Structural characterization, spectroscopic properties and phase transition in 4-aminopyridinium tetrachlorogallate(III): [4-NH22PyH][GaCl44]

Crystal structures of [4-NH2C5H4NH][GaCl4] ([4-NH2PyH][GaCl4]) have been determined at 80 and 120 K by single crystal X-ray diffraction (trigonal space groups R3R3 and R3mR3m, respectively). DSC studies indicate a presence of one reversible phase transition close to the second order at 110 K with ΔS≈1Jmol-1K-1. Infrared spectra of polycrystalline [4-NH2PyH][GaCl4] have been studied in the temperature range between 10 and 300 K. Substantial changes in the temperature evolution of internal modes of the 4-aminopyridinium cations are due to the freezing of the 4-aminopyridinium cations below 110 K. Dielectric investigations reveal three independent, well separated relaxation processes in temperature range between 90 and 300 K. Parameters of the relaxation processes have been estimated.