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The photochromic and solvatochromic behavior of four phenanthroline-containing spirooxazines bearing various alkyl long-chain substituents has been investigated in different polar and nonpolar solvents at various temperatures. These derivatives always appeared in an equilibrium mixture of spiro forms and open merocyanines. Depending on the substituents and the solvents, the percentage of the spontaneous merocyanine open form ranged from less than 10% to more than 30%. These results have been corroborated by independent NMR and photokinetic analysis. The main spectroscopic, thermodynamic, and photochromic parameters of such photo- and solvatochromic systems have been determined. Special illustrative diagrams showing quantitative substituent and solvent effects on absorption wavelengths, molar absorption coefficients, thermal equilibrium, interconversion rate constant, and quantum yields have been established. The two O-alkyl long-chain-substituted compounds 3 and 4 behave similarly, as do the N-alkyl derivatives 1 and 2. Opposition between polar and nonpolar solvents was also clearly illustrated. A global energy diagram including a short-lived cisoid merocyanine intermediate allows the interpretation of all solvent and temperature effects in terms of the relative solvation of the various short- and long-lived species and transition states.

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The photochromic, thermochromic and metallochromic behaviour of a series of three spiro[indoline-8-(benzothiazol-2-yl)-benzopyrans] has been investigated. The thermodynamic and kinetic parameters of their thermal equilibrium between the ring-closed (spiro) and ring-opened (merocyanine) isomeric forms have been determined using UV-Vis absorption and (1)H NMR spectroscopies. By adding Co(ii) and Ni(ii) ions in acetonitrile solution, 1 : 1 and 1 : 2 metal : merocyanine complexes are formed simultaneously. Using appropriate numerical methods, the kinetic analysis of the complexation allowed us to determine accurately key thermodynamic and spectroscopic parameters of the metal complexes. Results showed that the complexation strength is very sensitive to the size of the indoline nitrogen substituent. Complexation can be reversed by shining white light on the coloured complexes which regenerates the inactive spiropyran form, and releases the metallic ion; hence, these systems display fully reversible negative photochromism. The Zn(ii) complexes exhibit intense fluorescence in the 600-800 nm wavelength range. All these behaviours make these spiropyrans bearing benzothiazole heterocycles promising building blocks for the future construction of photodynamic chemosensors for transition metal ions.

The photo‐ and thermochromic behaviour of a series of spiro[indolinepyridobenzopyrans] 1–5 has been studied. The thermodynamic and kinetic parameters of the thermal equilibria between the ring‐closed and ring‐opened (merocyanine) isomeric forms of spiropyrans have been determined using UV–Vis absorption and 1H NMR spectroscopies techniques. The most stable form of 1‐(2‐hydroxyethyl)‐spiro[indoline‐pyridobenzopyran] 4 is represented by its trans‐(hydroxystyryl)oxazolidineindoline isomer coexisting in acetone solution with the ring‐closed spiroform. In the presence in solution of metal salts, spiro[indoline‐pyridobenzopyrans] exhibit strong ionochromic effect due to the formation of complexes with the merocyanine ligand. The composition of the complexes formed by Zn2+ and Ni2+ ions has been determined with the use of spectrophotometric and electrospray ionisation mass spectroscopy techniques. The stepwise stability constants and spectral properties of the most stable 1:1 and 1:2 metal/merocyanine complexes have been determined. Selectivity of the complexation reaction depends on the position of the thermochromic equilibrium. Copyright © 2007 John Wiley & Sons, Ltd.

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In solution, the photochromic molecule 5‐methoxyspiro[indole‐phenanthrolinoxazine] (SPO) is in equilibrium with its corresponding merocyanine open isomer. In pure acetonitrile, there is about 22.5% of the open form, whereas in acetonitrile–water binary solvents this proportion increases to more than 60% when the water molar fraction χ(H2O) is around 0.80. Irradiation in the visible range leads to a photobleached steady state in which the proportion of the merocyanine open isomer decreases significantly. When irradiation is switched off, a slow thermal reversion of the closed spirooxazine to the open merocyanine takes place until the initial equilibrium position is reached. Kinetic analysis of a whole set of relaxation curves recorded at various water contents was used to establish a model involving multiple equilibria between three merocyanines in different solvation states (solvated by acetonitrile, solvated by an acetonitrile–water complex and hydrated). Their relative proportions, which are dependent on the binary mixture composition, were determined, in addition to their corresponding visible spectra. Copyright © 2004 John Wiley & Sons, Ltd.