Methoxy-substituted phenylacrylonitrile bearing an m-CF3 group: crystal structure and solvent-dependent excitonic-thermodynamic behavior

The structural, electronic, and optical properties of the D-pi-A chromophore 3-(4-methoxyphenyl)-2-(3-(trifluoromethyl)phenyl)acrylonitrile (MTFMAN) were comprehensively investigated using a multiscale approach combining single crystal X-ray diffraction, UV-Vis spectroscopy, and Density Functional Theory (DFT), including Time-Dependent DFT (TD-DFT) and explicit solvent cluster modeling. X-ray analysis confirmed that the compound crystallizes in a monoclinic system (space group P2(1)/n) with a unit cell volume of 1520.4(4) & Aring;(3), stabilized by dominant non-covalent interactions, specifically pipi stacking and C-HF interactions. Optical measurements demonstrated significant solvatochromism; as solvent polarity increased from acetone to DMSO, the absorption maximum shifted from 339 to 344 nm, and the experimental optical band gap decreased from 3.116 to 3.062 eV. TD-DFT calculations confirmed that the dominant Intramolecular Charge Transfer (ICT) is stabilized by the polar DMSO environment. Explicit solvent cluster modeling validated these effects, by identifying a stable C - H & ctdot;O = S interaction with a stabilization energy of -35.58 kJ/mol. Furthermore, thermodynamic properties (heat capacity, entropy, and enthalpy) were evaluated over a wide temperature range of 100-1000 K, with all data accurately fitting second-order polynomial models (R-2 > 0.999). These quantitative results highlight the tunability and thermal stability of MTFMAN for solution-processed optoelectronic applications.