en مواد اپتیکی و فرامواد Optical Materials and Metamaterials پژوهشي Research <hr><span lang="fi" style="font-size:10.0pt"><span new="" roman="" style="font-family:" times="">The development of efficient molecular solar-thermal (MOST) energy storage systems and photochromic switches requires a profound understanding of the relationship between molecular structure and electronic properties. In this study, we systematically investigated the impact of various functional groups (-NH₂, &ndash;OMe, &ndash;Cl, &ndash;CN) and solvent environments (Gas phase vs. Aqueous phase) on the Dihydroazulene/ Vinylheptafulvene (DHA/ VHF) switching cycle using Density Functional Theory (DFT) and Time-Dependent DFT (TD-DFT) at the B3LYP/6-31G(d) level of theory. The importance of our system is due to the following reasons: 1. solar energy storage in chemical formore, 2. High reversibility, 3. Light -Controlled energy management, 4. Applications in sensors and photochromic materialsm, 5.&nbsp;Tunability through molecular engineering. The quantitative conversions of the photochemical forward reaction can be followed by NBO and spectral studies. In order to determine the optimized geometries, energies, dipole moments, atomic charges, thermochemical analysis and other properties. Through their strategic selection, it is possible to optimize the performance of smart materials and energy storage systems. Electron-donating and electron-withdrawing groups are key tools in molecular engineering. Our results demonstrate that electronic modulation via the phenyl ring&#39;s para-position significantly alters the HOMO-LUMO gap, with electron-donating groups (-NH₂ and -OMe) inducing a notable bathochromic (red) shift in the absorption spectra. Conversely, the electron-withdrawing cyanide (-CN) derivative enhances the electronic stability and global hardness of the VHF form, making it a superior candidate for long-term energy storage.Transition from the gas phase to an aqueous environment was found to dramatically increase the dipole moment and decrease the energy gap, suggesting that polar media facilitate the switching process and stabilize the polarized open-chain isomers. Natural Bond Orbital (NBO) analysis further confirms the role of n&rarr;&pi;* and &pi;&rarr;&pi;* interactions in these structural transitions. Furthermore, the calculated NMR parameters (&sigma;iso and &delta;) serve as sensitive probes for identifying structural fingerprints, revealing a clear deshielding effect in the aqueous phase. In conclusion, while the -NH2 derivative is optimized for visible-light activation, the -CN derivative offers the best performance for thermal energy storage, providing a roadmap for the design of dual-purpose photoresponsive materials. </span></span> Dihydroazulene/Vinylheptafulvene (DHA/VHF), DFT/TD-DFT, Energy Storage (MOST), NMR Shielding, Solvent Effects, Substituent Effects. 255 272 http://ijop.ir/browse.php?a_code=A-10-1019-1&slc_lang=en&sid=1 Azar Bagheri azbagheri@gmail.com 10031947532846005507 10031947532846005507 Yes Department of Chemistry, CT.C., Islamic Azad University, Tehran, Iran. Malika Pejman 10031947532846005508 10031947532846005508 No Faculty of Medicine, Iran University of Medical Sciences, Tehran, Iran.