Complete 1H and 13C NMR spectral assignment of symmetric and asymmetric bis-spiropyran derivatives

(1)H and (13)C NMR spectra of symmetric and asymmetric bis-spiropyrans, Series 1-3, were completely assigned. Especially, the (1)H assignment of asymmetric spiropyrans was achieved by utilizing (1)H-(1)H COSY and nOe experiments. All of the carbons in the dye molecules were investigated through a combination of heteronuclear 2D-shift correlation spectroscopy (HETCOR), together with an attached proton test (APT).     

Spiropyrans and spirooxazines. 3. Synthesis of photochromic 5′-(4,5-diphenyl-1,3-oxazol-2-yl)-spiro[indoline-2,3′-naphtho[2,3-<Emphasis Type="Italic">b</Emphasis>]pyran]

The reaction of 2-hydroxy-3-(4,5-diphenyl-1,3-oxazol-2-yl)-1-naphthaldehyde with 1,2,3,3-tetramethyl-3H-indolium perchlorate afforded photochromic spiro[indoline-2,3′-naphthopyran] containing a 4,5-diphenyloxazole group in position 5′ of the naphthopyran fragment. The merocyanine form of the spiropyran gave complexes with bivalent heavy cations.__________Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 3, pp. 693–697, March, 2005.     

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 with highly stable merocyanine forms

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DFT modeling of indoline spiropyrans with a cationic substituent in the gas phase

Isomeric forms of indoline spiropyrans show unusual behavior compared with similar compounds, according to experimental data. DFT modeling for gas phase was made to consider the simplest case without environmental effects, which revealed the intramolecular reasons for occurrence of ring opening reaction depending on the particular structure of the compound. The questions of charge redistributions, the changes of geometry and chemical bonds in the structures are also discussed.     

Cu (II)‐β‐cyclodextrin complex stabilized on magnetic nanoparticles: A retrievable hybrid promoter for green synthesis of spiropyrans

The magnetic core of manganese ferrite (MnFe₂O₄) nanoparticles has a significant stability in comparison with ferrite (Fe₃O₄) nanoparticles. The unique supramolecular properties of β‐cyclodextrin (β‐CD), such as hydrophobic cavity, hydrophilic exterior and ‐OH functional groups, make it a good candidate for functionalization and catalytic application. So, a surface‐modified magnetic solid support with the Cu (II)‐β‐CD complex was prepared. The structure of nanoparticles was characterized by Fourier transform‐infrared spectroscopy, X‐ray powder diffraction, thermogravimetric analysis, vibrating‐sample magnetometry, inductively coupled plasma‐optical emission spectrometry and scanning electron microscope analyses. The catalytic activity of these nanoparticles was investigated in the synthesis of spiropyrans and high yields of desired products obtained under green media. Some advantages of this novel catalyst for this reaction are high yields, short reaction times, green solvent and conditions, easy workup procedure, negligible copper leaching, reusability without a significant diminish in catalytic efficiency, and simple separation of nanocatalyst by using an external magnet alongside the environmental compatibility and sustainability.     

Cation-dependent pericyclic reactions of crown-containing photochromic compounds

The review is devoted to the photochromism of pericyclic reactions of crown-containing photochromic systems. The complex formation of photochromic crown ethers with metal cations has a substantial effect on both the spectral characteristics of molecules and occurrence of photochromic reactions. A possibility to create systems with photocontrolled complex-forming properties is an attractive feature of the novel systems.     

Dicondensed indolinobenzospiropyrans as precursors of thermo- and photochromic spiropyrans. Part II: Assignment of (1)H and (13)C NMR spectra

The (1)H and (13)C NMR spectra of dicondensed indolinobenzospiropyrans as precursors of thermo- and photochromic spiropyrans, DC1-DC5, were completely assigned. Especially, the (1)H assignment and coupling characteristics of the diastereotopic protons at the carbon-3 position of the benzopyran rings were achieved by conducting (1)H-(1)H COSY and nOe experiments. The dihedral angles (theta(1), theta(2) and theta(3)) calculated from the experimental values of the vicinal coupling constants ((3)J) of DC5 are in good agreement with the observed values in the solid state. All of the carbons in the DC dye molecules were investigated through a combination of heteronuclear 2D-shift correlation spectroscopy (HETCOR) and DEPT135.     

Photochromism of indoline spiropyrans of the coumarin series in polymeric matrices

The photochromic properties and aggregation processes of merocyanine forms of indoline spiropyrans of the coumarin series in the block and film poly(methyl methacrylate) (PMMA) were studied and compared by spectral and kinetic methods. Photochromism of the synthesized compounds depends on their structure. The efficient formation of J-aggregates was observed for indoline spiropyrans of the coumarin series based on 8-formyl-7-hydroxy-4-methylcoumarin and 3-formyl-4-hydroxycoumarin. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 5, pp. 870–875, May, 2007.     

Photo- and thermochromic spiropyrans. 21. 8"-Formyl-3,6"-dimethyl-4-oxospiro(3,4-dihydro-2H-1,3-benzoxazine-2,2"-[2H ]chromene) possessing photochromic properties in the solid phase

Spiropyran of the chromene series, viz., 8"-formyl-3,6"-dimethyl-4-oxospiro(3,4-dihydro-2H-1,3-benzoxazine-2,2"-[2H]chromene), was synthesized. In the solid phase, this compound exhibits photochromic properties. These properties were examined and the crystal structure of the compound was established by X-ray diffraction analysis. The compound is a convenient starting reagent for the synthesis of new spiropyrans containing functional groups at position 8".