Complexes of 2-Amino-3-methylpyridine and 2-Amino-4-methylbenzothiazole with Ag(I) and Cu(II): Structure and Biological Applications

Coordination complexes (1–4) of 2-amino-4-methylbenzothiazole and 2-amino-3-methylpyridine with Cu(CH3COO)2 and AgNO3 were prepared and characterized by UV/Vis and FT-IR spectroscopy. The molecular structure for single crystals of silver complexes (2 and 4) were determined by X-ray diffraction. The coordination complex (2) is monoclinic with space group P21/c, wherein two ligands are coordinated to a metal ion, affording distorted trigonal geometry around the central Ag metal ion. The efficient nucleophilic center, i.e., the endocyclic nitrogen of the organic ligand, binds to the silver metal. Ligands are coordinated to adopt cis arrangement, predominantly due to steric reasons. The O(2) and O(3) atoms of the NO3− group further play an important role in such type of ligand arrangement by hydrogen bonding with the NH2 group of ligands. Complex (4) is orthorhombic, P212121, comprising two molecules of 2-amino-3-methylpyridine as ligand coordinated with the metal ion, affording a polymeric structure. The coordination behavior of the ligand is identical to that in complex 2, wherein ring nitrogen is coordinated to the metal center and bridged to another metal ion through an NH2 group. The resulting product is polymeric in nature with the Ag metal in the backbone and ligand as the bridge. Compounds (2–4) were found to be luminescent, while 1 did not show such activity. All compounds were screened for their preliminary biological activities such as antibacterial, antioxidant and enzyme inhibition. Compounds exhibited moderate activity in these tests.

Silver(I) metallodrugs of thiosemicarbazones and naproxen: biocompatibility, in vitro anti-proliferative activity and in silico interaction studies with EGFR, VEGFR2 and LOX receptors

Four new heteroleptic silver(I) complexes with the general formula [Ag(L1-4)(nap)] (1-4), where L1-4 =  2-(1-(4-substitutedphenyl)ethylidene)hydrazinecarbothioamide and nap = naproxen, have been synthesized and characterized. The geometric parameters determined from density functional theory and UV-Vis studies indicate distorted tetrahedral geometry around silver(I) ion. Fourier transform infrared (FT IR) spectra evidenced asymmetric bidentate coordination mode of carboxyl oxygen atoms of naproxen with silver(I) ion. The complexes are stable for 72 h and biocompatibility was analysed towards normal human dermal fibroblast cells, which showed non-toxic nature up to 100 ng/ml. In vitro anti-proliferative activity of the complexes by MTT assay was tested against three human cancerous cell lines and one non-tumorigenic human breast epithelial cell line (MCF-10a) in which the complex 4 exhibited enhanced activity. The morphological changes observed by acridine orange/ethidium bromide and Hoechst 33258 staining method reveal apoptosis-inducing ability of the complexes. The molecular docking studies suggest hydrogen bonding, hydrophobic and π-pair interactions with the active site of epidermal growth factor receptor, vascular endothelial growth factor receptor 2 and lipoxygenase receptors.

Silver(I) Complexes of Diphenylpyridines: Crystal Structures, Luminescence Studies, Theoretical Insights, and Biological Activities

A series of simple two-coordinated cationic silver(I) complexes, namely, [Ag{4-(4-R¹ -phenyl)-2,6-diphenylpyridine}₂ ]X (X=ClO₄ ^- , BF₄ ^- , or SO₃ CF₃ ^- ), with different electron-donating or -withdrawing groups (e.g., R¹ =N(Me)₂ , Me, H, Cl, and Br) on the phenyl ring, were successfully prepared. Extensive characterization of these complexes by various NMR spectroscopy techniques and mass spectrometry was further corroborated by single-crystal XRD analyses. Detailed photophysical investigations of [Ag{4-(4-N,N-dimethylaminophenyl)-2,6-diphenylpyridine}₂ ]ClO₄ (C1) displayed a strong room-temperature fluorescence in solution with an anomalously high luminescence quantum yield of 0.83. The effects of distinct substituent groups (C2-C5), π-conjugated aromatic rings (C6 and C7), and anions (C8 and C9) on the photoluminescence properties were evaluated. Furthermore, DFT and time-dependent DFT calculations were performed to discern the composition of the excited state, as well as to confirm the obtained relative emission energies upon substitution with electronically different ligands. These results indicated that the strong electron-donating substituent of N,N-dimethylamine played an important role in the unprecedented high luminescence quantum yield of C1. In addition, preliminary antimicrobial studies and confocal microscopy fluorescent imaging of HeLa cells labeled with these complexes reveal their potential applications in biological activities.

Luminescent Silver-Purine Double Helicate: Synthesis, Self-Assembly and Antibacterial Action

The synthesis, self-assembly and antibacterial activity of a luminescent silver-purine double helicate is reported. The structure of the newly synthesized silver-supported helicate [C₃₆ H₂₄ N₁₆ O₄ Cl₅ Ag₁ ] was unambiguously characterized by single-crystal X-ray crystallography. It exhibited a bright bluish-green emission (λ_max =460 nm), when excited with 380 nm light. Microscopic investigations showed that the complex has a propensity to self-assemble into nanospheres. The antibacterial activity of this silver-containing helicate was studied against both Gram-positive and Gram-negative bacteria. MIC (minimal inhibitory concentration) values showed that the complex is very active against Gram-negative bacteria. Further internalization of the silver complex into E. coli bacteria was mapped with the help of microscopic techniques. These results are significant as silver was recently found to enhance antibiotic action against Gram-negative bacteria, raising hope in countering severe bacterial infections.

2-[4-(4,5-Dihydro-1H-imidazol-2-yl)phenyl]-4,5-dihydro-1H-imidazol-3-ium 4-aminobenzoate

In the cation of the title compound, C₁₂H₁₅N₄⁺·C₇H₆NO₂⁻, the benzene ring makes dihedral angles of 30.51 (9) and 25.64 (9)° with the imidazole and imidazolinium rings, respectively. In the crystal, inter­molecular N—H⋯O and N—H⋯N hydrogen-bonding inter­actions link the mol­ecules into a three-dimensional network.

[2,6-Bis(4,5-dihydro-1H-imidazol-2-yl)pyridine]dichloridomanganese(II)

In the title compound, [MnCl₂(C₁₁H₁₃N₅)], the Mn^II ion is five-coordinated in a distorted square-pyramidal geometry, with three N atoms from the neutral tridentate 2,6-bis­(4,5-dihydro-1H-imidazol-2-yl)pyridine ligand and one chloride ion forming the basal plane and the other chloride ion in the apical position. Both dihydro­imidazole rings adopt envelope conformations. In the crystal structure, mol­ecules are linked into a three-dimensional network by N—H⋯Cl and C—H⋯Cl hydrogen bonds.

Bis[μ-1,3-bis(4,5-dihydroimidazol-2-yl)benzene-κN:N']bis[dichloridozinc(II)] N,N'-dimethylformamide disolvate

The title compound, [Zn(2)Cl(4)(C(12)H(14)N(4))(2)]·2C(3)H(7)NO, is located on a centre of inversion with one half of a complex mol-ecule and one dimethyl-formamide solvent mol-ecule in the asymmetric unit. The Zn(II) ion is tetra-hedrally coordinated by two organic ligands and two chloride ions. Each organic ligand acts as a bidentate ligand, connecting two Zn(II) ions, resulting in a dimeric [2:2] metallamacrocyclic structure. Adjacent mol-ecules are further linked by N-H⋯Cl hydrogen bonds and the solvent is linked to the complex by N-H⋯O hydrogen bonds.

Bis[μ-1,4-bis-(4,5-dihydro-1H-imidazol-2-yl)benzene-κN:N]silver(I) dinitrate dihydrate

The reaction of 1,4-bis­(4,5-dihydro-1H-imidazol-2-yl)benzene (bib) with silver(I) nitrate in a 1:1 molar ratio generates the metallacyclic title complex, [Ag₂(C₁₂H₁₄N₄)₂](NO₃)₂·2H₂O, in which the bib ligand displays a cis configuration. Each bib ligand acts as a bidentate bridging ligand connecting a pair of Ag^I ions to form a [2 + 2] metallamacrocycle in which the Ag⋯Ag distance is 6.77 (2) Å. Each Ag^I ion has weak contacts (2.91 Å) with the nitrate anion. The uncoordinated water mol­ecules make hydrogen bonds with nitrate O atoms, forming chains. The H atoms attached to the uncoordinated nitro­gen inter­act with these chains through N—H⋯O hydrogen bonds, forming layers parallel to the (11) plane.

Recent Advances in Supramolecular Design and Assembly of Silver(I) Coordination Polymers

The supramolecular chemistry of Ag(i) coordination assemblies continues to attract attention due to their versatile structural diversity and potential physical and chemical functions. This article provides a short review of recent advances in the design and construction of Ag(i) coordination polymers with special emphasis on the Ag(i) ion coordination geometry, ligand functionality, and supramolecular interactions. The potential functions of Ag(i) coordination polymers are briefly summarized.