Yangfu Ming

‘ACIDICHROMICS’ of Photochromic Spirooxazines

Abstract Acidichromism of four photochromic spirooxazine compounds (SP) were investigated systematically. When hydroxyl group is introduced on the naphtho ring of spirooxazine, the spirooxazine compounds are found to have acidichromic properties in both acidic and basic solutions. Substituent effect on the absorption maximum of acidichromic products has been discussed. A comprehensive discussion of acidichromic, photochromic and thermochromic processes is included.

Synthesis and photochromic mechanism of 3,4-bis[2,5-dimethylthiophene-3-yl]-2,5-dihydrothiophene

Abstract A novel photochromic compound, 3,4-bis[2,5-dimethylthiophene-3-yl]-2,5-dihydrothiophene (BT), has been synthesized. The photochromic reactions of BT in a polar solvent (acetonitrile) and a non-polar solvent (cyclohexane) were investigated by means of steady state absorption spectra and time-resolved transient absorption spectra. The maximum absorption wavelengths of BT in acetonitrile and cyclohexane are at 232 and 233 nm, respectively, and the maximum absorption wavelengths of the photocyclization product (CBT) in acetonitrile and cyclohexane are 445 and 453 nm, respectively. Upon irradiation with ultraviolet light, BT is first excited to the excited singlet state, and then to the excited triplet state via inter-system crossing. Only the excited singlet state generates CBT. The excited triplet state, which has a maximum absorption wavelength at 390 nm, decays rapidly to the starting compound (BT) alone.

STUDIES ON FLUORESCENT SPECIES OF SPIRO-INDOLINONAPHTHOOXAZINES AND THEIR FLUORESCENCE SPECTRA

Photophysical behavior of spiro[1,3,3-trimethylindolino-2,3′-naphtho[2,1-b]-1,4-oxazine] (SP1) and spiro[1,3,3,2′-tetramethylindolino-2,3′-naphtho[2,1-b]-1,4-oxazine] (SP2) were studied. The fluorescent species and their spectra of SP1 and SP2 in polar solvents (acetonitrile and methanol) and non-polar solvent (cyclohexane) were investigated. The fluorescence decay in polar solvents was studied by picosecond time-correlated single photon counting. In most cases, fluorescence decay obeyed triexponential decay kinetics. The major fluorescent species is an excited intermediate which has similar conformation as its precursor (1SP*) formed after the bond cleavage between spirocarbon and oxygen in oxazine ring. The effects of molecular structure and solvent polarity on fluorescence spectra and fluorescence decay lifetime were studied.

Syntheses and photochromic behaviour of 1,2-bis(1-alkyl-2-methylindol-3-yl)cycloalkene derivatives

Abstract Six novel 1,2-bis(1-alkyl-2-methylindol-3-yl)cycloalkene derivatives were designed and synthesized by the intramolecular coupling reaction using low-valance titanium as catalyst. Photochromic properties of these compounds were initially investigated. The results show that the fatigue resistant properties of these compounds, the thermal stability and the absorption maxima of their photocyclization products are influenced by the ring size of cycloalkene and substituents on the heterocyclic rings.

Photochromic properties and reaction mechanism of naphthopyran

The photochromic properties and reaction mechanism of title compounds have been examined with steady method on compounds 3-phenyl-3-[3-methylbenzothiophene-2-yl]-3H-naphtho[2,1-b]pyran (1) and 3-phenyl-3-[benzofuran-2-yl]-3H-naphtho[2,1-b]pyran (2) and nanosecond laser flash photolysis techniques on compound 3-phenyl-3-[1,2-dimethylindol-3-yl]- 3H-naphtho[2,1-b]pyran (3). The influence of oxygen on transient spectra and decay kinetics of compound3 has been investigated. Both excited singlet state and triplet state are involved in the photochromic mechanism of compound3. The influence of molecular structure on photochromic behavior has been studied also. Decay kinetics indicated that the lifetime of colored forms of1 and2 were several orders of magnitude longer than that of3.

Structure effect on photochromic mechanism of spirooxazines

Abstract Structure effect on photochromic mechanism of 1,3,3-trimethylspiro[indoline-2,3′-[3H]naphtho[2,1,-b][1,4]oxazine] (SP1), 1,3-Dimethyl-3,2′-(1,3 -propylene)spiro[indoline-2,3′-[3H] naphtho[2,1-b][1,4]oxazine] (SP2) and 1,2′-(1,3-propylene),3,3-dimethylspiro[indo- line-2,3′ [3H]naphtho[2,1-b][1,4]oxazine](SP3) have been studied by nanosecond laser photolysis. Because of different connective positions of 1,3-propylene group in SP2 and SP3, the photochromic behaviours of them are quite different. One photoproduct of SP2 was only detected, and its lifetime is about 0.15μs. However, two colored forms of SP3 were detected after UV irradiation. The lifetimes of them are much longer than that of C-SP2. The semiempirical computational results by AM1 method were coincided with the experimental results.

Photochromic Mechanism of Heterofused Benzopyran Derivatives

Abstract ABATRACT The photochromic behavior of 2-phenyl-2-(thien-2-yl)-2H-benzo [b]furano[3,2-f]benzopyran (1) and 2,2-diphenyl-2H-benzo[b] furano[3,2-f]benzopyran (2) was examined by the nanosecond laser photolysis and normal time scale analysis. The results showed that the thienyl group could stabilize the colored forms as compared with the phenyl group and both singlet and triplet states were involved in the formation of the colored forms.

Synthesis and Photochromic Mechanism of 3-Phenyl-3-[1,2-Dimethylindol-3-yl]-3H-Naphtho[2,1-b]Pyran

Abstract A novel photochromic compound, 3-phenyl-3-(1,2-dimethylindol-3-yl)-3H-naphtho[2,1-b] pyran (I) was synthesized and the mechanism for photochromic process of I was investigated by nanosecond laser flash photolysis.

Synthesis and Photochromic Behavior of 1,2-bis(1,3-dimethylindol-2-yl)cycloalkenes

Abstract Two novel 1,2-bis(1,3-dimethylindol-2-yl)cycloalkenes(2) were designed and synthesized by intramolecular coupling reaction using low-valance titanium as catalyst. Photochromic properties of these compounds were initially investigated. The results show that the thermal stability of colored form of 2 is much better than that of 1,2-bis(1-ethyl-2-methylindol-3-yl)cycloalkenes(4), and the absorption maximum of them is shorter than that of 1,2-bis(1-ethyl-2-methylindol-3-yl)cycloalkenes.

1-(3-Methylbenzo[b]thiophen-2-yl)-2-(2-methylin dol-3-yl)cycloal-kenes, novel photochromic compounds responding to InGaN blue laser

Abstract A novel kind of photochromic compounds, the derivatives of 1-(3-Methylbenzo[b]thiophen-2-yl)-2-(2-methylindol-3-yl)cyclo-alkene was successfully synthesized. The absorption bands of the closed-forms of these compounds centered at 440 nm thus possessing the sensitivity within the wavelength range of InGaN blue laser.