title: A new Salen-type azo-azomethine ligand and its Ni(II), Cu(II) and Zn(II) complexes: Synthesis, spectral characterization, crystal structure and photoluminescence studies.
abstract: A novel Salen-type azo-azomethine ligand H2agen, 2,2'-{ethane-1,2-diylbis[nitrilomethylylidene]}bis{4-[ethylphenyldiazenyl]phenol}, formed by the 1:2M condensation of ethane-1,2-diamine with 5-[(4-ethylphenyl)diazenyl]-2-hydroxybenzaldehyde and its nickel(II), copper(II), and zinc(II) complexes were synthesized and characterized by the spectroscopic and analytical methods. The UV-vis spectra of the ligand were investigated in three organic solvents (DMSO, DMF and CHCl3). The ligand shows two absorption bands assigned to π-π(∗) and n-π(∗) transitions in the solvents used. Cu(II), and Ni(II) are tetra-coordinate binding to two phenolic oxygens and two imine nitrogens in approximate square planar geometry. Zn(II) also coordinates using the same sites like other metals but gave tetragonal configuration. Molecular structure of the Cu(II) complex [Cu(agen)] was determined by single crystal X-ray diffraction study. The X-ray data revealed that crystallographic imposed symmetry was absent for the complex molecule. In the structure, the Cu(II) ion is coordinated to two phenolate oxygen atoms and two imine nitrogen atoms of the azo-azomethine ligand with approximate square planar geometry. The ligand H2agen and its metal complexes exhibit strong blue emissions with irradiation. Fluorescence quantum yields and excited-state lifetimes for the ligand and its complexes were obtained. The H2agen ligand had a 35% quantum yield and a 3.27 ns excited-state lifetime. Complexation with metal ions caused reductions in intensities and quantum yields.
authors.affiliation: Department of Chemistry, Faculty of Science and Literature, Kahramanmaraş Sütçü İmam University, Kahramanmaraş 46050, Turkey.
authors.forename: Gozde
authors.initials: G
authors.lastname: Ozkan
authors.affiliation: Department of Chemistry, Faculty of Science and Literature, Kahramanmaraş Sütçü İmam University, Kahramanmaraş 46050, Turkey.
authors.forename: Muhammet
authors.initials: M
authors.lastname: Kose
authors.affiliation: Department of Chemistry, Faculty of Science and Literature, Gaziantep University, Gaziantep 27310, Turkey.
authors.forename: Huseyin
authors.initials: H
authors.lastname: Zengin
authors.affiliation: School of Chemical Sciences, Dublin City University, Glasnevin, Dublin 9, Ireland.
authors.forename: Vickie
authors.initials: V
authors.lastname: McKee
authors.affiliation: Department of Chemistry, Faculty of Science and Literature, Kahramanmaraş Sütçü İmam University, Kahramanmaraş 46050, Turkey. Electronic address: mkurtoglu@ksu.edu.tr.
authors.forename: Mukerrem
authors.initials: M
authors.lastname: Kurtoglu
keywords: Azo–azomethine; Photoluminescence; Solvent effect; Spectroscopy; Tetradentate; X-ray structure