Diverse structural assemblies of a series of ninhydrin derivatives: Quantitative analyses from experimental and theoretical studies

Three ninhydrin derivatives (2 -4) have been synthesized where the reaction of ninhydrin with Meldrum's acid yielded [3.3.3] propellanoid (2) and ethyl 2,2-bis (1,3-dioxo-2,3-dihydro-1H-inden-2-yl)acetate (3) while with malononitrile yielded a spiroindenopyran (4). The products being crystalline in nature and are characterized by single crystal X-ray diffraction in addition to other spectroscopic studies. X-ray crystallography reveals that solid-state structure of the title compounds exhibits C-H ... pi, pi-pi and lone-pair(l.p) ... pi interactions in building supramolecular assemblies. Indeed, compound (2) was stabilized through extended supramolecular C-H ... pi/pi-pi/pi ... H-C network whereas compounds (3) and (4) are stabilized through lone-pair (l.p) ... pi and pi-pi interaction respectively. The diverse intermolecular interactions via Hirshfeld surface analysis enables quantitative contributions to the crystal packing that exposes the similarities and differences in the interactions experienced by each compound. The distinctive energy frameworks have been calculated for individual molecules and the interaction energies suggest that the contacts are largely dispersive in nature. The binding energies associated with the non-covalent interactions observed in the crystal structures have been calculated using theoretical DFT calculations. Finally, the interplay between the interactions have been characterized by Bader's theory of atoms-in-molecules (AIM). (c) 2020 Published by Elsevier B.V.

Automated summary

Three ninhydrin derivatives (2-4) were synthesized and characterized by single crystal X-ray diffraction. The solid-state structures of these compounds show various intermolecular interactions, including C-H ... π, π-π, and lone-pair ... π interactions. The analysis through Hirshfeld surface reveals both similarities and differences in these interactions among the compounds.