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

Abstract

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 [λ_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 μmol g⁻¹ h⁻¹ rate under irradiation using a 300 W Hg/Xe lamp.