Chromium(III) Complexes with Different Chromospheres Macrocyclic Ligands: Synthesis and Spectroscopic Studies

Authors: RAJIV KUMAR, RAJEEV SINGH

Abstract: Symmetric tetradentate (L^1) and asymmetric pentadentate (L^2) macrocyclic ligands that possess 2 dissimilar coordination sites were prepared. One has a 4-coordinate (N_4) and the other has a 5-coordinate (N_2O_3S) donor set. Trivalent Cr(III) complexes were synthesized with L^1 and L^2 and their structures were investigated using elemental analyses and magnetic moment, electronic, IR, ^1H NMR, ^{13}C NMR and EPR spectra. All the Cr(III) complexes show magnetic moments corresponding to a high-spin configuration. \Delta values indicate the energy difference between the principle bands, which are formed due to ligand field absorption. The spin-orbit coupling parameter, z, gives no significance because the splitting of doublet transition lines is too large to be explained by spin-orbit coupling. \lambda values indicate that the complexes under study have a substantial covalent character. g-values were also calculated using the spin-orbital coupling constant, \lambda.

Keywords: Macrocyclic ligands, ^1H NMR, ^{13}C NMR, IR, EPR, Cr(III) complexes

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