New Mg2+, Mn2+ coordination complexes with quinoline-monoacylhydrazidate ligand via in situ acylation reaction

Through employing the in situ acylation of N 2 H 4 with 2, 3-quinoline dicarboxylic acid, three acylhydrazidate-extended coordination complexes, M(QLH)(H 2 O) 2 Cl (M = Mg ( 1 ) or Mn ( 2 ); QLH = 2, 3-quinolinedicarboxylhydrazidate) and Mn(QLH) 2 (H 2 O) 2 ( 3 ), were obtained under solvothermal conditions. The X-ray single-crystal diffraction analysis reveals that: (i) compounds 1 and 2 feature a dinuclear structure. Via two kinds of O–H⋯O and O–H⋯Cl hydrogen bonds, the discrete dinuclear units of 1 and 2 self-assemble into 3-D supramolecular networks, which are stabilized by the offset face-to-face π···π interactions; (ii) compound 3 features a mononuclear structure, which self-assembles into a 2-D supramolecular network via two types of O–H⋯O and N–H⋯N hydrogen bonds, and the strong face-to-face π···π interactions strengthen the 2D supramolecular layers. All of title compounds were characterized by IR spectroscopy, elemental analysis, power X-ray diffraction and TG analysis. The photoluminescent properties of 1 , 2 and 3 were investigated. Compounds 1 and 3 emitted green light with maxima at 529 nm for 1 ( λ ex = 364 nm), and 498 nm for 3 ( λ ex = 366 nm), while compound 2 emitted purple light with maxima at 381 nm ( λ ex = 338 nm). Furthemore, density functional theory (DFT) calculations were carried out on the excited electronic states of 1 , 2 and 3 in order to further investigate the emission mechanism. Meanwhile, variable-temperature magnetic susceptibilities of 2 and 3 indicated that there existed weak antiferromagnetic interactions between Mn (II) ions.