Photo-and thermochromic spiranes. 29. New photochromic indolinospiropyrans containing a quinoline fragment

Abstract

A new photochromic spiropyran of the indoline series, containing a quinoline fragment, has been synthesized. The photochromic properties of the spiropyran and its iodomethylate have been studied. Features of the molecular structure of the compounds were determined by X-ray structural investigations. It was established that the pyridopyran fragments of the cations in the crystal of the iodomethylate salt, unlike those in the crystal of the neutral spiropyran, emerge from 2 1 -stacks, disposed jointly with I -ions, which causes their higher mobility and aids the course of reversible photoconversions on UV irradiation in solution.Keywords: indolinospiropyran, quinoline fragment, X-ray structural analysis, photochromism.The synthesis of spiropyran salts (SP + X -), the investigation of their molecular, crystal structure, and photochromic conversions in the solid phase has caused immense interest [2][3][4][5][6][7] in the design of new polyfunctional materials based on them, combining in one crystal lattice several beneficial properties (photoswitching nonlinear optical properties [8] or photomagnetism [9]) and raising the prospect of using crystalline hybrids in miniature electronic instruments.Photochromic conversions of neutral spiropyrans, linked with cleavage of the C spiro -O bond and subsequent isomerization of the molecule, require a large open space and consequently is extremely hindered in crystals by the total packing in the lattice. As a rule the neutral spiropyrans in monocrystals and microcrystalline powders under stationary radiation conditions do not display photocoloration caused by the formation of open photomerocyanine structures [10], as was observed in solution or in the amorphous state.Investigation of ultrathin pressed microcrystalline samples of salts of spiropyrans and spiroxazines with N-methylated pyranopyridine rings [6,11,12] showed that at constant UV irradiation (365 nm) they are colored reversibly with the development of a broad absorption band between 500 and 650 nm, as was also observed in solution. The photochromic conversions are reversible and monocrystals survive some tens of cycles before structural and spectral changes. To establish the features of the molecular and crystal structure which provide reversible photochromic conversions of salts of spiropyrans under crystal packing conditions we carried out the synthesis and systemic investigation of the structure of new salts of various classes of spiropyrans [5,6,12,13].

Ferromagnetism, paramagnetism, and thermally induced magnetism in photomagnetic CrIII/MnII and CrIII oxalates with the 7-methyl-3,3-diphenyl-3H-pyrano[3,2-f]quinolinium cation

“…119.9(4) C(20)-C(21)-C (22) 120.6(5) C(17)-C(18)-C (19) 121.4 The C Sp -O bond in spiropyrans is elongated due to orbital interactions between the nitrogen lone pair and the antibonding σ* orbital of the C Sp -O bond, which leads to a weakening of this bond, resulting in that it can be effi ciently cleaved in the photoexcited state. In the chrome nium cation, the C-O bond appeared to be equal to that found in spiropyrans; however, efficient photochromic transformations analogous to those observed in spiropyr an salts, were detected neither in the solid state nor in solution.…”

“…The shortest distance between the I -anion and the C(10) atom is 3.88 Å, which is longer than the corresponding distance (3.76 Å) in the structure reported in the study. 19 In the crystal structure, there are short intermolecular con tacts between the carbon atoms (C (16)...C(17), 3.396 Å; C(17)...C(17), 3.152 Å) of the phenyl fragments B of two adjacent cations related by the inversion center (0 0 1/2) (see Fig. 4).…”

“…We compared the isomerization of the closed forms of chromene salt 1 and the iodide salt of spiropyran of the quinoline series 19 to the open forms in the ground state by quantum chemical methods.…”

Synthesis, structure, and the photomagnetic effect in crystals of 1,3,3,7′-tetramethylspiro[indoline-2,2′-2H-pyrano[3,2-f]quinolinium] tris(oxalato)chromate(III)

“…The oxalatochromate salt of photochromic spiropyran (Sp) 3 [Cr(ox) 3 ] (Sp is the 1 isopropyl 3,3,5´,6´ tetra methylspiro[indoline 2,2´ 2H pyrano [3,2 b]pyridinium] cation, and ох is C 2 O 4 2-) has been recently structurally characterized for the first time. 1 A hydrate of these salt, (Sp) 3 Cr(ox) 3 •4H 2 O, whose structure is unknown, was used as the starting compound in the synthesis of bimetallic ox alate (Sp)MnCr(ox) 3 having both magnetic and photochro mic properties.…”

“…1 A hydrate of these salt, (Sp) 3 Cr(ox) 3 •4H 2 O, whose structure is unknown, was used as the starting compound in the synthesis of bimetallic ox alate (Sp)MnCr(ox) 3 having both magnetic and photochro mic properties. 2 The crystal structure of the anhydrous salt consists of the structural units [3Sp + ...Cr(ох) 3 3-], in which the spiro pyran molecules [Sp] + exist in the closed form, the posi tively charged pyranopyridinium moieties being directed toward the oxalate groups, and the indoline moieties being directed into the cavities between the structural units. This structure appeared to be favorable for photochromic trans formations in the crystalline state (Scheme 1).…”