Theoretical investigation of para amino‐dichloro chalcone isomers, part I: A DFT structure—stability study

Abstract

AbstractChalcones are versatile compounds with various biological activities and nonlinear optical applications. This study investigated the trans and cis isomers of 3‐(x,y‐dichlorophenyl)‐1‐(4′‐NH2‐phenyl)‐2‐propen‐1‐one, where (x) and (y) represent the positions of the two chlorine atoms [(2,3), (2,4), (2,5), (2,6), (3,4) and (3,5)] and their cyclic chromene isomers. The B3LYP density functional theory (DFT) method was used, with a 6‐311G (d,p) basis set. Calculations revealed that trans chalcones prefer s‐cis conformations. The syn conformation, in which chlorine atoms at carbon (2) or (3) is parallel to the carbonyl group, was more stable than the anti‐syn in trans chalcones. However, in cis chalcones, the opposite result was obtained. In contrast, (3,4) chalcones behaved in the opposite manner, for both trans and cis isomers. This order of conformation stability did not change when dispersion correction (DC) was incorporated in the calculations. Geometry optimisation with DC revealed that the trans (3,5) chalcone is the most stable, and the cis (2,3) chalcone is the least stable isomer in both chalcone series. However, (2,6) chromene was the most stable in chromene series isomers and the (3,4) chromene as the least stable. Calculated heat of hydrogenations for cis and trans isomers revealed that trans and cis (3,4) chalcones are the most stable in each series. However, trans and cis (2,6) chalcones are the least stable in each series. The stability of the three isomers, with and without DC, was determined as the following order: trans > cis > chromene.