Dimethyl 6-(pyrazine-2-yl)pyridine-3,4-dicarboxylate (py-2pz) was used as a ligand for the synthesis of new copper(II) and silver(I) complexes, [CuCl₂(py-2pz)]₂ (1), [Cu(CF₃SO₃)(H₂O)(py-2pz)₂]CF₃SO₃·2H₂O (2), [Ag(py-2pz)₂]PF₆ (3) and {[Ag(NO₃)(py-2pz)]·0.5H₂O}_n (4). The complexes were characterized by spectroscopic and electrochemical methods, while their structures were determined by single crystal X-ray diffraction analysis. The X-ray analysis revealed the bidentate coordination mode of py-2pz to the corresponding metal ion via its pyridine and pyrazine nitrogen atoms in all complexes, while in polynuclear complex 4, the heterocyclic pyrazine ring of one py-2pz additionally behaves as a bridging ligand between two Ag(I) ions. DFT calculations were performed to elucidate the structures of the investigated complexes in solution. The antimicrobial potential of the complexes 1–4 was evaluated against two bacterial (Pseudomonas aeruginosa and Staphylococcus aureus) and two Candida (C. albicans and C. parapsilosis) species. Silver(I) complexes 3 and 4 have shown good antibacterial and antifungal properties with minimal inhibitory concentration (MIC) values ranging from 4.9 to 39.0 μM (3.9–31.2 μg mL⁻¹). All complexes inhibited the filamentation of C. albicans and hyphae formation, while silver(I) complexes 3 and 4 had also the ability to inhibit the biofilm formation process of this fungus. The binding affinity of the complexes 1–4 with calf thymus DNA (ct-DNA) and bovine serum albumin (BSA) was studied by fluorescence emission spectroscopy to clarify the mode of their antimicrobial activity. Catechol oxidase biomimetic catalytic activity of copper(II) complexes 1 and 2 was additionally investigated by using 3,5-di-tert-butylcatechol (3,5-DTBC) and o-aminophenol (OAP) as substrates.

Antifungal copper(ii) complexes with pyridine-4,5-dicarboxylate esters show the ability to inhibit the filamentation and biofilm formation of Candida albicans, and efficiently prevent the adhesion of this fungus.

The[Cu(L)Cl2]2and[Pt(L)Cl2]complexes were prepared from the simple Schiff-base ligand (E)-phenyl-N-((pyridin-2-yl)methylene)methanamine (L) and respectively, CuCl₂andcis-[PtCl₂(DMSO)₂].

The century-old, well-known odd–even effect phenomenon is still a very attractive and intriguing topic in supramolecular and nano-scale organic chemistry. As a part of our continuous efforts in the study of supramolecular chemistry, we have prepared three novel aromatic alcohols (1,2-bis[2-(hydroxymethyl)phenoxy]butylene (Do4OH), 1,2-bis[2-(hydroxymethyl)phenoxy]pentylene (Do5OH) and 1,2-bis[2-(hydroxymethyl)phenoxy]hexylene (Do6OH)) and determined their crystal and molecular structures by single-crystal X-ray diffraction. In all compounds, two benzyl alcohol groups are linked by an aliphatic chain of different lengths (CH₂)_n; n = 4, 5 and 6. The major differences in the molecular structures were found in the overall planarity of the molecules and the conformation of the aliphatic chain. Molecules with an even number of CH₂ groups tend to be planar with an all-trans conformation of the aliphatic chain, while the odd-numbered molecule is non-planar, with partial gauche conformation. A direct consequence of these structural differences is visible in the melting points—odd-numbered compounds of a particular series display systematically lower melting points. Crystal and molecular structures were additionally studied by the theoretical calculations and the melting points were correlated with packing density and the number of CH₂ groups. The results have shown that the generally accepted rule, higher density = higher stability = higher melting point, could not be applied to these compounds. It was found that the denser packaging causes an increase in the percentage of repulsive H‧‧‧H interactions, thereby reducing the stability of the crystal, and consequently, the melting points. Another interesting consequence of different molecular structures is their electrochemical and antioxidative properties—a non-planar structure displays the highest oxidation peak of hydroxyl groups and moderate antioxidant activity.