Comprehensive comparisons of crystal structure, Hirshfeld surface and thermochemical properties of two succinic acid metal complexes [LiC2H2O2]2(s) and [NaC2H2O2·3H2O]2(s)

Abstract

In this work, two aqueous and nonaqueous metal complexes of succinic acid were synthesized, namely Li-succinate (CCDC: 2284044) and hexahydrate Na-succinate (CCDC: 2296979). Their crystal structures were determined by single crystal X-ray crystallography. The Li-succinate crystallizes in trigonal space group R3¯ and the hexahydrate Na-succinate in triclinic P1¯. The Hirshfeld surfaces and the corresponding 2D fingerprints of the two complexes were recorded, showing that the nature of the intermolecular interactions between Li-succinate are mainly coordination bonds and that the intermolecular interactions between hexahydrate Na-succinate are mainly intermolecular hydrogen formation. The experimental heat capacities of the two complexes in the low-temperature interval were determined using a precise automatic adiabatic calorimeter, and the polynomial equations for the variation of the heat capacities with the folding transition temperature were obtained by fitting the measured experimental heat capacities using the least squares method, on the basis of which the values of their Sulpine heat capacities at intervals of 5 K in the low temperature interval and the values of their thermodynamic functions with respect to 298.15 K were calculated. The TG/DSC curves also reveal the molecular structure of the title complexes.