Energetics of tetradentate N2O2 Schiff bases containing different alkyldiimine brigdes

Abstract This work is part of a comprehensive study of the thermal properties of several molecules of tetradentate Schiff bases, obtained as condensation products of salicylaldehyde with alkyldiamines. Herein, we report an experimental thermochemical study of SALPN (N,N´-bis(salicylaldehydo)propylenediimine) and a computational thermochemical study of SALEN (N,N´-bis(salicylaldehydo)dimethylenediimine), SALPN and SALBUTEN (N,N´-bis(salicylaldehydo)tetramethylenediimine) ligands. The standard (p° =0.1 MPa) molar enthalpy of formation of crystalline SALPN, at T = 298.15 K, was determined using the static-bomb calorimetry technique. Also, the enthalpy of fusion of this ligand has been determined by differential scanning calorimetry. Additionally, using quantum chemical calculations at the CCSD(T) level of theory, we have calculated the gas-phase standard molar enthalpies of formation of three Schiff base ligands, SALEN, SALPN and SALBUTEN. Moreover, a computational study of the molecular structures of the ligands has been carried out.