Papers by Keyword: Photochromism

Abstract: A novel unsymmetrical isomeric photochromic diarylethene based on phenanthrene unit, {1-[2-methyl-5-(10-phenanthrenyl)-3-thienyl]-2-{2-methyl-5-[4-(2-(1,3-dioxolane)) phenyl]-3-thienyl}} perfluorocyclopentene (1o), was designed and synthesized. Its properties were investigated in detail, including photochromic, kinetics and fluorescent. The results showed that the compound exhibited excellent photochromism, changing from colorless to violet after irradiation with UV light in solution. What is more, the kinetic experiments illustrated that the cyclization/cycloreversion process of this compound was determined to be the zeroth/first reaction. Furthermore, the fluorescence intensity of the photochromic diarylethene 1o declined dramatically.

Abstract: Spiropyrans are among the most promising organic photochromic dyes. However, spiropyrans are very sensitive dyes and there are many independent factors that can affect the performance of these dyes. The effect of substituent on the optical absorption spectra, fading kinetic, and also the dye stability of spiropyrans in diphenyl ether by UV irradiation has been investigated. The 6-nitro BIPS displayed greater absorbance intensity of 0.740% at 600nm compared to 8-ethoxy-6-nitro BIPS of 0.651% at 620nm. Furthermore, 6-nitro BIPS is less stable as it has higher rate constant of 0.1003s^-1 and thus lower half-life time (50% decay of the photochromic effect) of 6.9s, in contrast to 8-ethoxy-6-nitro BIPS of 0.0594s^-1 and 11.7s respectively.

Abstract: Organic dyes namely 1,3,3-trimethylindolino-naphtospirooxazine (TINS) and 3,3-diphenyl-3H-napthol [2,1-pyran DNP) were used in studies of photochromic transformation in ethanol solution. The samples were exposed to UV light ranging from 5, 10 and 15s respectively. TINS absorbs UV light at 613nm for multiple exposure time. The absorption initiated the opening of oxazine spirostructure with formation of open merocyanine species. Irradiation of DNP with UV at 5, 10 and 15s absorbs at 413nm with formation of opening cyclicstucture of naphthopyran, namely allenyl-naphtol. The intensity peaks of TINS and DNP were increased with increasing the period of irradiation time. TINS and DNP dyes exhibit normal photochromic in the polar protic solvent by displaying color changes form transparent to color blue and light orange under exposed UV light. The photochromic activity of these compounds is due to the reversible light-induced cleavage of the C-O bond between the heterocyclic oxygen atom and the quaternary carbon.

Abstract: Photochromism behaviors of a spiropyran dye namely 5-bromo-8-methoxy-6-nitro BIPS (BNM) has been investigated in the present of papain as anti-oxidant at different H⁺ ions conditions. BNM has been dissolved and diluted in ethanol (EtOH) to a concentration of 1.0 x 10^-5M. The hydrochloric acid (HCL) was used to alter the acidity of the solution to be pH2 and pH7. The fine dispersed transparent solutions were exposed to UV light at 365nm for 5s and the absorption spectra were measured using UV-Vis spectrometer. Upon UV light irradiation, BNM exhibits photochromic behaviors by displaying coloration changes from transparent to light purplish with maximum absorbance spectrum, λ_max at 552nm with and without present of papain in both acidic (pH2) and neutral (pH7) conditions. It was found that incorporation of papain in both different pH conditions slightly decreased the intensities of absorbance spectrum for BNM photo-transformation activities. However, detection in time drive mode at 522nm with 5s UV irradiation showed that the addition of papain stabilize and prolongs the absorbance intensity. Incorporation of anti-oxidant molecules is significant in order to obtain long-life activities of the spiropyran in the photo-reversible activity of open-form merocyanine state to closed-form spiro state. This study reveals that the photo-transformation stability of BNM molecules is increased with addition of papain in neutral condition that acts as anti-oxidant agent towards the BNM photo-reversible process.

Abstract: An unsymmetrical photochromic diarylethene 1-(2-methyl-1-phenyl)-2-[2-methyl-5-(4-formylphenyl)-3-thienyperfluoroyclopentene (1o) was designed and constructed successfully. Its photochromic properties were examined. The results showed that the compound exhibits good photochromism with UV/Vis light irradiation. The diarylethene 1o changed the color from colorless to blueviolet upon irradiation with 297 nm UV light, in which absorption maxima were observed at 549 and 581nm in hexane and PMMA films, respectively.The photochromic cyclization/cycloreversion kinetics of 1o in hexane were determined by UV-Vis spectra upon alternating irradiation with UV and appropriate wavelength visible light.

Abstract: An unsymmetrical photochromic diarylethene compound, 1-(2-methyl-3-benzofuranyl)-2-[2-methyl-5-(4-cyanophenyl)-3-thienyperfluorocyclopentene was synthesized, and its photochromic properties, kinetics of the photochromic cyclization/cycloreversion and fluorescence were investigated in detail. The compound exhibited good photochromism, changing from colorless to red after irradiation with 297 nm UV light, in which absorption maxima were observed at 530 nm in hexane solution. Simultaneously, cyclization/cycloreversion kinetics of this diarylethene was researched. The open-ring isomer of the diarylethene exhibited relatively strong fluorescence at 377 nm in hexane solution (2 × 10^-5 mol L^-1), when excited at 327 nm. The fluorescence intensity decreased along with the photochromism upon irradiation with 297 nm light. The fluorescence spectra of the diarylethene are depended on the concentration.

Abstract: The photochchromic diarylethene was synthesized and explored, which is named 1-(2,4-dimethoxyl-5-pyrimidinyl)-2-[2-methyl-5-(2-trifluoromethylphenyl)-3-thienyperfluorocyclopentene. This compound has shown good photochromic behavior. When irradiated with UV light. The compound changed from colorless to violet, which showed a relatively strong fluorescence switch along with the photochromism from open-ring isomer to closed-ring isomer.

Abstract: A new unsymmetrical photochromic diarylethene with a pyrimidine unit has been successfully synthesized. The photochromism properties in both solution and poly-methylmethacrylate (PMMA) film were investigated in detail. Its fluorescence had a remarkable initial increase with subsequent dramatic decrease with increasing concentration. The results indicated that the pyrimidine moiety played a very important role during the process of photochromic reaction for the diarylethene derivative.

Abstract: A novel photochromic diarylethene bearing a six-membered pyrimidine as one aryl moiety was synthesized to investigate its photochromic behaviors. The diarylethene exhibited good photochromism and functioned as a fluorescence switch both in hexane and in PMMA film. The fluorescence had a remarkable initial increase with subsequent dramatic decrease with increasing concentration. The results suggested that the pyrimidine moiety played a vital role during the process of photoisomerization reaction for the diarylethene.

Abstract: An asymmetrical photochromic diarylethene 1-[2,5-dimethyl-3-thieny-2-[2-methyl-5-(p-N,N-dimethylaminophenyl)-3-thienyperfluorocyclopentene was synthesized and its photochemical properties were investigated in detail. The results demonstrated that the compound has excellent photochromic properties and good fluoresence. The cyclization/cycloreversion process of the compound was determined to be the zeroth/first order reaction. The fluorescence intensity increased with increasing concentration, but when the concentration increased enough high, the fluorescence intensity decreased rapidly.