M-II (M = Mn, Fe, Co, Ni and Cu) complexes with a chromone-derived neutral ligand: synthesis, structural characterization, photocatalytic and mycobacterial activity studies

The reaction of 2-(2-furyl)-3-hydroxychromone and nicotinoyl chloride produces a neutral ligand (L), which has nitrogen and oxygen donor atoms. Evidence of L polymorphism is discussed. The new molecule showed fluorescence emission in solution and in the solid state (intense emission at 556 nm [lambda(exc) 392 nm] in the solid state). Ligand L and coordination compounds [MCl2(L)(2)](n) (M = Mn (1), Fe (2), Co (3), Ni (4) and Cu (5)) and [Cu(NCS)(2)(L)(2)](n) (6) were characterized using spectroscopic techniques. The crystal structures were determined via single-crystal X-ray diffraction and powder X-ray diffraction. Biological tests with mycobacterial strains were conducted for compounds 1-5. The optical band gap energies of these compounds, which ranged from 3.29 to 3.39 eV, were estimated from diffuse reflectance spectroscopy data. Mesoporous TiO2-based photocatalysts were prepared and tested for hydrogen production. The m-TiO2-5 photocatalyst produced hydrogen at a 1052.5 mu mol g(-1) h(-1) rate under irradiation using a 300 W Hg/Xe lamp.