Synthesis of functionalized spiropyran and spirooxazine derivatives and their photochromic properties

Three series of functionalized spiropyrans and spirooxazines derivatives were synthesized and their photochromic properties were investigated in particular regard to the fatigue resistance, the lifetime of the colored merocyanine form and the interaction of the colored form molecule. (1) Spiropyrans 5 and spironaphthooxazines 6 having an antioxidant group as a pendant exhibited higher fatigue resistance than that of the parent spiro compounds in solution. In particular, spiropyrans 5 showed higher resistance than parent compound 1 in the presence of an equimolar amount of the corresponding antioxidant. (2) bis-Spironaphthooxazines 8a–8i and 10 connected through a phosphoryl group exhibited higher fatigue resistance and longer lifetime of the colored merocyanine form than those of the parent spirooxazine 7. (3) Symmetrical bis-spiro photochromic compounds 15 and 16 and unsymmetrical bis-spiro compounds 13, 14 and 17 were synthesized. The bis-spiro photochromic compounds were found to undergo intramolecular interaction between the colored merocyanine forms.     

Ultrafast dynamics of a spiropyran in water

The reversible switching of a water-soluble spiropyran compound is recorded over 1 ns by means of femtosecond vis-pump/vis- and IR-probe spectroscopy under aqueous conditions. Our investigations reveal that the photochemical conversion from the closed spiropyran to the open merocyanine takes 1.6 ps whereas the reversed photoreaction is accomplished within 25 ps. The combination of time-resolved and steady-state observations allows us to reveal central parts of the reaction pathway leading to either form. The enhanced water solubility, its fast and efficient switching behavior, and its stability against hydrolysis over a time range of several weeks make this compound an attractive and versatile tool for biological applications.     

Preparation and photochromic properties of oligomeric poly(dimethylsiloxane) with the spiropyran or spirooxazine moiety in the side chain

Spirobenzopyran 1 , with the 3-(diethoxymethylsilyl)-propyl group at the N atom, was synthesized. The condensation reaction of the spiropyran 1 and diethoxydimethylsilane gave oligomeric poly(dimethylsiloxane) with the spiropyran moiety in the side chain. The oligomer was photochromic; its colour changed from colorless to purple-red on uv irradiation and the color faded on visible irradiation or on standing in the dark. The half-decay time of the thermal decoloration was about twice that of monomeric spiropyran dissolved in the dimethylsiloxane oligomer. Photochromic poly(dimethylsiloxane) with the spirooxazine moiety in the side chain was also prepared.     

Quantum chemical study of the Cspiro-O bond dissociation in spiropyran molecules

To study the possibility of photochromic transformations in the crystals of bifunctional compounds, quantum chemical B3LYP/6-31G(d) calculations of the C_spiro-O bond dissociation energies were carried out with the Gaussian-03 program for two dissimilar neutral spiropyrans (Sp) and three cations of their salts in the singlet ground state. For C_spiro-O bond dissociation in the cations Sp ⁺ and the neutral systems SpI consisting of Sp ⁺ and I^?, the energy barriers do not exceed 10 kcal mol^?1, increasing when moving from the cations Sp ⁺ to the neutral systems SpI. The changes in the HOMO and LUMO energies when going from the closed to open form of the cations Sp ⁺ correlate with the energy barriers to the corresponding C_spiro-O bond dissociations.     

Isomerization dynamics of photochromic spiropyran molecular switches in phospholipid bilayers

Transient absorption spectroscopy was used to investigate the dynamics of the photochromic indolinobenzospiropyran reaction in toluene solution and in phosphatidylcholine bilayers (1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC), 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC), and 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC)). After excitation with UV light, colorless (R/S)-2-(3',3'-dimethyl-6-nitro-3'H-spiro[chromene-2,2'-indol]-1'-yl)ethanol derivatives are converted to colored merocyanine products in high yield; Phi = 0.45 in DMPC liposomes. We find that the reaction occurs in the bilayer aliphatic region in the gel (P(beta)(')) and liquid (L(alpha)) phases. The Arrhenius activation energy for the isomerization in DMPC bilayers was approximately 3.5 times larger in the liquid phase (L(alpha), E(a) = 26.0 +/- 1.0 kJ mol(-1)) than that in the gel phase (P(beta)('), E(a) = 7.3 +/- 1.6 kJ mol(-1)). Analysis of the isomerization rate constant temperature dependence allows an estimation of the bilayer viscosity and free volume properties in the L(alpha) phase.     

Gas-phase activation and reaction dynamics of chiral ion-dipole complexes

A family of enantiomerically pure oxonium ions, that is O-protonated 1-aryl-1-methoxyethanes, has been generated in the gas phase by the (CH(3))(2)Cl(+) methylation of the corresponding 1-arylethanols. Some information on their reaction dynamics was obtained from a detailed kinetic study of their inversion of configuration and dissociation. The activation parameters of the inversion reaction are found to obey two different isokinetic relationships depending upon the nature and the position of the substituents in the oxonium ions. In contrast, the activation parameters of the dissociation reaction obey a single isokinetic relationship. The inversion and dissociation rate constants do not follow simple linear free-energy relationships. This complicated kinetic picture has been rationalized in terms of different activation dynamics in gaseous CH(3)Cl, which, in turn, determine the reaction dynamics of the oxonium ion. When the predominant activation of the oxonium ion involves resonant energy exchange from the 1015 cm(-1) CH(3) rocking mode of unperturbed CH(3)Cl, the inversion reaction proceeds through the dynamically most favored TS, characterized by the unassisted C(alpha)bond;O bond elongation. When, instead, the activation of the oxonium ions requires the formation of an intimate encounter complex with CH(3)Cl, the inversion reaction takes place via the energetically most favored TS, characterized by multiple coordination of the CH(3)OH moiety with the H(alpha) and H(ortho) atoms of the benzylic residue. The activation dynamics operating in the intimate encounter complex with CH(3)Cl is also responsible for the dissociation of most selected oxonium ions.     

Kinetic nonequivalence of spiropyran molecules during their photochromic conversions in Langmuir-Blodgett layers

The kinetics of the photochromic conversions of spiropyran molecules in Langmuir-Blodgett layers based on stearic acid were investigated. It was shown that the molecules of spiropyran are nonequivalent in their reactivity both in the reverse, dark stage and in the direct photochemical stage of the process. A correlation between the reactivity of the molecules in the direct and reverse reactions was demonstrated. The sign of the correlation was positive: the relatively more reactive spiropyran molecules in the direct photochemical reaction also remain more reactive in the reverse dark process. A physical model for the influence of the cell environment on the reactivity of the molecule, in which the effective relaxation of the structure of the cell environment following each event of the chemical conversion is proposed, was put forward.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 9, pp. 2018–2024, September, 1991.     

A semiclassical molecular dynamics of the photochromic ring-opening reaction of spiropyran

The photochromic ring-opening reaction of spiropyran(SP) has been investigated by a realistic semiclassical dynamics simulation,accompanied by SA3-CASSCF(12 10)/MS-CASPT2 potential energy curves(PECs) of S0–S2.The main simulation results show the dominate pathway corresponds to the ringopening process of trans-SP to form the most stable merocyanine(MC) product.These findings provide more important complementarity for interpreting experimental observations.     

Reversible modulation of photoluminescence from conjugated polymer nanotubes by incorporation of photochromic spirooxazine molecules

A novel photo-switching system based on fluorescent polymer nanotubes incorporating spirooxazine molecules has been designed. Reversible photoluminescence modulation of up to 60% has been shown in individual nanotubes subjected to repeated photo-conversion cycles.     

Gas-phase Boudouard disproportionation reaction between highly vibrationally excited CO molecules

The gas-phase Boudouard disproportionation reaction between two highly vibrationally excited CO molecules in the ground electronic state has been studied in optically pumped CO. The gas temperature and the CO vibrational level populations in the reaction region, as well as the CO₂ concentration in the reaction products have been measured using FTIR emission and absorption spectroscopy. The results demonstrate that CO₂ formation in the optically pumped reactor is controlled by the high CO vibrational level populations, rather than by CO partial pressure or by flow temperature. The disproportionation reaction rate constant has been determined from the measured CO₂ and CO concentrations using the perfectly stirred reactor (PSR) approximation. The reaction activation energy, 11.6 ± 0.3 eV (close to the CO dissociation energy of 11.09 eV), was evaluated using the statistical transition state theory, by comparing the dependence of the measured CO₂ concentration and of the calculated reaction rate constant on helium partial pressure. The disproportionation reaction rate constant measured at the present conditions is k_f = (9 ± 4) × 10⁻¹⁸ cm³/s. The reaction rate constants obtained from the experimental measurements and from the transition state theory are in good agreement.     

Gas-phase protonation of simple inorganic molecules: A stimulating interplay between theory and experiment

A brief account of some of the results obtained recently during the investigation of the gas-phase protonation of some simple inorganic molecules. The combined use of structurally diagnostic mass spectrometric techniques, such as mass-analyzed ion kinetic energy (MIKE) and collisionally activated dissociation (CAD) spectrometry and ab initio calculations allows the successful probe of the corresponding potential energy surfaces. Information is obtained on the structure and the stability of the various protonated intermediates, as well as on the details of the mechanisms of their interconversion and unimolecular decomposition processes.     

Gas-phase DNA oligonucleotide structures. A QM/MM and atoms in molecules study

QM/MM calculations have been employed to investigate the role of hydrogen bonding and pi-stacking in single- and double-stranded DNA oligonucleotides. DFT calculations and Atoms in Molecules analysis on QM/MM-optimized structures allow characterization and estimation of the energies of pi-stacking and hydrogen-bond interactions. This shows that pi-stacking interactions depend on the number and the nature of the DNA bases for single-stranded nucleotides; for instance, guanines are found to be involved in strong hydrogen bonds, whereas adenines interact mainly via stacking interactions. The role of interbase hydrogen bonding was explored: the -NH2 groups of guanine, adenine, and cytosine participate in N-H...O and N-H...N interactions. These are much stronger in single-strand oligonucleotides, where the -NH2 groups are highly nonplanar. In double-stranded DNA, the strong base-pairing hydrogen bonds of complementary bases lead to more planar -NH2 groups, which tend to be involved in pi-stacking interactions rather than H-bonds. The use of AIM also allows us to evaluate the interplay of pi-stacking and H-bonding, suggesting that cooperativity does occur, but is generally limited to about 1-2 kcal/mol.     

Synthesis and photochromic properties of polymers containing spirooxazine groups

Two spirooxazine (SO) compounds containing bromobutyl substituents on 1-position (SO1) and 9′- position (SO2) have been synthesized and characterized by 1H-NMR, IR and ESI-MS in this paper. SO1-g-PMMA and SO2-g-PMMA polymer were prepared by grafting SO1 and SO2 onto PMMA through C-Br bonding sites. Also, SOs were doped into PMMA matrix to afford SO1-d-PMMA and SO2-d-PMMA. Photochromic behaviors of these compounds have been studied. Compared with SO1, SO2 exhibited better photoresponse and slower bleaching in dichloromethane solution. Inserted into polymer films, the decoloration process of SOs were significantly retarded and it was found that the fading curves fitted a first-order equation; As regard to four polymers, 1-position grafting (SO2-g-PMMA) can cause a higher reduction degree on the thermal fading rate.     

Amino-substituted spirooxazine and fulgimide for the nanostructurized photochromic systems

Comparative spectral kinetic studies of the photochromic properties of a novel N-aminofulgimide and the previously synthesized aminospirooxazine intended for the synthesis of organic-inorganic photochromic systems based on cyclotriphosphazene were performed. The results from the spectral kinetic studies evidence the fundamental suitability of these compounds for design of the multifunctional photochromic systems based on cyclotriphosphazene. Computer molecular models of aminospirooxazine and N-aminofulgimide were developed and optimization of geometric parameters was performed by the semiempirical quantum chemical method AM1.     

Internal dynamics of simple floppy molecules

The dynamical behavior of simple nonrigid molecules still attracts much interest both from experimentalists and theoreticians. On the one hand, modern laser-spectroscopic techniques like SEP allow for the detection of highly excited vibrational–rotational states of a molecule, and advanced theoretical methods, on the other hand, are more and more able to calculate accurate potential energy surfaces and to simulate the intramolecular dynamics. The aim of the present article was to contribute to the understanding of the dynamical properties of simple floppy molecules by means of a comparative study of the two triatomics HCN and HO₂. Continuing our earlier work, we start from an analysis of the potential energy surface topography, then we investigate the classical dynamical behavior and the localization of the quantum states. Several conclusions of probably more general validity are drawn. © 1994 John Wiley & Sons, Inc.     

Preparation of a spirooxazine grafted PMMA and its photochromic properties

A novel spirooxazine (SO) compound was designed and synthesized. Macromolecular materials, called SO-g-hPMMAs (where the g means grafting and the h means partial hydrolysis), were prepared using PMMA (polymethylmethacrylate) with different degrees of hydrolysis. SO-g-5%hPMMA was prepared by reacting SO-containing active C-Br bonds with 5% partially hydrolyzed PMMA. The SO was characterized using ¹H NMR and infrared. Beyond that, photochromic properties were studied in detail. We discuss the effects of hydrochloric acids and hPMMAs of different hydrolysis degrees on photochromic properties of SO-g-hPMMA. Additionally, mechanical properties of the material were studied. Results indicate that the colored ring-opening form (PMC) of SO-g-hPMMA exhibits a good performance in terms of thermal stability, in contrast to the homologous SO. Experiments additionally demonstrate that hydrochloric acid improves the PMC’s thermal stability. SO-g-9%hPMMA demonstrated a good performance of photochromic properties compared to those with different degrees of hydrolysis.