Structural investigation of oxovanadium(IV) Schiff base complexes: X-ray crystallography, electrochemistry and kinetic of thermal decomposition
| Autor: | Michal Dušek, Mozaffar Asadi, Zahra Asadi, Moslem Sedaghat, Mohammad Ranjkesh Shorkaei, Nooshin Savaripoor, Václav Eigner |
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| Rok vydání: | 2015 |
| Předmět: |
Models
Molecular Schiff base Ligand Thermal decomposition Inorganic chemistry Crystal structure Crystallography X-Ray Atomic and Molecular Physics and Optics Analytical Chemistry Kinetics chemistry.chemical_compound Crystallography chemistry Spectroscopy Fourier Transform Infrared X-ray crystallography Electrochemistry Thermodynamics Moiety Thermal stability Vanadates Cyclic voltammetry Instrumentation Schiff Bases Spectroscopy |
| Zdroj: | Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy. 136:625-634 |
| ISSN: | 1386-1425 |
| DOI: | 10.1016/j.saa.2014.09.076 |
| Popis: | 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: MeOHBrCl. 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-OMe5-H5-Br5-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. |
| Databáze: | OpenAIRE |
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