Infrared study and phase transformation of the new lithium–diphenyl carbazide complex (LiDPC)

Abstract

A complete IR investigation (400–4000cm−1) of orthorhombic, amorphous DPC and crystalline LiDPC (at room temperature and 80°C) is performed and new results are reported. Introducing lithium ions into diphenyl carbazide C13H14N4O forms a completely new complex associated with new properties. The IR spectroscopic analysis includes measurements and interpretation of the IR spectral band shape, intensities, and frequencies of the internal modes of vibrations.The principle modes of vibrations of amorphous DPC found to be 3445cm−1, 3292cm−1, 3052cm−1, 1670cm−1, 1602cm−1, 1495cm−1, 1305cm−1, 1254cm−1, 974cm−1, and 577cm−1 correspond to normal vibrations of NH, CH, NN, CO and monosubstituted benzene. A marked change could be recorded for these modes of vibrations in the presence of Li+ ions. The results strongly confirm the formation of a metal–organic complex. Anomalous spectroscopic changes could be recorded in LiDPC spectra. A proposed Li+ position in LiDPC complex is proposed. X-ray diffraction analysis is used to find out the crystal structure and parameters of LiDPC complex. The results obtained show triclinic crystal structure with a=5.6929Å, b=7.6378Å, c=17.8739Å, α=119.176°, β=63.322°, γ=85.378°. The results reveal the presence of an order–disorder phase transition in LiDPC complex at 60°C. The transformation process is monitored by clear variations in the spectral shape, band intensities and new eight different modes appeared in the high temperature disordered phase. An energy model is suggested for the interpretation of such phase transition process.