LAUSR

Abstract Two mononuclear M(II) complexes, [M(L2)2]·CH3OH (M = Mn(1) and Zn(2), HL2 = 1-(2-{[(E)-3,5-dibromo-2-hydroxybenzylidene]amino}phenyl)ethanone oxime), were synthesized via complexation of corresponding M(II) acetate with HL1 (2-(3,5-dibromo-2-hydroxyphenyl)-4-methyl-1,2-dihydroquinazoline-3-oxide, H is the deprotonatable hydrogen) originally. During the reaction, the C–N bond in the ligand HL1 is converted into the C N OH group in the HL2. The spectral data of both complexes were compared with the ligand HL1. Both complexes were determined by single crystal X-ray diffraction and display similar coordination geometry and have a 2:1 ligand-to-metal ratio. In the crystal structure, complexes 1 and 2 form an infinite 1-D chain and 2 into 3-D supramolecular frameworks. The electrochemical property of complex 1 was investigated by cyclic voltammetry. The electronic transitions and spectral features of HL1 and both complexes were discussed by DFT and TD-DFT calculations. Time dependent DFT calculations have been carried out on the optimised geometry to further understand the electronic transitions in the UV–Vis spectra of the compounds. In addition, the highest occupied molecular orbital (HOMO), lowest unoccupied molecular orbital (LUMO), and HOMO–LUMO gap were also calculated.