Investigations on the Rare Earth Terpyridyl System

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Abstract
Rare earth-mono-terpyridyl complexes of the type M (Terp) Cl3 · n H2O (M = Ce- Gd, Terp = terpyridyl and n = 1- 2.5) have been prepared and their ultraviolet, visible and infrared spectra have been investigated. Probable assignments of the excited levels of the tripositive rare earths to the observed bands are given. The f → f transitions of the rare earths show red shift in the methanolic solution of the chelates with respect to the aquo ions. Definite indications of 4f → 5d transition of the Ce (III) and electron transfer band from the highest filled M.O. of the ligand to the partly filled 4f shell of Eu (III) and possibility of the same in case of Pr (III), Nd (III) and Sm(III) have been obtained. The infrared studies of the solid chelates strongly suggest the coordinated nature of the terpyridyl molecule. Some infrared bands of the chelates show shift towards higher wavenumber and lowering of intensities compared to the free ligand. Of particular interest is the pyridine ring breathing vibration of terpyridyl at 988 cm-1 which shows a shift of ~ 25 cm-1 in the chelates. The out-of-plane inphase C -H deformation band at 830 cm-1 of terpyridyl shows considerable decrease of intensity in the chelates.

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