Preparation and properties of photochromic bacterial cellulose nanofibrous membranes

The photochromic bacterial cellulose (BC) nanofibrous membranes containing 1′,3′,3′-trimethyl-6-nitrospiro(2H-1-benzopyran-2,2′-indoline) (NO₂SP) were successfully prepared by surface modification of BC nanofibers with spiropyran photochromes, and their physical and photochromic properties were characterized. The FTIR spectra indicated the interaction between BC and NO₂SP which leads to the uniform dispersion of NO₂SP in the nanofibrous membrane. SEM results demonstrated that the introduction of NO₂SP maintains the nanofibrous network structure of BC. UV/vis spectrometry of the resulting BC-NO₂SP revealed that the membranes show reversible photochromic property by changing their color from colorless to pink forming a merocyanine structure upon UV irradiation, and returning back again to colorless spiropyran structure by visible light. The contact angle of the BC-NO₂SP with water was found to be reversibly regulated due to the reversible isomerization of the spiropyran moieties in BC-NO₂SP. The result indicates that the surface modification with spiropyran photochromes expands new applications of BC nanofibers and such photochromic nanofibers with excellent photosensitivity have great potentials for sensitive displays, biosensors and other optical devices.     

New photochromic 1,1,3-trimethylspiro[benzo[<Emphasis Type="Italic">e</Emphasis>]indoline-2,3′-[3<Emphasis Type="Italic">H</Emphasis>]-pyrano[3,2-<Emphasis Type="Italic">f</Emphasis>]quinoline]

A new photochromic spiropyran of the benzoindoline series containing the quinoline moiety was synthesized. Its structure was determined by IR and ¹H NMR spectroscopy. The crystal structure of the new compound was established by X-ray diffraction. The photochromic properties of the synthesized spiropyran were investigated.     

1-Benzyl-3,3,5′,6′-tetramethylspiro[indoline-2,2′-[2<Emphasis Type="Italic">H</Emphasis>]pyrano[3,2-<Emphasis Type="Italic">b</Emphasis>]-pyridinium] iodide,its hydrate,and a neutral precursor of the salts: synthesis,crystal structure,photochromic transformations in solutions and in crystals

A new 1-benzyl-3,3,5′,6′-tetramethylspiro[indoline-2,2′-[2H]pyrano[3,2-b]pyridinium] iodide, photochromic in the crystal state, was obtained. X-ray diffraction analysis was used for determination of crystal structures of the salt, its hydrate, and a neutral precursor. It was found that a replacement of the substituent in the indoline fragment leads to a considerable change in the crystal structure of both the neutral spiropyran and the salts as compared to the analogs studied earlier. Effects of crystal structure on photochromic properties were studied.     

Structure and photochromic and magnetic properties of 1-isopropyl-3,3,5′,6′-tetramethylspiro[indoline-2,2′-2<Emphasis Type="Italic">H</Emphasis>-pyrano[3,2-<Emphasis Type="Italic">b</Emphasis>]pyridinium] tris(oxalato)chromate(III)

Single crystals of 1-isopropyl-3,3,5′,6′-tetramethylspiro[indoline-2,2′-2H-pyrano[3,2-b]-pyridinium] tris(oxalato)chromate(III) (Sp)₃Cr(C₂O₄)₃ were prepared for the first time. The molecular and crystal structure of this salt was studied by X-ray diffraction. The crystal structure of the salt consists of the structural units [3(Sp)⁺…Cr(C₂O₄)₃ ³⁻], in which the charged pyranopyridinium moieties of the photochromic cations (Sp)+ are directed toward the oxalate groups, whereas the indoline moieties are directed into the cavities between the structural units. This structure appeared to be favorable for photochromic transformations in the crystals. Under UV irradiation of the (Sp)₃Cr(C₂O₄)₃ salt, the thermally stable closed form of spiropyran (λ_max = 370 nm) is transformed into the open form (λ_max = 574 and 603 nm). The reverse cyclization proceeds slowly in the dark (k = 1.0(2)·10⁻⁵ s⁻¹ and rapidly under visible light irradiation. The spectroscopic and photochromic properties of the oxalatochromate (Sp)₃Cr(C₂O₄)₃ are similar to those of the iodide SpI. The magnetic properties of (Sp)₃Cr(C₂O₄)₃ were studied before and after UV irradiation.     

Specific spectral properties of a photochromic ferromagnetic (C25H23N3O3Cl)CrMn(C2O4)3·H2O

A molecular magnetic (C₂₅H₂₃N₃O₃Cl)CrMn(C₂O₄)₃·H₂O whose spiropyran cation contains a quaternized pyridine fragment in the side aliphatic chain was synthesized for the first time. The compound possesses the properties of a ferromagnetic with T _c = 5.2 K and photochromic properties in the crystalline state. The photochemical properties of the hybrid compound were studied by electronic and IR spectroscopies. Photochromic transformations of the spiropyran cation are accompanied by the appearance of a broad absorption band in the region 400–600 nm in the electronic spectra and by reduction of intensity of the ν(C_spiro-O) IR band at 942 cm⁻¹. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 6, pp. 1055–1061, June, 2007.     

New Photochromic Salt Spiropyran with Benzyl Substituent

A new salt spiropyran of indoline series containing benzyl substituent in the 8'-position of the [2H]-chromene moiety of the molecule has been synthesized and studied. The structure of the obtained compound has been confirmed by methods ¹H NMR and IR spectroscopy. The study of spectral characteristics and photochromic behavior of the target compound has shown that growing of its single crystal resulted in destruction on account of hydrolysis in acetonitrile. The ¹H NMR spectra of the initial salt spiropyran and product of hydrolysis have been compared.     

Photo-and thermochromic spiranes 31.* Structure and photochromic properties of functionalized benzoxazine spiropyrans

An X-ray diffraction study gave the structure of a 4-oxohydro-2H-1,3-benzoxazine spiropyran with molecular formula C₂₈H₂₅N₃O₇, in which the π-electron-withdrawing formyl group is replaced with a chelatophoric hydrazine fragment containing a methoxy group. The structural parameters of this spiropyran were determined and compared with the data for similar spiropyrans. The photochromic properties of this compound in acetonitrile were studied in the presence of zinc ions. Dedicated to Professor A. F. Prozharskii on the occasion of his 70th jubilee. * For Communication 30 see [1]. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 11, pp. 1699–1706, November, 2008.     

Photo-and thermochromic spiranes 26. Comparative study of the structure of benzoxazinone series spiropyrans using X-ray analysis

X-Ray analysis has been used to study the structure of a spiropyran in the series 4-oxodihydro-2H-1,3-benzoxazine with the molecular formula C₂₇H₂₃N₃O₅. The structural parameters for this spiropyran, which contains a phenoxyacetic acid hydrazide substituent, have been compared with those of other spiropyrans in this series. Dedicated to Edmund Lukevics on his 70^th birthday __________ Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 1, pp. 103–108, January, 2007.     

Synthesis and photochemical and magnetic properties of Cr,Mn, Fe,and Co complexes based on the 1-{(1′,3′,3′-trimethylspiro[2<Emphasis Type="Italic">H</Emphasis>-1-benzopyran-2,2′-indolin]-8-yl)methyl}pyridinium cation

Paramagnetic (tris)oxalates with the composition (SP)₃M(C₂O₄)₃·4H₂O (M = Cr (2), Mn (3), Fe (4), and Co (5)) were synthesized for the first time based on the spiropyran salt SP⁺Br⁻ (1) with the SP⁺ cation containing the pyridine ring in the aliphatic chain of the benzopyran moiety, which was also prepared in the present study. According to X-ray diffraction data, the SP⁺ cations in the starting salt 1 are close-packed thus hindering photochromic transformations. The spin for paramagnet 4 is 5/2, which corresponds to the Fe^III atom in the high-spin state, the spin of the system remaining unchanged under UV irradiation. In complex 3, a crossover from ferromagnetic to antiferromagnetic correlations was observed after the replacement of the inorganic cation with the organic spiropyran cation. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 7, pp. 1424–1432, July, 2008.     

New indoline spiropyrans containing azomethine fragment

The new spiropyran systems with an azomethine bridge were synthesized from a spiropyran containing aminogroup at 6′ position of the benzopyran fragment and substituted aromatic aldehydes. The chemical structure of compounds is confirmed by elemental analysis data, NMR (¹H and ¹³C) and IR spectroscopy. Photochemical studies revealed the presence of photochromic properties at room temperature for one of the obtained spiropyrans.     

Synthesis,structure, and properties of the [RuNO(NH<Subscript>3</Subscript>)<Subscript>5</Subscript>][Co(CN)<Subscript>6</Subscript>] complex containing a photochromic cation

The salt of cobalt hexacyanide with the photochromic mononitrosyl cation [RuNO(NH₃)₅]³⁺ with the composition [RuNO(NH₃)₅][Co(CN)₆] was synthesized. Single crystals of the salt were grown, and the crystal structure was solved. The photochromic properties were studied by differential scanning calorimetry (DSC). Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 3, pp. 545–548, March, 2008.     

Synthesis,structure, and the photomagnetic effect in crystals of 1,3,3,7′-tetramethylspiro[indoline-2,2′-2<Emphasis Type="Italic">H</Emphasis>-pyrano[3,2-<Emphasis Type="Italic">f</Emphasis>]quinolinium] tris(oxalato)chromate(III)

Single crystals of 1,3,3,7′-tetramethylspiro[indoline-2,2′-2H-pyrano[3,2-f]quinolinium] tris(oxalato)chromate(III), in which the cation exists in the open merocyanine form, (Mc)₃Cr(ox)₃·11.56H₂O (ox is C₂O₄ ²⁻), were obtained for the first time. The molecular and crystal structure of the salt was established by X-ray diffraction. The crystal structure consists of two types of layers (cationic and anionic). In the cationic layer, the Mc⁺ cations are parallel to each other and form a close-packed arrangement. The anionic layer consists of oxalatochromate complexes and water molecules linked together by hydrogen bonds. The salt does not display photochromic properties typical of salts of cationic spiropyrans. However, UV irradiation (355 nm) causes a change in the average spin of the sample from 3/2 to 1 and a change in the Weiss constant from −7 to 7 K.     

Thermal and photostability of 5′,7′-dialkoxy-5,6′-dinitro-1,3,3-trimethylspiro(lndolin-2,2′-[2H]chromenes)

Some photochromic indoline spiropyrans have been synthesized and their thermal and photostability examined in films and in solution. Introduction of the NO₂ group into the indoline moiety of the molecule stabilizes the spiropyran form in solution and in films, but blocking the NO₂ group in the pyran moiety by adjacent alkoxy groups enhances the light stability of the compounds.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 9, pp. 1202–1205, September, 1987.     

Selective Acceleration of the Protonated Merocyanine‐Spiropyran Photochromic Transformation by Inclusion in Cucurbit[7]uril

The effect of cucurbit[7]uril (CB7) on the spiropyran‐merocyanine photochromic interconversion was studied in acidic and alkaline aqueous solutions. The merocyanine (MC) isomer was found to be the thermodynamically most stable form both in water and in the presence of CB7. A preferential binding of the protonated merocyanine (MCH⁺) to CB7 was observed with an equilibrium constant of 7.4 × 10⁴ m ^?1, and the complex formation led to significant diminution of acidity of the guest. The photoinduced transformation of MCH⁺ to the spiropyran isomer was accelerated 2.3‐fold upon addition of CB7, whereas the rates of the other photochromic processes were not affected. The partial inclusion of MCH⁺ in CB7 led to dual fluorescence due to the incomplete deprotonation in the singlet‐excited state.     

Spectral properties of Nd-doped BiB3O6 crystal

Transparent Nd: BiB₃O₆ crystal has been grown by top-seeded method. The refraction indices of the crystal were measured and the parameters of chromatic dispersion were fitted. The room temperature absorption spectra of the crystal have been measured and compared with that of 0.2 mol/L NdCl₃ solution. According to Judd-Ofelt (JO) theory, the spectral strength parameters Ω₂ = 0.1776×10⁻²⁰ cm², Ω₄ = 0.1282−10⁻²⁰1 cm² and Ω₆ = 0.1357X10^-20 cm² of Nd³⁺ ion were fitted. The radiative transition probabilities A_J,J’, oscillator strengths f_J,J’, radiative lifetime rand the branching ratio β_J’ have all been calculated. Based on these parameters, the properties and application perspective are discussed.     

Photo- and thermochromic spiranes. 31.* Photochromic cationic spiropyrans with a pyridinium fragment in the aliphatic side chain*2

Syntheses are reported for cationic indoline spiropyrans with a quaternized pyridinium fragment in the aliphatic side chain, which display photochromic properties in solution. The major effect of introducing a quaternized pyridinium fragment into the benzopyran part of the spiropyran entails a significant decrease in the rate of thermal relaxation processes. ^*For Communication 30 see [1]. ^*2Dedicated to Academician of the Russian Academy of Sciences B. A. Trofimov on his 70th jubilee. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 10, pp. 1513-1522, October, 2008.     

New Salt Spiropyran of Indoline Series with Fluorine Substituent

Synthesis, study of structure and photochromic properties of new salt spiropyran of indoline series containing a fluorine substituent in the 6′-position of the 2H-chromene moiety have been described in the work. The structure of the compound has been confirmed by ¹H NMR spectroscopy and X-ray diffraction analysis. Comparison of the structure of the compound with the previously studied analogue containing a methyl group instead of a fluorine atom in the 6′-position of the [2H]-chromene moiety has been made. This compound has been found to be photochromic, long-wavelength absorption maximum of its open form shows a bathochromic shift, and lifetime is increased three times as compared with the methyl analogue.     

Photochromic transformations in solutions of 8,8′-diquinolyl disulfide and di(mercaptoquinolinato)nickel(<Emphasis Type="SmallCaps">II</Emphasis>)

The nature of intermediate species and their reactions were studied by laser pulse photolysis for a photochromic system consisting of 8,8′-diquinolyl disulfide (RSSR) and a planar Ni^II complex di(mercaptoquinolinato)nickel(II) (Ni(SR)₂) in toluene and benzene solutions. Under exposure to laser radiation, disulfide RSSR dissociates to two RS^· radicals, whose spectrum has an intense absorption band with a maximum at λ = 400 nm (ε = 8400 L mol⁻¹ cm⁻¹). The radicals disappear by recombination (2k _rec = 4.6 · 10⁹ L mol⁻¹ s⁻¹). In the presence of the Ni(SR)₂ complex, coordination of the radical (k _coord = 4.4 · 10⁹ L mol⁻¹ s⁻¹) competes with recombination to form a radical complex RS^· Ni(SR)₂ having an intense absorption band with a maximum at 460 nm (ε = 16 600 L mol⁻¹ cm⁻¹). This species decays in the second-order reaction (2k = 4.6 · 10⁴ L mol⁻¹ s⁻¹). Since the photochromic system returns to the initial state, the reaction of two radical complexes is assumed to produce radical recombination and reduction of the disulfide and Ni(SR)₂ complex. Analysis of the kinetic data showed that some RS^· radicals decay in the microsecond time interval due to the reaction with the RS^· Ni(SR)₂ radical complex (k = 3.1 · 10⁹ L mol⁻¹ s⁻¹). Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 2291–2300, October, 2005.     

Effect of Heat Treatment and Additives on the Photochromic and Mechanical Properties of Sol-Gel Derived Photochromic Coatings Containing Spirooxazine

The experimental results on the photochromic and mechanical properties of coatings containing 1,3-dihydro-1,3,3-trimethylspiro[2H-indole-2,3′-(3H)-naphth(2,1-b)(1,4) oxazine] (SO) derived from 3-glycidyl-oxypropyltrimethoxysilane (GPTMS), bisphenolA (BPA) and 1-methylimidazole (MI) by sol-gel processing are presented. It is shown that heat treatment temperature is a conflicting factor to the photochromic intensity (ΔA ₀), photostability and abrasion resistance of the photochromic coatings. With increasing densification temperature the matrix rigidity increases leading to a decrease of ΔA ₀ and at the same time an enhancement of both abrasion resistance and photostability, the optimum heat treatment temperature is 110°C under our experimental conditions. By the use of certain additives, e.g., fluorosilanes (FAS), not only ΔA ₀ but also the photostability and the abrasion resistance of the photochromic coatings have been further improved.     

Photochromic nickel centers in diamons

Natural and synthetic (grown in the Fe−Ni−C system) diamonds were investigated by ESR and optical spectroscopy; five new photochromic nickel centers were found in addition to the interstitial sites and NE1-NE4 centers. Upon P, T-treatment at 2100 K and 55 kb, the interstitial nickel is partly transformed into nonparamagnetic defects; these may become ESR-active as a result of transformation of nickel to the Ni⁺ state by photoexcitation at λ<360 nm. Paramagnetic photochromic nickel-containing defects of three types were found: NE5 with g₁=2.0903, g₂=2.039, and g₃=2.0044 and with hfs from two magnetically equivalent nitrogen atoms, A_‖=12.25 G and A_⊥=9.5 G; NE6 without hfs and with g₁=1.995, g₂=2.0207, and g₃=2.0109, and finally, NE7 with hfs from one nitrogen atom in the range of 6–10 G and g-factors significantly larger than 2.0024. In the optical obsorption spectra, two lines (at 546 and 552 nm) are induced by light in the UV-visible range on irradiation, but no correlation with the paramagnetic centers was found. The samples were subjected to annealing and photobleaching combined with thermoluminescence measurements. For NE5 in the ESR spectra as well as for the 546 and 552 nm lines in the optical spectra, the photochromic processes are due to the internal rearrangement of the electronic configuration of the defects; for NE6 and NE7, they are caused by recharge of small electron traps. Institute of Inorganic Chemistry, Siberian Branch, Russian Academy of Sciences. Translated fromZhurnal Strukturnoi Khimii, Vol. 35, No. 6, pp. 74–80, November–December, 1994. Translated by L. Smolina