LASER RAMAN AND IR SPECTRA OF COMPLEXES OF LANTHANIDE (III) WITH 5- AMINOURACIL V K Rastogi , M A Palafox 1 , Virendra Kumar 2 , H.P Mital 2 and Rekha Sharma 2* Department of Physics, CCS University, Meerut, 250 004, India. 1 Departamento de Quimica-Fisica(Espectroscopia I),Facultad de Ciencias Quimicas , Universidad Complutense, Madrid-280 040 ,Spain 2* Department of Physics, Meerut College, Meerut, India, 250 001. Keywords: Raman spectra, ir spectra, lanthanide complexes Abstract: Lanthanide (III ) ion complexes with organic ligands can be used as luminescent materials and luminescent labels in fluoroimmunoassays due to their unique luminescence properties such as long luminescence decay time and narrow emission bands [1,2]. Recently, FTIR and FT Raman studies of the series of six coordinated complexes of LnCl 3 (PyNO) 3 , where Ln = Pr, Nd, Sm, Eu, Gd, Dy and PyNO = 3-Br-4-CH 3 OC 7 H 7 NO) have been reported [2]. In the present work, we describe the IR and Raman spectra of complexes of Ln +3 (Ln = Pr, Nd, Sm, Gd, and Dy) with 5- aminouracil (5-AU). The complex was synthesised by the method given in literature [3]. FTIR and Raman spectra of the ligand (5-AU) and complexes in solid phase have been recorded by KBr pellet technique on Perkin-Elmer Model 1710 in the region 400-4000 cm -1 and Jasco K-500 Raman spectrophotometer in the region 50-4000 cm -1 respectively. The other experimental details are given elsewhere [3]. The complexes formed possess 1:3 stoichiometry and the chemical analyses correspond to the molecular formula [Ln(C 4 H 5 N 3 O 2 ) 3 ]Cl 3 . The complexes are insoluble in common organic solvents and do not melt upto 330 ° C. The vibrational spectra of 5-AU have been analysed by assuming planar geometry and C s point group symmetry and the assignments of fundamental frequencies are made on the basis of magnitude and relative intensities of the observed bands and help has been taken from the assignments made by the earlier workers in the similar molecules [3], and as well theoretically predicted spectra of 5-AU [4]. In the case of 5-aminouracil, Rastogi and Palafox [4] have assigned the bands at 3398 cm -1 (scaled value) to asymmetric and symmetric stretching modes of NH 2 group respectively.In the region 3700-3300 cm -1 , as we observe only two bands ,therefore, the higher wavenumber band which is strong in IR spectrum (3370 cm -1 ) and weak in Raman spectrum (3380 cm -1 ) has been assigned to asymmetric stretch amino group vibration.The symmetric stretch amino mode has been identified at 3300 cm -1 in conformationm with the assignment proposed by other workers in the case of related molecules . In the case of 5-AU , Rastogi and Palafox [4] have shown that the scaled value 1586 cm -1 at B3LYP/ 6-311++G(2d,p) level corresponds to this mode. Therefore, we assign the band at 1588 cm - 1 to NH 2 scissoring mode. The rocking mode , ρ(NH 2 ) was computed at 1098 cm -1 (scaled value 1082 cm -1 ) in the case of 5- aminouracil [4] . Therefore, in conformity with this, the IR band observed at 1108 cm -1 has been identified as ρ(NH 2 ) mode. In the case of 5-AU ,wagging NH 2 mode is calculated at 705 cm -1 by B3LYP/ 6-311++ G(2d,p) level . However , in this range was not observed experimental band , and the nearest one appears at 749 cm -1 , therefore , we correlate the band with NH 2 wagging mode . 150