Effects of substituents and charge on the RCHOa <-X-Y {X = Cl, Br, I; Y = -CF3, -CF2H, -CFH2, -CN, -CCH, -CCCN; R = -OH, -OCH3, -NH2, -O-} halogen-bonded complexes

摘要

Noncovalent interactions involving halogen bonding interactions, one of the emerging interactions due to its directionality, have been a subject of interest for various researchers, owing to its role played in construction of supramolecular structures and crystal engineering. In this article, the RCHOa <-X-Y {X = Cl, Br, I; Y = -CF3, -CF2H, -CFH2, -CN, -CCH, -CCCN; R = -OH, -OCH3, -NH2, -O-} halogen-bonded complexes have been investigated with aid of quantum chemical calculations at MP2/aug-cc-pVDZ(-PP) level. The geometrical, spectroscopic and energetic properties have been analyzed for these complexes with QTAIM, MEP and NBO analyses. For same RCHO molecule, the interaction energies increase in the order of Oa <-Cl < Oa <-Br < Oa <-I and for the same X-Y; the trend is (HO)CHO < (CH3O)CHO < (H2N)CHO. The present article also compares the neutral complexes involving (HO)CHO, (CH3O)CHO and (H2N)CHO carbonyl molecules with those of charged carbonyl species HCOO-. It has been found that strength of the latter complexes is highest among all of the four. The role of substituents in the complex formation has been analyzed on the basis of results obtained from MEP, QTAIM and NBO studies.