Pyridine aided progression from amorphous to crystalline bis([5-(aryl)-1-diazenyl]quinolin-8-olato)zinc(II) compounds − Solution and solid-state structural characterization, nanoparticle formation and antibacterial activity

[Display omitted] •Ten new pyridine assisted bis(quinolin-8-olato) zinc(II) compoundswith distorted octahedral and square-pyramidal geometries have been synthesized.•Characterizations of the compounds were accomplished from IR,NMR,Uv-Vis and fluoroscence spectroscopy.•All the compounds have been characterized by single crystal X-ray crystallography.•Formation of nanomaterials and antibacterial activity are reported. Ten new zinc(II) compounds, viz. [Zn(LQ)2(4-MePy)2]·H2O (1), [Zn(LMeAQ)2(Py)2]·C6H6 (2a), [Zn(LMeAQ)2(H2O)2] (2b), [Zn(LOMeAQ)2(H2O)2] (3), [Zn(LEtAQ)2(3-MePy)2] (4), [Zn(LOEtAQ)2(4-MePy)2]·0.5C6H7N (5a), [Zn(LOEtAQ)2(H2O)2] (5b), [Zn(LNMe2AQ)2(Py)2]·1.5C6H6·H2O (6), [Zn(LCAQ)2(Py)] (7) and [Zn(LBAQ)2(Py)] (8) (primary ligands: LQ = quinolin-8-olate and LXAQ = 4-substituted 5-[(E)-2-(aryl)-1-diazenyl]quinolin-8-olate; secondary ligands: Py = pyridine, 3-MePy = 3-methylpyridine, 4-MePy = 4-methylpyridine) have been synthesized and characterized by elemental analysis, IR, NMR, UV-vis and fluorescence spectroscopy and single-crystal X-ray diffraction analysis. The structural characterization revealed distorted octahedral geometries for 1–6, in which trans-disposed 8-quinolate ligands occupy the equatorial and the secondary ligands the axial positions. Compounds 7–8 comprise five-coordinate molecular structures with square-pyramidal coordination polyhedra based on trans-oriented quinolate ligands and a Py molecule in the apical position. In the crystal structures of 1–8, the molecules are assembled by π–stacking interactions and for the aquo-compounds additionally by OH⋅⋅⋅O hydrogen bonds. As representative example, compound 2a was used as starting material for the synthesis of ZnO nanoparticles in an average size range of 70–120 nm, as illustrated by PXRD analysis and TEM images. The antimicrobial activity of the pro-ligands and zinc(II) compounds studied herein was assessed by inhibition zone test in agar cultures against five indicator bacterial strains, i.e. Escherichia coli MTCC 730, Streptococcus pyogenes MTCC 1925, Klebsiella pneumoniae MTCC 109, Bacillus cereus MTCC 430 and Salmonella enterica MTCC 735.