Syntheses and X-ray crystal structure studies of four new coordination complexes and salts based on proton-transferred pyridine-2,6-dicarboxylic acid N-oxide

Structural and Antimicrobial Characterization of Co-Crystal [Ni(bpy)(acr)2(H2O)]·MA

A new co-crystal with the formula [Ni(bpy)(acr)2(H2O)]·MA (bpy = 2,2′-bipyridine, acr = acrylate and MA = melamine) has been synthesized and characterized using IR, UV-Vis, thermogravimetric analysis and single crystal X-ray diffraction. The complex contains discrete unities of [Ni(bpy)(acr)2(H2O)] and melamine linked in a complex network by both hydrogen bonds and π-π stacking interactions. Structural characterization revealed that Ni(II) adopts an octahedral distorted stereochemistry, and acrylate ions present both unidentate and chelate coordination modes. Thermal decomposition occurs in four steps, the ligands being stepwise released in the order of water, acrylate, bipyridine and melamine. The antimicrobial activity of the obtained complex, its precursor ([Ni(bpy)(acr)2(H2O)]) and melamine were assessed against planktonic (minimal inhibitory concentration—MIC) and biofilm-embedded (minimal biofilm eradication concentration—MBEC) Gram-positive and Gram-negative bacterial strains. The obtained results revealed that the new complex and its precursor exhibited a superior activity compared to MA, the highest susceptibility being recorded for the Staphylococcus aureus strain. The MIC and MBEC ranges were very similar, indicating the potential of this complex and its precursor to develop novel anti-biofilm agents.

On the importance of π-stacking interactions in the complexes of copper and zinc bearing pyridine-2,6-dicarboxylic acid N-oxide and N-donor auxiliary ligands

Using N- and O-donor ligands in a mixed-ligand system, three new coordination complexes have been X-ray characterized, exhibiting strong π–π stacking interactions.

A redetermination of the structure and Hirshfeld surface analysis of poly[di-aquadi-μ-hydroxido-tetra-kis-(μ-nicotinato N-oxide)tricopper(II)]

The product obtained from the reaction of pyridine-2,3-di-carb-oxy-lic acid and hydrated copper(II) chloride in hot aqueous NaOH solution was determined by low temperature X-ray diffraction to be [Cu3(C6H4NO3)4(OH)2(H2O)2] n or [Cu3(μ-OH)2(μ-nicNO)4(H2O)2] n (nicNO is pyridine-3-carboxyl-ate N-oxide), a structure obtained from room temperature data and reported previously. The present determination is improved in quality and treatment of the H atoms. A Hirshfeld surface analysis of the inter-molecular inter-actions is presented.