Syntheses, structures, photoluminescence, and theoretical studies of a novel class of d¹⁰metal complexes of 1H-[1,10]phenanthrolin-2-one

A novel asymmetric mono-substituted 1,10-phenanthroline, Hophen·0.5H2O (1, Hophen = 1H-[1,10]phenanthrolin-2-one), was generated by a facile route, and a novel class of crystalline, d10-metal, monomeric or oligomeric complexes of this ligand, namely [Hg(ophen)2]·4H2O·CH2Cl2(2), [Cd3Cl(ophen)5]·1.5 H2O·2 CH2Cl2(3), and [Zn4O(ophen)4(OAc)2]·4H2O· 2 CH2Cl2(4), were obtained by means of liquid diffusion, and were characterized by X-ray crystallography and photoluminescence studies. Complex 1 exhibits a hydrogen-bonded dimeric structure, 2 is a neutral monomeric complex, 3 has a trinuclear structure with the ophen ligand acting as a bridge through the ketone groups, and 4 features a tetranuclear Zn4O core that is consolidated further by bridging ophen and acetate ligands. All the complexes display photoluminescent properties in the blue/green region. The photoluminescent mechanisms were investigated by means of molecular orbital calculations, which showed that the photoluminescent properties are ligand-based and can be tuned upon ligation to different metal ions.