Cu(II), Co(II), and Mn(II) Complexes of Rhodamine C and Rhodamine 640 Perchlorate: Synthesis, Spectroscopic, Thermal, Fluorescence, and Photostability Studies

A goal of our work was to design and synthesize novel Mn(II), Co(II), and Cu(II) complexes with rhodamine C (RHC) and rhodamine 640 perchlorate (RHP) to obtain knowledge about the thermal stability of rhodamine itself compared with its complexes. The complexes prepared have the general formulas {[}M(L)(2)(H(2)O)(2)]center dot nH(2)O and {[}Cu(L)(2)]center dot H(2)O, where (M= Mn (II) or Co(II), L = RHC or RHP, n = 2 or 4). The complexes obtained were characterized using elemental analysis, magnetic measurements, molar conductivity, and infrared and electronic spectra as well as thermal measurements. The results suggested that all the RHC and RHP complexes had a 1:2 molar ratio (metal:L). Both RHC and RHP act as a bidentate chelating ligand through the carboxylic groups. The molar conductance measurements proved that the Mn(II), Co(II), and Cu(II) complexes of RHC and RHP are nonelectrolytes. Kinetic thermodynamic parameters such as E{*}, Delta H{*}, Delta S{*}, and Delta G{*} were calculated from differential thermogravimetric curves. The fluorescence and photostability studies were checked for both fluorescence dyes and their complexes.