Structural and energetics of weak non-covalent interactions in two chemically distinct classes of O/N-heterocycles: X-ray and theoretical exploration

Abstract

Two different classes of compounds namely xanthenedione and acridinedione derivatives have been synthesized and crystal structures of these compounds (9-(p-tolyl)-3,4,5,6,7,9-hexahydro-1H-xanthene-1,8(2H)-dione, C20H20O3, 1 and 9-(p-tolyl)-3,4,6,7,9,10-hexahydroacridine-1,8(2H,5H)-dione, C20H21NO2, 2) are reported. The X-ray analysis reveals that the central heterocyclic ring exhibits boat conformation and the cyclohexene rings have envelope conformations in both structures. The Hirshfeld surface analysis suggests that the relative contribution of H···H, H···O and H···C contacts have not changed due to the positional isomers (ortho and para) of 1. The same is true when NH group replaces the O atom in the central ring as well. The PIXEL energy analysis suggests that the intermolecular C–H···O and C–H···C(π) interactions stabilize the crystal structure of 1. In 2, the intermolecular N–H···O, C–H···O and C–H···C(π) interactions existing in different dimers. The isostructurality analysis indicates that the structure 1 shares 2D isostructurality with one of its closely related structure, whereas structure 2 shares only 0D isostructurality with its closely related structure. The lattice energy calculation for 1 and its ortho isomer and compound 2 is reported. The energy frameworks analysis was performed in order to visualize the topology of the energy frameworks for these crystals. The topological analysis is presented for intermolecular interactions existing in 1 and 2. The frontier molecular orbital analysis suggests that the HOMO orbital's localization shows distinct features for 1 and 2.