Investigation of structural and conformational stability, electronic transition, NLO, FMO, and DSSC parameters of trans-dichloro-nitro chalcone isomers: a DFT insight

The density functional theory (DFT) with Becke’s three-parameter Lee–Yang–Parr (B3LYP) hybrid functional and the 6-311G(d,p) basis set was utilized to investigate the structural and conformational stability, the energies of the highest occupied molecular orbital (HOMO), and lowest unoccupied molecular orbital (LUMO), as well as related reactivity parameters, electrostatic potential, electronic transitions, nonlinear optical (NLO) properties, and dye-sensitized solar cell (DSSC) characteristics of six isomers of (E)-3-(i,j-dichlorophenyl)-1-(4′-nitrophenyl)prop-2-en-1-one, where i, j = 2–6 and i ≠ j. The s-cis conformers are more stable than the s-trans conformers. The syn conformers are more stable for five of the isomers than their anti-syn counterparts. The (3,5) isomer was the most stable among the isomers. All isomers demonstrated the ability to inject and recover electrons. The (2,5) isomer exhibited the highest exciton binding energy, while the (3,4) isomer showed the lowest dye regeneration driving force. The highest open-circuit voltage was observed for the (2,6) and (2,3) isomers. The (3,4) isomer had the highest light-harvesting efficiency, whereas the (2,5) isomer had the lowest. All chalcones exhibit higher first-order hyperpolarizability β values than urea, with the anti-(3,4) isomer having the highest β and the smallest (HOMO–LUMO) energy gap. TD-DFT (B3LYP/6-311G(d,p)) in the gas phase reveals that the chalcones display two UV bands. Band 1 arises from the electronic transition between the HOMO and LUMO. However, band 2 consists of electron excitation from HOMO and HOMO-2 to LUMO + 1. The chalcones investigated show promise as candidates for NLO and DSSC applications.

Graphical abstract