Effect of the anion nature on crystal structure of Zn-complexes of spironaphthopyran and their chromogenic properties in solution were studied. Complexes with zinc chloride and zinc picrate exhibited tertahedral and octahedral coordination environment of the metal ion respectively. The structure of the complex with zinc picrate demonstrates a rare example of the co-crystallization of two types of complexes differing in the number of coordinated picrate anions. The composition, stability, and absorption properties of zinc complexes in acetone essentially depend on the counter anion nature. When the coordinating ability of the counter ion increases in the range BF4- , ClO4- , NO3-, Pic-, I-, Cl-, CH3COO-, (CH3)3CCOO- the complex stability is reduced from logK = 8.7 to 2.96. This is accompanied by the chromogenic effect which is related to the decrease in the spectral shift of the long-wavelength absorption band of the complex relative to the merocyanine ligand from 846 up to 168 cm-1. The complex photo-initiated processes include fluorescence and thermally reversible dissociation. Fluorescence is characterized by band maxima in the 622-637 nm region and normal Stokes shifts of 1087-1454 cm-1 with an efficiency being weakly dependent on the anion nature. In contrast, the negative photochromism of the complexes demonstrates a significant dependence of the photo-bleaching efficiency on the anion nature in the range 0.012-0.17. The presence of a chromogenic photochromic effect along with fluorescence makes it possible to consider the complex as fluorescent switch.

The reaction of fluorescein-substituted 2-hydroxybenzaldehyde with 3H-indolium perchlorate has led to the formation of 1,3-dihydrospiro[indole-2,2′-chromene] bearing a fluorescein fragment at position 8 of chromene. In a solution, the obtained compound has existed in the cyclic form and has exhibited photochromic properties. Adding transition metal perchlorates to the spiropyran solution has led to intense coloration due to the complex formation. Zinc and cadmium complexes of the spiropyran have exhibited red fluorescence and negative photochromism.

Novel photochromic spirobipyrans bearing benzoxazole group in the 3H-naphthopyran fragment have been synthesized. Spiro-conjugated benzopyran and naphthopyran fragments cause the observed dual photochromism of the molecules. In the presence of Cd2+, Mn2+, Co2+, Ni2+, Zn2+, Cu2+ metal ions thermal isomerization of the spirobipyrans is observed, followed by the formation of the intensely coloured complexes of the merocyanine form. The long-wavelength absorption band of the complexes is located at ?>600 nm.

Novel photochromic spirobipyrans containing benzothiazole group in the 2H-chromene moiety have been synthesized. The spirobipyrans combine with Co2+, Ni2+, Zn2+, and Cu2+ ions to give intensely colored complexes of merocyanine form with long-wavelength absorption bands at λ > 600 nm.

Thermal and photoinduced processes accompanying complexation of photochromic spiropyrans (SPP) with Zn ions in acetone solution were characterized by means of UV-vis and X-ray absorption spectroscopies in operando regime. SPP ligands are usually transparent at lambda > 350 nm, but after mixing with Zn ions, they produce a stable colored (epsilon = 32 000-38 000 M-1 cm(-1)) complex with maximum absorption at 525 nm, which makes them a powerful tool for monitoring metal-ion concentration in solution. The complex revealed fluorescence and photochromic behavior under static irradiation with visible light with constant photoreaction quantum yield across its characteristic absorption band. Zn K-edge X-ray absorption spectra show prominent changes in Zn local atomic structure between free Zn ions and Zn complex. The pump-flow-probe scheme was adapted to measure operando changes in Zn coordination upon light irradiation. Within experimental time resolution, we have determined that 20 mu s after light irradiation, Zn ion is released out of the complex. This is the first example of the direct spectroscopic probe of the Zn photorelease from the spiropyran complex.

New 8-(5-(p-tolyl)-1,3,4-oxadiazol-2-yl) substituted spirobenzopyrans appear as polychromogenic molecular system demonstrating both positive photochromism and ionochromic properties. Introduction of electron withdrawing formyl group into 6-position of the pyran part leads to increasing of spiropyran photocoloration reaction efficiency but decreases thermodynamical stability of merocyanine form complexes. Upon irradiation with visible light colored solutions of complexes with Zn2+, Cd2+ ions exhibiting negative photochromism, undergo reversible discoloration as a result of photodissociation characterized by the quantum yields reaching 46%. On one side this allows realizing controlled by light irradiation cation induced isomerizations into complexes of the merocyanine form. On the other hand, a system, in which direction of photochromic transformations can be driven by transition metal ions, can be designed.

8-Benzoxazolyl-6-formyl-substituted spirobenzopyrans with different acceptor groups in the 5'- position of the indoline moiety have been synthesized. Novel spiropyrans exhibit photochromic properties in an acetone solution at room temperature and form intensely colored complexes with heavy metal cations.

New benzoxazolyl-substituted spiroindoline-benzopyrans with electron-withdrawing groups in the indoline fragment were obtained. These compounds exhibit positive P- and T-type photochromism. Structural correlations of the spectrokinetic properties depending on the variation of substituents in the indoline part of the spiropyran molecules were established. Electronwithdrawing groups were found to cause a bathochromic shift of the long-wavelength absorption maxima of the merocyanine isomers as compared to the unsubstituted spiropyran and decrease their lifetime. Conversely, an introduction of electron-donating groups results in a hypso chromic shift of the absorption maxima and an increase in the lifetime of the colored isomers of spiropyrans. Electron-withdrawing substituents at the position 5 of the indoline fragment cause the increase of the colorability of the spiropyrans.

Novel spirobenzopyranindolines containing a rhodamine fragment linked to a benzopyran fragment with an aminomethylene spacer were synthesized by the reaction of 7-hydroxy-6-formyl-substituted spiropyrans and rhodamine B hydrazide. The synthesized spiropyrans in toluene and acetone are present in the spiropyran‒spirolactam form. The 5-methyl-substituted was the only to exhibit photochromism. Adding Zn(II), Ni(II), Co(II), and Cd(II) perchlorates to the spiropyran solutions leads to intense coloration due to complex formation.

8-(1,3-Benzoxazol-2-yl) substituted spirobenzopyrans 1A appear as a chromogenic system susceptible of switching between positive and negative photochromism under complexation with metal ions. The thermal and photochemical reactions accompanying metal ion-induced transformation of spiropyrans 1A to the complexes formed by their photoinduced merocyanine isomers 1B were investigated. In the dark, the colorless spiropyrans interact with Mn2+, Cd2+ and Zn2+ transition metal ions to yield deeply colored 1:1 complexes possessing fluorescence, while Co2+, Ni2+, Cu2+ ions prefer to form non-fluorescent complexes with two merocyanines. Under irradiation with visible light solutions of the merocyanine-metal complexes undergo photobleaching. This effect was quantified using photokinetic method.

An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.

Metal coordination by spironaphthopyran derived merocyanines bearing benzazol substituents has been studied by means of experimental and theoretical methods. The formation of N-O coordinated chelate complexes have been observed by means of X-ray diffraction. Merocyanine scaffolds of these complexes possess trans-trans-cis conformation independently of both substituents in positions 1 and 5 of indoline moiety and benzazole heteroatom. Stability of merocyanine-metal complexes significantly depends on two factors: relative thermodynamic stability of spirocyclic and open isomers and complexation energy. Variation of the ligand structure involving chelating group significantly changes stability of complexes while replacement of the substituents in the indoline ring peripheral to the chelating parts of the molecules and biasing the spiropyran – merocyanine equilibrium provide the fine tuning of complexation selectivity. Complexes of diamagnetic ions (Mg2+, Zn2+, Cd2+) undergo photodissociation. The complexes of benzoxazole containing ligands demonstrate higher quantum yields comparing to their benzothiazole analogue.

8-(1,3-Benzoxazol-2-yl)-substituted spirobenzopyran is a new chromogenic system in which complexation with metal ions accompanied by a change in color can be controlled by photoirradiation. According to X-ray crystallography, the merocyanine ligand in the zinc complex has the TTT conformation.

A new spirobenzopyranindoline containing a rhodamine fragment bonded by an azomethine spacer with the benzopyran fragment was synthesized based on 6-formyl-7-hydroxy-substituted spiropyran; the new compound exhibited complexation properties in solutions.

New photochromic 5′-(1,3-benzoxazol-2-yl)-substituted spiro[indoline-naphthopyrans] exhibiting luminescent properties in the spirocyclic form were synthesized. Their reverse thermal reaction barrier decreases with the increase in the electron-withdrawing properties of substituent in the indoline fragment.

Novel photochromic spirooxazinoquinolines, their cationic derivatives, and cationic spirooxazine containing pyridinium cation in the aliphatic side chain of the oxazine moiety of the molecule were synthesized. Quaternization of the quinoline fragment leads to a substantial increase in the thermal stability of the merocyanine isomers of cationic spirooxazines and a decrease in the efficiency of photocoloration. Pyridinium cation in the aliphatic side chain of the spirooxazine does not exert a substantial effect on the kinetics of photocoloration and thermal bleaching.

Formylation of 2-(2-hydroxyphenyl)benzoxazole gave 5-benzoxazolyl-substituted 4-hydroxyisophthalic aldehyde, which served as a precursor to the synthesis of novel photochromic spiro[indoline-benzopyrans] containing a benzoxazole group at position 8 of the benzopyran moiety. The obtained compounds possess photochromic properties in solution.

New symmetrical bisspiropyrans of the indoline series, which have photochromic properties and are characterized by substantially higher absorption capacity of cyclic isomers in comparison to the monospiropyrans, were obtained on the basis of 4,6-dihydroxy-5-methylisophthalaldehyde.