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The structures of four stereomers (enantiomers) of photochromic indolinospirobenzothiopyran (ISTP) in the closed form were studied by the DFT method. The most stable structure was found. IR spectra of ISTP in KBr pellets and as a film on single-crystalline KBr plates (in the region 400–4000 cm −1 ) and as a powder between polyethylene plates (100–400 cm −1 ) were measured. An interpretation of the obtained IR spectra was proposed. Specific features of normal modes of ISTP caused by the presence of the spiro center were revealed.

The structures of four stereoisomers (enantiomers) of the closed form of an indolinospiropyran were studied by the DFT method. The most stable structure was found. IR absorption spectra of the compound as fi lms on single-crystalline KBr plates (400–4000 cm–1) and as powders between polyethylene plates (100–400 cm–1) were measured. An interpretation of the obtained IR spectra and literature Raman spectra was proposed. Specifi cs of the normal vibrations of the indolinospiropyran that were caused by the spiro node in its structure were revealed.

IR absorption spectra of indolinospironaphthooxazine (ISNO) are presented. The geometric structure and normal coordinates of the ISNO molecule have been calculated using a quantum mechanical DFT method. The IR spectrum of ISNO in its original spiro form has been interpreted for the first time. Four normal modes in the range 800–1200 cm–1 with the largest amplitudes of Cspiro–O bond change are identified. The excited ISNO molecule spiro form may experience photoconversion to the merocyanine form through them.

In an approximation of the generalized valence force field, the frequencies and forms of the normal vibrations of the free molecule of spiroanthraceneoxazine (SAO) are calculated. The vibrational spectra of SAO are measured: the IR absorption spectra in an NaCl disk and the Raman spectra in a KBr disk. The calculated and experimental data were correlated with the aid of a method of refined initial data. The results obtained agree with the calculated and experimental spectra of model and related compounds.

Spectral and photochromic properties of spironaphthooxazines (SNOs) with piperidine and morpholine substituents have been studied at different temperatures in various solvents. It has been recognized that introduction of these substituents in naphthooxazine fragment leads to fluorescence of the initial form of SNO molecules at low temperatures, which disappears with temperature rise. The dependences of the photoinduced form in non-polar solvents. It is proposed that the coloured form of substituted SNOs has a bipolar structure with a positive charge on piperidine or morpholine nitrogen atom contrary to the quinonoic form of unsubstituted SNO.