The stable and efficient photochromic and photoswitchable molecular systems designed from spirooxazines are of increasing scientific and practical interest because of their present and future applications in advanced technologies. Among these compounds, chelating spironaphthoxazines have received widespread attention due to their efficient optical response after complexation with some metal ions being of biomedical interest and environmental importance, as well as their good cycle performance and high reliability, especially by metal ion sensing. In this mini-review, we summarize our results in the design of novel photoswitchable chelating spironaphthoxazines with specific substituents in their naphthoxazine or indoline ring systems in view of recent progress in the development of such molecular systems and their applications as metal ion sensors. The design, synthesis methods, and photoresponse of such spirooxazine derivatives relevant to their applications, as well as quantum-chemical calculations for these compounds, are presented. Examples of various design concepts are discussed, such as sulfobutyl, hydroxyl, benzothiazolyl, or ester and carboxylic acid as substituents in the chelating spironaphthoxazine molecules. Further developments and improvements of this interesting and promising kind of molecular photoswitches are outlined.

This research focuses on the merocyanine form of a new synthesized spiroindolinonaphthoxazine compound. The merocyanine molecule (abbreviated as MC) 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 Molecular Dynamics simulations, providing insights into how they orient and interact with each other and with solvent molecules. The molecular packing of MC in presence and in absence 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.

An economically benign solvent-free approach to synthesise 2,3-dimethylbenzoxazolium methosulfate is reported in the present work. The title compound is derived from 2-methylbenzoxazole reacting with a slight excess of dimethylsulfate, at room temperature. The reaction proceeds via an intrinsic exothermic reaction, and the benzoxazolium salt crystallized after a short time into a white crystalline form. The product was filtered off and washed with acetone and diethyl ether to provide the desired product in 89% yield. The target compound was evaluated by ESI/MS analysis.

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.