Yang, YT (reprint author), Nanjing Univ, Inst Acoust, Minist Educ, Key Lab Modern Acoust, Nanjing 210093, Peoples R China.
Metallomesogens Ln(bta)(3)L(2) (Ln(3+): La(3+), Eu(3+), and Ho(3+); bta: benzoyltrifluoroacetonate; L: Schiff base) were prepared. Photoacoustic (PA) spectroscopy was used to study physicochemical properties of the liquid crystalline metal complexes. In the region of ligand absorption, PA intensity increases for Eu(bta)(3)L(2), La(bta)(3)L(2), and Ho(bta)(3)L(2), in that order. It is found that the PA intensity of the ligand bears a relation to the intramolecular energy transfer process. For the first time, phase transitions of Eu(bta)(3)L(2) from glass state to smectic A (SmA) phase and SmA phase to isotropic liquid are monitored by PA and fluorescence (FL) spectroscopy from two aspects: nonradiative and radiative transitions. The results show that PA technique may serve as a new tool for investigating the spectral properties and phase transitions of liquid crystals containing metal ions.