⁵¹V NMR, ¹⁷O NMR, and UV-Vis computational studies of new VBPO functional models: Bromide oxidation reaction

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• 作者：Mohammad Chahkandi ; ^{m.chahkandi@hsu.ac.ir" class="auth_mail" title="E-mail the corresponding author} ; ^{chahkandimohammad@gmail.com" class="auth_mail" title="E-mail the corresponding author}
• 关键词：VBPO ; 51V NMR ; 17O-NMR ; LMCT ; Tripodal amine ligand
• 刊名：Polyhedron
• 出版年：2016
• 出版时间：18 April 2016
• 年：2016
• 卷：109
• 期：Complete
• 页码：92-98
• 全文大小：1449 K

文摘

Vanadium oxo-peroxo complexes are known as the best functional models of vanadium haloperoxidases (VHPOs) enzymes. Their quantity and quality structure activity and property relationship can be followed up by NMR calculations. The DFT/B3LYP/6-311+G (d,p)/LANL2DZ method has been used to calculate the geometry and electronic structures and ⁵¹V and ¹⁷O NMR chemical shifts of a series of 7 oxo-peroxo vanadium (V) complexes mimicking the active site of vanadium bromoperoxidase (VBPO) in the gas and solvent (acetonitrile) phases. They contain tetradentate tripodal amine ligands (TPALs). Compilation of NMR, electronic, and vibrational spectroscopic data and metric parameters for the studied complexes permits us to draw correlations among ⁵¹V and ¹⁷O peroxo chemical shift, the electronic charge transfer band, the O–O vibrational frequency, and the O–O bond length. A direct dependence of the magnetic shielding of the vanadium center and peroxide group on the electronic character of the ligand was observed in all cases. Studied complexes exhibit ⁵¹V and ¹⁷O NMR chemical shifts of −590 to −430 ppm and 650–740 ppm, respectively. A Ramsey-type correlation between the chemical shifts and the energy of the ligand-to-metal charge transfer (LMCT) was found that suggests the electron donating ability of the ligands and the energy gap HOMO–LUMO of the peroxo complexes are linearly correlated. Vibrational frequency and length of the O–O bond also correlate with the inverse LMCT energy. The calculated values of ν_O–O place above 900 cm⁻¹ and O–O distances in the range of 1.40–1.42 Å. In general, the more reactive complexes within bromide oxidation contain weakly electron donating TPALs and represent higher energy LMCT, longer O–O length, and lesser ⁵¹V and ¹⁷O chemical shifts.