantum Chemistry, Thessaloniki 54124, Greece
| | - Michael P Sigalas
- Aristotle University of Thessaloniki , Department of Chemistry, Laboratory of Applied Quantum Chemistry, Thessaloniki 54124, Greece
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Anastasiadou D, Zianna A, Gdaniec M, Sigalas MP, Coutouli-Argyropoulou E, Czapik A, Lalia-Kantouri M. Unusual coordination mode of 3-methoxysalicylaldehyde in mononuclear zinc(II) complexes with nitrogenous bases: Synthesis, structural characterization and theoretical studies. Polyhedron 2015. [DOI: 10.1016/j.poly.2014.11.030] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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Tziouris PA, Tsiafoulis CG, Vlasiou M, Miras HN, Sigalas MP, Keramidas AD, Kabanos TA. Interaction of chromium(III) with a N,N'-disubstituted hydroxylamine-(diamido) ligand: a combined experimental and theoretical study. Inorg Chem 2014; 53:11404-14. [PMID: 25329981 DOI: 10.1021/ic501778d] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Reaction of hydroxylamine hydrochloride with prop-2-enamide in dichloromethane in the presence of triethylamine resulted in the isolation of the N,N'-disubstituted hydroxylamine-(diamido) ligand, 3,3'-(hydroxyazanediyl)dipropanamide (Hhydia). The ligand Hhydia was characterized by multinuclear NMR, high-resolution electrospray ionization mass spectrometry (ESI-MS), and X-ray structure analysis. Interaction of Hhydia with trans-[Cr(III)Cl2(H2O)4]Cl·2H2O in ethanol yields the ionization isomers [Cr(III)(Hhydia)2]Cl3·2H2O(1·2H2O) and cis/trans-[Cr(III)Cl2(Hhydia)2]Cl·2H2O (2·2H2O). The X-ray structure analysis of 1 revealed that the chromium atom in [Cr(III)(Hhydia)2](3+) is bonded to two neutral tridentate O,N,O-Hhydia ligands. The twist angle, θ, in [Cr(III)(Hhydia)2](3+) is 54.5(6)(0), that is, very close to an ideal octahedron. The intramolecular hydrogen bonds developed between the N-OH group of the first ligand and the amidic oxygen atom of the second ligand and vice versa contribute to the overall stability of the cation [Cr(III)(Hhydia)2](3+). The reaction rate constant of the formation of Cr(III) complexes 1·2H2O and 2·2H2O was found to be 8.7(±0.8) × 10(-5) M(-1) s(-1) at 25 °C in methyl alcohol and follows a first-order law kinetics based on the biologically relevant ligand Hhydia. The reaction rate constant is considerably faster in comparison with the corresponding water exchange rate constant for the hydrated chromium(III). The modification of the kinetics is of fundamental importance for the chromium(III) chemistry in biological systems. Ultraviolet-visible and electron paramagnetic resonance studies, both in solution and in the solid state, ESI-MS, and conductivity measurements support the fact that, irrespective of the solvent used in the interaction of Hhydia with trans-[Cr(III)Cl2(H2O)4]Cl·2H2O, the ionization isomers[Cr(III)(Hhydia)2]Cl3·2H2O (1·2H2O) and cis/trans-[Cr(III)Cl2(Hhydia)2]Cl·2H2O (2·2H2O) are produced.The reaction medium affects only the relevant percentage of the isomers in the solid state. The thermodynamic stability of the ionization isomers 1·2H2O and cis/trans-2·2H2O, their molecular structures as well as the vibrational spectra and the energetics of the Cr(III)- Hhydia/hydia(-) were studied by means of density functional theory calculations and found to be in excellent agreement with our experimental observations.
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Affiliation(s)
- Petros A Tziouris
- Section of Inorganic and Analytical Chemistry, Department of Chemistry and #NMR Center, University of Ioannina , Ioannina 45110, Greece
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Karavas E, Koutris E, Papadopoulos AG, Sigalas MP, Nanaki S, Papageorgiou GZ, Achilias DZ, Bikiaris DN. Application of density functional theory in combination with FTIR and DSC to characterise polymer drug interactions for the preparation of sustained release formulations between fluvastatin and carrageenans. Int J Pharm 2014; 466:211-22. [PMID: 24613179 DOI: 10.1016/j.ijpharm.2014.02.049] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2014] [Revised: 02/28/2014] [Accepted: 02/28/2014] [Indexed: 01/19/2023]
Abstract
In the present study, ι- and λ-carrageenans were used as appropriate carriers for sustained release formulations of fluvastatin drug. From viscosity measurements, it was found that both carrageenans can give miscible blends with fluvastatin due to the interactions between the sulfate groups of carrageenans and hydroxyl groups of fluvastatin. This was predicted by computational analysis using density functional theory and proved by FTIR spectroscopy. These interactions, which are in higher intensity using ι-carrageenan, lead to the formation of complexes between polymeric matrices and fluvastatin drug. DSC experiments also confirmed that miscible blends between carrageenans and fluvastatin can be formed since in all concentrations only one glass transition temperature was recorded. Fluvastatin release depends on the drug content and in all formulations of λ-carrageenans containing 10, 25 and 50 wt% drug, almost sustained release profiles were observed. Fluvastatin/carrageenan complexes have lower dissolution profiles compared with physical mixtures. Polymer swelling seems to be the dominant drug release mechanism. Besides to neat ι- and λ-carrageenans, their blends can be also used as effective matrices for sustained release.
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Affiliation(s)
- Evangelos Karavas
- Pharmathen S.A., Pharmaceutical Industry, Dervenakion Str 6, Pallini Attikis, Pallini Attiki 153 51, Greece
| | - Efthymios Koutris
- Pharmathen S.A., Pharmaceutical Industry, Dervenakion Str 6, Pallini Attikis, Pallini Attiki 153 51, Greece
| | - Anastasios G Papadopoulos
- Laboratory of Applied Quantum Chemistry, Department of Chemistry, Aristotle University of Thessaloniki, Thessaloniki, Greece
| | - Michael P Sigalas
- Laboratory of Applied Quantum Chemistry, Department of Chemistry, Aristotle University of Thessaloniki, Thessaloniki, Greece
| | - Stavroula Nanaki
- Laboratory of Polymer Chemistry and Technology, Chemistry Department, Aristotle University of Thessaloniki, Thessaloniki 541 24, Greece
| | - George Z Papageorgiou
- Laboratory of Polymer Chemistry and Technology, Chemistry Department, Aristotle University of Thessaloniki, Thessaloniki 541 24, Greece
| | - Dimitris Z Achilias
- Laboratory of Polymer Chemistry and Technology, Chemistry Department, Aristotle University of Thessaloniki, Thessaloniki 541 24, Greece
| | - Dimitrios N Bikiaris
- Laboratory of Polymer Chemistry and Technology, Chemistry Department, Aristotle University of Thessaloniki, Thessaloniki 541 24, Greece.
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9
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Charistos ND, Papadopoulos AG, Sigalas MP. Interpretation of Electron Delocalization in Benzene, Cyclobutadiene, and Borazine Based on Visualization of Individual Molecular Orbital Contributions to the Induced Magnetic Field. J Phys Chem A 2014; 118:1113-22. [DOI: 10.1021/jp411410r] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Affiliation(s)
- Nickolas D. Charistos
- Department of Chemistry, Laboratory of Applied
Quantum Chemistry, Aristotle University of Thessaloniki, Thessaloniki 54 124, Greece
| | - Anastasios G. Papadopoulos
- Department of Chemistry, Laboratory of Applied
Quantum Chemistry, Aristotle University of Thessaloniki, Thessaloniki 54 124, Greece
| | - Michael P. Sigalas
- Department of Chemistry, Laboratory of Applied
Quantum Chemistry, Aristotle University of Thessaloniki, Thessaloniki 54 124, Greece
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Lalia-Kantouri M, Papadopoulos CD, Hatzidimitriou AG, Sigalas MP, Quirós M, Skoulika S. Different geometries of novel cobalt(II) compounds with 2-hydroxy-benzophenones and neocuproine: Crystal and molecular structures of [Co(2-hydroxy-benzophenone)2(neoc)], [Co(2-hydroxy-4-methoxybenzophenone)(neoc)Br] and [Co(neoc)Br2]·CH3OH·H2O. Polyhedron 2013. [DOI: 10.1016/j.poly.2012.06.012] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/28/2022]
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Papazoglou I, Cox PJ, Papadopoulos AG, Sigalas MP, Aslanidis P. Copper(i) complexes of 1,10-phenanthroline and heterocyclic thioamides: an experimental and theoretical (DFT) investigation of the photophysical characteristics. Dalton Trans 2013; 42:2755-64. [DOI: 10.1039/c2dt32167j] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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Stylianou M, Nikolakis VA, Chilas GI, Jakusch T, Vaimakis T, Kiss T, Sigalas MP, Keramidas AD, Kabanos TA. Molybdenum(VI) Coordination Chemistry of the N,N-Disubstituted Bis(hydroxylamido)-1,3,5-triazine Ligand, H2bihyat. Water-Assisted Activation of the MoVI═O Bond and Reversible Dimerization of cis-[MoVIO2(bihyat)] to [MoVI2O4(bihyat)2(H2O)2]. Inorg Chem 2012; 51:13138-47. [DOI: 10.1021/ic301282q] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Marios Stylianou
- Department of Chemistry, University of Cyprus, Nicosia 1678,
Cyprus
| | - Vladimiros A. Nikolakis
- Section of Inorganic
and Analytical
Chemistry, Department of Chemistry, University of Ioannina, Ioannina 45110, Greece
| | - George I. Chilas
- Section of Inorganic
and Analytical
Chemistry, Department of Chemistry, University of Ioannina, Ioannina 45110, Greece
| | - Tamas Jakusch
- Department of Inorganic
and Analytical Chemistry, University of Szeged, Szeged, Hungary
| | - Tiverios Vaimakis
- Section of Inorganic
and Analytical
Chemistry, Department of Chemistry, University of Ioannina, Ioannina 45110, Greece
| | - Tamas Kiss
- Department of Inorganic
and Analytical Chemistry, University of Szeged, Szeged, Hungary
| | - Michael P. Sigalas
- Laboratory of Applied Quantum
Chemistry, Department of Chemistry, Aristotle University of Thessaloniki, Thessaloniki
54124, Greece
| | | | - Themistoklis A. Kabanos
- Section of Inorganic
and Analytical
Chemistry, Department of Chemistry, University of Ioannina, Ioannina 45110, Greece
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Dowling-Mitchell SAM, Henderson W, Tiekink ERT, Petrakopoulou J, Sigalas MP. Cis–Trans Ring Substituent Isomerism in Cyano-Substituted Metallathietane-3,3-dioxide Complexes of Platinum(II) and Palladium(II). Organometallics 2012. [DOI: 10.1021/om2011497] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
| | - William Henderson
- Department of Chemistry, University of Waikato, Private Bag 3105, Hamilton 3240,
New Zealand
| | | | - J. Petrakopoulou
- Laboratory
of Applied Quantum
Chemistry, Department of Chemistry, Aristotle University of Thessaloniki, 54 124 Thessaloniki, Greece
| | - Michael P. Sigalas
- Laboratory
of Applied Quantum
Chemistry, Department of Chemistry, Aristotle University of Thessaloniki, 54 124 Thessaloniki, Greece
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Papadopoulos CD, Hatzidimitriou AG, Quirós M, Sigalas MP, Lalia-Kantouri M. Synthesis, characterization, thermal and theoretical studies of cobalt(II) addition compounds with 2-hydroxy-phenones and α-diimines. Crystal and molecular structures of [Co(2-hydroxy-benzophenone)2(bipy)]·2-hydroxy-benzophenoneH (3) and [Co(2-hydroxy-benzophenone)2(phen)] (8). Polyhedron 2011. [DOI: 10.1016/j.poly.2010.11.010] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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Tsalavoutis JT, Sigalas MP. Density functional investigation and bonding analysis of pentacoordinated iron complexes with mixed cyano and carbonyl ligands. J Comput Chem 2010; 31:1969-78. [DOI: 10.1002/jcc.21481] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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Nikolakis VA, Tsalavoutis JT, Stylianou M, Evgeniou E, Jakusch T, Melman A, Sigalas MP, Kiss T, Keramidas AD, Kabanos TA. Vanadium(V) Compounds with the Bis-(hydroxylamino)-1,3,5-triazine Ligand, H2bihyat: Synthetic, Structural, and Physical Studies of [V2VO3(bihyat)2] and of the Enhanced Hydrolytic Stability Species cis-[VVO2(bihyat)]−. Inorg Chem 2008; 47:11698-710. [DOI: 10.1021/ic801411x] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Affiliation(s)
- Vladimiros A. Nikolakis
- Department of Chemistry, Section of Inorganic and Analytical Chemistry, University of Ioannina, Ioannina 45110, Greece, Department of Chemistry, Laboratory of Applied Quantum Chemistry, Aristotle University of Thessaloniki, Thessaloniki 54124, Greece, Department of Chemistry, University of Cyprus, Nicosia 1678, Cyprus, Department of Chemistry and Biomolecular Science, Clarkson University, Potsdam, New York 13699, and Department of Inorganic and Analytical Chemistry, University of Szeged, Szeged, Hungary
| | - John T. Tsalavoutis
- Department of Chemistry, Section of Inorganic and Analytical Chemistry, University of Ioannina, Ioannina 45110, Greece, Department of Chemistry, Laboratory of Applied Quantum Chemistry, Aristotle University of Thessaloniki, Thessaloniki 54124, Greece, Department of Chemistry, University of Cyprus, Nicosia 1678, Cyprus, Department of Chemistry and Biomolecular Science, Clarkson University, Potsdam, New York 13699, and Department of Inorganic and Analytical Chemistry, University of Szeged, Szeged, Hungary
| | - Marios Stylianou
- Department of Chemistry, Section of Inorganic and Analytical Chemistry, University of Ioannina, Ioannina 45110, Greece, Department of Chemistry, Laboratory of Applied Quantum Chemistry, Aristotle University of Thessaloniki, Thessaloniki 54124, Greece, Department of Chemistry, University of Cyprus, Nicosia 1678, Cyprus, Department of Chemistry and Biomolecular Science, Clarkson University, Potsdam, New York 13699, and Department of Inorganic and Analytical Chemistry, University of Szeged, Szeged, Hungary
| | - Evgenios Evgeniou
- Department of Chemistry, Section of Inorganic and Analytical Chemistry, University of Ioannina, Ioannina 45110, Greece, Department of Chemistry, Laboratory of Applied Quantum Chemistry, Aristotle University of Thessaloniki, Thessaloniki 54124, Greece, Department of Chemistry, University of Cyprus, Nicosia 1678, Cyprus, Department of Chemistry and Biomolecular Science, Clarkson University, Potsdam, New York 13699, and Department of Inorganic and Analytical Chemistry, University of Szeged, Szeged, Hungary
| | - Tamas Jakusch
- Department of Chemistry, Section of Inorganic and Analytical Chemistry, University of Ioannina, Ioannina 45110, Greece, Department of Chemistry, Laboratory of Applied Quantum Chemistry, Aristotle University of Thessaloniki, Thessaloniki 54124, Greece, Department of Chemistry, University of Cyprus, Nicosia 1678, Cyprus, Department of Chemistry and Biomolecular Science, Clarkson University, Potsdam, New York 13699, and Department of Inorganic and Analytical Chemistry, University of Szeged, Szeged, Hungary
| | - Artem Melman
- Department of Chemistry, Section of Inorganic and Analytical Chemistry, University of Ioannina, Ioannina 45110, Greece, Department of Chemistry, Laboratory of Applied Quantum Chemistry, Aristotle University of Thessaloniki, Thessaloniki 54124, Greece, Department of Chemistry, University of Cyprus, Nicosia 1678, Cyprus, Department of Chemistry and Biomolecular Science, Clarkson University, Potsdam, New York 13699, and Department of Inorganic and Analytical Chemistry, University of Szeged, Szeged, Hungary
| | - Michael P. Sigalas
- Department of Chemistry, Section of Inorganic and Analytical Chemistry, University of Ioannina, Ioannina 45110, Greece, Department of Chemistry, Laboratory of Applied Quantum Chemistry, Aristotle University of Thessaloniki, Thessaloniki 54124, Greece, Department of Chemistry, University of Cyprus, Nicosia 1678, Cyprus, Department of Chemistry and Biomolecular Science, Clarkson University, Potsdam, New York 13699, and Department of Inorganic and Analytical Chemistry, University of Szeged, Szeged, Hungary
| | - Tamas Kiss
- Department of Chemistry, Section of Inorganic and Analytical Chemistry, University of Ioannina, Ioannina 45110, Greece, Department of Chemistry, Laboratory of Applied Quantum Chemistry, Aristotle University of Thessaloniki, Thessaloniki 54124, Greece, Department of Chemistry, University of Cyprus, Nicosia 1678, Cyprus, Department of Chemistry and Biomolecular Science, Clarkson University, Potsdam, New York 13699, and Department of Inorganic and Analytical Chemistry, University of Szeged, Szeged, Hungary
| | - Anastasios D. Keramidas
- Department of Chemistry, Section of Inorganic and Analytical Chemistry, University of Ioannina, Ioannina 45110, Greece, Department of Chemistry, Laboratory of Applied Quantum Chemistry, Aristotle University of Thessaloniki, Thessaloniki 54124, Greece, Department of Chemistry, University of Cyprus, Nicosia 1678, Cyprus, Department of Chemistry and Biomolecular Science, Clarkson University, Potsdam, New York 13699, and Department of Inorganic and Analytical Chemistry, University of Szeged, Szeged, Hungary
| | - Themistoklis A. Kabanos
- Department of Chemistry, Section of Inorganic and Analytical Chemistry, University of Ioannina, Ioannina 45110, Greece, Department of Chemistry, Laboratory of Applied Quantum Chemistry, Aristotle University of Thessaloniki, Thessaloniki 54124, Greece, Department of Chemistry, University of Cyprus, Nicosia 1678, Cyprus, Department of Chemistry and Biomolecular Science, Clarkson University, Potsdam, New York 13699, and Department of Inorganic and Analytical Chemistry, University of Szeged, Szeged, Hungary
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Affiliation(s)
- Nikolaos Nenadis
- Laboratory of Applied Quantum Chemistry, Department of Chemistry, Aristotle University of Thessaloniki, 541 24 Thessaloniki, Greece
| | - Michael P. Sigalas
- Laboratory of Applied Quantum Chemistry, Department of Chemistry, Aristotle University of Thessaloniki, 541 24 Thessaloniki, Greece
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Miras HN, Stone DJ, McInnes EJL, Raptis RG, Baran P, Chilas GI, Sigalas MP, Kabanos TA, Cronin L. Solution identification and solid state characterisation of a heterometallic polyoxometalate {Mo(11)V(7)}: [Mo(VI)(11)V(V)(5)V(IV)(2)O(52)(mu(9)-SO(3))](7-). Chem Commun (Camb) 2008:4703-5. [PMID: 18830465 DOI: 10.1039/b811279g] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
A polyoxomolybdenum/vanadium-sulfite {M(18)} cluster-based compound, [Mo(VI)(11)V(V)(5)V(IV)(2)O(52)(mu(9)-SO(3))](7-), is reported that exhibits a unique structural motif, arising from the incorporation of five V(V) and two V(IV) ions into a {M(18)} cluster framework templated by SO(3)(2-); this cluster compostion was first identified using cryospray mass spectrometry.
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Affiliation(s)
- Haralampos N Miras
- WestCHEM, Department of Chemistry, The University of Glasgow, Glasgow, Scotland, UK G12 8QQ
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Kapakoglou NI, Panagiotis BI, Kazianis SE, Kosmidis CE, Drouza C, Manos MJ, Sigalas MP, Keramidas AD, Kabanos TA. Polyoxomolybdenum(V/VI)−Sulfite Compounds: Synthesis, Structural, and Physical Studies. Inorg Chem 2007; 46:6002-10. [PMID: 17592836 DOI: 10.1021/ic700460b] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Reaction of Na(2)Mo(VI)O(4) x 2H(2)O with (NH(4))(2)SO(3) in the mixed-solvent system H(2)O/CH(3)CN (pH = 5) resulted in the formation of the tetranuclear cluster (NH(4))(4)[Mo(4)(VI)SO(16)] x H(2)O (1), while the same reaction in acidic aqueous solution (pH = 5) yielded (NH(4))(4)[Mo(5)(VI)S(2)O(21)] x 3H(2)O (2). Compound {(H(2)bipy)(2)[Mo(5)(VI)S(2)O(21)] x H(2)O}(x) (3) was obtained from the reaction of aqueous acidic solution of Na(2)Mo(VI)O(4) x 2H(2)O with (NH(4))(2)SO(3) (pH = 2.5) and 4,4'-bipyridine (4,4'-bipy). The mixed metal/sulfite species (NH(4))(7)[Co(III)(Mo(2)(V)O(4))(NH(3))(SO(3))(6)] x 4H(2)O (4) was synthesized by reacting Na(2)Mo(VI)O(4) x 2H(2)O with CoCl(2) x 6H(2)O and (NH(4))(2)SO(3) with precise control of pH (5.3) through a redox reaction. The X-ray crystal structures of compounds 1, 2, and 4 were determined. The structure of compound 1 consists of a ring of four alternately face- and edge-sharing Mo(VI)O(6) octahedra capped by the trigonal pyramidal sulfite anion, while at the base of the Mo(4) ring is an oxo group which is asymmetrically shared by all four molybdenum atoms. Compound 3 is based on the Strandberg-type heteropolyion [Mo(5)(VI)S(2)O(21)](4-), and these coordinatively saturated clusters are joined by diprotonated 4,4'-H(2)bipy(2+) through strong hydrogen bonds. Compound 3 crystallizes in the chiral space group C2. The structure of compound 4 consists of a novel trinuclear [Co(III)Mo(2)(V)SO(3)(2-)] cluster. The chiral compound 3 exhibits nonlinear optical (NLO) and photoluminescence properties. The assignment of the sulfite bands in the IR spectrum of 4 has been carried out by density functional calculations. The cobalt in 4 is a d(6) octahedral low-spin metal atom as it was evidenced by magnetic susceptibility measurements, cw EPR, BVS, and DFT calculations. The IR and solid-state UV-vis spectra as well as the thermogravimetric analyses of compounds 1-4 are also reported.
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Affiliation(s)
- Nikolaos I Kapakoglou
- Section of Inorganic and Analytical Chemistry, Department of Chemistry, University of Ioannina, 45110, Greece
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Karavas E, Georgarakis E, Sigalas MP, Avgoustakis K, Bikiaris D. Investigation of the release mechanism of a sparingly water-soluble drug from solid dispersions in hydrophilic carriers based on physical state of drug, particle size distribution and drug–polymer interactions. Eur J Pharm Biopharm 2007; 66:334-47. [PMID: 17267194 DOI: 10.1016/j.ejpb.2006.11.020] [Citation(s) in RCA: 152] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2006] [Revised: 11/22/2006] [Accepted: 11/23/2006] [Indexed: 11/21/2022]
Abstract
In the present study the release mechanism of the sparingly water-soluble drug felodipine (FELO) from particulate solid dispersions in PVP or PEG was investigated. FT-IR data indicated that a N-H...O hydrogen bond is formed between FELO and polymers. The drug-polymer interaction was theoretically studied with the density functional theory with the B3LYP exchange correlation function. The interaction energies have been estimated at -31.8 kJ/mol for PVP and -18.8 kJ/mol for PEG. Also, detailed vibrational analysis of the complexes showed that the red shift of the N-H bond stretching in FELO molecule due to H-bonding was higher in the FELO-PVP complex than in the FELO-PEG complex. Both the experimental and theoretical data indicated that a stronger interaction of FELO with PVP than with PEG was developed. The interactions of FELO with the polymer appeared to control the physical state (amorphous or crystalline) and the particle size of FELO in the solid dispersions. In the FELO/PVP dispersions, the drug is found as amorphous nanoparticles whereas in FELO/PEG dispersions the drug is dispersed as crystalline microparticles. The size of drug particles in the dispersion was also influenced by drug proportion, with an increase in drug content of the dispersion resulting in increased drug particle size. The particle size of drug, the proportion of drug in the dispersion and the properties of the polymer (molecular weight) appeared to determine the mechanism of drug release from the solid dispersions, which was drug diffusion (through the polymer layer)-controlled at low drug contents and drug dissolution-controlled at high drug contents. In situ DLS measurements indicate that the large initial particles of FELO/PVP and FELO/PEG solid dispersions with low drug content (10-20 wt%) are very rapidly decreased to smaller particles (including nanoparticles) during dissolution, leading to the observed impressive enhancement of FELO release rate from these dispersions.
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Miras HN, Raptis RG, Lalioti N, Sigalas MP, Baran P, Kabanos TA. A Novel Series of Vanadium-Sulfite Polyoxometalates: Synthesis, Structural, and Physical Studies. Chemistry 2005; 11:2295-306. [PMID: 15685580 DOI: 10.1002/chem.200400203] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Reaction of NH4VO3 with sulfur dioxide affords the hexanuclear cluster (NH4)2(Et4N)[(V(IV)O)6(mu4-O)2(mu3-OH)2(mu3-SO3)4(H2O)2]Cl x H2O (1), and the decapentanuclear host-guest compound (Et4N)5{Cl subset [(VO)15(mu3-O)18(mu-O)3]} x 3 H2O (2). Sequential addition of magnesium oxide to an acidic aqueous solution of NH4VO3 (pH approximately 0) followed by (NH4)2SO3 resulted in the formation of either the non-oxo polymeric vanadium(IV) compound trans-(NH4)2[V(IV)(OH)2(mu-SO3)2] (3) or the polymeric oxovanadium(IV) sulfite (NH4)[V(IV)O(SO3)1.5(H2O)] x 2.5 H2O (4) at pH values of 6 and 4, respectively. The decameric vanadium(V) compound {Na4(mu-H2O)8(H2O)6}[Mg(H2O)6][V(V)10(O)8(mu6-O)2(mu3-O)14] x 3 H2O (5) was synthesised by treating an acidic aqueous solution of NH4VO3 with MgO and addition of NaOH to pH approximately 6. All the compounds were characterised by single-crystal X-ray structure analysis. The crystal structure of compound 1 revealed an unprecedented structural motif of a cubane unit [M4(mu4-O)2(mu3-OH)2] connected to two other metal atoms. Compound 3 comprises a rare example of a non-oxo vanadium(IV) species isolated from aqueous solution and in the presence of the reducing agent SO3(2-), while compound 4 represents a rare example of an open-framework species isolated at room temperature (20 degrees C). In addition to the synthesis and crystallographic studies, we report the IR and magnetic properties (for 1, 2 and 3) of these vanadium clusters as well as theoretical studies on compound 3.
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Affiliation(s)
- Haralampos N Miras
- Department of Chemistry, Section of Inorganic and Analytical Chemistry, University of Ioannina, 45110 Ioannina, Greece
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Drouza C, Gramlich V, Sigalas MP, Pashalidis I, Keramidas AD. Synthesis, Structure, and Solution Dynamics of UO22+−Hydroxy Ketone Compounds [UO2(ma)2(H2O)] and [UO2(dpp)(Hdpp)2(H2O)]ClO4[ma = 3-Hydroxy-2-methyl-4-pyrone, Hdpp = 3-Hydroxy-1,2-dimethyl-4(1H)-pyridone]. Inorg Chem 2004; 43:8336-45. [PMID: 15606180 DOI: 10.1021/ic049167+] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Reaction of [UO(2)(NO(3))(2)] with the hydroxy ketones 3-hydroxy-2-methyl-4-pyrone (Hma) and 3-hydroxy-1,2-dimethyl-4(1H)-pyridone (Hdpp) in aqueous acidic solutions (pH approximately 3) yields the compounds [UO(2)(ma)(2)(H(2)O)].H(2)O (1.H(2)O) and [UO(2)(dpp)(Hdpp)(2)(H(2)O)]ClO(4) (2), respectively. X-ray diffraction shows that the geometry around the metal ion in both complexes is pentagonal bipyramid. Uranium ion in the crystal structure of 1 were found to be ligated with two chelate ma(-) groups and one unidentate H(2)O molecule (C coordination mode) at the equatorial plane, while in 2 with two single-bonded Hdpp there were one chelate dpp(-) and one H(2)O molecule (P coordination mode). Crystal data (Mo Kalpha; 293(2) K) are as follows: (1) monoclinic space group C2/c, a = 14.561(7) A, b = 14.871(9) A, c = 7.250(4) A, beta = 95.40(4) degrees , Z = 4; (2) monoclinic space group P2(1)/c, a = 19.080(2) A, b = 9.834(1) A, c = 15.156(2) A, beta = 104.62(1) degrees , Z = 4. (1)H NMR measurements indicate that complex 2 retains its structure in CD(3)CN solution; however, in DMSO-d(6) both complexes adopt the C structure. Line-shape analysis for the (1)H NMR peaks of 2 at various temperatures shows a fast intramolecular exchange process between the chelate dpp(-) and one of the single bonded Hdpp ligands and one slower exchange between all three ligands. The activation parameters and the decrease of the exchange rate by replacing unidentate ligand with DMSO indicate the dissociation of the unidentate ligand as the rate-determining step for the former exchange. Density functional calculations (DFT) support this mechanism and give a quantitative interpretation of the electronic structure of the two ligands and the geometries adopted by the complexes.
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Triantafillou GD, Tolis EI, Terzis A, Deligiannakis Y, Raptopoulou CP, Sigalas MP, Kabanos TA. Monomeric Oxovanadium(IV) Compounds of the General Formula cis-[VIV(O)(X)(LNN)2]+/0 {X = OH-, Cl-, SO42- and LNN = 2,2‘-Bipyridine (Bipy) or 4,4‘-Disubstituted Bipy}. Inorg Chem 2003; 43:79-91. [PMID: 14704056 DOI: 10.1021/ic034440d] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Reaction of [V(IV)OCl(2)(THF)(2)] in aqueous solution with 2 equiv of AgBF(4) or AgSbF(6) and then with 2 equiv of 2,2'-bipyridine (bipy), 4,4'-di-tert-butyl-2,2'-bipyridine (4,4'-dtbipy), or 4,4'-di-methyl-2,2'-bipyridine (4,4'-dmbipy) affords compounds of the general formula cis-[V(IV)O(OH)(L(NN))(2)]Y [where L(NN) = bipy, Y = BF(4)(-) (1), L(NN) = 4,4'-dtbipy, Y = BF(4)(-) (2.1.2H(2)O), L(NN) = 4,4'-dmbipy, Y = BF(4)(-) (3.2H(2)O), and L(NN) = 4,4'-dtbipy, Y = SbF(6)(-) (4)]. Sequential addition of 1 equiv of Ba(ClO(4))(2) and then of 2 equiv of bipy to an aqueous solution containing 1 equiv of V(IV)OSO(4).5H(2)O yields cis-[V(IV)O(OH)(bipy)(2)]ClO(4) (5). The monomeric compounds 1-5 contain the cis-[V(IV)O(OH)](+) structural unit. Reaction of 1 equiv of V(IV)OSO(4).5H(2)O in water and of 1 equiv of [V(IV)OCl(2)(THF)(2)] in ethanol with 2 equiv of bipy gives the compounds cis-[V(IV)O(OSO(3))(bipy)(2)].CH(3)OH.1.5H(2)O (6.CH(3)OH.1.5H(2)O) and cis-[V(IV)OCl(bipy)(2)]Cl (7), respectively, while reaction of 1 equiv of [V(IV)OCl(2)(THF)(2)] in CH(2)Cl(2) with 2 equiv of 4,4'-dtbipy gives the compound cis-[V(IV)OCl(4,4'-dtbipy)(2)]Cl.0.5CH(2)Cl(2) (8.0.5CH(2)Cl(2)). Compounds cis-[V(IV)O(BF(4))(4,4'-dtbipy)(2)]BF(4) (9), cis-[V(IV)O(BF(4))(4,4'-dmbipy)(2)]BF(4) (10), and cis-[V(IV)O(SbF(6))(4,4'-dtbipy)(2)]SbF(6) (11) were synthesized by sequential addition of 2 equiv of 4,4'-dtbipy or 4,4'-dmbipy and 2 equiv of AgBF(4) or AgSbF(6) to a dichloromethane solution containing 1 equiv of [V(IV)OCl(2)(THF)(2)]. The crystal structures of 2.1.2H(2)O, 6.CH(3)OH.1.5H(2)O, and 8.0.5CH(2)Cl(2) were demonstrated by X-ray diffraction analysis. Crystal data are as follows: Compound 2.1.2H(2)O crystallizes in the orthorhombic space group Pbca with (at 298 K) a = 21.62(1) A, b = 13.33(1) A, c = 27.25(2) A, V = 7851(2) A(3), Z = 8. Compound 6.CH(3)OH.1.5H(2)O crystallizes in the monoclinic space group P2(1)/a with (at 298 K) a = 12.581(4) A, b = 14.204(5) A, c = 14.613(6) A, beta = 114.88(1) degrees, V = 2369(1), Z = 4. Compound 8.0.5CH(2)Cl(2) crystallizes in the orthorhombic space group Pca2(1) with (at 298 K) a = 23.072(2) A, b = 24.176(2) A, c = 13.676(1) A, V = 7628(2) A(3), Z = 8 with two crystallographically independent molecules per asymmetric unit. In addition to the synthesis and crystallographic studies, we report the optical, infrared, magnetic, conductivity, and CW EPR properties of these oxovanadium(IV) compounds as well as theoretical studies on [V(IV)O(bipy)(2)](2+) and [V(IV)OX(bipy)(2)](+/0) species (X = OH(-), SO(4)(2)(-), Cl(-)).
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Rikkou M, Manos M, Tolis E, Sigalas MP, Kabanos TA, Keramidas AD. NMR and theoretical investigations on the structures and dynamics of octahedral bis(chelate)dichloro V(III) compounds isolated by an unusual reduction of non-oxo V(IV) species. Inorg Chem 2003; 42:4640-9. [PMID: 12870955 DOI: 10.1021/ic034221s] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Reaction of the non-oxo V(IV) species [V(IV)Cl(2)(L(OO))(2)] [L(OO) = acetylacetonate (acac(-)) or benzoylacetonate (bzac(-))] with a chelate nitrogen-donor ligand L(NN) in acetonitrile leads to the reduction of V(IV) to V(III) and the formation of the mononuclear V(III) compounds of the general formula [V(III)Cl(2)(L(OO))(L(NN))] (L(OO) and L(NN) are acac(-) and bipy for 1; acac- and 5,5'-me(2)bipy for 2; acac(-) and 4,4'-tb(2)bipy for 3; acac(-) and phen for 4; bzac(-) and bipy for 5; bzac(-) and phen for 6). The reduction of the V(IV) complexes was monitored by GC-MS and (1)H NMR spectroscopy. Both one- and two-dimensional (2D COSY and 2D EXSY) (1)H NMR techniques were used to assign the observed (1)H NMR resonances of 1-6 in CD(2)Cl(2) or CDCl(3) solution. It appeared that in solution these V(III) complexes form two isomers which are in equilibrium: cis-[V(III)Cl(2)(L(OO))(L(NN))] <==> trans-[V(III)Cl(2)(L(OO))(L(NN))]. 2D EXSY cross-peaks were clearly observed between bipy- and acac-hydrogen atoms of the two geometrical isomers of 1-3 as well as between bipy and acac(-) protons of the cis isomer, indicating a dynamic process that corresponds to cis-trans isomerization and a cis-cis racemization. The thermodynamic and kinetic parameters of the equilibrium between these two isomers were calculated for compounds 1 and 2 by using variable temperature (VT) NMR data. Both cis-trans isomerization and cis-cis racemization processes probably proceed with an intramolecular twist mechanism involving a trigonal prismatic transition state. Density functional calculations (DFT) also indicated such a rearrangement mechanism.
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Affiliation(s)
- Maria Rikkou
- Department of Chemistry, University of Cyprus, 1678 Nicosia, Cyprus
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Manos MJ, Tasiopoulos AJ, Tolis EJ, Lalioti N, Woollins JD, Slawin AMZ, Sigalas MP, Kabanos TA. A new class of ferromagnetically-coupled mixed valence vanadium(IV/V) polyoxometalates. Chemistry 2003; 9:695-703. [PMID: 12569462 DOI: 10.1002/chem.200390078] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Reaction of [V(VI)OCl(2)(thf)(2)] with a bidentate nitrogen-donor ligand (L: phen=1,10-phenanthroline, 5-mephen=5-methyl-1,10-phenanthroline, bipy=2,2'-bipyridine, 5,5'-me(2)bipy=5,5'-dimethyl-2,2'-bipy) in methyl alcohol, in the presence of triethylamine, leads to the formation of hexameric [V(2) (IV)V(4) (V)] oxo-alkoxo-vanadates of the general formula [V(6)O(12)(mu(2)-OCH(3))(4)(L)(4)].x H(2)O [L=phen (1.4 H(2)O), 5-mephen (2.6 H(2)O), bipy (3.4 H(2)O), 5,5'-me(2)bipy (4.H(2)O)]. X-ray structure analysis of 1.2 H(2)O and 4.8 CH(3)OH revealed a pair of V(3)O(13)N(4) trimeric units sharing two corners, with a centrosymmetric planar V(6)-core. In addition, a fully oxidized V(V) species [V(V) (4)O(8)(OCH(3))(2)(mu(3)-OCH(3))(2)(5,5'-me(2)bipy)(2)].3 CH(3)OH (5.3 CH(3)OH) was isolated from the reaction mixture used for the synthesis of 4.H(2)O. The crystal structure of 5.3 CH(3)OH revealed a dicubane-like framework with two missing vertices. Electron paramagnetic resonance (EPR) and variable temperature magnetic susceptibility studies for the hexamers 1.4 H(2)O and 3.4 H(2)O showed the complete localization of the single 3d electrons on the V(IV) ions and unusual ferromagnetic interaction between the two paramagnetic vanadium(IV) ions separated by a distance of about 5.1 A. Furthermore, intermolecular antiferromagnetic interactions through pi-contacts of phenyl rings were observed for these species below 8 K. The ferromagnetic exchange coupling observed in the hexanuclear compounds 1.4 H(2)O and 3.4 H(2)O is also discussed using ab initio UHF calculations on a model compound. The value of the exchange coupling constant (3.7 cm(-1)) for this model compound, calculated using the broken symmetry approach, is in good agreement, both in sign and magnitude, with the experimental J values (6.00 cm(-1) for 1.4 H(2)O and 8.54 cm(-1) for 3.4 H(2)O).
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Affiliation(s)
- Manolis J Manos
- Department of Chemistry Section of Inorganic and Analytical Chemistry University of Ioannina 45110 Ioannina, Greece.
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Pachini S, Sigalas MP. Ab initio and density functional study of structure and bonding of cage compounds containing boron, phosphorus and group 14 atomsElectronic supplementary information (ESI) available: optimized bond lengths and angles. See http://www.rsc.org/suppdata/nj/b3/b301191g/. NEW J CHEM 2003. [DOI: 10.1039/b301191g] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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Drouza C, Tolis V, Gramlich V, Raptopoulou C, Terzis A, Sigalas MP, Kabanos TA, Keramidas AD. p-Hydroquinone-metal compounds: synthesis and crystal structure of two novel VV-p-hydroquinonate and VIV-p-semiquinonate species. Chem Commun (Camb) 2002:2786-7. [PMID: 12478746 DOI: 10.1039/b207330g] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Reaction of the p-hydroquinone derivative H2Na4bicah.4H2O with either VIVOSO(4).3H2O and NaVVO3 in equivalent quantities or with NaVVo3 yields the tetranuclear VIVO2+ macrocycle-semiquinonate compound Na6[(VIVO)4-(mu2-O)2[mu2-bicas.(-5)-N,O,O,O]2].Na2SO(4).20H2O (1.Na2SO(4).20H2O) and the dinuclear cis-VVO2(+)-hydroquinone species Na4[(VVO2)2[mu2-bicah(-6)-N,O,O,O]].11H2O (2.11H2O) respectively. Compounds 1.Na2SO(4).20H2O and 2.11H2O were characterized by X-ray structure analysis and ab initio calculations.
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Tolis EJ, Manos MJ, Tasiopoulos AJ, Raptopoulou CP, Terzis A, Sigalas MP, Deligiannakis Y, Kabanos TA. Monomeric Compounds Containing thecis-[V(O)(OH)]+ Core. Angew Chem Int Ed Engl 2002. [DOI: 10.1002/1521-3757(20020802)114:15<2921::aid-ange2921>3.0.co;2-w] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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Tolis EJ, Manos MJ, Tasiopoulos AJ, Raptopoulou CP, Terzis A, Sigalas MP, Deligiannakis Y, Kabanos TA. Monomeric compounds containing the cis-[V([double bond]O)(OH)+ core. Angew Chem Int Ed Engl 2002; 41:2797-801. [PMID: 12203490 DOI: 10.1002/1521-3773(20020802)41:15<2797::aid-anie2797>3.0.co;2-r] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Affiliation(s)
- Evangelos J Tolis
- Department of Chemistry, Section of Inorganic and Analytical Chemistry, University of Ioannina, 45110 Ioannina, Greence
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Teberekidis VI, Sigalas MP. Density functional study of potential energy surfaces and relative stabilities of halonium cations of ethylene and cyclopentenes. Tetrahedron 2002. [DOI: 10.1016/s0040-4020(02)00617-8] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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Poulton JT, Sigalas MP, Eisenstein O, Caulton KG. Modulation of reactivity and stereochemistry of substrate binding by the group X in RuHX(CO)(P-tert-Bu2Me)2. Inorg Chem 2002. [DOI: 10.1021/ic00076a015] [Citation(s) in RCA: 65] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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Sigalas MP, Tsipis CA. Electronic ground states and spectra of square-planar nickel(II) complexes with aromatic dithiocarboxylato ligands. Inorg Chem 2002. [DOI: 10.1021/ic00231a033] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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Haakansson M, Oertendahl M, Jagner S, Sigalas MP, Eisenstein O. Splitting dioxygen with mesitylcopper(I). An arylcopper(I) intermediate, formed in a coupling reaction, containing two trapped trigonal pyramidally coordinated oxides. Inorg Chem 2002. [DOI: 10.1021/ic00062a025] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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Poulton JT, Sigalas MP, Folting K, Streib WE, Eisenstein O, Caulton KG. RuHX(CO)(PR3)2: Can .nu.CO Be a Probe for the Nature of the Ru-X Bond? Inorg Chem 2002. [DOI: 10.1021/ic00085a043] [Citation(s) in RCA: 105] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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Lu Z, Jun CH, de Gala SR, Sigalas MP, Eisenstein O, Crabtree RH. Geometrically Distorted and Redox-Active Organometallic Iridium Complexes Containing Biphenyl-2,2'-diyl. Organometallics 2002. [DOI: 10.1021/om00003a018] [Citation(s) in RCA: 67] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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Tsipis AC, Sigalas MP. Mechanistic aspects of the complete set of hydrolysis and anation reactions of cis - and trans -DDP related to their antitumor activity modeled by an improved ASED-MO approach. ACTA ACUST UNITED AC 2002. [DOI: 10.1016/s0166-1280(02)00007-6] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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Tolis EJ, Teberekidis VI, Raptopoulou CP, Terzis A, Sigalas MP, Deligiannakis Y, Kabanos TA. The effect of charged axial ligands on the EPR parameters in oxovanadium(IV) compounds: an unusual reduction of the Az (51V) values. Chemistry 2001; 7:2698-710. [PMID: 11465461 DOI: 10.1002/1521-3765(20010618)7:12<2698::aid-chem26980>3.0.co;2-2] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Two series of octahedral oxovanadium(IV) compounds, containing charged or neutral axial ligands, with the tetradentate amidate molecules Hcapca and H2capcah of the general formulae trans-[V(IV)OX(capca)]0/+ (where X = Cl- (1.CH2Cl2), SCN- (2), N3 (3), CH3COO- (4), PhCOO- (5), imidazole (6. CH3NO2), and eta-nBuNH2 (7)) and cis-[V(VI)OX(Hcapcah)]0/+ (where X = Cl- (8.0.5CH2Cl2), SCN (9), N3 (10.2CH3OH), and imidazole (11)), were synthesized and characterized by X-ray crystallography (1.CH3OH,8.CHCl3, 9.2CH3CN, 10.CH3CN and cis-[VO(imidazole)(Hcapcah)+) and continuous-wave electron paramagnetic resonance (cw EPR) spectroscopy. In addition to the synthesis, crystallographic and EPR studies, the optical, infrared and magnetic properties (room temperature) of these compounds are reported. Ab initio calculations were also carried out on compound 8 CHCl3 and revealed that this isomer is more stable than the trans isomer, in good agreement with the experimental data. The cw EPR studies of compounds 1-5, that is, the V(IV)O2+ species containing monoanionic axial ligands, revealed a novel phenomenon of the reduction of their A, components by about 10% relative to the N4 reference compounds ([V(IV)O-(imidazole)4]2+ and [V(IV)O(2,2-bipyridine)2]2+). In marked contrast, such a reduction is not observed in compounds 6. CH3NO2-11, which contain neutral axial ligands. Based on the spin-Hamiltonian formalism a theoretical explanation is put forward according to which the observed reduction of Az is due to a reduction of the electron - nuclear dipolar coupling (P). The present findings bear strong relevance to cw EPR studies of oxovanadium(IV) in vanadoproteins, V(IV)O2+-substituted proteins, and in V(IV)O2+ model compounds, since the hyperfine coupling constant, Az, has been extensively used as a benchmark for identification of equatorial-donor-atom sets in oxovanadium(IV) complexes.
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Affiliation(s)
- E J Tolis
- Department of Chemistry, University of Ioannina, Greece
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Caballero A, Gómez-de la Torre F, Jalón FA, Manzano BR, Rodríguez AM, Trofimenko S, Sigalas MP. Synthesis and characterisation of a series of ruthenium scorpionate complexes with B–H · · · M agostic interactions. Crystal structure of [RuH(κ2-N,BH TpTn)(PMe3)(cod)] (TpTn = hydrotris[3-(2-thienyl)pyrazol-1-yl]borate) † ‡. ACTA ACUST UNITED AC 2001. [DOI: 10.1039/b008986i] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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Vlahos AT, Tolis EI, Raptopoulou CP, Tsohos A, Sigalas MP, Terzis A, Kabanos TA. Model investigations of vanadium-protein interactions: novel vanadium(III) and oxovanadium(IV) compounds with the diamidate ligand 1,2-bis(2-pyridinecarboxamide)benzene (H2bpb). Inorg Chem 2000; 39:2977-85. [PMID: 11196892 DOI: 10.1021/ic990837z] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Novel vanadium(III) and oxovanadium(IV) compounds with the diamidate ligand 1,2-bis(2-pyridinecarboxamide)benzene (H2bpb) were synthesized and structurally characterized. H2bpb is capable of binding to vanadium in either its anionic (dianionic-monoanionic) or its neutral form, resulting in complexes of various geometries and stoichiometries. The dianionic form (bpb2-), in NHEt3(trans-[VCl2(bpb)]) (1) and [VO(bpb)(H2O)]05dmso036CH3OH013H2O (6x05dmsox036CH3OHx013H2O), acts as a planar tetradentate bis[N-amidate-N-pyridine] equatorial ligand. The monoanionic form (Hbpb-) behaves as an (Npy,Oam) or (Npy,Nam) chelator in [V(Hbpb)3]2CHCl3 (22CHCl3) as well as a mu 2-bridging-eta 4-(Npy,Oam-Npy,Nam) in [VOCl(Hbpb)](2)x2CH3NO2 (3x2CH3NO2), while the neutral H2bpb behaves as a mu 2-bridging-eta 4-bis(Npy,Oam) in [VOCl(H2bpb)](2)x104CH3OHx123thfx074H2O (4x104CH3OH123thf074H2O). Compound 4x104CH3OHx123thfx074H2O crystallizes in the triclinic system P1, with (at 25 degrees C) a = 9140(2) A, b = 11058(2) A, c = 14175(2) A, alpha = 99013(5) degrees, beta = 104728(7) degrees, gamma = 102992(7) degrees, V = 13149(4) A3, Z = 1, while compound 605dmso036CH3OH013H2O crystallizes in the monoclinic space group P2(1)/n with (at 25 degrees C) a = 11054(5) A, b = 11407(5) A, c = 16964(7) A, beta = 932(1) degrees, V = 2136(2) A3, Z = 4. Variable temperature magnetic susceptibility studies of the dimeric compounds 3x2CH3NO2 and 4x104CH3OH show g values for the V(IV) centers that are slightly smaller than 20 (as expected for d1 ions) and indicate small antiferromagnetic coupling between the two vanadium(IV) centers. Ab initio calculations were also carried out, providing results concerning the effect of the relative strength and the deformation energy involved in the eta 2-(Npy,Nam) and eta 2-(Npy,Oam) bonding modes in the ligation of Hbpb- to vanadium.
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Affiliation(s)
- A T Vlahos
- Department of Chemistry, Section of Inorganic and Analytical Chemistry, University of Ioannina, 451 10 Ioannina, Greece
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Mylonas VE, Sigalas MP, Katsoulos GA, Tsipis CA, Varvoglis AG. Electronic structure and bonding in polycoordinated iodine compounds. ACTA ACUST UNITED AC 1994. [DOI: 10.1039/p29940001691] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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Tsipis CA, Sigalas MP, Papageorgiou VP, Bakola-Christianopoulou MN. Investigation of the possible pathways for magnetic exchange interactions in homobinuclear chelates of naphthazarin. CAN J CHEM 1983. [DOI: 10.1139/v83-261] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Homobinuclear complexes of the binucleating naphthazarinato ligand of the general formula [Formula: see text] where M = Cu, Ni, and Zn, C10H4O4 = naphthazarinato ligand, and C10H8N2 = 2,2′-bipyridyl, have been prepared and studied. In these complexes the naphthazarinato ligand, acting as a bridging unit between the two metal centers, supports the propagation of magnetic exchange interactions through its extensive π-electron system. The spectroscopic and magnetic data of the compounds showed that each metal ion is surrounded by two oxygen and two nitrogen donor atoms in a nearly tetrahedral configuration (C2v point group) with the naphthazarinato ligand adopting a centrosymmetrical structure of C2h symmetry. The room-temperature magnetic data of the copper(II) and nickel(II) homobinuclear chelates (1.32 and 1.73 BM per metal ion at 8000 G, respectively), as well as the slight decrease of the magnetic moments as the magnetic field strength decreases are indicative of the operation of antiferromagnetism in these chelates. Quantum mechanical calculations of the Hückel LCAO-MO type improved by ω-technique have been used to provide a qualitative guide to the possible pathways for the superexchange processes observed in the tetrahedral copper(II) and nickel(II) chelates, as well as to explain qualitatively why there is no antiferromagnetic interactions propagated by the bridging naphthazarinato ligand in analogous homobinuclear chelates with other coordination geometries such as square planar, square-pyramidal, trigonal bipyramidal, and octahedral.
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