A detail investigation of synergistic effects between the intramolecular hydrogen bond and π-electron delocalization in 3-hydroxy prop-2-en thial and its derivatives

Abstract

In the present work, a detailed investigation of synergistic effects between the intramolecular hydrogen bond (IMHB) and π-electron delocalization (π-ED) of 3-hydroxy prop-2-en thial (HPT) and its halogenated derivatives was performed. For this purpose, at first, the π-ED in the enol form of the benchmark systems by various aromaticity indices such as λ, λ, HOMA, NICS, PDI, ATI, and FLUπ were evaluated. On the other hand, the strength of IMHB by various descriptors such as energetical, geometrical, spectral, topological, and molecular orbital parameters was also estimated. For better understanding the nature of the synergistic phenomenon, we examined and compared the linear relationships between the π-ED indices with the HB descriptors. Our results show that the geometrical indicators have the best linear relationships with all of the mentioned HB parameters. Also, according to their absolute linear correlation coefficients, the following order is concluded: λ > λ > HOMA > FLUπ > ATI > NICS (1) > PDI > NICS (0)Finally, the synergistic effect between the π-ED and IMHB from the position and nature point of views is discussed. These results clearly show that the synergistic effect of R1 derivatives is negative, while the corresponding effects of R2 and R3 ones are positive. Moreover, the synergetic effects also depend on the nature of substitutions especially their electronegativity values (F > Br > Cl).