Structural, spectroscopic, thermal, electrical and mechanical properties of lanthanum chloride coordinated with salicylic acid and lanthanum chloride coordinated with glycine and salicylic acid complexes

Abstract

Lanthanum chloride coordinated with salicylic acid (LaS) and lanthanum chloride coordinated with glycine and salicylic acid (LaGS) have been grown by slow evaporation technique at room temperature. The coordination and modes of vibration of different molecular group in the complexes are confirmed by Fourier transform infrared spectroscopy. Scanning electron microscopy (SEM) revealed the impact of glycine on the morphology of LaS complex. Absorbance spectrums are recorded, and the absence of absorbance peaks in the visible region suggests the potential of both the complexes to be used in second-harmonic generations. Optical parameters like band gap and extinction coefficient are determined. With the incorporation of glycine in LaS, the value of extinction coefficient decreases with an increase in energy. Photoluminescence spectroscopy shows a broad emission band with Gaussian-like curve shape for both the complexes. The highest peaks for LaS and LaGS lie in violet emission in the visible region; hence, such complexes find their applications for violet LED devices. The thermal stability and thermal decomposition of the complexes have been analyzed by thermogravimetric/differential thermo-analytical (TG/DTA). Kinetic and thermodynamic parameters such as activation energy, frequency factor, entropy and order of reaction were calculated using three equations, viz. Horowitz–Metzger, Coats–Redfern and Piloyan–Novikova. Dielectric constant decreases with the increase in temperature as well as frequency. Vickers hardness test revealed that hardness increases with the increase in load for both crystals, thereby representing reverse ISE effect. Meyer’s index (n) is found to be greater than ‘2’ and hence both the grown complexes belong to soft material category.