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The solvent-controllable photoreaction of 4-methoxyazobenzenes to afford 1-aryl-1H-benzimidazoles or N-arylbenzene-1,2-diamines has been studied. The irradiation of 4-methoxyazobenzenes in DMF containing 0.5 M hydrochloric acid provided N2-aryl-4-methoxybenzene-1,2-diamines as the major product, while irradiation in acetal containing 0.16 M hydrochloric acid led to 1-aryl-6-methoxy-2-methyl-1H-benzimidazoles as the major product. A possible reaction mechanism explaining the selectivity was also discussed.

Homogeneous catalysts PtCl2[5,5&prime, bis-(n-ClCF2(CF2)3CH2OCH2)-2,2&prime, bpy] (2A) and PtCl2[5,5&prime, bis-(n-HCF2(CF2)3CH2OCH2)-2,2&prime, bpy] (2B), which contained short fluorous chains, were synthesized and used in catalysis of hydrosilylation of alkynes. In these reactions the thermomorphic mode was effectively used to recover these catalysts from the reaction mixture up to eight cycles by taking advantage of heterogeneous phase separation at ice temperature. This kind of catalysis had previously been observed in fluorous catalysts of platinum containing about 50% F-content, but in this work the percentage of F-content is decreased to only about 30%, by which we termed them as &ldquo, very light fluorous&rdquo, Our new type of catalyst with limited number of F-content is considered as the important discovery in the fluorous technology field as the reduced number of fluorine atoms will help to be able to comply the EPA 8-carbon rule. The metal leaching after the reaction has been examined by ICP-MS, and the testing results show the leaching of residual metal to be minimal. Additionally, comparing these results to our previous work, fluorous chain assisted selectivity has been observed when different fluorous chain lengths of the catalysts are used. It has been found that there exists fluorous chain assisted better selectivity towards &beta, (E) form in the Pt-catalyzed hydrosilylation of non-symmetric terminal alkyne when the Pt catalyst contains short fluorous chain (i.e., 4 Cs). Phenyl acetylenes showed the opposite regioselectivity due to pi-pi interaction while using the same catalyst via Markovnikov&rsquo, s addition to form terminal vinyl silane, which is then a major product for Pt-catalyzed hydrosilylation of terminal aryl acetylene with triethylsilane. Finally, the kinetic studies indicate that the insertion of alkyne into the Pt-H bond is the rate-determining step.

The solvent-controllable photoreaction of 4-methoxyazobenzenes to afford 1-aryl-1

The objective of this study was to synthesize the 9-/13-position substituted berberine derivatives and evaluate their cytotoxic and photocytotoxic effects against three human cancer cell lines. Among all the synthesized compounds, 9-O-dodecyl- (5e), 13-dodecyl- (6e), and 13-O-dodecyl-berberine (7e) exhibited stronger growth inhibition against three human cancer cell lines, (HepG2, HT-29 and BFTC905), in comparison with structurally related berberine (1). These three compounds also showed the photocytotoxicity in human cancer cells in a concentration-dependent and light dose-dependent manner. Through flow cytometry analysis, we found out a lipophilic group at the 9-/13-position of berberine may have facilitated its penetration into test cells and hence enhanced its photocytotoxicity on the human liver cancer cell HepG2. Further, in cell cycle analysis, 5e, 6e, and 7e induced HepG2 cells to arrest at the S phase and caused apoptosis upon irradiation. In addition, photodynamic treatment of berberine derivatives 5e, 6e, and 7e again showed a significant photocytotoxic effects on HepG2 cells, induced remarkable cell apoptosis, greatly increased intracellular ROS level, and the loss of mitochondrial membrane potential. These results over and again confirmed that berberine derivatives 5e, 6e, and 7e greatly enhanced photocytotoxicity. Taken together, the test data led us to conclude that berberine derivatives with a dodecyl group at the 9-/13-position could be great candidates for the anti-liver cancer medicines developments.

The objective of this study was to synthesize 9-/13-position substituted berberine derivatives and evaluated their cytotoxic and photocytotoxic effects against three human cancer cell lines. Among all the synthesized compounds, 9-O-dodecyl- (5e), 13-dodecyl- (6e) and 13-O-dodecyl-berberine (7e) exhibited stronger growth inhibition against three human cancer cell lines, (HepG2, HT-29 and BFTC905), in compare with structurally related berberine (1). These three compounds also showed the photocytotoxicity in human cancer cells in a concentration-dependent and light dose-dependent manner. Through flow cytometry analysis, we found out a lipophilic group at 9-/13-position of berberine may have facilitated its penetration into test cell and hence enhanced its photocytotoxicity on human liver cancer cell HepG2. Further, in cell cycle analysis, 5e, 6e and 7e induced HepG2 cells to arrest at S phase and caused apoptosis upon irradiation. In addition, photodynamic treatment of berberine (1) and its derivatives 5e, 6e and 7e again showed a significant photocytotoxic effects on HepG2 cells, induced remarkable cell apoptosis, greatly increased intracellular ROS level and the loss of mitochondrial membrane potential. These results over and again confirmed that berberine derivatives 5e, 6e and 7e greatly enhanced photocytotoxicity. Taking together, the test data led us to conclude that berberine derivatives with a dodecyl group at 9-/13-position could be great candidates for the anti-liver cancer medicines developments.

Herein, we prepared dual-stabilizer-capped CuInZnS/ZnS (CIZS/ZnS) quantum dots (QDs) in aqueous media via hydrothermal routes. On using the combination of poly (styrenesulfonic acid-co maleic acid) and glutathione stabilizers, we found that dual stabilizers effectively coat the surface of CIZS/ZnS QDs, resulting in high quantum yields and carboxylic acid groups that conjugate with various materials. To demonstrate their potential biomedical application, the dual-stabilizer-capped CIZS/ZnS QDs were conjugated with 3-aminophenylboronic acid, termed CIZS/ZnS@APBA, for HeLa tumor cell labeling. In vitro and in vivo assessments using HeLa cells and zebrafish embryos, respectively, revealed that these CIZS/ZnS@APBA nanoprobes exhibit low cytotoxicity under our experimental conditions. Confocal scanning laser imaging demonstrated that the nanoprobes can be efficiently internalized and are localized in the cytoplasm of HeLa cells. This work reveals the potential for use of CIZS/ZnS@APBA as a safe and effective targeted probe for in vivo imaging of cancer.

The 1,4-diarylnaphthalenes, 1,4-diarylanthracenes, and 9,10-diarylanthracenes containing the different side arenes, including phenyl, 2-thienyl, and 2-furyl groups, were synthesized to study the influence of structures on π-conjugation. According to photophysics and computation, the smaller dihedral angles and the lateral benzene of anthracene would increase the π-conjugation in some cases. Compared to 1,4-diarylnaphthalenes, 1,4-di(thien-2-yl)anthracene, 1,4-di(fur-2-yl)anthracene, and 9,10-di(fur-2-yl)anthracene displayed better π-conjugation in both of the ground and fluorescing excited states, but 9,10-di(thien-2-yl)anthracene only showed better π-conjugation in the fluorescing excited state.

The construction of different types of substituted arenes was demonstrated through the photocyclization of 2-(fur-3-yl)ethenylarenes using a 3-furyl group as an isopropenyl equivalent synthon in the photocyclization reaction. The furan portion of the photocyclization intermediate could be fragmented via a base-induced elimination reaction to yield a series of substituted polyaromatics, including naphthalene, benzofuran, benzothiophene, phenanthrene, phenalene, acenaphthene, and triphenylene. Using different reagents, this method made it possible to introduce methyl or 2-hydroxyethyl groups as substituents at specific positions in these arenes.

A novel stilbene-ether type of photolabile protecting group (PPG) for hydroxyl group has been developed. It contains a stable aryl ether group in the protected form and can be deprotected by acid-catalyzed photorearrangement under 300-nm irradiation. The selective deprotection has also been achieved by irradiation of the mixture of 4-alkoxystilbene and 2-(4-alkoxystyryl)furan at 365 nm.

Five pentiptycene-derived stilbene systems ( 1R ; R = H, OM, NO, Pr, and Bu) have been prepared and investigated as light-driven molecular brakes that have different-sized brake components ( 1H < 1O M< 1N O< 1P r< 1B u). At room temperature (298 K), rotation of the pentiptycene rotor is fast (krot = 10 8 -10 9 s � 1 ) with little interaction with the brake compo- nent in the trans form ((E)- 1R ), which corresponds to the brake-off state. When the brake is turned on by photo- isomerization to the cis form ((Z)- 1R ), the pentiptycene rotation can be arrest- ed on the NMR spectroscopic time- scale at temperatures that depend on the brake component. In the cases of (Z)- 1N O ,( Z)- 1P r, and (Z)- 1B u, the rotation is nearly blocked (krot = 2- 6s � 1 ) at 298 K. It is also demonstrated that the rotation is slower in (D6)DMSO than in CD2Cl2. A linear relationship between the free energies of the rotational barrier and the steric parameter A values is present only for (Z)- 1H ,( Z)- 1O M, and (Z)- 1N O, and it levels off on going from (Z)- 1N O to (Z)- 1P r and (Z)- 1B u. DFT calcula- tions provide insights into the substitu- ent effects in the rotational ground and transition states. The molar reversibili- ty of the E-Z photoswitching is up to 46 %, and both the E and Z isomers are stable under the irradiation condi

The synthesis, photophysics, cyclic voltammetry, spectroelectrochemistry, and electrogenerated chemiluminescence (ECL) properties of a series of unsymmetrical star-shaped oligophenylenes IT1-IT4 are reported. The electronic couplings among the three oligofluorene arms in IT1-IT4 are strong due to the para-ortho branched isotruxene core. The ortho conjugation effect results in band splitting in the absorption spectra for both the neutral and the radical ionic form with a stronger effect for the latter. However, such an ortho conjugation effect becomes weaker as the oligofluorene arms are longer. The same fluorescence maxima displayed by IT2-IT4 suggest that the exciton coherence size (or the bound electron-hole pair) is no larger than 16 phenylene rings. The little chain-length dependence of the first reduction and oxidation potentials for IT1-IT4 suggests that the reversible electron-transfer processes of the neutral species are mainly associated with the isotruxene core. The ECL of IT1-IT4 is from the singlet excited state, but the spectra are red shifted with respect to the fluorescence spectra of dilute solutions due to the reabsorption effect. Our results also reveal that the meta conjugation interactions in the previously reported C 3-symmetrical truxene-oligofluorene analogs T1-T4 (Kanibolotsky, A. L.; Berridge, R.; Skabara, P. J.; Perepichka, I. F.; Bradley, D. D. C.; Koeberg, M. J. Am. Chem. Soc. 2004, 126, 13695-13702) are rather weak.

The reactivity of the >CH2 and >NH groups of barbituric acid (BTA) toward the two terminal -C=C- groups of N,N’-bismaleimide-4,4′-diphenylmethane (BMI) was studied with the aid of three model compounds (N-phenylmaleimide (PMI) containg one -C=C- group, 1,3-dimethylbarbituric acid (1,3DMBTA) containing 1 >CH2 group and 5,5-dimethylbarbituric acid (5,5DMBTA) containing 2 >NH groups per molecule) and a molecular probe (hydroquinone (HQ)) that was capable of detecting free radical polymerization. Kinetics studies (DSC) and molecular structure characterization (1H-NMR) showed that it was the >CH2 group of BTA that predominated in the isothermal polymerization of BMI with BTA in N-methyl-2-pyrrolidone in the temperature range 373–403 K. On the contrary, the 2 >NH groups of BTA did not contribute to polymerization of BMI with BTA to an appreciate extent.

The reactions of 3-substituted-diphenylamine cation radicals in acetonitrile were studied using an electron transfer stopped-flow method. In the reactions of the 3-chloro-diphenylamine cation radicals (mCl-DPA·+), the main reaction route was the formation of the benzidine dimer, which was similar to the case of the diphenylamine cation radical (DPA·+). Although the reaction of DPA·+ proceeded via the cation radical-cation radical coupling as verified from the rate law of −d[DPA·+]/dt=k[DPA·+]2, the present kinetic analysis has revealed that the decay rate of mCl-DPA·+ was dependent on the concentration of the neutral molecules, i.e., the rate law was expressed as −d[mCl-DPA·+]/dt=k[mCl-DPA·+]2 [mCl-DPA]. In contrast, the reaction of the 3-methoxy-diphenylamine cation radical (mMeO-DPA·+) was too fast to be observed using the stopped-flow method, which is quite in contrast to the 4-methoxy-diphenylamine cation radical (pMeO-DPA·+) which was very stable in acetonitrile. In the case of mMeO-DPA·+, the cyclization reaction was confirmed to proceed soon after the generation of mMeO-DPA·+, which is similar to the case of the 3-methyl-diphenylamine cation radical (mMe-DPA·+). Thus, it was found that the substituent on the 3-position changed the reaction pathways of DPA·+ significantly, as well as their reactivity.

A series of substituted p -terphenyls and 11,12-dihydroindeno[2,1- a ]fluorene were successfully synthesized by one-pot benzannulation of Diels–Alder reaction with 1,2-dichloroethene as an acetylene equivalent dienophile. Two chlorine atoms could be good leaving groups to easily undergo subsequent elimination reactions of Diels–Alder products at a high temperature.

Photoinduced electron transfer from the singlet excited state of 2-styrylthiophenes (1a-1f) to p-DCB (p-dicyanobenzene) has been proposed from the negative value of ΔG E T (the free energy of the electron transfer) calculated by the Rehm-Weller equation. This leads to the formation of radical cations of 1a- 1f and a radical anion of p-DCB. The p-nitro derivative 1g can not result in the radical cation due to the positive ΔG E T value which results from the unfavorable singlet excitation energy (E 0 , 0 ) and oxidation potential. Regioselective amination by ammonia to the radical cations of 1a-1e has occurred to afford 1-amino-1-aryl-2-(thien-2-yl)ethanes (2a-2e) in reasonable yields (50-90%). The regioselectivity arises from the attack of ammonia at the localized positive charge on C-1 of the ethene bond of the radical cations of 1a-1e.

Irradiation of 3-(4-substituted styryl)furans in basic media yielded a series of 7-substituted-2-methylnaphthalenes, including methoxy, isopropyl, ethyl, methyl, fluoro, and cyano substituents. This base-induced photorearrangement involves cis–trans photoisomerization, 6e photocyclization, base-induced elimination, and a Norrish Type I photoreaction and is a novel method to synthesize unsymmetrical 2,7-disubstituted naphthalenes.

The construction of different types of substituted arenes was demonstrated through the photocyclization of 2-(fur-3-yl)ethenylarenes using a 3-furyl group as an isopropenyl equivalent synthon in the photocyclization reaction. The furan portion of the photocyclization intermediate could be fragmented via a base-induced elimination reaction to yield a series of substituted polyaromatics, including naphthalene, benzofuran, benzothiophene, phenanthrene, phenalene, acenaphthene, and triphenylene. Using different reagents, this method made it possible to introduce methyl or 2-hydroxyethyl groups as substituents at specific positions in these arenes.

A sterically hindered water-soluble porphyrin, tetrakis(3-sulfonatomesityl)porphyrin (H2TSMP), could form stable radical cation in aqueous media after electrochemical one electron oxidation. The anodic oxidation of H2TSMP in the presence of tripropylamine or C2O42− as a coreactant in aqueous solution produces electrogenerated chemiluminescence (ECL) with maxima at 640 and 700 nm. The same emission spectrum of ECL and fluorescence indicates that the ECL emission is from the singlet state of H2TSMP. The annihilation reactions of ZnTSMP +and ZnTSMP −, which are generated electrochemically, in CH3CN+H2O (1:1) mixed solution results in an emission which is identical to the photoluminescence. Protection of the active sites against the nucleophilic attack of water or OH− by sterical hinderance is a successful strategy in designing new ECL-active compounds in aqueous media. Both ECL reaction mechanisms are proposed.

A series of substituted phenanthroquinones (PQ’s) was prepared, their phosphorescence spectra and decay rate constants, cyclic voltammograms, and photoreaction in the presence of tetramethylethylene (TME) were investigated. With 450 nm irradiation their triplet excited state cyclized with TME to give the corresponding dioxenes, 2′,2′,3′,3′-tetramethyl-1′,4′-dioxa-1′,2′,3′,4′-tetrahydrotriphenylene, cleanly and much faster than that with 300 nm irradiation. The pattern of the reaction was effected weakly in random fashion by the substituent at the 3-position of PQ’s. The photocycloaddition, as exemplified by PQ itself, is so efficient that it occurred even by room light and during optical spectroscopic recordings; its limiting quantum yield in benzene is established to be unity with 450 nm irradiation. It owes the unusual efficiency to a long lifetime of the PQ triplet excited state with the n – ∗ π configuration, and to the successful cyclization in every diffusion controlled collision as implicated by TME quenching of PQ phosphorescence intensity in CCl 4 solution. The triplet excited state reaction was supported by competitive quenching of the dioxene formation by triplet quenchers as well as by oxygen. These PQ’s do not fluoresce in solution, but show phosphorescence in solid solution with lifetimes of about 10 ms and in CCl 4 solution with lifetimes in the order of 100 μs in the room temperature range. PQ’s with 3-cycano, 3-chloro, 3-methoxy, and without substitutions photocyclized to cyclohexene to give the corresponding dioxenes with small stereochemical scrambles, that was interpreted that the extent of electron transfer in the 1,6-diradical stage is small. Similar photocycloadditions to isobutene gave a 1:1 mixture of two regio-isomers, this was taken as evidence for a direct radical attack on olefins to give 1,6-diradical intermediates.

Four polyimides (PIa-PId) containing 4,4′-hexafluoroisopropylidene-bisphthalic anhydride (6FDA) units in the backbone were prepared via one-step synthesis. The effects of different doses of gamma radiation from a cobalt-60 source are studied. The irradiated and the unirradiated polyimides are characterized by using tensile strength, infrared (IR), viscosity, differential scanning calorimeter (DSC), and gel permeation chromatography (GPC). All polyimides show the increase of tensile strength and elongation at low doses (>350 Mrad). The molecule weights decrease as the irradiation doses increase. All samples showed a drastic degradation of the mechanical and thermal properties at doses above 1400 Mrad. Samples irradiated at a dose of 2800 Mrad were completely brittle. The major difference of the radiation effect of the polyimides depends largely on their structural differences. PId with an extra hexafluoroisopropylidene moiety is most sensitive to irradiation at high doses.

The unconstrained green fluorescence protein (GFP)-like chromophore m-DMABDI displays a high solvatofluorochromicity in aprotic solvents, but the fluorescence is quenched in protic solvents. According to the site-specific intramolecularly hydrogen-bonded analogs 1OH and 2OH, the hydrogen bonding to the carbonyl oxygen is more important than that to the imino nitrogen of the imidazolinone group in the fluorescence quenching.

Irradiation of 3-(4-substituted styryl)furans in basic media yielded a series of 7-substituted-2-methylnaphthalenes, including methoxy, isopropyl, ethyl, methyl, fluoro, and cyano substituents. This base-induced photorearrangement involves cis–trans photoisomerization, 6e photocyclization, base-induced elimination, and a Norrish Type I photoreaction and is a novel method to synthesize unsymmetrical 2,7-disubstituted naphthalenes.

Photochemical reaction pathways during direct irradiation of stilbene analogues (1a−1d) can be switched completely by adjusting the concentration of hydrochloric acids. Competitive ring opening and...

A novel photochemical transformation from N-alkyl(p-methoxyphenyl)arylamines (1a-1f) to 1,2,4-trihydro(4aH)-carbazol-3-ones (2a-2f) is reported with the assistance of protonation at the dihydrocarbazole intermediate followed by sequential formal [1,5]hydrogen, [1,3]hydrogen shifts and proton assisted hydrolysis.

A room-temperature light-driven molecular brake (1), consisting of a pentiptycene rotator, a 3,5-dinitrophenyl brake, and a photoisomerizable ethenyl spacer, is reported. The rotation rates of the rotator differ by about 9 orders of magnitude between the brake-on (cis-1) and brake-off (trans-1) states.

New photorearrangement product 2 and hydrolysis product 3 are obtained by irradiating acidic halostyrylheterocycles 1a – f . The competing formal [1,3]hydrogen shift and ring opening of dihydrophenanthrene intermediate is responsible for the product formation. The halogen substituent effect on the product distribution has been studied. Photolysis of 5 can reversibly be converted to 2 . Similar photoreactivity for the styrylfuran and styrylthiophene systems is observed.

In this study, we demonstrate that Cu2ZnSn(SxSe1−x)4 nanocrystals with a tunable bandgap could be synthesized by a “hot-injection” protocol. In this protocol, metal stearates dissolved in oleylamine were injected into a hot solution of anion precursors in 1-octadecene (ODE) at a given reaction temperature. ODE, which is a low-cost, low-hazard, and air-stable liquid, was used as the solvent. Oleylamine was chosen as both the reagent to activate the precursors and as the capping agent for the nanocrystals. The composition of the Cu2ZnSn(SxSe1−x)4 nanocrystals could be adjusted across the x range from 0 to 1 by varying the S/Se reactant ratio. The lattice parameters (a and c) measured from X-ray diffraction patterns decreased linearly with increasing Se content. This trend was consistent with Vegard's law, which confirmed the formation of homogeneous Cu2ZnSn(SxSe1−x)4 nanocrystals. The A1 symmetry modes of the Cu2ZnSn(SxSe1−x)4 nanocrystals seen by Raman spectroscopy gradually shifted with decreasing x (S content) to the lower frequency side and completely disappeared when x = 0. The absorption spectra of the Cu2ZnSn(SxSe1−x)4 nanocrystals revealed that the bandgaps of the nanocrystals could be adjusted over the range 1.0–1.5 eV by decreasing the S content. The relatively small value for the bowing parameter indicated that the synthesized Cu2ZnSn(SxSe1−x)4 nanocrystals had good miscibility.

A novel photochemical transformation from N-alkyl(p-methoxyphenyl)arylamines (1a-1f) to 1,2,4-trihydro(4aH)-carbazol-3-ones (2a-2f) is reported with the assistance of protonation at the dihydrocarbazole intermediate followed by sequential formal [1,5]hydrogen, [1,3]hydrogen shifts and proton assisted hydrolysis.