Cadmium(II) and calcium(II) complexes with N,O-bidentate ligands derived from pyrazinecarboxylic acid

The synthesis and characterization of cad- mium(II) and calcium(II) complexes with N , O -bidentate ligands derived from pyrazinecarboxylic acid (3-hydroxy- 2-quinoxalinecarboxylic acid HL 1 , pyrazine-2-carboxylic acid HL 2 ) are reported. Obtained compounds [Cd(L 1 ) 2 (H 2 O) 2 ](H 2 O) 2 ( 1 ), [Cd(L 2 ) 2 ] n ( 2 ) and [Ca(L 2 ) 2 (H 2 O) 4 ]( 3 ) were studied by elemental analyses, IR, Raman spectros- copy and thermogravimetric methods (TG, DTG, DSC). In addition, the molecular structure of complex 1 has been determined by X-ray single crystal diffraction. Thermal analysis reveals a decomposition process of 1 , 3 complexes in multiple stages. The data obtained from TG and DSC curves for 1 , 3 confirm not only the presence but also the nature of water (crystallization and coordination) and the stoichiometry of the studied metal complexes. The results of thermal studies are in good agreement with their crystal structures. Thermal behavior of complex 2 indicates a single complete decomposition process of the sample. In addition, complex 2 as a coordination polymer is the most stable all of them and the thermal stability of the obtained complexes can be ordered in the following sequence: 1 \ 3 2

Ruthenium(IV) complexes as potential inhibitors of bacterial biofilm formation

With increasing antimicrobial resistance there is an urgent need for new strategies to control harmful biofilms. In this study, we have investigated the possibility of utilizing ruthenium(IV) complexes (H3O)2(HL1)2[RuCl6]·2Cl·2EtOH (1) and [RuCl4(CH3CN)2](L32)·H2O (2) (where L1-2-hydroxymethylbenzimadazole, L32-1,4-dihydroquinoxaline-2,3-dione) as effective inhibitors for biofilms formation. The biological activities of the compounds were explored using E. coli, S. aureus, P. aeruginosa PAO1, and P. aeruginosa LES B58. The new chloride ruthenium complexes were characterized by single-crystal X-ray diffraction analysis, Hirshfeld surface analysis, FT-IR, UV-Vis, magnetic and electrochemical (CV, DPV) measurements, and solution conductivity. In the obtained complexes, the ruthenium(IV) ions possess an octahedral environment. The intermolecular classical and rare weak hydrogen bonds, and π···π stacking interactions significantly contribute to structure stabilization, leading to the formation of a supramolecular assembly. The microbiological tests have shown complex 1 exhibited a slightly higher anti-biofilm activity than that of compound 2. Interestingly, electrochemical studies have allowed us to determine the relationship between the oxidizing properties of complexes and their biological activity. Probably the mechanism of action of 1 and 2 is associated with generating a cellular response similar to oxidative stress in bacterial cells

Novel eight-coordinated Cd(II) complexes with two homologous pyridine alcohols : crystal structure, spectroscopic and thermal properties

Two novel cadmium(II) complexes with homologous pyridine alcohols: [Cd(2-MeOHPy) 2 (NO 3 ) 2 ]( 1 ) and [Cd(2-EtOHPy) 2 (NO 3 ) 2 ]( 2 ) have been prepared and characterized by elemental analysis, X-ray crystallo- graphic studies, spectroscopic (IR, 1 H and 13 C NMR) and thermal properties. IR, NMR and X-ray analysis have confirmed a bidentate fashion of coordination of heteroaromatic alcohols with Cd(II) ions. 2-MeO- HPy bound directly to the central ion by N, O-donor atoms giving five-membered chelate ring but 2- EtOHPy formed less stable six-membered chelate ring. In the complex ( 1 ) and ( 2 ) bidentate nitrate ligands are arranged in cis position for organic ligands. In both cases cadmium(II) ions are eight-coordi- nated and shape of coordination polyhedral can be described as pseudo-dodecahedron (CdN 2 O 6 chromo- phore type). The crystal packing of Cd(II) complexes are stabilized by intermolecular classical hydrogen bonds of O A H O and non-classical C A H O type. In addition, there are p – p stacking interactions between almost parallel-displaced pyridine rings of 2-hydroxymethylpyridine in the two neighbouring complex ( 1 ) molecules but the hydrogen interactions in ( 2 ) are formed by C A H donor group of Py rings and p -electron system of neighbouring one