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The Role of Axial Ligation in Nitrate Reductase: A Model Study by DFT Calculations on the Mechanism of Nitrate Reduction
Author(s) -
Pal Kuntal,
Sarkar Sabyasachi
Publication year - 2008
Publication title -
european journal of inorganic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.667
H-Index - 136
eISSN - 1099-0682
pISSN - 1434-1948
DOI - 10.1002/ejic.200800514
Subject(s) - chemistry , nitrate reductase , nitrate , reactivity (psychology) , dissociation (chemistry) , density functional theory , catalysis , solvent , computational chemistry , stereochemistry , inorganic chemistry , organic chemistry , medicine , alternative medicine , pathology
The reactivity differences of the model anionic complexes [Mo(mnt) 2 (X)(PPh 3 )] – [mnt 2– = 1,2‐dicyanoethylenedithiolate; X = SPh ( 1a ), SEt ( 1b ), Cl ( 1c ), Br ( 1b )] towards oxygen atom transfer from nitrate, which is a key step performed by nitrate reductase, has been investigated by density functional theory calculations. Unlike complexes 1a and 1b , complexes 1c and 1d do not react with nitrate. Thermodynamically, all these complexes have a similar ability to generate the pentacoordinate active state [Mo(mnt) 2 (X)] – by dissociation of PPh 3 , although the inaccessibility of the d xy orbital in 1c , d and the instability of the corresponding nitrate‐bound enzyme substrate (ES) type complex contributes to their failure to reduce nitrate. The nature of the ES complex for 1a , b is described. The variation in the experimental data due to the change of axial ligation from SPh to SEt on the catalytic pathway has also been addressed. The gas‐phase and solvent‐corrected potential energy surface for the reaction of 1a , b with nitrate are established with fully optimized minima and transition states.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)