Photoacoustic detection of d-d transitions and electronic structure of three polyamine copper complexes

The potential of photoacoustic spectroscopy to resolve the crystal field levels of Cu2+ ions in three polyamine copper complexes, aqua spermine copper sulfate trihydrate [NH2(CH2)(3)NH(CH2)(4)NH(CH2)(3)NH2. Cu2+.H2O]. SO42-. 3H(2)O, norspermine copper sulfate trihydrate [NH2(CH2)(3)NH(CH2)(3)NH(CH2)(3)NH2. Cu2+. SO42-]. 3H(2)O, and homospermine copper sulfate dihydrate [NH2(CH2)(3)NH(CH2)(2)NH(CH2)(3)NH2. Cu2+. SO42-]. 2H(2)O, has been explored along with UV/VIS and electron paramagnetic resonance (EPR) spectroscopy. Intense absorption is detected in the photoacoustic spectrum corresponding to the d-d transition band weakly traced in the corresponding optical spectrum. The observed fine structure photoacoustic lines are assigned to the individual d-d transitions of Cu2+ ions, which are further exploited to determine the diverse metal-ligand interaction of the studied compound employing simple crystal field analysis.