Synthesis of 2H-benzo[g]furo/thieno/pyrrolo[2,3-e]indazoles via Intramolecular Dehydrogenation Photocyclization

A catalyst-,acid-and base-free,environmental-friendly method for synthesis of 2/7-benzo[g]furo[2,3-e]indazoles,2H-benzo[g]-thieno[2,3-e]indazoles and 2H-benzo[g]pyrrolo[2,3-e]indazoles via UV light irradiation of 3-phenyl-4-(2-heteroaryl)pyrazoles(aryl=furanyl,thiophenyl and N-methylpyrrolyl)in EtOH/H_(2)O at room temperature under argon atmosphere was described.

Crystal Structure and ESIPT Phenomena of Anionic 2H-Phenanthro[9,10-c]pyrazol-11-ols

Using 4＇-methoxy-5-hydroxyisoflavone and 4＇,5-dihydroxy-7-methoxyisoflavone as leding compounds,6-methoxy-2 H-phenanthro[9,10-c]pyrazol-11-ol（1 a） and 9-methoxy-2 Hphenanthro [9,10-c]pyrazol-6,11-diol（1 b） were synthesized by two dehydration processes in the EtOH solution.They were characterized by IR,^1H NMR and ^13C NMR.The black prism crystal of 1 a was grown by the slow solvent evaporation technique from 40：1（v/v） CHCl3/MeOH,and it was determined by single-crystal X-ray diffraction.In the crystal structure,1 a was stabilized by intramolecular（O–H···N） and intermolecular（N–H···O,O–H···O,π···π,C–H···π） interactions.In addition,the fluorescence properties of 1 a and 1 b in the base and neutral media revealed that they possessed excited state intramolecular proton transfer phenomena（ESIPT）.

Enhancing tetraphenylethene cyclization as photoswitch

Tetraphenylethene(TPE),a star building block with promising aggregationinduced emission,has received much interest.Given that its intramolecular Woodward-Hoffmann cyclic intermediate instantaneously converts back to the original state within several picoseconds,the essentially photochromic characteristic of TPE is little investigated.Achieving a visible photocyclization of TPE is still an unsolved issue and considered as the bottleneck in the further advancement of applications.We report a strategy of attaching carbonate ester onto the TPE skeleton(TPE-4C)to enhance TPE photocyclization stability.As demonstrated,the incorporated cholesteryloxycarbonyloxy substituents in TPE-4C can increase the energy barrier for cycloreversion,thereby exhibiting extremely thermal stability of photocyclic intermediate upon UV irradiation,prolonging its lifetime from 63 picoseconds to 46 s by 7.2×10^(11)-fold.The photoinduced cyclization of TPE-4C could be monitored with naked eyes,and the photocyclization/cycloreversion is achieved by turning on/off UV light along with a relative fatigue resistance.Encapsulation of TPE-4C into the liquid crystal can induce a striking phase transformation(achiral↔chiral),which can be applicable to encode optical information.Employing carbonate ester into the TPE unit plays a vital role in enhancing the unprecedented TPE photocyclization stability,providing a toolbox to allow TPE-based photocyclization to be visually monitored.

Photochromism of cis(z)-1,2-bispyrryl-substituted ethene derivatives

Photochromism of two bispyrryl-substituted ethenes, 2, 3-bis-(1-p-methoxyphenyl-5-phenyl-2-methyl-3-pyrryl)-2-butene (BPE1) and 2,3-bis(1-p-bromophenyl-4-phenyl-2-methyl-3-pyrryl)-2-butene (BPE2), was studied by laser flash photolysis technique. The results indicate that photocyclization of these compounds proceeds mainly via the excited triplet state, and the cis-trans isomerization proceeds mainly via the excited singlet state. After UV laser pulse irradiation, both photocylization and cis-trans isomerization of BPEl occur, but photocydization is the main reaction. On the other hand, laser photolysis of BPE2 leads mainly to photocydization. The effects of the substituents on the photochromic mechanism are also discussed.

Tunable photocycle kinetics of a hybrid bacteriorhodopsin/quantum dot system

The inclusion of inorganic nanoparticles in biological environments has led to the creation of hybrid nanosystems that are employed in a variety of applications. One such system includes quantum dots (QDs) coupled with the photoactive protein, bacteriorhodopsin (BR), which has been explored in developing enhanced photovoltaic devices. In this work, we have discovered that the kinetics of the BR photocycle can be manipulated using CdSe/CdS (core/shell) QDs. The photocycle lifetime of protein samples with varying QD amounts were monitored using time-resolved absorption spectroscopy. Concentration-dependent elongations of the bR and M state lifetimes were observed in the kinetic traces, thus suggesting that excitonic coupling occurs between BR and QDs. We propose that the pairing of BR with QDs has the potential to be utilized in protein-based computing applications, specifically for real-time holographic processors, which depend on the temporal dynamics of the bR and M photointermediates.

pH-dependence of interaction between melittin and bacteriorhodopsin

Melittin differentially slowed down the fast (M412f) and the slow (M412s) decay components of the photocyde intermediate M of trimeric bacteriorhodopsin in purple membrane while it accelerated the M412s of Triton X-100-solubilized bacteriorhodopsin monomers. Raising the bulk pH could enhance the effect of melittin on the M412s of bacteriorhodopsin in these two states. From pH 5.5 to 8.8, melittin slightly influenced the yield of intermediate M in purple membrane, whereas the yield of M412s decreased and subsequently reversed with the addition of melittin. Moreover, the monomeric bacteriorhodopsin bleached more readily in the presence of melittin and the higher pH made the bleaching effect of melittin more intensive as well. These results re-certify our former suggestions that there was electrostatic interaction between melittin and bacteriorhodopsin, and indicate that the biphasic M decay may not result from the well-known linear kinetic scheme (M→N →BR). At last the mechanisms underlying the interaction of melittin with purple membranes and bacteriorhodopsin monomers are analyzed.