title: Structural investigation of oxovanadium(IV) Schiff base complexes: X-ray crystallography, electrochemistry and kinetic of thermal decomposition.
abstract: A series of new VO(IV) complexes of tetradentate N2O2 Schiff base ligands (L(1)-L(4)), were synthesized and characterized by FT-IR, UV-vis and elemental analysis. The structure of the complex VOL(1)⋅DMF was also investigated by X-ray crystallography which revealed a vanadyl center with distorted octahedral coordination where the 2-aza and 2-oxo coordinating sites of the ligand were perpendicular to the "-yl" oxygen. The electrochemical properties of the vanadyl complexes were investigated by cyclic voltammetry. A good correlation was observed between the oxidation potentials and the electron withdrawing character of the substituents on the Schiff base ligands, showing the following trend: MeO<H<Br<Cl. We also studied the thermodynamics of formation of the complexes and kinetic aspects of their thermal decomposition. The formation constants with various substituents on the aldehyde ring follow the trend 5-OMe>5-H>5-Br>5-Cl. Furthermore, the kinetic parameters of thermal decomposition were calculated by using the Coats-Redfern equation. According to the Coats-Redfern plots the kinetics of thermal decomposition of studied complexes is of the first-order in all stages, the free energy of activation for each following stage is larger than the previous one and the complexes have good thermal stability. The preparation of VOL(1)⋅DMF yielded also another compound, one kind of vanadium oxide [VO]X, with different habitus of crystals, (platelet instead of prisma) and without L(1) ligand, consisting of a V10O28 cage, diaminium moiety and dimethylamonium as a counter ions. Because its crystal structure was also new, we reported it along with the targeted complex.
authors.affiliation: Department of Chemistry, College of Science, Shiraz University, Shiraz 71454, Iran. Electronic address: asadi@susc.ac.ir.
authors.forename: Mozaffar
authors.initials: M
authors.lastname: Asadi
authors.affiliation: Department of Chemistry, College of Science, Shiraz University, Shiraz 71454, Iran.
authors.forename: Zahra
authors.initials: Z
authors.lastname: Asadi
authors.affiliation: Department of Chemistry, College of Science, Shiraz University, Shiraz 71454, Iran.
authors.forename: Nooshin
authors.initials: N
authors.lastname: Savaripoor
authors.affiliation: Institute of Physics AS CR, v.v.i., Na Slovance 2, 182 21 Prague, Czech Republic.
authors.forename: Michal
authors.initials: M
authors.lastname: Dusek
authors.affiliation: Institute of Physics AS CR, v.v.i., Na Slovance 2, 182 21 Prague, Czech Republic; Department of Solid State Chemistry, Institute of Chemical Technology, 166 28 Prague, Czech Republic.
authors.forename: Vaclav
authors.initials: V
authors.lastname: Eigner
authors.affiliation: Department of Chemistry, College of Science, Shiraz University, Shiraz 71454, Iran.
authors.forename: Mohammad Ranjkesh
authors.initials: MR
authors.lastname: Shorkaei
authors.affiliation: Department of Chemistry, College of Science, Shiraz University, Shiraz 71454, Iran.
authors.forename: Moslem
authors.initials: M
authors.lastname: Sedaghat
mesh_terms: D018360:Crystallography, X-Ray; D004563:Electrochemistry; D007700:Kinetics; D008958:Models, Molecular; D012545:Schiff Bases / Q000737:chemistry*; D017550:Spectroscopy, Fourier Transform Infrared; D013816:Thermodynamics; D014638:Vanadates / Q000737:chemistry*
chemical_list: D012545:Schiff Bases; C075743:oxovanadium IV; D014638:Vanadates
keywords: Electrochemistry; Kinetics of thermal decomposition; Oxovanadium(IV) complexes; Schiff base