Abstract

M.L. Sehgal¹, Amit Aggarwal², K.N. Kaul³ and Md. Irshad Ahmad⁴

DOI : http://dx.doi.org/10.13005/ojc/330103

Computational chemistry was used to predict the number of ESR peaks in the 2^nd and 3^rd transition metal ion complexes by applying DFT implemented in ADF 2012.01.Only a limited experimental ESR research had been carried out in this field because high values of spin orbit coupling constants of these metal  ions which provide an important energy transfer mechanism would adversely affect the values of ESR and NMR parameters (especially A_ten) of their complexes. Therefore, theoretical predictions were useful. ESR (A_ten) and NQR (NQCC,η) parameters of transition metal ions and the coordinating atoms of ligands were obtained from the ESR/EPR program while their shielding constants (σ) and chemical shifts (δ) were obtained from the NMR/EPR program after optimization of the complexes. Ligands whose coordinating atoms (CA) possessed the same values of the five parameters (A_ten, NQCC, δ,η, σ) were expected to be spatially equivalent and would undergo the same hyperfine interaction with the central metal ion. 34 complexes of 10 metal ions consisting of five congeners: Zr (III), Hf (III); Nb (IV) ,Ta(IV) ; Tc (II), Re (II);  Ru (III) ,Os(III) ;Rh (IV), Ir (IV) were selected to  predict the number of ESR peaks.

Chemical Shift; Total NMR Shielding Tensor; Nuclear Quadrupole Coupling Constant; Effective Spin Hamiltonian, Asymmetric Coefficient

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