Photoacoustic spectrum of a new, 12-fold-coordinated Ho(III) hydrazone complex

A new, 12-fold-coordinated holmium(III) compound [Ho(NO3)3(PBH)2]NO3 · 1.5H2O has been prepared and studied with high-resolution photoacoustic spectrometry (PAS). The spectroscopic parameters of the obtained photoacoustic lines attributed to the f–f transitions were analyzed and compared with the parameters for a similar 10-fold-coordinated holmium(III) complex [Ho(NO3)2(PicBH)2]. Computer fitting of the obtained spectra allowed decomposing them into Gaussian components and calculating the spectral parameters of each transition. It was found that of the five observed f–f transitions, the 5I8 → 5G6 and the 5I8 → 5G3 transitions were found to be the most sensitive to the change of ligand coordination. The charge transfer π → π∗ and n → π∗ transitions registered in the UV part of the photoacoustic spectrum showed a significant variation due to the change in the coordination number and the shift of ligands toward greater wavenumbers.