Electronic structure of polycrystalline polyamine copper dinitrate complexes investigated by photoacoustic and electron paramagnetic resonance spectroscopy

Photoacoustic and electron paramagnetic resonance (EPR) spectroscopies have been applied to resolve the electronic structure in powder polycrystalline samples of three biogenic polyamine copper complexes, spermine copper dini trate, aqua norspermine copper dinitrate, and homospermine copper dinitrate . The fine structure of the intense absorption band in the photoacoustic sp ectra is assigned to the d-d transitions between the crystal field split le vels of copper ions, that cannot be discriminated in the UV/vis solution ab sorption spectra. Combination with the EPR results allows one to probe the variation of the electronic properties and bonding interaction at the coppe r site, consistent with the structural data for the crystalline complexes a nd further supports the reliability of the photoacoustic method to resolve the d-d transition band. A dominant contribution of the in-plane ligand fie ld due to equatorial nitrogen atoms is deduced for the complexes of polyami nes with copper salts. (C) 2001 American Institute of Physics.