A photoluminescent dinuclear silver(I) complex exhibits CH···Ag close interactions and a new coordination mode of the pyridine-2,3-dicarboxylate

Synthesis and Antimicrobial Activity of 2-Trifluoroacetonylbenzoxazole Ligands and Their Metal Complexes

Three 2-fluoroacetonylbenzoxazole ligands 1a-c and their new Zn(II) complexes 2a-c have been synthesized. In addition, syntheses of new metal [Mg(II), Ni(II), Cu(II), Pd(II), and Ag(I)] complexes from 1a have been also described. The molecular and crystal structures of six metal complexes 2b and 2d-h were determined by single-crystal X-ray diffraction analyses. Their antibacterial activities against six Gram-positive and six Gram-negative bacteria were evaluated by minimum inhibitory concentrations (MIC), which were compared with those of appropriate antibiotics and silver nitrate. The results indicate that some metal compounds have more antibacterial effects in comparison with free ligands and have preferred antibacterial activities that may have potential pharmaceutical applications. Noticeably, the Ag(I) complex 2h exhibited low MIC value of 0.7 µM against Pseudomonas aeruginosa, which was even superior to the reference drug, Norfloxacin with that of 1.5 µM. Against P. aeruginosa, 2h is bacteriostatic, exerts the cell surface damage observed by scanning electron microscopy (SEM) and is less likely to develop resistance. The new 2h has been found to display effective antimicrobial activity against a series of bacteria.

Synthesis, Structures, and Properties of Polynuclear Silver(I) Complexes Containing Tetra-Phosphine Ligand with Ag⋅⋅⋅C Interactions

Reaction of AgNO3 and N,N,N′,N′-tetrakis((diphenylphosphino)methyl)benzene-1,4-diamine (pbaa) with sodium N-ethyldithiocarbamate (Na(Etdtc)) in CH3CN/toluene and CH3CN/DMF solvents produced two Ag4S4-based coordination complexes [Ag4(pbaa)(µ-κ1S,κ2S-Etdtc)4] (1) and [Ag4(pbaa)(µ-κ1S,κ2S-Etdtc)2(µ-κ1S,κ1S-Etdtc)2] (2). Structural analysis shows that the Ag4S4 cores in 1 are interconnected by one pbaa ligand in a tetradentate mode and four Etdtc– anions in a µ-κ1S,κ2S mode to form a three-layer conformation, whereas the Ag4S4 cores in 2 are linked by ligands pbaa (the tetradentate mode) and Etdtc– (the µ-κ1S,κ1S and µ-κ1S,κ2S modes) to yield the other type of three-layer conformation. In addition, in different solvent systems, the Ag atoms also form different types of weak Ag···C interactions with Ag···C distances of 3.297–3.344 Å in 1 and 3.237–3.416 Å in 2. The emission spectrum of complex 1 in DMF solution displays a broad orange–red emission peak at 518 nm, which may be assigned to the ligand-to-metal charge transfer transition.