Interdisciplinary Studies on Applied Science

Research Article

Theoretical Study of Thermochromic Behavior in Donor–Acceptor Organic Molecules Based on 2, 5-Diphenylthiophene for Smart Color-Changing Materials

  • By Farked Wahoody Salman, Jawad Kadhim Alshams, Nisreen Qasim Shaker, Ihsan Alrubaie, Ali Jabbar Radhi - 29 Aug 2025
  • Interdisciplinary Studies on Applied Science, Volume: 2(2025), Issue: 1(August), Pages: 34 - 43
  • https://doi.org/10.58613/isas216
  • Received: 15.07.2025; Accepted: 20.08.2025; Published: 29.08.2025

Abstract

This study carries out an in-depth quantum chemical study of eight new donor–acceptor organic molecules (D1–D8) to check their  hermochromic behavior and possibility to integrate in smart color-changing materials. Done with Density Functional Theory and Time Dependent DFT at the B3LYP/6-311++G(d,p) level, the electronic structure, optical absorption, and t hemodynamic properties were systematically analyzed at three temperatures: 298 K, 323 K, and 348 K. Compounds D3, D6, and D7 showed the best coloration results; the λmax values were found to shift by +17 nm, +20 nm, and +12 nm, respectively, from 298 K to 348 K. Some substantial reductions in the HOMO–LUMO gaps were observed for these molecules as well, like that for D6, from 2.86 eV to 2.68 eV, indicating a strong temperature-dependent intramolecular charge transfer process. The dipole moments were found to reach as high as 6.18 D in the most polar structure D6, showing increased polarity and deformity necessary for optical activity; however, for planar systems such as D1 and D4, the spectral shifts were minimal (<5 nm), so they would have little potential as thermochromics. Thermodynamic analyses confirmed structural stability for all compounds, with no imaginary frequencies and Gibbs free energies remaining favorable at all temperatures. An electronic flexible nature combined with thermal robustness makes D3, D6, and D7 likely contenders for applications in temperature-sensitive coatings, sensors, and adaptive display technologies. This work shows how molecular design, together with theoretical screening, may hasten the finding of efficient thermochromic materials.