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Bencini A, Benelli C, Gatteschi D, Zanchini C. ESR spectra of low-symmetry high-spin cobalt(II) complexes. 3. Square-pyramidal nitratotetrakis(methyldiphenylarsine oxide)cobalt(II) nitrate. Inorg Chem 2002. [DOI: 10.1021/ic50199a038] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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Bencini A, Benelli C, Gatteschi D. Preparation of [Co2(tren)2OH](ClO4)3.H2O (tren = tris(2-aminoethyl)amine) and magnetic exchange interactions in binuclear monohydroxo-bridged copper(II) and cobalt(II) complexes. Inorg Chem 2002. [DOI: 10.1021/ic00145a020] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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Bencini A, Gatteschi D, Reedijk J, Zanchini C. Anisotropic exchange in transition-metal dinuclear complexes. 4. (.mu.-Benzotriazolato-N1,N3)bis[[tris(N1-methylbenzimidazol-2-ylmethyl)amine-N,N3,N3',N3'']copper(II)]trinitrate. Inorg Chem 2002. [DOI: 10.1021/ic00196a018] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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Bencini A, Benelli C, Caneschi A, Dei A, Gatteschi D. Crystal and molecular structure and magnetic properties of a trinuclear complex containing exchange-coupled GdCu2 species. Inorg Chem 2002. [DOI: 10.1021/ic00224a036] [Citation(s) in RCA: 164] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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Bencini A, Gatteschi D. Electron spin resonance spectra of low-symmetry pseudotetrahedral high-spin cobalt(II) complexes. Tetra-n-butylammonium tribromo(quinoline)cobaltate(II). Inorg Chem 2002. [DOI: 10.1021/ic50174a071] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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Bencini A, Di Vaira M, Fabretti AC, Gatteschi D, Zanchini C. Anisotropic exchange in transition-metal dinuclear complexes. 2. Crystal and molecular structure and EPR spectra of a dinuclear copper oxamidato complex. Inorg Chem 2002. [DOI: 10.1021/ic00179a033] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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Bencini A, Caneschi A, Dei A, Gatteschi D, Zanchini C, Kahn O. Low-lying electronic energy levels in a series of heterodinuclear complexes containing octahedral nickel(II) and tetrahderal metal(II) (copper, cobalt, and manganese) species. Inorg Chem 2002. [DOI: 10.1021/ic00229a016] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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Bencini A, Gatteschi D, Zanchini C. Anisotropic exchange in transition-metal dinuclear complexes. 5. Bis(-.mu.-hydroxo)bis[(2-methylimidazole)copper(II)] diperchlorate dihydrate. Inorg Chem 2002. [DOI: 10.1021/ic00199a013] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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Bencini A, Benelli C, Gatteschi D, Zanchini C. ESR spectra of low-symmetry high-spin cobalt(II) complexes. 7. Trigonal-bipyramidal pentakis(picoline N-oxide)cobalt(II) perchlorate. Inorg Chem 2002. [DOI: 10.1021/ic50214a050] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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Bencini A, Benelli C, Fabretti AC, Franchini G, Gatteschi D. Magnetic properties and crystal structure of a linear-chain copper(II) compound with bridging acetate and oxamidate ligands. Inorg Chem 2002. [DOI: 10.1021/ic00227a036] [Citation(s) in RCA: 40] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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Bencini A, Benelli C, Gatteschi D, Zanchini C. Magnetic coupling in a linear-chain copper(II)-imidazolate compound. Mechanism of the exchange interaction through bridging imidazolate ligands. Inorg Chem 2002. [DOI: 10.1021/ic00223a038] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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37
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Bencini A, Benelli C, Gatteschi D, Zanchini C. Electron spin resonance spectra of low-symmetry high-spin cobalt(II) complexes. 4. Tetragonal-octahedral dichlorotetrakis(pyridine)- and dichlorotetrakis(pyrazole)cobalt(II). Inorg Chem 2002. [DOI: 10.1021/ic50207a038] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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Bencini A, Gatteschi D, Zanchini C. Anisotropic exchange in transition-metal dinuclear complexes. 6. Bis(-.mu.-chloro)bis(dichlorocuprates(II)). Inorg Chem 2002. [DOI: 10.1021/ic00199a014] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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Bencini A, Gatteschi D, Sacconi L. Electron spin resonance investigation of the mixed-valence dinuclear tetra(.mu.-1,8-naphthyridine-N,N')-bis(bromonickel) tetraphenylborate complex. Inorg Chem 2002. [DOI: 10.1021/ic50187a058] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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Banci L, Bencini A, Gatteschi D. Anisotropic exchange in transition-metal dinuclear complexes. 3. Bis(.mu.-(1,3-azido)bis(1,1,4,7,7-pentamethyldiethylenetriamine)dicopper(II) bis(tetraphenylborate). Inorg Chem 2002. [DOI: 10.1021/ic00182a030] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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Lodeiro C, Pina F, Parola AJ, Bencini A, Bianchi A, Bazzicalupi C, Ciattini S, Giorgi C, Masotti A, Valtancoli B, de Melo JS. Exploring the photocatalytic properties and the long-lifetime chemosensor ability of Cl(2)[Ru(Bpy)(2)L] (L = 2,5,8,11,14-pentaaza[15])-2,2'-bipyridilophane). Inorg Chem 2001; 40:6813-9. [PMID: 11735495 DOI: 10.1021/ic0105213] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
In this work a new water-soluble long-lifetime chemosensor, containing a polyamine unit connected to a complexed Ru(II) metal center, is described. Its crystal structure has been characterized by X-ray analysis. The polyamine macrocyclic unit is capable of anchoring cationic or anionic substrates, according to its protonation state. Examples of electron transfer involving the ruthenium complex core and the bound substrate are presented. The photocatalytic ability of such a system is illustrated by the oxidation of iodide to iodine promoted by light absorption at 436 nm.
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Arranz P, Bazzicalupi C, Bencini A, Bianchi A, Ciattini S, Fornasari P, Giorgi C, Valtancoli B. Cd(II) and Pb(II) complexation by dipyridine-containing macrocycles with different molecular architecture. Effect of complex protonation on metal coordination environment. Inorg Chem 2001; 40:6383-9. [PMID: 11720491 DOI: 10.1021/ic010597z] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The coordination features of the three dipyridine-containing polyamine macrocycles 2,5,8,11,14-pentaaza[15]-[15](2,2')[1,15]-bipyridylophane (L1), 5,8,11-trimethyl-2,5,8,11,14-pentaaza[15]-[15](2,2')[1,15]-bipyridylophane (L2), and 4,4'-(2,5,8,11,14-pentaaza[15]-[15](2,2')-bipyridylophane) (L3) toward Cd(II) and Pb(II) have been studied by means of potentiometric, microcalorimetric, and spectrophotometric UV-vis titrations in aqueous solutions. All ligands form 1:1 metal complexes. In the L1 and L2 complexes the metals are lodged inside the macrocyclic cavity, coordinated to the heteroaromatic nitrogens. On the other hand, the insertion of a rather rigid dipyridine moiety within a macrocyclic structure does not allow all the aliphatic amine groups to coordinate to the metals and several protonated complexes are found in solution. The particular molecular architecture of L3, which displays two well-separated binding moieties, strongly affects its coordination behavior. In the [PbL3](2+) complex and in its protonated species, the metal is lodged inside the macrocyclic cavity, not bound to the heteroaromatic nitrogens. A similar coordination environment is found in [CdL3](2+). In this case, however, protonation of the complex takes place on the aliphatic amine groups and gives rise to translocation of the metal outside the cavity, coordinated by the dipyridine moiety.
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Bazzicalupi C, Bencini A, Berni E, Bianchi A, Giorgi C, Fusi V, Valtancoli B, Lodeiro C, Roque A, Pina F. Coordination properties of a polyamine cryptand with two different binding moieties. A case of a pH-modulated antenna device based on a new Eu(III) cryptate complex. Inorg Chem 2001; 40:6172-9. [PMID: 11703116 DOI: 10.1021/ic010638r] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Protonation and alkali- and alkaline-earth-metal coordination by the dipyridine-containing cryptand L have been studied by means of potentiometric and spectroscopic (UV-vis, (1)H NMR) measurements in aqueous solutions. This ligand is constituted by an aliphatic polyamine chain and a coordinating cleft, delimited by two dipyridine units, where the metal ion is lodged. The resulting complexes are characterized by an unusually high stability. The polyamine chain is not involved, or weakly involved, in metal coordination, and facile protonation can occur on the nitrogen atoms of this moiety. Similar coordination features are found in the Eu(III) complex. A fluorescence emission study reveals that the Eu(III) cryptate shows the characteristic visible emission of the metal, due to the intramolecular energy transfer to the metal ion mainly from the lower energy triplet state of the cryptand. On the other hand, the emission intensity is modulated by pH, giving a maximum at neutral pH and decreasing at both acidic and alkaline pH values.
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Lodeiro C, Parola AJ, Pina F, Bazzicalupi C, Bencini A, Bianchi A, Giorgi C, Masotti A, Valtancoli B. Protonation and Zn(II) coordination by dipyridine-containing macrocycles with different molecular architecture. A case of pH-controlled metal jumping outside-inside the macrocyclic cavity. Inorg Chem 2001; 40:2968-75. [PMID: 11399162 DOI: 10.1021/ic001381k] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The synthesis of the macrocyclic ligand 4,4'-(2,5,8,11,14-pentaaza[15])-2,2'-bipyridylophane (L3), which contains a pentaamine chain linking the 4,4'-positions of a 2,2'-dipyridine moiety, is reported. Protonation and Zn(II) complexation by L3 and by macrocycle L2, containing the same pentaamine chain connecting the 6,6'-positions of 2,2'-dipyridine, were studied by means of potentiometric, UV-vis, and fluorescent emission measurements. While in L2 all the nitrogen donor atoms are convergent inside the macrocyclic cavity, in L3 the heteroaromatic nitrogen atoms are located outside. Both ligands form mono- and dinuclear Zn(II) complexes in aqueous solution. In the mononuclear Zn(II) complexes with L2, the metal is coordinated inside the macrocyclic cavity, bound to the heteroaromatic nitrogen donors and three amine groups of the aliphatic chain. As shown by the crystal structure of the [ZnL2](2+) complex, the two benzylic nitrogens are not coordinated and facile protonation of the complex takes place at slightly acidic pH values. Considering the mononuclear [ZnL3](2+) complex, the metal is encapsulated inside the cavity, not coordinated by the dipyridine unit. Protonation of the complex occurs on the aliphatic polyamine chain and gives rise to translocation of the metal outside the cavity, bound to the heteroaromatic nitrogens.
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Bencini A, Daul CA, Dei A, Mariotti F, Lee H, Shultz DA, Sorace L. Charge distribution in bis-dioxolene radical metal complexes. synthesis and DFT characterization of dinuclear Co(III) and Cr(III) complexes with a mixed-valent, S = 1/2 semiquinone-catecholate ligand. Inorg Chem 2001; 40:1582-90. [PMID: 11261968 DOI: 10.1021/ic0007052] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Bis-dioxolene bridged dinuclear metal complexes of general formula M2(CTH)2(diox-diox)(PF6)n (n = 2, 3; M = Co(III), Cr(III); CTH = tetraazamacrocycle) have been synthesized using the bis-bidentate ligand 5,5'-di-tert-butyl-3,3',4,4'-tetrahydroxybiphenyl. These complexes were characterized by means of ESR, UV-vis, temperature dependent magnetic susceptibility, and cyclic voltammetry. Our results unambiguously suggest that the tripositive dimetal cations can be described as containing a fully delocalized bis-dioxolene trinegative radical ligand (Cat-Sq) bridging two tripositive metal cations. In this frame the sextet electronic ground state characterizes the Cr2(CTH)2(Cat-SQ)3+ as a result of the antiferromagnetic coupling of the radical bridging ligand with the two equivalent paramagnetic metal centers. The electronic and geometrical structure and the magnetic properties of Cat-Sq and of its complexes have been studied with density functional theory.
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Chand DK, Schneider HJ, Bencini A, Bianchi A, Giorgi C, Ciattini S, Valtancoli B. Affinity and nuclease activity of macrocyclic polyamines and their CuII complexes. Chemistry 2000; 6:4001-8. [PMID: 11126962 DOI: 10.1002/1521-3765(20001103)6:21<4001::aid-chem4001>3.3.co;2-i] [Citation(s) in RCA: 61] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
The stability constants of Cu(II) complexes that consist of either an oxaaza macrocycle with two triamine moieties linked by dioxa chains, or two macrocyclic ligands with a polyamine chain which are connecting the 2 and 9 positions of phenanthroline, have been determined by means of potentiometric measurements. The results are compared to those reported for other ligands with a similar molecular architecture. Of the complexes that contain phenanthroline in their macrocycle, the Cu(II) ion of the complex with the smallest and most rigid macrocycle (L3) has an unsaturated coordination sphere, while in the complex with the largest macrocycle (L5) the Cu(II) ion is coordinatively almost saturated. These results are corroborated by the crystal structure of the [CuL5](ClO4)2 complex. The affinity of the ligands and the complexes towards nucleic acids was studied by measuring the changes in the melting temperature, which showed that the affinity of the macrocyclic ligands towards double-stranded DNA or RNA is generally smaller than that of their linear analogues that bear a similar charge, with a strong preference for polyA-polyU, a model for RNA. However, the complexes of two of the changed macrocyclic ligands which contain a phenanthroline unit (L4, L5) showed a distinctly larger increase in their melting temperature deltaTm with DNA (polydA-polydT), which is reversed again in favor of RNA upon metallation to the dinuclear copper complex with L5. Experiments with supercoiled plasmid DNA showed a particularly effective cleavage with a mononuclear Cu(II) complex that contains a phenanthroline unit (L6). Related ligands showed less activity towards DNA, but not so towards the biocidic bis(p-nitrophenyl)phosphate (BNPP). In both cases (with DNA and BNPP) the activity seemed to increase with decrease of coordinative saturation of the Cu(II) ion, with the exception of one particular ligand (L6). Experiments with radical scavengers in the DNA experiments showed some decrease in cleavage, which indicates the participation of redox processes.
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Secco F, Tinè M, Venturini M, Bencini A, Giorgi C, Valtancoli B. Equilibria and kinetics of complex formation between nickel(II) and the polyamine Me2octaen. Polyhedron 2000. [DOI: 10.1016/s0277-5387(00)00551-9] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
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Pontillon Y, Bencini A, Caneschi A, Dei A, Gatteschi D, Gillon B, Sangregorio C, Stride J, Totti F. Spin-Density Map of the Triplet Ground State of a Titanium(IV) Complex with Schiff-Base Diquinone Radical Ligands: An Investigation Using Polarized-Neutron Diffraction and Density-Functional Theory This work was supported by the 3MD EU network (contract ERB 4061 PL 97-0197). Angew Chem Int Ed Engl 2000; 39:1786-1788. [PMID: 10934361 DOI: 10.1002/(sici)1521-3773(20000515)39:10<1786::aid-anie1786>3.0.co;2-i] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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Bencini A, Bill E, Mariotti F, Totti F, Scozzafava A, Vargas A. Density functional description of the early stages of the dioxygenation of [(MeC(CH2PPh2)3)M(catecholate)]+ complexes [M = Co(III), Ir(III)]: toward a rationalization of the catalytic mechanism of ring-opening dioxygenases. Inorg Chem 2000; 39:1418-25. [PMID: 12526444 DOI: 10.1021/ic990633i] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Density Functional Theory (DFT) has been applied to characterize the early stages of the reaction of dioxygenation of [(triphos)M(catecholate)]+ complexes [M = Co(III), Ir(III); triphos = MeC(CH2PPh2)3], which have been considered to be models of ring-opening dioxygenases. The structural features of the starting complexes and of the intermediate complexes formed by addition of O2 to the coordinated catecholato ion are well reproduced. The calculations showed that this preliminary stage can be obtained only when the oxygen molecule attacks the molecule on the catecholato site.
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Bencini A, Ercolanelli R, Sbaragli A, Verrucchi C. Groundwaters of Florence (Italy): Trace element distribution and vulnerability of the aquifers. ACTA ACUST UNITED AC 1993. [DOI: 10.1007/bf00767403] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
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