Pro-aromaticity in the ۱,۱-Dithiol Systems as a Driver of Red-Shift in UV-visible Spectra of Pyrazolone-۱,۳-Dithiol Hybrids

Aromaticity, a cornerstone in understanding the stability and chemical behavior of л-conjugated systems, is thoroughly investigated in this study to uncover its pivotal role in pyrazolone-based hybrid compounds. In these derivatives, an exocyclic C=C bond connects the pyrazolone moiety to the ۱,۳-dithiol (DT) ring, facilitating resonance structures that stabilize the molecular ground state. This resonance delocalizes ۶ л-electrons in each moiety, significantly enhancing their aromatic character. Furthermore, extended resonance across molecular frameworks influences both coloration and absorption properties, causing a red shift to longer wavelengths. Resonance between the C=C bond and the pyrazolone ring induces aromaticity in the ۱,۳-dithiol ring, contributing to the absorption behavior and coloration observed in these compounds. Density Functional Theory (DFT) calculations reveal bond length variations indicative of pro-aromaticity and confirm the dominance of resonance structure I. Additionally, charge density analysis and charge separation highlight the role of pro-aromaticity and its contribution to the stability and optical behavior of these hybrid systems, as validated by UV-visible spectroscopy.

کلیدواژه ها:

Conjugation ، Pro-aromaticity ، Red-Shift ، Hybrid compounds ، UV-Visible Spectra