Specifics of the Molecular Conformations and Physicochemical Properties of Merocyanine Form of Spirooxazine Derivative: Insights from Experimental and Annealing-Molecular Dynamics Studies

This research focuses on the merocyanine (MC) form of a spiroindolinonaphthoxazine compound whose IUPAC signature is 4‐[(2E)‐1,1‐dimethyl‐2‐({[(1Z)‐2‐oxo‐1,2‐dihydronaphthalen‐1‐ylidene]amino}methylidene)‐1H,2H,3H‐benzo[e]indol‐3‐yl]butane‐1‐sulfonic acid. The MC molecule has multiple fragments with different degrees of mobility. The conformational changes and the flexibility of MC in presence and in absence of the solvent molecules were studied by Annealing-Molecular Dynamics (MD) cycles, providing insights into how they orient and interact with each other and with solvent molecules. The molecular packing of MC in presence and in ab-sence of solvents with different polarities was thoroughly investigated in order to determine, how the physicochemical interactions with the solvent influence the structure and stability of the MC molecule. Furthermore, the powders of MC obtained from its solutions in water, methanol, ethanol and acetonitrile were experimentally characterized using differential scanning calorimetry, thermogravimetry, Fourier transform infrared spectroscopy, and scanning electron microscopy. Both calculations and experimental results reveal the effect of the solvent polarity on the dissolved MC molecule.