Structural Analysis of Powder Tris(phenanthroline) nickel(II) Trifluoroacetate

Abstract

The powder complex of tris(phenanthroline)nickel(II) trifluoroacetate has been synthesized by interaction of the corresponding nitrate salt in an aqueous solution and slightly excess of 1,10-phenanthroline in water/ethanol, whereupon the precipitate was produced on addition of an excess of saturated sodium trifluoroacetate solution while reducing the solvent. AAS measurement showed the content of metal to be 6.43 % being relatively close to the corresponding theoretical value of 6.60 % masss in [Ni(phen)3](CF3COO)2.3.5H2O. Moreover, the TGA confirmed the lost of 6.943% mass of complex corresponding to 3.43 H2O. The analysis of conductance producing the charge ratio of cation by anion to be 2:1, clearly fonfirms the formula. The magnetic moment, meff, of this complex which was to be 3.19-3.31 BM, indicates that the complex is paramagnetic corresponding to two unpaired electrons which is clearly higher than the spin only value (2.87 BM) due to the spin-orbit coupling. UV-Vis spectrum of the complex revealed the first two main ligand field bands observed at about 12700 and 19250 cm-1, which are associated with the spin-allowed transition, 3A2g ® 3T2g and 3A2g ® 3T1g(F), respectively. The expected third band at higher energy was not well resolved due to the masked strong intensity of charge transfer band. The infrared spectrum shows absorptions of functional group of ligand which is influenced by the metal-ligand interaction in this complex. The powder XRD analysis of this complex was refined using Rietica-Le Bail method (within cycle number of 75) and found to be fit as monoclinic crystal system with space group of P21/M, and cell parameters of a = 12.8182 , b = 30.8076 , c = 16.7725 , a = 90°, b = 88.7349°, g = 90°, V = 6621.8145 3, Z=4, with figure of merit: Rp = 1.7, Rwp = 4.08 and Rexp = 0.32. The goodness of the fitting (GOF = 167.4) was also reflected by the derived Bragg R-Factor of 0.06.