Influence of pseudo-polymorphism on the structure and thermal behavior of the new barium β-diketonate complexes [Ba(adtfa)2(18-crown-6)] and [Ba(adtfa)2(18-crown-6)](CDCl3)2

Abstract

The new barium β-diketonate complexes with 18-crown-6 [Ba(adtfa)2(18-crown-6)] (1) and [Ba(adtfa)2(18-crown-6)](CDCl3)2 (2) (adtfa = 1,1,1-trifluoro-4-(1-adamantyl)-2,4-butanedionato, 18-crown-6 = 1,4,7,10,13,16-hexaoxacycloocta-decane) were synthesized and characterized by elemental analysis, IR-, 1H NMR-spectroscopy and X-ray diffraction analysis. The mutual arrangement of the β-diketonate ligands relative to the barium atoms in 1 and 2 was found to be different. The nature of chemical interactions and charges distribution in 1 and 2 was investigated using an experimental-theoretical approach based on crystal (asymmetric unit–cell aspherical scattering factor) and molecular (whole–molecule aspherical scattering factor) invarioms within the framework of Bader theory. It was shown that the less favorable conformation of complex 2 is stabilized in the crystal by the higher energy of intermolecular interactions as compared to 1. The energy of intermolecular interactions (94.3 kJ/mol) in 1 was estimated by electron density topological analysis and agrees well with the experimentally obtained sublimation enthalpy (83.2 ± 1.1 kJ/mol).