ISSN : 0970 - 020X, ONLINE ISSN : 2231-5039
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Abstract

Predicting ESR Peaks in the 4d and 5d Transition Metal Ion Complexes by NMR, ESR and NQR Parameters: A DFT Study

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

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


Abstract:

Computational chemistry was used to predict the number of ESR peaks in the 2nd and 3rd 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 Aten) of their complexes. Therefore, theoretical predictions were useful. ESR (Aten) 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 (Aten, 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.

Keywords:

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

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