Performance of 4,5-diphenyl-1H-imidazole derived highly selective 'Turn-Off' fluorescent chemosensor for iron(III) ions detection and biological applications

Two fluorescent chemosensors, denoted as chemosensor 1 and chemosensor 2, were synthesized and subjected to comprehensive characterization using various techniques. The characterization techniques employed were Fourier-transform infrared (FTIR), proton (1 H)- and carbon-13 (13 C)-nuclear magnetic resonance (NMR) spectroscopy, electrospray ionization (ESI) mass spectrometry, and single crystal X-ray diffraction analysis. Chemosensor 1 is composed of a 1H-imidazole core with specific substituents, including a 4-(2-(4,5-c-2-yl)naphthalene-3-yloxy)butoxy)naphthalene-1-yl moiety. However, chemosensor 2 features a 1H-imidazole core with distinct substituents, such as 4-methyl-2-(4,5-diphenyl-1H-imidazole-2-yl)phenoxy)butoxy)-5-methylphenyl. Chemosensor 1 crystallizes in the monoclinic space group C2/c. Both chemosensors 1 and 2 exhibit a discernible fluorescence quenching response selectively toward iron(III) ion (Fe3+ ) at 435 and 390 nm, respectively, in dimethylformamide (DMF) solutions, distinguishing them from other tested cations. This fluorescence quenching is attributed to the established mechanism of chelation quenched fluorescence (CHQF). The binding constants for the formation of the 1 + Fe3+ and 2 + Fe3+ complexes were determined using the modified Benesi-Hildebrand equation, yielding values of approximately 2.2 × 103 and 1.3 × 104  M-1 , respectively. The calculated average fluorescence lifetimes for 1 and 1 + Fe3+ were 2.51 and 1.17 ns, respectively, while for 2 and 2 + Fe3+ , the lifetimes were 1.13 and 0.63 ns, respectively. Additionally, the applicability of chemosensors 1 and 2 in detecting Fe3+ in live cells was demonstrated, with negligible observed cell toxicity.

70th anniversary of Acta Chimica Slovenica

Dear readers of Acta Chimica Slovenica, In this year Acta Chimica Slovenica, the journal published by Slovenian Chemical Society, is celebrating 70th anniversary.

Synthesis, crystal structure and molecular docking study of novel isoxazole derivatives as CYP450 inhibitors in search of anticancer agents

Synthesis of some novel isoxazole derivatives and their molecular docking with enzymes from CYP450 family carried out using erlotinib, gemcitabine and ketoconazole as reference drugs are reported in this work. Eight isoxazole derivatives of 3,4-substituted phenyl 3-chloroacrylaldehyde and one isoxazole derivative of cinnamaldehyde were synthesized. A molecular docking study of all nine compounds shows good docking score compared to standard drugs erlotinib, gemcitabine and ketoconazole. 4-OH and 4-F derivatives were found to have strong affinity for all six CYP450 proteins under study in the present work. 4-F and 3-NO2 derivatives could be a suitable lead compound inhibitor to CYP1A2 followed by 4-OH derivatives. 4-OH derivative with significant binding affinity showed encouraging inhibition of CYP1A2, CYP2C9, CYP2C8, CYP2C19 and CYP2D6. The current predictions over these nine isoxazole derivatives of 3,4-substituted phenyl 3-chloroacrylaldehyde will be needed to be further investigated in vivo and in vitro conditions to identify the optimum therapeutic efficacy. Synthesis of the isoxazole derivatives is the first known report of the Knoevenagal condensation of acrylaldehyde derivatives to form isoxazole derivatives as per the literature survey. A detailed crystal structure study of five analogues gives insight into the solid-state structural features of this new framework with isoxazole moieties.Communicated by Ramaswamy H. Sarma.

Four Slip-Stacked Arrangements, Three Types of Photophysics: Crystal Structure and Solid-State Fluorescence of 3,6-Diaryl Substituted Furo[3,4-c]furanone Polymorphs and Regioisomers

Six symmetrical 3,6-diaryl (aryl=phenyl, 2-, 3- and 4-tolyl, 2,4- and 3,5-xylyl) substituted furo[3,4-c]furanones (DFF) were synthesized. The computational analysis, based on density functional theory, found eight possible centrosymmetrical slipped π-stack arrangements, formed according to electron repulsion minimization principle, as for previously reported for π-isoelectronic diketopyrrolopyrroles (DPP). One of these slipped stack arrangements was found to form infinite columns in the crystals of a new polymorph of parent phenyl derivative (with centre-to-centre distance CC=6.975 Å), other three types of stacks were found for 3-tolyl (CC=6.153 Å), 4-tolyl (CC=3.849 Å) and 2,4-xylyl (CC=4.856 Å) derivatives by single crystal X-ray diffractometry. All six derivatives show intense solution fluorescence in blue/green region, with a maximum driven entirely by a number and position of methyl substituents on phenyl rings. On the other hand, the solid-state fluorescence from yellow over orange to red is observed only for four derivatives and its presence/absence, spectral position and vibronic structure is driven exclusively by the slips in π-stacks (with interplanar distance always less than 3.5 Å) of almost planar DFF molecules, resulting in J-type emission, H-type excimer-like emission and H-type quenching.

Three-Component Reaction of 3-Formyl-6-Methylchromone, Primary Amines, and Secondary Phosphine Oxides: A Synthetic and Mechanistic Study

A fast, mild, and efficient catalyst-free approach has been developed for the synthesis of chromonyl-substituted α-aminophosphine oxides by the three-component reaction of 3-formyl-6-methylchromone, primary amines, and secondary phosphine oxides at ambient temperature. Carrying out the reaction with aliphatic amines or aminoalcohols at a higher temperature (80 °C), phosphinoyl-functionalized 3-aminomethylene chromanones were formed instead of the corresponding chromonyl-substituted α-aminophosphine oxides. No reaction occurred when 3-formyl-6-methylchromone and secondary phosphine oxides were reacted with aromatic amines in the absence of any catalyst. Applying a basic catalyst, the formation of the phosphinoyl-functionalized 3-aminomethylene chromanones was observed; however, the reaction was not complete. Detailed experimental and quantum chemical studies were performed to study the transformation. Moreover, the in vitro cytotoxicity of phosphinoyl-functionalized 3-aminomethylene chromanones was also investigated in three different cell lines, such as human lung adenocarcinoma (A549), mouse fibroblast (NIH/3T3), and human promyelocytic leukemia (HL60) cells. Several derivatives showed modest activity against the human promyelocytic leukemia (HL60) cell line.

Crystal structures and Hirshfeld surface analyses of hypoxanthine salts involving 5-sulfosalicylate and perchlorate anions

Two salts of 1,9-dihydropurin-6-one (hypoxanthine), namely, 6-oxo-1,9-dihydropurin-7-ium 5-sulfosalicylate dihydrate, C5H5N4O+·C7H5O6S−·2H2O, (I), and 6-oxo-1,9-dihydropurin-7-ium perchlorate monohydrate, C5H5N4O+·ClO4 −·H2O, (II), have been synthesized and characterized using single-crystal X-ray diffraction and Hirshfeld analysis. In both salts, the hypoxanthine molecule is protonated at the N7 position of the purine ring. In salt (I), the cation and anion are connected through N—H...O interactions. The protonated hypoxanthine cations of salt (I) form base pairs with another symmetry-related hypoxanthine cation through N—H...O hydrogen bonds with an R 2 2(8) ring motif, while in salt (II), the hypoxanthine cations are paired through a water molecule via N—H...O and O—H...N hydrogen bonds with an R 3 3(11) ring motif. The packings within the crystal structures are stabilized by π–π stacking interactions in salt (I) and C—O...π interactions in salt (II). The combination of several interactions leads to the formation of supramolecular sheets extending parallel to (010) in salts (I) and (II). Hirshfeld surface analysis and fingerprint plots reveal that O...H/H...O contacts play the major role in the crystal packing of each of the salts, with a 54.1% contribution in salt (I) and 62.3% in salt (II).

Metal(II) Complexes of the Fluoroquinolone Fleroxacin: Synthesis, Characterization and Biological Profile

A series of complexes of divalent transition metals (Cu(II), Mn(II), Zn(II), Co(II) and Ni(II)) with the quinolone antibacterial agent fleroxacin, in the absence or presence of an α-diimine such as 2,2′-bipyridine, 1,10-phenanthroline or 2,2′-bipyridylamine, were prepared and characterized. The complexes were characterized by various physicochemical and spectroscopic techniques and by single-crystal X-ray crystallography. The in vitro antibacterial activity of the complexes was studied against the bacterial strains Staphylococcus aureus, Bacillus subtilis and Xanthomonas campestris and was higher than that of free quinolone. The affinity of the complexes for bovine and human serum albumin was studied by fluorescence emission spectroscopy and the determined binding constants showed tight and reversible binding to the albumins. The interaction of the complexes with calf-thymus DNA was studied by various techniques, which showed that intercalation was the most plausible mode of interaction.

Macrocyclic "tet a"-Derived Cobalt(III) Complex with a N,N'-Disubstituted Hexadentate Ligand: Crystal Structure, Photonuclease Activity, and as a Photosensitizer

A cobalt(III) complex, [Co(L)]Cl (complex 1, where L = 1,8-[N,N-bis{(3-formyl-2-hydroxy-5-methyl)benzyl}]-1,4,8,11-tetraaza-5,5,7,12,12,14-hexamethylcyclotetradecane) with distorted octahedral geometry has been synthesized and characterized using various spectroscopic techniques. The structure of the ligand has remarkably rich hydrogen intermolecular interactions such as H···H, H···C/C···H, and H···O/O···H that vary with the presence of the metal ion, and the structure of complex 1 has Cl···H interactions; this result has been proved by Hirshfeld surface and two-dimensional (2D) fingerprint maps analyses. The complex exhibits a quasi-reversible Co(III)/Co(II) redox couple with E _1/2 = -0.76 V. Calf thymus DNA (CT DNA) binding abilities of the ligand and complex 1 were confirmed by spectroscopic and electrochemical analyses. According to absorption studies, the ligand and complex 1 bind to CT DNA via intercalative binding mode, with intrinsic binding strengths of 1.41 × 10³ and 8.64 × 10³ M^-1, respectively. A gel electrophoresis assay shows that complex 1 promotes the pUC19 DNA cleavage under dark and light irradiation conditions. Complex 1 has superior antimicrobial activity than the ligand. The cytotoxicity of complex 1 was tested against MDA-MB-231 breast cancer cells with values of IC₅₀ of 1.369 μg mL^-1 in the dark and 0.9034 μg mL^-1 after light irradiation. Besides, cell morphological studies confirmed the morphological changes with AO/EB dual staining, reactive oxygen species (ROS) staining, mitochondria staining, and Hoechst staining on MDA-MB-231 cancer cells by fluorescence microscopy. Complex 1 was found to be a potent antiproliferative agent against MDA-MB-231 cells, and it can induce mitochondrial-mediated and caspase-dependent apoptosis with activation of downregulated caspases. The biotoxicity assay of complex 1 on the development of Artemia nauplii was evaluated at an IC₅₀ value of 200 μg mL^-1 and with excellent biocompatibility.

High temperature spin crossover behaviour of mononuclear bis-(thiocyanato)iron(ii) complexes with judiciously designed bidentate N-donor Schiff bases with varying substituents

We present herein the solvent and substituent dependent diverse spin crossover behaviours of molecular bis-(thiocyanato)iron(ii) complexes with smartly designed bidentate Schiff bases above room temperature.

Three-component synthesis, utilization and biological activity of phosphinoyl-functionalized isoindolinones

A new method for the synthesis of 3-oxoisoindolin-1-ylphosphine oxides bearing same or different substituents on the phosphorus atom is described. The one-pot three-component reaction of 2-formylbenzoic acid, primary amines and achiral or P-stereogenic secondary phosphine oxides provided the target compounds under catalyst-free, mild conditions and for short reaction times. The deoxygenation of a 3-oxoisoindolin-1-ylphosphine oxide was also studied, and the phosphine obtained could be converted to a sulphide and to a platinum complex. The crystal structures of a selected phosphine oxide and the corresponding platinum species were investigated by X-ray diffraction analysis. The biological activity, such as in vitro cytotoxicity on different cell lines and antibacterial activity of the 3-oxoisoindolin-1-ylphosphine oxides was also investigated. Based on the IC₅₀ values obtained, several derivatives showed moderate activity against the HL-60 cell line and two compounds containing 3,5-dimethylphenyl groups on the phosphorus atom showed promising activity against Bacillus subtilis bacteria.

PMDTA-catalyzed multicomponent synthesis and biological activity of 2-amino-4H-chromenes containing a phosphonate or phosphine oxide moiety

A new approach for the preparation of (2-amino-3-cyano-4H-chromen-4-yl)phosphonate derivatives is described. The multicomponent reaction of salicylaldehydes, malononitrile and dialkyl phosphites catalyzed by pentamethyldiethylenetriamine (PMDTA) provided the bicyclic derivatives in high yields. The method developed did not require chromatographic separation, since the products could be recovered from the reaction mixture by simple filtration. Our approach made also possible condensation with secondary phosphine oxides, and this reaction has not been previously reported in the literature. The crystal structures of five derivatives were studied by single-crystal XRD analysis. The in vitro cytotoxicity on different cell lines and the antibacterial activity of the (2-amino-4H-chromen-4-yl)phosphonates synthesized were also explored. According to the IC₅₀ values determined, several derivatives showed moderate or promising activity against mouse fibroblast (NIH/3T3) and human promyelocytic leukemia (HL-60) cells. Furthermore, three (2-amino-3-cyano-4H-chromen-4-yl)phosphine oxides were active against selected Gram-positive bacteria.

Structural Characterization, Antimicrobial Activity and BSA/DNA Binding Affinity of New Silver(I) Complexes with Thianthrene and 1,8-Naphthyridine

Three new silver(I) complexes [Ag(NO3)(tia)(H2O)]n (Ag1), [Ag(CF3SO3)(1,8-naph)]n (Ag2) and [Ag2(1,8-naph)2(H2O)1.2](PF6)2 (Ag3), where tia is thianthrene and 1,8-naph is 1,8-naphthyridine, were synthesized and structurally characterized by different spectroscopic and electrochemical methods and their crystal structures were determined by single-crystal X-ray diffraction analysis. Their antimicrobial potential was evaluated against four bacterial and three Candida species, and the obtained results revealed that these complexes showed significant activity toward the Gram-positive Staphylococcus aureus, Gram-negative Pseudomonas aeruginosa and the investigated Candida species with minimal inhibitory concentration (MIC) values in the range 1.56-7.81 μg/mL. On the other hand, tia and 1,8-naph ligands were not active against the investigated strains, suggesting that their complexation with Ag(I) ion results in the formation of antimicrobial compounds. Moreover, low toxicity of the complexes was detected by in vivo model Caenorhabditis elegans. The interaction of the complexes with calf thymus DNA (ct-DNA) and bovine serum albumin (BSA) was studied to evaluate their binding affinity towards these biomolecules for possible insights into the mode of antimicrobial activity. The binding affinity of Ag1-3 to BSA was higher than that for DNA, indicating that proteins could be more favorable binding sites for these complexes in comparison to the nucleic acids.

Manganese(II) β-Diketonate Complexes with Pyridin-4-one, 3-Hydroxypyridin-2-one and 1-Fluoropyridine Ligands: Molecular Structures and Hydrogen-bonded Networks

Manganese(II) bis(4,4,4-trifluoro-1-phenylbutane-1,3-dionate) complexes with pyridin-4-one (pyon), 3-hydroxypyridin-2-one (hpyon), 1-fluoropyridine (pyF) and methanol were prepared and the solid-state structures were determined by single-crystal X-ray analysis. The coordination of the metal center in all complexes was found to be octahedral. In compounds [Mn(tfpb)2(pyon)2] (1) and [Mn(tfpb)2(hpyon)2] (2) extended hydrogen bonding is present facilitating the formation of a three-dimensional supramolecular structure in 1 and a layered structure in 2 through N–H···O hydrogen bonding enhanced by C–H···O interactions as well as C–F···π interactions. In [Mn(tfpb)2(pyF)2] (3) a layered structure is formed through C–H···O and C–H···F interactions as well as π···π and C–F···π interactions. In [Mn(tfpb)2(MeOH)2] (4) a layered structure is formed through a combination of O–H···O and C–F···π interactions.

Manganese(II) β-Diketonate Complexes with Pyridin-4-one, 3-Hydroxypyridin-2-one and 1-Fluoropyridine Ligands: Molecular Structures and Hydrogen-bonded Networks

Manganese(II) bis(4,4,4-trifluoro-1-phenylbutane-1,3-dionate) complexes with pyridin-4-one (pyon), 3-hydroxypyridin-2-one (hpyon), 1-fluoropyridine (pyF) and methanol were prepared and the solid-state structures were determined by single-crystal X-ray analysis. The coordination of the metal center in all complexes was found to be octahedral. In compounds [Mn(tfpb)2(pyon)2] (1) and [Mn(tfpb)2(hpyon)2] (2) extended hydrogen bonding is present facilitating the formation of a three-dimensional supramolecular structure in 1 and a layered structure in 2 through N-H···O hydrogen bonding enhanced by C-H···O interactions as well as C-F···π interactions. In [Mn(tfpb)2(pyF)2] (3) a layered structure is formed through C-H···O and C-H···F interactions as well as π···π and C-F···π interactions. In [Mn(tfpb)2(MeOH)2] (4) a layered structure is formed through a combination of O-H···O and C-F···π interactions.

Copper(II) ions mediated crystal formation of 3-(3-hydroxy phenyl)-1-phenyl-1h-pyrazole- 4-carbaldehyde

Schiff base obtained from 3-hydroxyacetophenone and phenylhydrazine was subjected to Vilsmeier-Haack reaction to obtain 3-(3-hydroxyphenyl)-1-phenyl-1H-pyrazole-4-carbaldehyde (2). Successful formation of crystals of 2 was achieved using copper ions (Cu2+) as template. Present paper reports study of spectroscopic characterization and single-crystal X-ray study of 2. Hydrogen bonding network between 2 and water molecules enable the formation of 2D layer along ab-plane supported also by π···π stacking interactions of parallel molecules in head-to-head fashion.                     KEY WORDS: Cu2+ assisted crystal growth, Pyrazole-4-carbaldehyde, X-ray crystal study, Hydrogen bonding study   Bull. Chem. Soc. Ethiop. 2020, 34(3), 589-596. DOI: https://dx.doi.org/10.4314/bcse.v34i3.13

Synthesis, structural determination, in vitro and in silico biological evaluation of divalent or trivalent cobalt complexes with indomethacin

The interaction of cobalt chloride with the non-steroidal anti-inflammatory drug indomethacin (Hindo) led to the formation of the polymeric complex [Co(indo-O)2(H2O)2(μ-Cl)]n·n(MeOH·H2O) bearing one chlorido bridge between the cobalt atoms. The presence of the nitrogen-donor co-ligands 2,2'-bipyridine (bipy), 2,2'-bipyridylamine (bipyam), 1,10-phenanthroline (phen) or 1H-imidazole (Himi) resulted in the isolation of complexes [Co2(μ-indo-O,O')2(indo-O)2(bipy)2(μ-H2O)]·3.3MeOH, [Co(indo-O,O')2(bipyam)]·0.9MeOH·0.2H2O, [Co(indo-O,O')2(phen)] (4) and [Co(indo-O)2(Himi)2] (5), respectively, where the indomethacin ligands were coordinated in diverse manners. The study of the affinity of the complexes for calf-thymus DNA revealed their intercalation between the DNA-bases. The binding of the complexes to albumins was also examined and the corresponding binding constants and binding subdomain were determined. The free radical scavenging activity of the compounds was evaluated towards 1,1-diphenyl-picrylhydrazyl and 2,2'-azinobis(3-ethylbenzothiazoline-6-sulfonic acid). Molecular modeling calculations may usually provide a molecular basis for the understanding of both the impairment of DNA by its binding with the studied complexes and the ability of these compounds to transportation through serum albumin proteins. This study can provide information for the elucidation of the mechanism of action of the compounds in a molecular level.

Self-Assembly of Multinuclear Sandwich Silver(I) Complexes by Cooperation of Hexakis(azaheteroaryl)benzene Ligands, Argentophilic Interactions, and Fluoride Inclusion

Self-assembly of AgOTf and AgF with the hexatopic ligands hexakis(pyridin-2-yl)benzene (2) and 2,4,6-tris(pyridin-2-yl)-1,3,5-tris(quinolin-2-yl)benzene (3) affords the discrete sandwich-shaped complexes [Ag₄F(2)₂](OTf)₃, [Ag₄F(3)₂](OTf)₃, and [Ag₅F(2)₂](OTf)₄. The solid-state structures of the complexes were characterized by single-crystal X-ray diffraction analysis, which revealed that the fluoride anion is coordinated in the center of the Ag₄-square or Ag₅-pentagon units which are positioned between two molecules of the hexakis(azaheteroaryl)benzene. The generation of complexes is dictated by a unique cooperation of ligand coordination, argentophilicity, and fluoride anion inclusion. All three complexes adopt highly symmetrical structures in solution, as evidenced by appearance of one set of proton resonances for the two ligands arranged face to face.

Multinuclear sandwich-shaped silver(I) complexes are readily assembled by a unique cooperation of nitrogen-coordinating hexaheteroarylbenzene ligands, silver atoms, and fluoride anion.

Role of Ligands in the Uptake and Reduction of V(V) Complexes in Red Blood Cells

The interaction with erythrocytes of four [V^VO₂L₂]^- complexes, with L = picolinate (pic), 5-cyanopicolinate (picCN), 3-aminopyrazine-2-carboxylate (przNH₂), and 1,2-dimethyl-3-hydroxy-4(1 H)-pyridinonate (dhp), was studied. The thermodynamic stability at physiological pH is: [V^VO₂(dhp)₂]^- > [V^VO₂(przNH₂)₂]^- > [V^VO₂(pic)₂]^- > [V^VO₂(picCN)₂]^-. With picCN and pic, V exists at physiological pH as H₂V^VO₄^-, with przNH₂ as a mixture of H₂V^VO₄^- and [V^VO₂(przNH₂)₂]^- and with dhp as [V^VO₂(dhp)₂]^-. In the systems with pic and picCN, H₂V^VO₄^- and the ligands cross the erythrocyte membrane independently, with dhp the uptake occurs by diffusion, whereas with przNH₂ both the mechanisms are active. Inside erythrocytes stable V^IVOL₂ complexes are formed, indicating that there is no relationship with the stability and redox state of the administered compounds and that, if the metal ion changes its oxidation state in the cytosol as V does, unstable complexes in the extracellular medium could become stable inside the cells and contribute to the pharmacological action.

Ruthenium(II)-Catalyzed Microwave-Promoted Multiple C-H Activation in Synthesis of Hexa(heteroaryl)benzenes in Water

A series of hexa(heteroaryl)benzenes were synthesized by the Ru(II)-carboxylate-catalyzed multiple C-H activation of benzenes carrying pyridyl, pyrimidyl, or pyrazolyl directing groups using N-heteroaryl bromides as coupling partners. The reactions proceeded with high selectivity under microwave irradiation in water. Iterative penta-arylation could be implemented via activation of C-H bonds of generated intermediates by cascade chelation assistance of in situ installed pyridyl groups. This strategy provides multidentate ligands for selective complexation of transition metals and potential building of photoredox systems.

Supramolecular hydrogen-bonding patterns in salts of the antifolate drugs trimethoprim and pyrimethamine

Nine salts of the antifolate drugs trimethoprim and pyrimethamine, namely, trimethoprimium [or 2,4-diamino-5-(3,4,5-trimethoxybenzyl)pyrimidin-1-ium] 2,5-dichlorothiophene-3-carboxylate monohydrate (TMPDCTPC, 1:1), C₁₄H₁₉N₄O₃⁺·C₅HCl₂O₂S^-, (I), trimethoprimium 3-bromothiophene-2-carboxylate monohydrate, (TMPBTPC, 1:1:1), C₁₄H₁₉N₄O₃⁺·C₅H₂BrO₂S^-·H₂O, (II), trimethoprimium 3-chlorothiophene-2-carboxylate monohydrate (TMPCTPC, 1:1:1), C₁₄H₁₉N₄O₃⁺·C₅H₂ClO₂S^-·H₂O, (III), trimethoprimium 5-methylthiophene-2-carboxylate monohydrate (TMPMTPC, 1:1:1), C₁₄H₁₉N₄O₃⁺·C₆H₅O₂S^-·H₂O, (IV), trimethoprimium anthracene-9-carboxylate sesquihydrate (TMPAC, 2:2:3), C₁₄H₁₉N₄O₃⁺·C₁₅H₉O₂^-·1.5H₂O, (V), pyrimethaminium [or 2,4-diamino-5-(4-chlorophenyl)-6-ethylpyrimidin-1-ium] 2,5-dichlorothiophene-3-carboxylate (PMNDCTPC, 1:1), C₁₂H₁₄ClN₄⁺·C₅HCl₂O₂S^-, (VI), pyrimethaminium 5-bromothiophene-2-carboxylate (PMNBTPC, 1:1), C₁₂H₁₄ClN₄⁺·C₅H₂BrO₂S^-, (VII), pyrimethaminium anthracene-9-carboxylate ethanol monosolvate monohydrate (PMNAC, 1:1:1:1), C₁₂H₁₄ClN₄⁺·C₁₅H₉O₂^-·C₂H₅OH·H₂O, (VIII), and bis(pyrimethaminium) naphthalene-1,5-disulfonate (PMNNSA, 2:1), 2C₁₂H₁₄ClN₄⁺·C₁₀H₆O₆S₂^2-, (IX), have been prepared and characterized by single-crystal X-ray diffraction. In all the crystal structures, the pyrimidine N1 atom is protonated. In salts (I)-(III) and (VI)-(IX), the 2-aminopyrimidinium cation interacts with the corresponding anion via a pair of N-H...O hydrogen bonds, generating the robust R₂²(8) supramolecular heterosynthon. In salt (IV), instead of forming the R₂²(8) heterosynthon, the carboxylate group bridges two pyrimidinium cations via N-H...O hydrogen bonds. In salt (V), one of the carboxylate O atoms bridges the N1-H group and a 2-amino H atom of the pyrimidinium cation to form a smaller R₂¹(6) ring instead of the R₂²(8) ring. In salt (IX), the sulfonate O atoms mimic the role of carboxylate O atoms in forming an R₂²(8) ring motif. In salts (II)-(IX), the pyrimidinium cation forms base pairs via a pair of N-H...N hydrogen bonds, generating a ring motif [R₂²(8) homosynthon]. Compounds (II) and (III) are isomorphous. The quadruple DDAA (D = hydrogen-bond donor and A = hydrogen-bond acceptor) array is observed in (I). In salts (II)-(IV) and (VI)-(IX), quadruple DADA arrays are present. In salts (VI) and (VII), both DADA and DDAA arrays co-exist. The crystal structures are further stabilized by π-π stacking interactions [in (I), (V) and (VII)-(IX)], C-H...π interactions [in (IV)-(V) and (VII)-(IX)], C-Br...π interactions [in (II)] and C-Cl...π interactions [in (I), (III) and (VI)]. Cl...O and Cl...Cl halogen-bond interactions are present in (I) and (VI), with distances and angles of 3.0020 (18) and 3.5159 (16) Å, and 165.56 (10) and 154.81 (11)°, respectively.

Supramolecular architectures in cytosinium 6-chloronicotinate monohydrate and 5-bromo-6-methylisocytosinium hydrogen sulfate

Aminopyrimidine derivatives are biologically important as they are components of nucleic acids and drugs. The crystals of two new salts, namely cytosinium 6-chloronicotinate monohydrate, C₄H₆N₃O⁺·C₆H₃ClNO₂^-·H₂O, (I), and 5-bromo-6-methylisocytosinium hydrogen sulfate (or 2-amino-5-bromo-4-oxo-6-methylpyrimidinium hydrogen sulfate), C₅H₇BrN₃O⁺·HSO₄^-, (II), have been prepared and characterized by single-crystal X-ray diffraction. The pyrimidine ring of both compounds is protonated at the imine N atom. In hydrated salt (I), the primary R₂²(8) ring motif (supramolecular heterosynthon) is formed via a pair of N-H...O(carboxylate) hydrogen bonds. The cations, anions and water molecule are hydrogen bonded through N-H...O, N-H...N, O-H...O and C-H...O hydrogen bonds, forming R₂²(8), R₃²(7) and R₅⁵(21) motifs, leading to a hydrogen-bonded supramolecular sheet structure. The supramolecular double sheet structure is formed via water-carboxylate O-H...O hydrogen bonds and π-π interactions between the anions and the cations. In salt (II), the hydrogen sulfate ions are linked via O-H...O hydrogen bonds to generate zigzag chains. The aminopyrimidinium cations are embedded between these zigzag chains. Each hydrogen sulfate ion bridges two cations via pairs of N-H...O hydrogen bonds and vice versa, generating two R₂²(8) ring motifs (supramolecular heterosynthon). The cations also interact with one another via halogen-halogen (Br...Br) and halogen-oxygen (Br...O) interactions.

Supra-molecular inter-actions in 2,6-di-amino-4-chloro-pyrimidin-1-ium 5-chloro-salicylate and bis-(2,6-di-amino-4-chloro-pyrimidin-1-ium) naphthalene-1,5-di-sulfonate

The crystals of two new salts, 2,6-di-amino-4-chloro-pyrimidin-1-ium 5-chloro-salicylate, C4H6ClN4+·C7H4ClO3-, (I), and bis-(2,6-di-amino-4-chloro-pyrimidin-1-ium) naphthalene-1,5-di-sulfonate, 2C4H6ClN4+·C10H6O6S22-, (II), have been synthesized and characterized by single-crystal X-ray diffraction. In both compounds, the N atom of the pyrimidine group in between the amino substituents is protonated and the pyrimidinium cation forms a pair of N-H⋯O hydrogen bonds with the carboxyl-ate/sulfonate ion, leading to a robust R22(8) motif (supra-molecular heterosynthon). In compound (I), a self-complementary base pairing involving the other pyrimidinium ring nitro-gen atom and one of the amino groups via a pair of N-H⋯N hydrogen bonds [R22(8) homosynthon] is also present. In compound (II), the crystallographic inversion centre coincides with the inversion centre of the naphthalene-1,5-di-sulfonate ion and all the sulfonate O atoms are hydrogen-bond acceptors, generating fused-ring motifs and a quadruple DDAA array. A halogen-bond (Cl⋯Cl) inter-action is present in (I) with a distance and angle of 3.3505 (12) Å and 151.37 (10)°, respectively. In addition, a C-Cl⋯π inter-action and a π-π inter-action in (I) and a π-π inter-action in (II) further stabilize these crystal structures.

Bis(picolinato) complexes of vanadium and zinc as potential antidiabetic agents: synthesis, structural elucidation and in vitro insulin-mimetic activity study

The studied vanadium(iv), vanadium(v) and zinc(ii) complexes show inhibition of the free fatty acid release from rat adipocytes.

Extending the family of quinolone antibacterials to new copper derivatives: self-assembly, structural and topological features, catalytic and biological activity

New copper(ii) compounds with quinolone pefloxacin were synthesized and fully characterized; they exhibit notable catalytic activity and promising biological profiles.

A 26-Membered Macrocycle Obtained by a Double Diels-Alder Cycloaddition Between Two 2H-Pyran-2-one Rings and Two 1,1'-(Hexane-1,6-diyl)bis (1H-pyrrole-2,5-dione)s

With the application of a double dienophile 1,1'-(hexane-1,6-diyl)bis(1H-pyrrole-2,5-dione) for a [4+2] cycloaddition with a substituted 2H-pyran-2-one a novel 26-membered tetraaza heteromacrocyclic system 3 was prepared via a direct method under solvent-free conditions with microwave irradiation. The macrocycle prepared is composed of two units of the dienophile and two of the diene. The structure of the macrocycle was characterized on the basis of IR, 1H and 13C NMR and mass spectroscopy, as well as by the elemental analysis and melting point determination. With X-ray diffraction of a single crystal of the macrocycle we have determined that the two acetyl groups (attached to the bridging double bond of the bicyclo[2.2.2]octene fragments) are oriented towards each other (and also towards the inside of the cavity of the macrocycle), therefore, mostly filling it completely.

Copper(II) bis(4,4,4-trifluoro-1-phenylbutane-1,3-dionate) complexes with pyridin-2-one, 3-hydroxypyridine and 3-hydroxypyridin-2-one ligands: molecular structures and hydrogen-bonded networks

Copper(II) bis(4,4,4-trifluoro-1-phenylbutane-1,3-dionate) complexes with pyridin-2-one (pyon), 3-hydroxypyridine (hpy) and 3-hydroxypyridin-2-one (hpyon) were prepared and the solid-state structures of (pyridin-2-one-κO)bis(4,4,4-trifluoro-3-oxo-1-phenylbutan-1-olato-κ²O,O')copper(II), [Cu(C₁₀H₆F₃O₂)₂(C₅H₅NO)] or [Cu(tfpb-κ²O,O')₂(pyon-κO)], (I), bis(pyridin-3-ol-κO)bis(4,4,4-trifluoro-3-oxo-1-phenylbutan-1-olato-κ²O,O')copper(II), [Cu(C₁₀H₆F₃O₂)₂(C₅H₅NO)₂] or [Cu(tfpb-κ²O,O')₂(hpy-κO)₂], (II), and bis(3-hydroxypyridin-2-one-κO)bis(4,4,4-trifluoro-3-oxo-1-phenylbutan-1-olato-κ²O,O')copper(II), [Cu(C₁₀H₆F₃O₂)₂(C₅H₅NO₂)₂] or [Cu(tfpb-κ²O,O')₂(hpyon-κO)₂], (III), were determined by single-crystal X-ray analysis. The coordination of the metal centre is square pyramidal and displays a rare example of a mutual cis arrangement of the β-diketonate ligands in (I) and a trans-octahedral arrangement in (II) and (III). Complex (II) presents the first crystallographic evidence of κO-monodentate hpy ligation to the transition metal enabling the pyridine N atom to participate in a two-dimensional hydrogen-bonded network through O-H...N interactions, forming a graph-set motif R₂²(7) through a C-H...O interaction. Complex (III) presents the first crystallographic evidence of monodentate coordination of the neutral hpyon ligand to a metal centre and a two-dimensional hydrogen-bonded network is formed through N-H...O interactions facilitated by C-H...O interactions, forming the graph-set motifs R₂²(8) and R₂²(7).

Supramolecular architectures in the salt trimethoprimium ferrocene-1-carboxylate and the cocrystal 4-amino-5-chloro-2,6-dimethylpyrimidine-ferrocene-1-carboxylic acid (1/1)

In the salt trimethoprimium ferrocenecarboxylate [systematic name: 2,4-diamino-5-(3,4,5-trimethoxybenzyl)pyrimidin-1-ium ferrocene-1-carboxylate], (C₁₄H₁₉N₄O₃)[Fe(C₅H₅)(C₆H₄O₂)], (I), of the antibacterial compound trimethoprim, the carboxylate group interacts with the protonated aminopyrimidine group of trimethoprim via two N-H...O hydrogen bonds, generating a robust R₂²(8) ring motif (heterosynthon). However, in the cocrystal 4-amino-5-chloro-2,6-dimethylpyrimidine-ferrocene-1-carboxylic acid (1/1), [Fe(C₅H₅)(C₆H₅O₂)]·C₆H₈ClN₃, (II), the carboxyl-aminopyrimidine interaction [R₂²(8) motif] is absent. The carboxyl group interacts with the pyrimidine ring via a single O-H...N hydrogen bond. The pyrimidine rings, however, form base pairs via a pair of N-H...N hydrogen bonds, generating an R₂²(8) supramolecular homosynthon. In salt (I), the unsubstituted cyclopentadienyl ring is disordered over two positions, with a refined site-occupation ratio of 0.573 (10):0.427 (10). In this study, the two five-membered cyclopentadienyl (Cp) rings of ferrocene are in a staggered conformation, as is evident from the C...Cg...Cg...C pseudo-torsion angles, which are in the range 36.13-37.53° for (I) and 22.58-23.46° for (II). Regarding the Cp ring of the minor component in salt (I), the geometry of the ferrocene ring is in an eclipsed conformation, as is evident from the C...Cg...Cg...C pseudo-torsion angles, which are in the range 79.26-80.94°. Both crystal structures are further stabilized by weak π-π interactions.

Supra-molecular hydrogen-bonding patterns in a 1:1 co-crystal of the N(7)-H tautomeric form of N6-benzoyl-adenine with 4-hy-droxy-benzoic acid

The asymmetric unit of the title co-crystal, C12H9N5O·C7H6O3, contains one mol-ecule of N6-benzoyl-adenine (BA) and one mol-ecule of 4-hy-droxy-benzoic acid (HBA). The N6-benzoyl-adenine (BA) has an N(7)-H tautomeric form with nonprotonated N-1 and N-3 atoms. This tautomeric form is stabilized by a typical intra-molecular N-H⋯O hydrogen bond between the carbonyl (C=O) group and the N(7)-H hydrogen on the Hoogsteen face of the purine ring, forming a graph-set S(7) ring motif. The primary robust R22(8) ring motif is formed in the Watson-Crick face via N-H⋯O and O-H⋯N hydrogen bonds (involving N1, N6-H and the carboxyl group of HBA). Weak inter-actions, such as, C-H⋯π and π-π are also observed in this crystal structure.

Vanadium and zinc complexes of 5-cyanopicolinate and pyrazine derivatives: synthesis, structural elucidation and in vitro insulino-mimetic activity study

Inhibition of free fatty acid release from rat adipocytes was observed for vanadium(iv), vanadium(v) and zinc(ii) complexes.

CuII and ZnII β-diketonate coordination polymers based on pyrimidin-2-amine, pyrazine and 1,2-bis(4-pyridyl)ethane

Copper(II) and zinc(II) bis(4,4,4-trifluoro-1-phenylbutane-1,3-dionato) compounds with pyrimidin-2-amine (pyr2a), pyrazine (pyz) and 1,2-bis(4-pyridyl)ethane (dpet) were prepared and solid-state structures of coordination polymers [M(tfpb)₂(pyr2a)]_∞ [M = Cu (1), Zn (2); tfpb = 4,4,4-trifluoro-1-phenylbutane-1,3-dionate], [M(tfpb)₂(pyz)]_∞ [M = Cu (3), Zn (4a, 4b)] and [Cu(tfpb)₂(dpet)]_∞ (5), respectively, were determined by single-crystal X-ray analysis. The coordination of metal centers in all compounds is octahedral with nitrogen ligands occupying the axial positions. Compound (1) crystallizes in the triclinic space group P\bar 1, whereas (2) crystallizes in the monoclinic space group P2/n. Differences are due to the different orientation of adjacent M(tfpb)₂ units, whereas the orientation of pyrimidin-2-amine is the same in both compounds. Polymeric chains in (1) and (2) contain intramolecular N-H...O hydrogen bonding between amino and carbonyl groups. Room-temperature structures (3) and (4a) are isomorphous adopting the monoclinic space group C2/m; however, on cooling crystals (4a) to 150 K a single-crystal-to-single-crystal transformation to (4b) possessing the triclinic space group P\bar 1 was observed. Compound (5) crystallizes in the triclinic space group P\bar 1 and contains a parallel aggregation of chains in contrast to the known structure of the non-fluorinated benzoylacetonato ligand, where chains aggregate in a perpendicular fashion. In the compounds studied intramolecular C-H...O and/or C-H...F interactions are present. The neighboring chains are linked by π...π interactions and in some compounds also by C-H...π interactions [(1), (4b), (5)].

Synthesis and Structural Evaluation of 5-Methyl-6-acetyl Substituted Indole and Gramine

The synthesis and crystal structures of 1-(5-methyl-1H-indol-6-yl)ethan-1-one (7), C11H11NO, and 1-3-[(dimethylamino) methyl]-5-methyl-1H-indol-6-ylethan-1-one (8), C14H18N2O, are reported. The synthesis is based on the Diels-Alder cycloaddition of a substituted 2H-pyran-2-one derivative, followed by an acid-catalyzed cyclization and concomitant deprotection (the last two steps were carried out as a one-pot domino process) yielding substituted indole 7, which was further derivatized via Mannich reaction to the gramine derivative 8. Both structures 7 and 8 were determined on the basis of IR, 1H NMR and mass spectroscopy, as well as by the elemental analysis and melting point determination. According to the single-crystal X-Ray diffraction analysis, the structure 7 has a single unique molecule in the asymmetric unit whereas the structure 8 contains four unique molecules in the asymmetric unit. Molecules 7 are linked via N-H···O hydrogen bonds between the secondary amine group and carbonyl moiety of the acetyl group of adjacent molecules, whereas molecules 8 are linked via N-H···N hydrogen bonds between the secondary and tertiary amine groups of adjacent molecules. Both structures are further stabilized by weak C-H···O, C-H···π and π···π interactions.

Regioselective Hydrolysis and Transesterification of Dimethyl 3-Benzamidophthalates Assisted by a Neighboring Amide Group

An efficient, highly regioselective hydrolysis and transesterification of dimethyl 3-benzamidophthalates into the corresponding carboxylic acid monoesters and mixed esters (including tert-butyl esters) under basic conditions is presented. The selectivity is governed by the neighboring 3-benzamido moiety's participation and by the nature of the solvent. In alcohols the reaction occurred exclusively at the ortho-position to the benzamido functionality, in pyridine or acetonitrile at both ester groups. An insight into the mechanistic pathway was obtained from a (1)H NMR study in perdeuteromethanol.

Supra-molecular architecture in a co-crystal of the N(7)-H tautomeric form of N (6)-benzoyl-adenine with adipic acid (1/0.5)

The asymmetric unit of the title co-crystal, C12H9N5O·0.5C6H10O4, consists of one mol-ecule of N (6)-benzoyl-adenine (BA) and one half-mol-ecule of adipic acid (AA), the other half being generated by inversion symmetry. The dihedral angle between the adenine and phenyl ring planes is 26.71 (7)°. The N (6)-benzoyl-adenine mol-ecule crystallizes in the N(7)-H tautomeric form with three non-protonated N atoms. This tautomeric form is stabilized by intra-molecular N-H⋯O hydrogen bonding between the carbonyl (C=O) group and the N(7)-H hydrogen atom on the Hoogsteen face of the purine ring, forming an S(7) ring motif. The two carboxyl groups of adipic acid inter-act with the Watson-Crick face of the BA mol-ecules through O-H⋯N and N-H⋯O hydrogen bonds, generating an R 2 (2)(8) ring motif. The latter units are linked by N-H⋯N hydrogen bonds, forming layers parallel to (10-5). A weak C-H⋯O hydrogen bond is also present, linking adipic acid mol-ecules in neighbouring layers, enclosing R (2) 2(10) ring motifs and forming a three-dimensional structure. C=O⋯π and C-H⋯π inter-actions are also present in the structure.

Supramolecular architectures in Co(II) and Cu(II) complexes with thiophene-2-carboxylate and 2-amino-4,6-dimethoxypyrimidine ligands

The coordination chemistry of mixed-ligand complexes continues to be an active area of research since these compounds have a wide range of applications. Many coordination polymers and metal-organic framworks are emerging as novel functional materials. Aminopyrimidine and its derivatives are flexible ligands with versatile binding and coordination modes which have been proven to be useful in the construction of organic-inorganic hybrid materials and coordination polymers. Thiophenecarboxylic acid, its derivatives and their complexes exhibit pharmacological properties. Cobalt(II) and copper(II) complexes of thiophenecarboxylate have many biological applications, for example, as antifungal and antitumor agents. Two new cobalt(II) and copper(II) complexes incorporating thiophene-2-carboxylate (2-TPC) and 2-amino-4,6-dimethoxypyrimidine (OMP) ligands have been synthesized and characterized by X-ray diffraction studies, namely (2-amino-4,6-dimethoxypyrimidine-κN)aquachlorido(thiophene-2-carboxylato-κO)cobalt(II) monohydrate, [Co(C5H3O2S)Cl(C6H9N3O2)(H2O)]·H2O, (I), and catena-poly[copper(II)-tetrakis(μ-thiophene-2-carboxylato-κ(2)O:O')-copper(II)-(μ-2-amino-4,6-dimethoxypyrimidine-κ(2)N(1):N(3))], [Cu2(C5H3O2S)4(C6H9N3O2)]n, (II). In (I), the Co(II) ion has a distorted tetrahedral coordination environment involving one O atom from a monodentate 2-TPC ligand, one N atom from an OMP ligand, one chloride ligand and one O atom of a water molecule. An additional water molecule is present in the asymmetric unit. The amino group of the coordinated OMP molecule and the coordinated carboxylate O atom of the 2-TPC ligand form an interligand N-H...O hydrogen bond, generating an S(6) ring motif. The pyrimidine molecules also form a base pair [R2(2)(8) motif] via a pair of N-H...N hydrogen bonds. These interactions, together with O-H...O and O-H...Cl hydrogen bonds and π-π stacking interactions, generate a three-dimensional supramolecular architecture. The one-dimensional coordination polymer (II) contains the classical paddle-wheel [Cu2(CH3COO)4(H2O)2] unit, where each carboxylate group of four 2-TPC ligands bridges two square-pyramidally coordinated Cu(II) ions and the apically coordinated OMP ligands bridge the dinuclear copper units. Each dinuclear copper unit has a crystallographic inversion centre, whereas the bridging OMP ligand has crystallographic twofold symmetry. The one-dimensional polymeric chains self-assemble via N-H...O, π-π and C-H...π interactions, generating a three-dimensional supramolecular architecture.

Supra-molecular inter-actions in a 1:1 co-crystal of acridine and 3-chloro-thio-phene-2-carb-oxy-lic acid

In the title co-crystal, C5H3ClO2S·C13H9N, the components inter-act with each other via an O-H⋯N hydrogen bond. Acridine-acridine stacking, thio-phene-thio-phene stacking and acridine-thio-phene C-H⋯π inter-actions also occur in the crystal.

Supra-molecular hydrogen-bonding patterns in the N(9)-H protonated and N(7)-H tautomeric form of an N(6) -benzoyl-adenine salt: N (6)-benzoyl-adeninium nitrate

In the title molecular salt, C12H10N5O(+)·NO3 (-), the adenine unit has an N (9)-protonated N(7)-H tautomeric form with non-protonated N(1) and N(3) atoms. The dihedral angle between the adenine ring system and the phenyl ring is 51.10 (10)°. The typical intra-molecular N(7)-H⋯O hydrogen bond with an S(7) graph-set motif is also present. The benzoyl-adeninium cations also form base pairs through N-H⋯O and C-H⋯N hydrogen bonds involving the Watson-Crick face of the adenine ring and the C and O atoms of the benzoyl ring of an adjacent cation, forming a supra-molecular ribbon with R 2 (2)(9) rings. Benzoyl-adeninum cations are also bridged by one of the oxygen atoms of the nitrate anion, which acts as a double acceptor, forming a pair of N-H⋯O hydrogen bonds to generate a second ribbon motif. These ribbons together with π-π stacking inter-actions between the phenyl ring and the five- and six-membered adenine rings of adjacent mol-ecules generate a three-dimensional supra-molecular architecture.

Structure and biological activities of metal complexes of flumequine

Co(ii)–flumequine complexes were characterized and their biological activity was evaluated in regard to DNA- and albumin-binding and antimicrobial and antiproliferative activity.

Supramolecular hydrogen-bonding patterns in two cocrystals of the N(7)–H tautomeric form ofN6-benzoyladenine:N6-benzoyladenine–3-hydroxypyridinium-2-carboxylate (1/1) andN6-benzoyladenine–DL-tartaric acid (1/1)

Two novel cocrystals of the N(7)—H tautomeric form ofN6-benzoyladenine (BA), namelyN6-benzoyladenine–3-hydroxypyridinium-2-carboxylate (3HPA) (1/1), C12H9N5O·C6H5NO3, (I), andN6-benzoyladenine–DL-tartaric acid (TA) (1/1), C12H9N5O·C4H6O6, (II), are reported. In both cocrystals, theN6-benzoyladenine molecule exists as the N(7)—H tautomer, and this tautomeric form is stabilized by intramolecular N—H...O hydrogen bonding between the benzoyl C=O group and the N(7)—H hydrogen on the Hoogsteen site of the purine ring, forming anS(7) motif. The dihedral angle between the adenine and phenyl planes is 0.94 (8)° in (I) and 9.77 (8)° in (II). In (I), the Watson–Crick face of BA (N6—H and N1; purine numbering) interacts with the carboxylate and phenol groups of 3HPA through N—H...O and O—H...N hydrogen bonds, generating a ring-motif heterosynthon [graph setR22(6)]. However, in (II), the Hoogsteen face of BA (benzoyl O atom and N7; purine numbering) interacts with TA (hydroxy and carbonyl O atoms) through N—H...O and O—H...O hydrogen bonds, generating a different heterosynthon [graph setR22(4)]. Both crystal structures are further stabilized by π–π stacking interactions.

Supramolecular Potential of Vanadium β-Diketonate and Picolinate Compounds and The First One-dimensional Oxidovanadium(IV) Complex with β-Diketonate Ligand

Three vanadium compounds with β-diketonato or picolinato ligands were prepared and structurally characterized. In compounds [VO(tfpb)2]∞ (1) (tfpb = 4,4,4-trifluoro-1-phenylbutane-1,3-dionate) and [VO(acac)2(2-pyridone)] (2) the coordination of vanadium atom is octahedral and in the compound Hpy[VO2(pic)Cl] (3) the central atom is pentacoordinated. X-Ray crystallographic studies reveal infinite chain formation due to V=O···V=O interactions in 1, while 2 and 3 are mononuclear compounds. Centrosymmetric hydrogen-bonded dimers are formed in 2 via N-H···O interactions due to the 2-pyridone ligand. In 3 the Hpy+ cation is hydrogen bonded to the complex anion and crystal structure is further stabilized by π···π and C-H···O interactions.