Synthesis, characterization, and cancer cell-selective cytotoxicity of mixed-ligand cobalt(III) complexes of 8-hydroxyquinolines and phenanthroline bases

Transition metal complexes exhibiting selective toxicity towards a broad range of cancer types are highly desirable as potential anticancer agents. Herein, we report the synthesis, characterization, and cytotoxicity studies of six new mixed-ligand cobalt(III) complexes of general formula [Co(B)2(L)](ClO4)2 (1-6), where B is a N,N-donor phenanthroline base, namely, 1,10-phenanthroline (phen in 1, 2), dipyrido[3,2-d:2',3'-f]quinoxaline (dpq in 3, 4), and dipyrido[3,2-a:2',3'-c]phenazine (dppz in 5, 6), and L is the monoanion of 8-hydroxyquinoline (HQ in 1, 3, 5) and 5-chloro-7-iodo-8-hydroxyquinoline (CQ in 2, 4, 6). The X-ray single crystal structures of complexes 1 and 2 as PF6- salts revealed a distorted octahedral CoN5O coordination environment. Complexes demonstrated good stability in an aqueous buffer medium and in the presence of ascorbic acid as a reductant. Cytotoxicity studies using a panel of nine cancer cell lines showed that complex 6, with the dppz and CQ ligands, was significantly toxic against most cancer cell types, yielding IC50 values in the range of 2 to 14 μM. Complexes 1, 3, and 5, containing the HQ ligand, displayed lower toxicity compared to their CQ counterparts. The phenanthroline complexes demonstrated marginal toxicity towards the tested cell lines, while the dpq complexes exhibited moderate toxicity. Interestingly, all complexes demonstrated negligible toxicity towards normal HEK-293 kidney cells (IC50 > 100 μM). The observed cytotoxicity of the complexes correlated well with their lipophilicities (dppz > dpq > phen). The cytotoxicity of complex 6 was comparable to that of the clinical drug cisplatin under similar conditions. Notably, neither the HQ nor the CQ ligands alone demonstrated noticeable toxicity against any of the tested cell lines. The Annexin-V-FITC and DCFDA assays revealed that the cell death mechanism induced by the complexes involved apoptosis, which could be attributed to the metal-assisted generation of reactive oxygen species. Overall, the dppz complex 6, with its remarkable cytotoxicity against a broad range of cancer cells and negligible toxicity toward normal cells, holds significant potential for cancer chemotherapeutic applications.

Syntheses, characterizations, crystal structures and Hirshfeld surface analyses of methyl 4-[4-(di-fluorometh-oxy)phen-yl]-2,7,7-trimethyl-5-oxo-1,4,5,6,7,8-hexa-hydro-quinoline-3-carboxyl-ate, isopropyl 4-[4-(di-fluoro-meth-oxy)phen-yl]-2,6,6-trimethyl-5-oxo-1,4,5,6,7,8-hexa-hydro-quinoline-3-carboxyl-ate and tert-butyl 4-[4-(di-fluoro-meth-oxy)phen-yl]-2,6,6-trimethyl-5-oxo-1,4,5,6,7,8-hexa-hydro-quinoline-3-carboxyl-ate

The crystal structures and Hirshfeld surface analyses of three similar compounds are reported. Methyl 4-[4-(di-fluoro-meth-oxy)phen-yl]-2,7,7-trimethyl-5-oxo-1,4,5,6,7,8-hexa-hydro-quinoline-3-carboxyl-ate, (C21H23F2NO4), (I), crystallizes in the monoclinic space group C2/c with Z = 8, while isopropyl 4-[4-(di-fluoro-meth-oxy)phen-yl]-2,6,6-trimethyl-5-oxo-1,4,5,6,7,8-hexa-hydro-quinoline-3-carb-oxyl-ate, (C23H27F2NO4), (II) and tert-butyl 4-[4-(di-fluoro-meth-oxy)phen-yl]-2,6,6-trimethyl-5-oxo-1,4,5,6,7,8-hexa-hydro-quinoline-3-carboxyl-ate, (C24H29F2NO4), (III) crystallize in the ortho-rhom-bic space group Pbca with Z = 8. In the crystal structure of (I), mol-ecules are linked by N-H⋯O and C-H⋯O inter-actions, forming a tri-periodic network, while mol-ecules of (II) and (III) are linked by N-H⋯O, C-H⋯F and C-H⋯π inter-actions, forming layers parallel to (002). The cohesion of the mol-ecular packing is ensured by van der Waals forces between these layers. In (I), the atoms of the 4-di-fluoro-meth-oxy-phenyl group are disordered over two sets of sites in a 0.647 (3): 0.353 (3) ratio. In (III), the atoms of the dimethyl group attached to the cyclo-hexane ring, and the two carbon atoms of the cyclo-hexane ring are disordered over two sets of sites in a 0.646 (3):0.354 (3) ratio.

Hydrogen-bonding interactions in 5-fluorocytosine-urea (2/1), 5-fluorocytosine-5-fluorocytosinium 3,5-dinitrosalicylate-water (2/1/1) and 2-amino-4-chloro-6-methylpyrimidine-6-chloronicotinic acid (1/1)

Three new compounds, namely, 5-fluorocytosine-urea (2/1), 2C4H4FN3O·CH4N2O, (I), 5-fluorocytosine-5-fluorocytosinium 3,5-dinitrosalicylate-water (2/1/1), 2C4H4FN3O·C4H5FN3O+·C7H2N2O7-·H2O, (II), and 2-amino-4-chloro-6-methylpyrimidine-6-chloronicotinic acid (1/1), C6H4ClNO2·C5H6ClN3, (III), have been synthesized and characterized by single-crystal X-ray diffraction. In compound (I), 5-fluorocytosine (5FC) molecules A and B form two different homosynthons [R22(8) ring motif], one formed via N-H...O hydrogen bonds and the second via N-H...N hydrogen bonds. In addition to this interaction, a sequence of fused-ring motifs [R21(6), R33(8), R22(8), R43(10) and R22(8)] are formed, generating a supramolecular ladder-like hydrogen-bonded pattern. In compound (II), 5FC and 5-fluorocytosinium are linked by triple hydrogen bonds, generating two fused-ring motifs [R22(8)]. The neutral 5FC and protonated 5-fluorocytosinum cation form a dimeric synthon [R22(8) ring motif] via N-H...O and N-H...N hydrogen bonds. On either side of the dimeric synthon, the neutral 5FC, 5-fluorocytosinium cation, 3,5-dinitrosalicylate anion and water molecule are hydrogen bonded through N-H...O, N-H...N, N-H...OW and OW-HW...O hydrogen bonds, forming a large ring motif [R1010(56)], leading to a three-dimensional supramolecular network. In compound (III), 2-amino-4-chloro-6-methylpyrimidine (ACP) interacts with the carboxylic acid group of 6-chloronicotinic acid via N-H...O and O-H...O hydrogen bonds, generating an R22(8) primary ring motif. Furthermore, the ACP molecules form a base pair via N-H...N hydrogen bonds. The primary motif and base pair combine to form tetrameric units, which are further connected by Cl...Cl interactions. In addition to this hydrogen-bonding interaction, compounds (I) and (III) are further enriched by π-π stacking interactions.

Chemistry of a series of heterobimetallic complexes MnIII2(CaII/SrII)X2 (X = Cl-, Br-)

This manuscript describes the syntheses, structures and magnetism of MnIII-CaII/SrII complexes which are compositionally relevant in the context of the oxygen evolving complex (OEC) of photosystem II (PS II). A series of trimetallic tetraoxo complexes containing redox-inactive metal ions CaII or SrII were synthesized using a tetranucleating ligand framework. The structural characteristics of these complexes, with the oxido ligands bridging the redox-inactive metals and the manganese centres, make them particularly relevant to biological and heterogeneous metal-oxido clusters. Electrochemical studies of these compounds show that the reduction potentials are highly dependent upon the Lewis acidity of the redox-inactive metal, identifying the chemical basis for the observed differences in electrochemistry. This correlation provides insights into the role of the CaII/SrII ion in modulating the redox potential of the OEC and of other redox-inactive ions in tuning the redox potentials of other metal-oxide electrocatalysts. Temperature dependent magnetic measurements have also been performed for the complexes.

Synthesis, characterization, crystal structure and Hirshfeld surface analysis of isobutyl 4-[4-(di-fluoro-meth-oxy)phen-yl]-2,6,6-trimethyl-5-oxo-1,4,5,6,7,8-hexa-hydro-quinoline-3-carboxyl-ate

In the title compound, C24H29F2NO4, which crystallizes in the ortho-rhom-bic Pca21 space group with Z = 4, the 1,4-di-hydro-pyridine ring adopts a distorted boat conformation, while the cyclo-hexene ring is in a distorted half-chair conformation. In the crystal, the mol-ecules are linked by N-H⋯O and C-H⋯O inter-actions, forming supra-molecular chains parallel to the a axis. These chains pack with C-H⋯π inter-actions between them, forming layers parallel to the (010) plane. The cohesion of the crystal structure is ensured by van der Waals inter-actions between these layers. Hirshfeld surface analysis shows the major contributions to the crystal packing are from H⋯H (56.9%), F⋯H/H⋯F (15.7%), O⋯H/H⋯O (13.7%) and C⋯H/H⋯C (9.5%) contacts.

Late-stage Ligand Modification After Coordination Strengthens Stereoselectively Self-Assembled Hemiaminal Ether Complexes

Fragile hemiaminal ether linkages present in the backbone of koneramines (LR OR'), tridentate ligands, bound to copper(II) in stereoselectively self-assembled syn-[Cu(LR OR')X2 ] complexes were transformed into sturdy methylene linkages to make corresponding rac-[Cu(LR H)Cl2 ] complexes by late-stage ligand modification after coordination with the retention of coordination sphere. The generality of stereoselective self-assembly of koneramine complexes is shown by utilising a number of metal ions, anions, amines, alcohols and thiols with complete characterisations.

Synthesis, crystal structure, Hirshfeld surface analysis, DFT and NBO study of ethyl 1-(4-fluoro-phen-yl)-4-[(4-fluoro-phen-yl)amino]-2,6-diphenyl-1,2,5,6-tetra-hydro-pyridine-3-carboxyl-ate

The title com-pound, C32H28F2N2O2, a highly functionalized tetra-hydro-pyridine, was synthesized by a one-pot multi-com-ponent reaction of 4-fluoro-aniline, ethyl aceto-acetate and benzaldehyde at room temperature using sodium lauryl sulfate as a catalyst. The com-pound crystallizes with two mol-ecules in the asymmetric unit. The tetra-hydro-pyridine ring adopts a distorted boat conformation in both mol-ecules and the dihedral angles between the planes of the fluoro-substituted rings are 77.1 (6) and 77.3 (6)°. The amino group and carbonyl O atom are involved in an intra-molecular N-H⋯O hydrogen bond, thereby generating an S(6) ring motif. In the crystal, mol-ecules are linked by C-H⋯F hydrogen bonds forming a three-dimensional network and C-H⋯π inter-actions. A Hirshfeld surface analysis of the crystal structure indicates that the most important contributions to the crystal packing are from H⋯H (47.9%), C⋯H/H⋯C (30.7%) and F⋯H/H⋯F (12.4%) contacts. The optimized structure calculated using density functional theory (DFT) at the B3LYP/6-311+G(2d,p) level is compared with the experimentally determined molecular structure in the solid state. The HOMO-LUMO behaviour was used to determine the energy gap and the Natural Bond Orbital (NBO) analysis was done to study donor-acceptor interconnections.

Supramolecular interactions in some organic hydrated 2,4,6-triaminopyrimidinium carboxylate and sulfate salts

Four salts, namely, 2,4,6-triaminopyrimidinium 6-chloronicotinate dihydrate, C4H8N5+·C6H3ClNO2-·2H2O, (I), 2,4,6-triaminopyrimidinediium pyridine-2,6-dicarboxylate dihydrate, C4H9N52+·C7H3NO42-·2H2O, (II), 2,4,6-triaminopyrimidinediium sulfate monohydrate, C4H9N52+·SO42-·H2O, (III), and 2,4,6-triaminopyrimidinium 3,5-dinitrobenzoate dihydrate, C4H8N5+·C7H3N2O6-·2H2O, (IV), were synthesized and characterized by X-ray diffraction techniques. Proton transfer from the corresponding acid to the pyrimidine base has occurred in all four crystal structures. Of the four salts, two [(I) and (IV)] exist as monoprotonated bases and two [(II) and (III)] exist as diprotonated bases. In all four crystal structures, the acid interacts with the pyrimidine base through N-H...O hydrogen bonds, generating an R22(8) ring motif. The sulfate group mimics the role of the carboxylate anions. The water molecules present in compounds (I)-(IV) form water-mediated large ring motifs. The formation of water-mediated interactions in these crystal structures can be used as a model in the study of the hydration of nucleobases. Water molecules play an important role in building supramolecular structures. In addition to these strong hydrogen-bonding interactions, some of the crystal structures are further enriched by aromatic π-π stacking interactions [(I) and (II)].

Coordination Behavior of the Tellurium Incorporated Mercuraazametallamacrocycle and Investigation of d10 ⋅⋅⋅d10 Interactions between Closed Shell (Ag+ Hg2+ ) Metal Ions

Herein, a new tellurium and mercury containing mercuraazametallamacrocycle has been prepared via (2+2) condensation of bis(o-aminophenyl)telluride and bis(o-formylphenyl)mercury(II). The isolated bright yellow solid of mercuraazametallamacrocycle has adopted unsymmetrical figure-of-eight conformation in the crystal structure. To study the metallophilic interactions between closed shell metal ions, the macrocyclic ligand has been treated with two equiv. of AgOTf (OTf=trifluoromethansulfonate) and AgBF4 , which afforded greenish-yellow bimetallic silver complexes. The isolated silver complexes displayed intramolecular Hg⋅⋅⋅Ag, Te⋅⋅⋅Ag interactions as well as intermolecular Hg⋅⋅⋅Hg interactions and formed an extended 1D molecular chain by directing six atoms to interact as TeII ⋅⋅⋅AgI ⋅⋅⋅HgII ⋅⋅⋅HgII ⋅⋅⋅AgI ⋅⋅⋅TeII in a non linear fashion. The Hg⋅⋅⋅Ag, Te⋅⋅⋅Ag interactions have also been studied in solution by 199 Hg, 125 Te NMR spectroscopy, absorption, and emission spectroscopy. In DFT calculations, the Atom in Molecule (AIM) analysis, non-covalent interactions (NCI), natural bonding orbital (NBO) analysis strongly supported for experimental evidences and revealed that the intermolecular Hg⋅⋅⋅Hg interaction is stronger than the intramolecular Hg⋅⋅⋅Ag interactions.

Isolation of potassium salt of oxadiazole-2-thione and in vitro anticancer activities of its Cu(II) and Zn(II) complexes against MDA-MB-231 human breast carcinoma cells

A potassium 4-(pyridyl)-1,3,4-oxadiazole-2-thione was isolated in a basic medium, and its complexes [Cu(en)₂(pot)₂] (1) and [Zn(en)₂(pot)₂]HBr·CH₃OH (2) containing ethylenediamine (en) as secondary ligand were synthesized and fully characterized. Upon changing the reaction conditions, the Cu(II) complex (1) adopts an octahedral geometry around the metal center. The cytotoxic activity of ligand (Kpot·H₂O) along with complexes 1 and 2 was tested, and their anticancer activity against MDA-MB-231 human breast cancer cells was demonstrated, with complex 1 exhibiting superior cytotoxicity against these cells as compared to Kpot·H₂O and complex 2. According to the DNA nicking assay, the ligand (Kpot·H₂O) was found to be more potent to scavenge hydroxyl radicals even at a lower concentration (50 μg mL^-1) than that of both complexes. The wound healing assay revealed that ligand Kpot·H₂O and its complexes 1 and 2 attenuated the migration of the above-mentioned cell line. The loss of cellular and nuclear integrity and induction in the activity of Caspase-3 suggest the anticancer potential of ligand Kpot·H₂O and its complexes 1 and 2 against MDA-MB-231 cells.

Catalytic Acceptorless Dehydrogenation (CAD) of Secondary Benzylic Alcohols into Value-Added Ketones Using Pd(II)-NHC Complexes

For the creation of adaptable carbonyl compounds in organic synthesis, the oxidation of alcohols is a crucial step. As a sustainable alternative to the harmful traditional oxidation processes, transition-metal catalysts have recently attracted a lot of interest in acceptorless dehydrogenation reactions of alcohols. Here, using well-defined, air-stable palladium(II)-NHC catalysts (A-F), we demonstrate an effective method for the catalytic acceptorless dehydrogenation (CAD) reaction of secondary benzylic alcohols to produce the corresponding ketones and molecular hydrogen (H2). Catalytic acceptorless dehydrogenation (CAD) has been successfully used to convert a variety of alcohols, including electron-rich/electron-poor aromatic secondary alcohols, heteroaromatic secondary alcohols, and aliphatic cyclic alcohols, into their corresponding value-added ketones while only releasing molecular hydrogen as a byproduct.

Synthesis, crystal structure and Hirshfeld surface analysis of tert-butyl 4-[4-(di-fluoro-meth-oxy)phen-yl]-2,7,7-trimethyl-5-oxo-1,4,5,6,7,8-hexa-hydro-quinoline-3-carboxyl-ate

The 1,4-di-hydro-pyridine ring of the title compound, C24H29F2NO4, adopts a distorted boat conformation, while the cyclo-hexene ring is in an almost twist-boat conformation. In the crystal, N-H⋯O and C-H⋯O hydrogen bonds as well as C-H⋯π inter-actions connect mol-ecules, forming layers parallel to the (100) plane. These layers are linked by van der Waals forces and C-H⋯F inter-actions, which consolidate the crystal structure. Hirshfeld surface analysis shows the major contributions to the crystal packing are from H⋯H (54.1%), F⋯H/H⋯F (16.9%), O⋯H/H⋯O (15.4%) and C⋯H/H⋯C (12.6%) contacts.

Syntheses and crystal structures of three salts of 1-(4-nitro-phenyl)-piperazine

The crystal structures and Hirshfeld surface analyses of three salts of 1-(4-nitro-phenyl)-piperazine with 2-chloro-benzoic acid, 2-bromo-benzoic acid and 2-iodo-benzoic acid are reported. The chloro-benzoate salt, C₁₀H₁₄N₃O₂ ⁺·C₇H₄ClO₂ ^-, contains whole-ion-disordered cations and anions, which were modeled with two equivalent conformations with occupancies of 0.745 (10)/0.255 (10) and 0.563 (13)/0.437 (13), respectively. The bromo-benzoate and iodo-benzoate derivatives are isomorphous and crystallize as hemihydrates, viz. C₁₀H₁₄N₃O₂ ⁺·C₇H₄BrO₂ ^-·0.5H₂O and C₁₀H₁₄N₃O₂ ⁺·C₇H₄IO₂ ^-·0.5H₂O, respectively [the water mol-ecule is disordered over two locations with occupancies of 0.276 (3)/0.223 (3) for the iodo-benzoate derivative]. In the extended structures, all three salts feature an R ⁴ ₄(12) loop of two anions and two cations linked by N-H⋯O hydrogen bonds.

Syntheses, crystal structures and Hirshfeld surface analysis of three salts of 1-(4-nitro-phenyl)-piperazine

The structures and Hirshfeld surface analysis of three salts of 1-(4-nitro-phenyl)-piperazine are discussed. In 4-(4-nitro-phen-yl)piperazin-1-ium salicylate (C₁₀H₁₄N₃O₂ ⁺·C₇H₅O₃ ^-), there are strong hydrogen bonds between cation and anion and the 4-nitro-phenyl substituent occupies an equatorial position in the piperazinium ring. The cation and anion are linked together by supra-molecular inter-actions [graph-set notation of hydrogen bonding (6) propagating in the a-axis direction]. Additionally, there is π-π stacking involving the salicylate anion and the piperazinium cation in adjacent asymmetric units as well as a C-H⋯π inter-action between a hydrogen atom on the piperazine ring and the phenyl ring within the salicyclate anion. In bis-[4-(4-nitro-phen-yl)piperazin-1-ium] bis-(4-fluoro-benzoate) trihydrate (2C₁₀H₁₄N₃O₂ ⁺·2C₇H₄FO₂ ^-·3H₂O), there are two cations, two anions, and three water mol-ecules of solvation in the asymmetric unit, all linked by hydrogen bonds [graph-set notation of hydrogen bonding R ² ₂(20) between adjacent cations and R ³ ₃(9) between a cation and its adjacent anion]. In the anion, the 4-nitro-phenyl ring occupies an axial substitution position in the piperazinium ring, which is relatively rare. Within the asymmetric unit, the phenyl groups in the cations show an offset π-π inter-action. Additionally, there is a C-H⋯π inter-action between a hydrogen atom on the phenyl ring within a cation and the phenyl ring within an anion. In 4-(4-nitro-phen-yl)piperazin-1-ium 3,5-di-nitro-benzoate (C₁₀H₁₄N₃O₂ ⁺·C₇H₄N₂O₆ ^-), there is a strong N-H⋯O hydrogen bond linking the cation and anion and the 4-nitro-phenyl ring occupies an axial substitution position in the piperazinium ring, as seen in the previous structure. In the crystal, the cation and the anion form a complex three-dimensional hydrogen-bonded array involving R ² ₂(8), R ⁴ ₄(12) and R ⁴ ₄(20) rings propogating in the a-axis direction. The nitro-phenyl group is disordered with occupancies of 0.806 (10) and 0.194 (10).

5-([(Z)-Meth-oxy-imino]{2-[(2-methyl-phen-oxy)meth-yl]phen-yl}meth-yl)-1,3,4-oxa-diazole-2(3H)-thione dimethyl sulfoxide monosolvate

The title compound, C₁₈H₁₇N₃O₃S·C₂H₆OS, crystallizes in the monoclinic space group P2₁ /c. In the crystal, C ₁ ¹(9) chains of C-H⋯O inter-actions are formed, propogating in the c-axis direction. The N-H hydrogen atom forms a strong hydrogen bond with the oxygen atom of a DMSO solvate mol-ecule.

Supramolecular interactions in salts/cocrystals involving pyrimidine derivatives of sulfonate/carboxylic acid

The crystal structures of three compounds involving aminopyrimidine derivatives are reported, namely, 5-fluorocytosinium sulfanilate-5-fluorocytosine-4-azaniumylbenzene-1-sulfonate (1/1/1), C₄H₅FN₃O⁺·C₆H₆NO₃S^-·C₄H₄FN₃O·C₆H₇NO₃S, I, 5-fluorocytosine-indole-3-propionic acid (1/1), C₄H₄FN₃O·C₁₁H₁₁NO₂, II, and 2,4,6-triaminopyrimidinium 3-nitrobenzoate, C₄H₈N₅⁺·C₇H₄NO₄^-, III, which have been synthesized and characterized by single-crystal X-ray diffraction. In I, there are two 5-fluorocytosine (5FC) molecules (5FC-A and 5FC-B) in the asymmetric unit, with one of the protons disordered between them. 5FC-A and 5FC-B are linked by triple hydrogen bonds, generating two fused rings [two R₂²(8) ring motifs]. The 5FC-A molecules form a self-complementary base pair [R₂²(8) ring motif] via a pair of N-H...O hydrogen bonds and the 5FC-B molecules form a similar complementary base pair [R₂²(8) ring motif]. The combination of these two types of pairing generates a supramolecular ribbon. The 5FC molecules are further hydrogen bonded to the sulfanilate anions and sulfanilic acid molecules via N-H...O hydrogen bonds, generating R₄⁴(22) and R⁶₆(36) ring motifs. In cocrystal II, two types of base pairs (homosynthons) are observed via a pair of N-H...O/N-H...N hydrogen bonds, generating R₂²(8) ring motifs. The first type of base pair is formed by the interaction of an N-H group and the carbonyl O atom of 5FC molecules through a couple of N-H...O hydrogen bonds. Another type of base pair is formed via the amino group and a pyrimidine ring N atom of the 5FC molecules through a pair of N-H...N hydrogen bonds. The base pairs (via N-H...N hydrogen bonds) are further bridged by the carboxyl OH group of indole-3-propionic acid and the O atom of 5FC through O-H...O hydrogen bonds on either side of the R₂²(8) motif. This leads to a DDAA array. In salt III, one of the N atoms of the pyrimidine ring is protonated and interacts with the carboxylate group of the anion through N-H...O hydrogen bonds, leading to the primary ring motif R₂²(8). Furthermore, the 2,4,6-triaminopyrimidinium (TAP) cations form base pairs [R₂²(8) homosynthon] via N-H...N hydrogen bonds. A carboxylate O atom of the 3-nitrobenzoate anion bridges two of the amino groups on either side of the paired TAP cations to form another ring [R₃²(8)]. This leads to the generation of a quadruple DADA array. The crystal structures are further stabilized by π-π stacking (I and III), C-H...π (I and II), C-F...π (I) and C-O...π (II) interactions.

Crystal structure and Hirshfeld surface analysis of isopropyl 4-[2-fluoro-5-(tri-fluoro-meth-yl)phen-yl]-2,6,6-trimethyl-5-oxo-1,4,5,6,7,8-hexa-hydro-quinoline-3-carboxyl-ate

In the title compound, C₂₃H₂₅F₄NO₃, the 1,4-di-hydro-pyridine ring adopts a distorted boat conformation, while the cyclo-hexene ring is almost showing a half-chair conformation. In the crystal, inter-molecular N-H⋯O hydrogen bonds connect the mol-ecules into chains with graph-set motif C(6) parallel to the a-axis. These chains are linked together by C-H⋯O and C-H⋯F inter-actions, forming a three-dimensional network. In addition, C-H⋯π inter-actions link the mol-ecules into layers parallel to the (100) plane. A Hirshfeld surface analysis was performed to further investigate the inter-molecular inter-actions.

Synthesis and structures of dinuclear palladium complexes with 1,3-benzimidazolidine-2-thione and 1,3-imidazoline-2-thione

The synthesis and structures of dinuclear palladium complexes with 1,3-benz-imidazolidine-2-thione (bzimtH) and 1,3-imidazoline-2-thione (imtH) are reported, namely, bis-(μ-1H-benzimidazole-2-thiol-ato)-κ² N ³:S;κ² S:N ³-bis-[cyanido(tri-phenyl-phosphine-κP)palladium(II)], [Pd₂(C₇H₅N₂S)₂(CN)₂(C₁₈H₁₅P)₂] or [Pd₂(μ-N,S-bzimtH)₂(CN)₂(PPh₃)₂] (1), and bis-(μ-1H-imidazole-2-thiol-ato)-κ² N ³:S;κ² S:N ³-bis-[cyanido(tri-phenyl-phosphine-κP)palladium(II)] aceto-nitrile 0.58-solvate, [Pd₂(C₃H₃N₂S)₂(CN)₂(C₁₈H₁₅P)₂]·0.58C₂H₃N or [Pd₂(μ-N,S-imtH)₂(CN)₂(PPh₃)₂]·0.58C₂H₃N (2). The compound [Pd₂(μ-N,S-bzimtH)₂(CN)₂(PPh₃)₂] is located on a crystallographic twofold axis while [Pd₂(μ-N,S-imtH)₂(CN)₂(PPh₃)₂]. 0.58(C₂H₃N) contains two partially occupied aceto-nitrile solvent mol-ecules with occupancies of 0.25 and 0.33. In both of these compounds, the anionic bzimtH^- and imtH^- ligands coordinate through N,S-donor atoms in a bridging mode, covering four coordination sites of two metal centers and other two sites are occupied by two PPh₃ ligand mol-ecules. Finally, the remaining two sites of two metal centers are occupied by cyano groups, abstracted by the metals from the solvent during reaction. In the packing of the 1,3-benzimidazolidine- 2-thione and 1,3-imidazoline-2-thione complexes, there are intra-molecular π-π inter-actions involving the thione moiety as well as an N-H⋯N hydrogen bond linking the thione and cyano ligands. In addition, in 2, as well as the π-π inter-action involving the thione moieties, there is an additional π-π inter-action involving one of the thione moieties and an adjacent phenyl ring from the tri-phenyl-phosphine ligand. There are also C-H⋯N inter-actions between the imidazoline rings and the aceto-nitrile N atoms.

2-Ethyl-4-methyl-1H-imidazol-3-ium bromide

In the title mol-ecular salt, C₆H₁₁N₂ ⁺·Br^-, the components are linked by N-H⋯Br⋯H-N hydrogen bonds into C(8)chains of alternating cations and anions propagating in the b-axis direction; these chains are cross-linked in the c-axis direction by weak C-H⋯Br hydrogen bonds.

2,5,8,11-Tetramethyl-2,5,8,11-tetraazadodecane-2,11-diium bis[hydroxytris(pentafluorophenyl)borate] benzene 2.5-solvate

The title compound of overall stoichiometry, C12H32N4 2+·2C18HBF15O−·2.5C6H6, crystallizes in the triclinic space group P\overline{1} and the stoichiometry of the asymmetric unit consists of two [C12H32N4]2+ dications, two [C18HBF15O]− anions, and 2.5 molecules of benzene as solvate. The dications are both at half occupancy and located on a center of inversion, as is one of the benzene solvate molecules. In the two anions the O—H groups participate in different hydrogen-bonding schemes. In anion A, the OH group participates in a bifurcated 2R 2 2(6) scheme with F atoms on different rings of an adjacent hydroxy[tris(pentafluorophenyl)]borate moiety with an additional N—H...O hydrogen bond with a dication. For anion B, the OH group participates in a single O—H...F R 2 2(6) scheme. In addition, there are both O—H...N and N—H...O hydrogen bonds involving dication D and anion B in an R 2 2(7) motif. There are numerous C—H...π interactions between the dications and all the three benzene solvate molecules. For solvate 3, the C—H...π interactions are on both sides of the benzene ring and link both dications and solvate into a linear chain in the c-axis direction.

5-(4-Methoxyphenyl)-1-[4-(4-methoxyphenyl)thiazol-2-yl]-3-[4-(prop-2-ynyloxy)phenyl]-4,5-dihydro-1H-pyrazole

The title compound, C29H25N3O3S, crystallizes in the monoclinic space group P21/n. The molecule contains a central four-ring system in which all of the rings are almost coplanar. Both the 4-methoxyphenyl ring and the prop-2-ynyloxy substituent are disordered over two equivalent conformations with occupancy ratios of 0.903 (2):0.097 (2) and 0.776 (5):0.224 (5), respectively. In the crystal, π–π interactions [centroid–centroid distance = 3.7327 (11) Å] between the dihydropyrazole ring and the 4-methoxyphenyl ring link the molecules into centrosymmetric dimers. In addition, there are weak C—H...S, C—H...N and C—H...O interactions, which link the molecules into a complex three-dimensional array.

5-(4-Fluorophenyl)-1-[4-(4-methylphenyl)thiazol-2-yl]-3-[4-(prop-2-ynyloxy)phenyl]-4,5-dihydro-1H-pyrazole

In the title compound, C28H22FN3OS, four rings are almost coplanar, with the fluorophenyl ring substantially twisted. In the extended structure, aromatic π–π stacking interactions between the pyrazole ring and the tolyl ring link the molecules into centrosymmetric dimers.

3-(3-Nitrophenyl)-1-[4-(prop-2-ynyloxy)phenyl]prop-2-en-1-one

The structure of the title compound, C18H13NO4, shows that the whole molecule is almost planar but with a dihedral angle between the two phenyl rings of 19.22 (5)°. The molecules are linked by C—H...O interactions, forming sheets in the (21\overline{1}) plane.

Titania Nanorods Embedded with 2-Bromo-3-(methylamino)naphthalene-1,4-dione for Dye-Sensitized Solar Cells

In a recent study, TiO₂ nanorod electrodes were prepared by the hydrothermal approach followed by calcination at various temperatures from 300 to 600 °C. The effects of calcination temperature on the morphological and structural properties were investigated. The novel analogue of aminonaphthoquinone(2R-(n-alkylamino)-1,4-naphthoquinone) photosensitizer, viz. BrA1, 2-bromo-3-(methylamino)naphthalene-1,4-dione was synthesized from 2,3-dibromonaphthalene-1,4-dione. X-ray crystallographic data collection and refinement confirm that BrA1 crystallizes in the triclinic space group P 1̅. After loading BrA1, the photosensitizer on the annealed TiO₂ nanorod (TiO₂NR) electrodes, the optical properties of the photoanodes showed broadbands in each of the UV and visible regions, which are attributed to the π →π* and n → π* charge-transfer transitions, respectively. The dye-sensitized solar cell (DSSC) system was formed by loading the BrA1 photosensitizer on TiO₂NR. The electrochemical impedance spectroscopy (EIS) analyses confirm that calcination temperature improves the charge transportation by lowering the resistance path during the photovoltaic process in TiO₂NR (400 °C) photoanode-based DSSCs due to the sufficient photosensitizer adsorption and fast electron injection. Due to the effective light harvesting by the BrA1 photosensitizer and charge transport through the TiO₂ nanorod, the power conversion efficiencies (PCE) of the TiO₂NR (400 °C/BrA1-based) DSSCs were improved for 2-bromo-3-(methylamino)naphthalene-1,4-dione.

The structures of eleven (4-phen-yl)piperazinium salts containing organic anions

Eleven (4-phen-yl)piperazinium salts containing organic anions have been prepared and structurally characterized, namely, 4-phenyl-piperazin-1-ium 4-fluoro-benzoate monohydrate, C₁₀H₁₅N₂ ⁺·C₇H₄FO₂ ^-·H₂O, 1; 4-phenyl-piperazin-1-ium 4-bromo-benzoate monohydrate, C₁₀H₁₅N₂ ⁺·C₇H₄BrO₂ ^-·H₂O, 3; 4-phenyl-piperazin-1-ium 4-iodo-benzoate, C₁₀H₁₅N₂ ⁺·C₇H₄IO₂ ^-, 4; 4-phenyl-piperazin-1-ium 4-nitro-benzoate, C₁₀H₁₅N₂ ⁺·C₇H₄NO₄ ^-, 5; 4-phenyl-piperazin-1-ium 3,5-di-nitro-salicylate, C₁₀H₁₅N₂ ⁺·C₇H₃N₂O₇ ^-, 6; 4-phenyl-piperazin-1-ium 3,5-di-nitro-benzoate, C₁₀H₁₅N₂ ⁺·C₇H₃N₂O₆ ^-, 7; 4-phenyl-piperazin-1-ium picrate, C₁₀H₁₅N₂ ⁺·C₆H₂N₃O₇ ^-, 8; 4-phenyl-piperazin-1-ium benzoate monohydrate, C₁₀H₁₅N₂ ⁺·C₇H₅O₂ ^-·H₂O, 9; 4-phenyl-piperazin-1-ium p-toluene-sulfonate, C₁₀H₁₅N₂ ⁺·C₇H₇O₃S^-, 10; 4-phenyl-piperazin-1-ium tartarate monohydrate, C₁₀H₁₅N₂ ⁺·C₄H₅O₆ ^-·H₂O, 11; and 4-phenyl-piperazin-1-ium fumarate, C₁₀H₁₅N₂ ⁺·C₄H₃O₄ ^-, 12. Compounds 1 and 3-12 are all 1:1 salts with the acid proton transferred to the phenyl-piperaizine basic N atom (the secondary amine) with the exception of 3 where there is disorder in the proton position with it being 68% attached to the base and 32% attached to the acid. Of the structures with similar stoichiometries only 3 and 9 are isomorphous. The 4-phenyl substituent in all cases occupies an equatorial position except for 12 where it is in an axial position. The crystal chosen for structure 7 was refined as a non-merohedral twin. There is disorder in 5, 6, 10 and 11. For both 5 and 6, a nitro group is disordered and was modeled with two equivalent orientations with occupancies of 0.62 (3)/0.38 (3) and 0.690 (11)/0.310 (11), respectively. For 6, 10 and 11, this disorder is associated with the phenyl ring of the phenyl-piperazinium cation with occupancies of 0.687 (10)/0.313 (10), 0.51 (7)/0.49 (7) and 0.611 (13)/389 (13), respectively. For all salts, the packing is dominated by the N-H⋯O hydrogen bonds formed by the cation and anion. In addition, several structures contain C-H⋯π (1, 3, 4, 8, 9, 10, and 12) and aromatic π-π stacking inter-actions (6 and 8) and one structure (5) contains a -NO₂⋯π inter-action. For all structures, the Hirshfeld surface fingerprint plots show the expected prominent spikes as a result of the N-H⋯O and O-H⋯O hydrogen bonds.

Isopropyl 4-aminobenzoate

The title compound crystallizes with two mol­ecules in the asymmetric unit, which form double chains in the crystal linked by N—H⋯O and N—H⋯N hydrogen bonds.

The title compound, C₁₀H₁₃NO₂, crystallizes with two mol­ecules (A and B) in the asymmetric unit. For A, the dihedral angle between the plane of the phenyl ring and the i-propyl substituent is 65.4 (3)° while for B this angle is 67.8 (3)°. In the crystal, the mol­ecules are linked by N—H⋯O and N—H⋯N hydrogen bonds to generate double chains propagating in the [100] direction.

3-Methyl-5-(4-methylphenoxy)-1-phenyl-1H-pyrazole-4-carbaldehyde

In the title compound, C18H16N2O2, the phenyl and pyrazole rings subtend a dihedral angle of 22.68 (8)°. The packing of the title compound features aromatic π–π stacking and weak C—H...π interactions.

Synthesis, Covalency Sequence, and Crystal Features of Pentagonal Uranyl Acylpyrazolone Complexes along with DFT Calculation and Hirshfeld Analysis

Three uranyl acylpyrazolone complexes [UO₂(PCBPMP)₂(CH₃CH₂OH)] (complex I), [UO₂(PCBMCPMP)₂(CH₃CH₂OH)] (complex II), and [UO₂(PCBPTMP)₂(CH₃CH₂OH)] (complex III) were synthesized from σ-donating acypyrazolone ligands to analyze their sequence of covalent characteristics, reactivity, and redox properties (PCBPMP: p-chlorobenzoyl 1-phenyl 3-methyl 5-pyrazolone; PCBMCPMP: p-chlorobenzoyl 1-(m-chlorophenyl) 3-methyl 5-pyrazolone; PCBPTMP: p-chlorobenzoyl 1-(p-tolyl) 3-methyl 5-pyrazolone). An examination of the structure, pentagonal bipyramidal geometry, and composition of these complexes was conducted mainly through their single-crystal X-ray diffraction (XRD) data, ¹H nuclear magnetic resonance (NMR) δ-values, plots of thermogravimetric-differential thermal analysis (TG-DTA), significant Fourier transform infrared (FTIR) vibrations, gravimetric estimation, and molar conductivity values. The covalency order was found to be complex II > III > I, which mainly depends on values of stretching frequencies, average bond lengths of axial uranyl bonds, values of average bond lengths on the pentagonal equatorial plane, solvent coordination on the fifth site of a pentagonal plane, and the type of aryl group on the nitrogen of the pyrazolone ring. This was confirmed by FTIR spectroscopy and single-crystal spectral characterization. To verify experimental results by comparison with theoretical results, density functional theory (DFT) calculations were carried out, which further gives evidence for the covalency order through theoretical frequencies and the gap of highest occupied molecular orbital (HOMO)-lowest unoccupied molecular orbital (LUMO) energies. Theoretical bond properties were also examined by the identification of global index parameters. Intermolecular noncovalent surface interactions were studied by the Hirshfeld surface analysis. The irreversible redox behavior of uranyl species was identified through electrochemical cyclic voltammetry-differential pulse voltammetry (CV-DPV) plot analysis.

Synthesis, characterization, crystal structure and Hirshfeld surface analysis of a hexahydroquinoline derivative: tert-butyl 4-([1,1′-biphenyl]-4-yl)-2,6,6-trimethyl-5-oxo-1,4,5,6,7,8-hexahydroquinoline-3-carboxylate

C—H⋯O and N—H⋯O hydrogen bonds connect mol­ecules in the crystal, generating layers parallel to the (100) plane with (6) and C(7) graph-set motifs. C—H⋯π inter­actions help to reinforce this layered mol­ecular structure.

The title compound, C₂₉H₃₃NO₃, crystallizes with three mol­ecules (A, B and C) in the asymmetric unit. They differ in the twist of the phenyl and benzene rings of the 1,1′-biphenyl ring with respect to the plane of the 1,4-di­hydro­pyridine ring. In all three mol­ecules, the 1,4-di­hydro­pyridine ring adopts a distorted boat conformation. The cyclo­hexene ring has an envelope conformation in mol­ecules A and B, while it exhibits a distorted half-chair conformation for both the major and minor components in the disordered mol­ecule C. In the crystal, mol­ecules are linked by C—H⋯O and N—H⋯O hydrogen bonds, forming layers parallel to (100) defining R¹₄(6) and C(7) graph-set motifs. Additional C—H⋯π inter­actions consolidate the layered structure. Between the layers, van der Waals inter­actions stabilize the packing, as revealed by Hirshfeld surface analysis. The greatest contributions to the crystal packing are from H⋯H (69.6% in A, 69.9% in B, 70.1% in C), C⋯H/H⋯C (20.3% in A, 20.6% in B, 20.3% in C) and O⋯H/H⋯O (8.6% in A, 8.6% in B, 8.4% in C) inter­actions.

A BOPHY based fluorescent probe for Hg2+via NTe2 chelation

A BOPHY-based organotellurium-containing probe was synthesized and characterized via single crystal XRD for the selective and sensitive detection of Hg²⁺ over other metal ions. The probe detects Hg²⁺ in less than 1 s with a 2.5-fold enhancement in fluorescent intensity. Due to the chalcogenophilicity of mercury, Hg²⁺ was facilely trapped in the NTe₂ chelating cavity of the probe. The probe can detect Hg²⁺ in the nanomolar range (62 nM) and it showed reversibility with S^2- ions. The sensitivity of the probe for the detection of Hg²⁺ was confirmed in living HeLa cells.

Dichlorido(4-methylaniline-κN)[N-(4-methylphenyl)-1-(thiophen-2-yl)methanimine-κN]palladium(II)

The structure of a mono-amine Pd^II complex is reported in which the Pd—NH₂ length is slightly shorter than the observed mean value for other complexes involving Pd attached to the nitro­gen of an aniline derivative.

The structure of a mono-amine Pd^II complex, [PdCl₂(C₇H₉N)(C₁₂H₁₁NS)], which crystallizes in the triclinic space group, P, is reported. The primary geometry around the Pd^II atom closely resembles square planar (τ₄′ = 0.069). In the (E)-1-(thio­phen-2-yl)-N-(p-tol­yl)methanimine ligand, the phenyl and thio­phene rings are not coplanar, subtending a dihedral angle of 38.5 (1)° because of steric effects. The PdCl₂N₂ coordination plane is almost perpendicular to the planes of the coordinated o-toluidine and the NC₂ fragment [dihedral angles of 84.7 (1) and 72.50 (4)°, respectively]. The Pd—NH₂ length of 2.040 (2) Å is slightly shorter than the observed mean value for other complexes involving a Pd atom attached to the nitro­gen of an aniline derivative. The mol­ecules display an inter­esting supra­molecular synthon based on reciprocal inter­molecular N–H⋯Cl hydrogen-bonding inter­actions of the p-toluidine amine fragment, which results in centrosymmetric dimeric units. These units are further linked by C—H⋯Cl inter­actions, resulting in chains in the c-axis direction where the mean-planes of the repeating fragment are oriented in the (110) plane.

Incorporation of in situ generated 3,3′-(sulfanediyl)bis(1-methyl-1,3-imidazolidine-2-thione) into a one-dimensional CuI coordination polymer with sulfur-bridged {CuI 4S10} n central cores

The reaction of [Cu(CH₃CN)₄](BF₄) with 1-methyl-1,3-imidazolidine-2-thione {SC₃H₄(NMe) NH} forms the one-dimensional coordination polymer [Cu₄(κ⁵:L¹—N—S—N—L¹)₂(κ¹:L¹—NH)₂(κ²: L¹—NH)₂]_n(BF₄)_4n {L¹ = SC₃H₄(NMe)NH} with sulfur-bridged {Cu^I₄S₁₀}_n central cores.

The reaction of [Cu(CH₃CN)₄](BF₄) with 1-methyl-1,3-imidazolidine-2-thione {SC₃H₄(NMe)NH}, under aerobic conditions at room temperature, yielded an unusual one-dimensional coordination polymer, namely, catena-poly[[[(1-meth­yl-1,3-imidazolidine-2-thione-κS)copper(I)]-μ-(1-methyl-1,3-imidazolidine-2-thione)-κ²S:S-copper(I)-μ-[3,3′-(sulfanedi­yl)bis­(1-methyl-1,3-imidazolidine-2-thione)]-κ⁵S,S′,S′′:S,S′′] bis­(tetra­fluorido­borate)], {[Cu₂(C₄H₈N₂S)₂(C₈H₁₄N₄S₃)](BF₄)₂}_n or [Cu₄(κ⁵:L¹—N—S—N—L¹)₂(κ¹:L¹—NH)₂(κ²:L¹—NH)₂]_n(BF₄)_4n1 [L¹ = SC₃ H₄(NMe)NH] with sulfur-bridged {Cu^I₄S₁₀}_n central cores. The in situ generated bis­(1-methyl-1,3-imidazolidinyl-2-thione) sulfide [{SC₃H₄(NMe)NSN(NMe)C₃H₄S; abbrev. L¹—N—S—N—L¹] ligand, in combin­ation with 1-methyl-1,3-imidazolidine-2-thione (L¹—NH) ligands, construct this coordination polymer. Each Cu^I ion is bonded to four sulfur donor atoms in a distorted tetra­hedral geometry and the formation of this polymer solely by sulfur donor atoms with {Cu^I₄S₁₀}_n central cores, is the first such example in copper–heterocyclic-2-thione chemistry.

Distorted zinc coordination polyhedra in bis(1-ethoxy-2-{[(2-methoxyethyl)imino]methyl}propan-1-olato)zinc, a possible CVD precursor for zinc oxide thin films

The coordination polyhedra of the zinc atoms in the title complex display long Zn—O bonds as parts of distorted trigonal bipyramids and octa­hedra.

A new metal–organic precursor for the chemical vapor deposition of zinc oxide thin films, [Zn(C₉H₁₆NO₃)₂], has been synthesized and characterized by ¹H and ¹³C NMR spectroscopy, single-crystal X-ray diffraction and thermogravimetric analysis. The asymmetric unit of the title compound consists of two mol­ecules (Z′ = 2), with different zinc coordination polyhedra. In one mol­ecule, the metal atom is in a distorted trigonal–bipyramidal ZnN₂O₃ environment (τ₅ = 0.192) with a long bond to an ether O donor atom [Zn—O = 2.727 (6) Å]. In the other, the Zn atom is in a distorted ZnN₂O₄ octa­hedral environment with long bonds to the ether O donors of both ligands [Zn—O = 2.514 (4) and 2.661 (4) Å; O—Zn—O = 82.46 (14)°]. The crystal structure features weak C—H⋯·O inter­actions.

A tetranuclear nickel(II) complex, [Ni4(L)4](ClO4)4·C2H3N·2H2O, with an asymmetric Ni4O4 open-cubane-like core

A tetra­nuclear complex with an open-cubane like structure was synthesized from 2-meth­oxy-6-(pyridin-2-yl-hydrazonometh­yl)-phenol and characterized using micro-analytical and spectroscopic techniques, and single-crystal X-ray diffraction analysis.

A tetra­nuclear complex with an open-cubane-like core structure was synthesized from 2-meth­oxy-6-(pyridin-2-yl-hydrazonometh­yl)phenol (HL), namely, cyclo-tetra­kis­(μ-2-meth­oxy-6-{[2-(pyridin-2-yl)hydrazin-1-yl­idene]meth­yl}pheno­lato)tetra­nickel(II) tetra­kis­(perchlorate) aceto­nitrile monosolvate dihydrate, [Ni₄(C₁₃H₁₂N₃O₂)₄](ClO₄)₄·C₂H₃N·2H₂O, and characterized using micro-analytical and spectroscopic techniques. The crystal-structure determination reveals the formation of a distorted Ni₄O₄ cubane-like core architecture encapsulated by four hydrazone Schiff base (HL) mol­ecules. A open-cube tetra­nuclear architecture is created in which nickel(II) ions of the NiN₂O₃ unit are connected by μ₂-O anions of the phenolate moiety of HL. In this complex, each Ni centre has a slightly distorted square-pyramidal coordination environment. The supra­molecular architectures are stabilized via the presence of various inter­molecular hydrogen bonds and (ar­yl–aryl, ar­yl–chelate and chelate–chelate) stacking inter­actions.