Synthesis, modification, and optical properties of C3-ethynylated chlorophyll derivatives

3-Ethynyl-chlorin was prepared from methyl pyropheophorbide-d using Bestmann-Ohira reagent. The mono-substituted acetylene was subjected to copper-free, Pd-mediated coupling to form chlorin derivatives possessing a series of substituted ethynyl groups at the C3-position. Its 1,3-dipolar cycloadditions with azido compounds were also demonstrated.     

Synthesis,stereochemistry and fluorescence properties of polystyrenes having carbazole substituents

Poly(styrene)s bearing carbazole substituents at various positions were synthesised by homopolymerisation of 3-(9-carbazolylmethyl)styrene and 4-(9-carbazolylmethyl)styrene and by chemical modification of preformed poly(styrene)s prepared in the presence of different initiators. Main chain stereochemistry of the polymer samples was investigated by ¹³C-NMR and related to the initiation process. The fluorescence emission spectra were independent of the stereochemistry of polymer backbone and exhibited only monomer emission. In no case was there any evidence of excimer fluorescence. In contrast, energy migration appeared to be very efficient, as evaluated by measurements of the degree of fluorescence polarisation relative to that of a structurally related model compound     

Radiation-induced polymerization of styrene derivatives having alkylamino substituents

The polymerizability of styrene derivatives having alkylamino substituents, such as 1-(2-isopropylaminoethyl)-4-vinylbenzene (IPVB), 1-(2-diethylaminoethyl)-4-vinylbenzene (DEVB) and 1-(2-dimethylaminoethyl)-4-vinylbenzene (DMVB), was investigated in the range −96 to +25° with gamma-rays from a ⁶⁰Co source. The glass transition temperatures were found to be −94° for IPVB, −102° for DEVB and −114° for DMVB. The polymer yield of these monomers prepared by 4 × 10⁶ rad irradiation at −55° was 39.9, 10.4 and 4.9% respectively. On the other hand, the polymer yield of IPVB as a function of irradiation temperature (irradiation dose: 4 × 10⁶ rad) was 2.4% at −96°, 27.4% at −78°, 39.9% at −55°, 35.7% at −37°, 36.4% at −24°, 54.8% at 0° and 71.3% at +25°. Such a trend of temperature-dependent polymer yield also decreased markedly in the order IPVB, DEVB and DMVB. The polymers prepared were soft and gummy, although polymers prepared by irradiating at the doses of 1 × 10⁷ or above were hard and transparent.     

Preparation and nonlinear optical properties of inorganic-organic hybrid films with various substituents on chromophores

Four kinds of hydroxy-ended azobenzene-type chromophores containing different substituent groups as electron donor or electron acceptor were synthesized and further reacted with 3-isocyanatopropyltriethoxysilane (ICTES) to give alkoxysilane dyes via a urethane reaction. Following a sol-gel process of the alkoxysilane dyes, the inorganic-organic hybrid nonlinear optical (NLO) films were successfully prepared. Molecular structures of the resultant films were confirmed by elemental analysis, FTIR, and 1H NMR. The betaCT mu(g) values of the chromophores were evaluated by a solvatochromic method, and the second harmonic coefficients (d33) of the hybrid films were measured by in situ second harmonic generation (SHG) measurement. The hybrid films exhibited large optical nonlinearity and full transparency in the visible range. The effects of substituent group and position on betaCT mu(g) values of the chromophores and d33 values of the films were also discussed.     

Synthesis and mesomorphic properties of benzoxazole derivatives with lateral multifluoro substituents

Fluorinated aromatics is generally chosen as mesogenic cores to design novel liquid crystal compounds. Here, a series of benzoxazole derivatives with laterally multifluorinated biphenyl units, 2-(3′,3-difluoro ?4′-alkoxy-1,1′-biphenyl-4-yl)-benzoxazole derivatives (coded as nPF(3)PF(3)Bx), are synthesized and characterized, where methyl and nitro moieties are selected as terminal groups to investigate the effects of different polar substituents on the liquid crystal properties. The compounds nPF(3)PF(3)Bx show enantiotropic mesophases with mesophase ranges of 0–40°C and 0–63°C on heating and cooling for hydrogen-terminated derivatives (nPF(3)PF(3)BH), 43–93°C and 54–123°C for methyl-terminated ones (nPF(3)PF(3)BM), 60–108°C and 74–152°C for nitro terminated ones (nPF(3)PF(3)BN), respectively. They exhibit photoluminescence emission peaks at 390–392 nm and UV–vis absorption bands with maxima at 327–330 nm, respectively. The results reveal that lateral multifluoro substituents lead to a decrease in melting/clearing points, while electron-withdrawing terminal nitro moiety results in increases in both melting point and mesophase range.     

具有不同取代基团偶氮苯系列分子的二阶非线性光学性质的DFT研究

采用密度泛函理论B3LYP／6-31＋G（d）方法,对实验合成的具有不同取代基团偶氮苯系列分子的电子性质和二阶非线性光学（NLO）效应进行计算分析．结果表明：偶氮（N—N）在分子中分别起到拉电子和传递电荷的作用．对8个分子进行比较发现,含有氨基的分子1b-4b的二阶NLO系数明显的高于含有羟基的分子1a-4a．各分子前线分子轨道跃迁对二阶NLO效应有主要贡献．     

γ-Radiolysis of 5-fluorouracil and 5-fluorouridine derivatives having sulfur-containing substituents

γ-Radiolysis reactions of eight 5-fluorouracil (5-FU) derivatives having sulfonyl group-containing substituents at the 1-position and five 5-fluorouridine (5-FUR) derivatives having thioureido group-containing substituents were studied under the conditions where hydrated electron (e_aq^?) and hydroxyl radical (HO·) become the principal reactive species. The 5-FU and 5-FUR derivatives were radiolyzed to give 5-FU and 5-FUR, respectively. The efficiency of the reactions depended upon the nature of reactive species and also upon the nature of substituents. The reactivity features of the γ-radiolysis reactions are discussed.     

Synthesis, characterization, thermal and optical properties of styrene derivatives having pendant p-substituted benzylic ether groups

The derivatives of styrene monomer, 4-chlorophenyl-4-vinylbenzyl ether (M1), 4-methoxyphenyl-4-vinylbenzyl ether (M2), 4-ethylphenyl-4-vinylbenzyl ether (M3) and 1-naphtylphenyl-4-vinylbenzyl ether (M4) were synthesized. The normal free radical polymerization of monomers in 1,4-dioxane were performed by using 2,2′-azobisisobutyronitrile as an initiator at 65 °C. The monomers and their homopolymers were characterized by FT-IR, NMR and elemental analyses measurements. The thermal stability of polymers was investigated by thermogravimetric and differential scanning calorimetric analysis. Thermal degradation activation energies of the polymers were calculated by the Ozawa and Kissinger methods. In addition, photo-stability tests of the polymers under near-UV irradiation were performed.     

Synthesis and chiroptical properties of cryptophanes having C1-symmetry

New enantiopure cryptophanes 3-7 having C(1)-symmetry have been synthesized. Electronic circular dichroism (ECD) and vibrational circular dichroism (VCD) have been used to investigate their chiroptical properties, and the results are compared to those obtained for cryptophane-A (1) having D(3)-symmetry. The ECD spectra of compounds 3-7 show Cotton effects that differ from those of cryptophane-A. However, our results suggest that a confident determination of the absolute configuration of the monofunctionalized cryptophanes can be made using ECD spectroscopy. Interestingly, we have found that the ECD spectra of cryptophanes, especially the (1)L(b) transition, are very sensitive to the nature of the solvent. These spectral modifications are essentially due to bulk solvent properties rather than the ability of a particular solvent to insert into the cavity of cryptophanes. On the other hand, VCD spectra of the monofunctionalized cryptophanes have not revealed significant spectral modifications with respect to the VCD spectrum of the CHCl(3) at cryptophane-A complex, except for CHCl(3) at 7 and to a smaller extent for CHCl(3) at 6. These spectral modifications, which essentially consist in lower intensities of VCD bands associated with the cryptophane backbone, were perfectly reproduced by ab initio calculations performed at DFT (B3PW91/6-31G*) level. These results clearly demonstrate that VCD measurements associated with DFT calculations allow an easy determination of the absolute configuration of cryptophane-A derivatives.     

Synthesis of methacryloyl-L-alanine derivatives having various carboxyl-protecting groups and thermo-response of its polymer hydrogels

Methacryloyl-L-alanine derivatives having various carboxyl-protecting groups, for example, hydrogen, methyl, ethyl and benzyl groups, were synthesized by reacting L-alanine ester hydrochlorides with methacrylic acid in the presence of triethylamine, by a so-called dicyclohexylcarbodiimide-mediated condensation method. These polymer hydrogels showed a typical thermo-response such as low-temperature-swelling and high-temperature-deswelling, in water, in the range of 0–40°C. Such a response was characterized with regard to kind of carboxyl-protecting group in the hydrogel.     

Elongation of the pi-system of phthalocyanines by introduction of thienyl substituents at the peripheral beta positions. Synthesis and characterization

1,4,8,11,15,18,22,25-octabutoxyphthalocyanines ((OBu)8Pcs) having eight 2-thienyl (1) and [2,2'-bithiophene]-5-yl (2) groups at beta positions and their zinc(II) and cobalt(II) derivatives were prepared from 2-thienyl- (3) or [2,2'-bithiophene]-5-yl (4)-substituted phthalonitriles in moderate to good yields. The electronic absorption spectra of the Pcs showed red-shifted Q-bands relative to beta-unsubstituted (OBu)8Pcs. The longer substituent, the [2,2'-bithiophene]-5-yl group, is more effective than the 2-thienyl group in enlarging the pi-conjugated system of the Pcs. The ring oxidation potential obtained by cyclic voltammetry shifted cathodically with increasing chain length, indicating destabilization of the HOMOs. Due to the shift of the Q-band, 2-thienyl- and [2,2'-bithiophene]-5-yl-substituted Pcs exhibit a remarkable color change from the original green color.     

Synthesis and second-order nonlinear optical properties of push-pull BODIPY derivatives

A series of boron dipyrromethene derivatives bearing an electron-donating 4-(dimethylamino)phenylethynyl group and an electron-withdrawing 4-nitrophenylethynyl group in the opposite 2- and 6-positions have been synthesized by Knoevenagel condensation followed by sequential Sonogashira coupling reactions. The compounds have been fully characterized with various spectroscopic methods. Their electrochemical properties have also been studied by cyclic voltammetry in CH₂Cl₂. It has been found that expansion of the π systems by introduction of the 4-dodecyloxystyryl or 4-(dimethylamino)phenylethynyl group results in lowering of the first oxidation potential, while the first reduction potential remains relatively unaffected. The second-order nonlinear optical properties of these compounds have also been studied by electric-field-induced second-harmonic generation method in CHCl₃. The values of the dot product μ·β are in the range from 94×10^?48 to 330×10^?48 esu at 1907 nm, depending the substituents at the 3- and 5-positions.     

Synthesis and properties of a fluorene-capped isotruxene: a new unsymmetrical star-shaped pi-system

An unsymmetrical star-shaped pi-system (1) with an isotruxene core and three fluorene arms has been synthesized, and its photophysical, electrochemical, and thermochemical properties have been investigated and compared with the corresponding symmetrical truxene derivatives 2a-d (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). Stronger electronic couplings between the arms in 1 vs 2a-d lead to lower optical band gap, larger splitting in oxidation potentials, and superior thermostability. [structure: see text]     

双查尔酮衍生物的合成和三阶非线性光学性质

合成一种新颖的D-π-A-π-D型双查尔酮衍生物4,4?-二[3-(芘-1-基)丙烯酰基]联苯,经IR、1H NMR、MS和元素分析对其结构进行表征.在波长为480 nm、脉宽为4 ns的激光脉冲激发下,应用4f相位相干成像技术测量了其三阶光学非线性性质,并测定了紫外光谱和DSC曲线.     

Synthesis and optical properties of β-arylethylene derivatives of 2,5-diphenyloxazole

A series of arylethylene derivatives of 2,5-diphenyloxazole derivatives is synthesized, and the absorption and fluorescent spectra of their toluene solutions are investigated. Joining in one molecule of 2,5-diphenyloxazole and arylethylene groups leads to long wave displacement of the absorption and fluorescence bands, and in most cases to greater intensity of absorption and increase in the photoluminescence quantum yield.     

Synthesis and polymerization of vinyl esters and vinyl ethers having bulky substituents

In order to clarify the effect of bulky substituents on the stereoregulation of vinyl monomers, vinyl-1-adamantanecarboxylate and vinyl 1-adamantyl ether were synthesized and polymerized by radical and cationic mechanisms, respectively. As open-chain models of the adamantyl group, vinyl trialkylacetate (alkyl = ethyl, n-propyl, and n-butyl) and vinyl tri-n-propylcarbinyl ether were also synthesized and polymerized. The adamantly group in the vinyl ester favored syndiotactic propagation in a manner similar to the trimethylcarbinyl group. Higher homologs of tri-n-alkylcarbinyl group showed higher syndiotacticity but this effect was saturated in higher members of the series. The effect of the adamantyl group in vinyl ether was similar to that of the tert-butyl group, leading to high isotacticity on cationic polymerizations in nonpolar solvents and to atactic polymers in polar solvents, but the tri-n-propylcarbinyl group was found unique in leading to what was assumed to be a heterotactic polymer. Polymers with the adamantyl group showed much higher softening points than polymers of the corresponding open-chain groups.     

Fluorinated Alq3 derivatives with tunable optical properties

This communication reports that not only the emission colour but also the photoluminescence quantum yield of Alq3 can be tuned by introducing fluorine atoms at different positions; with fluorination at C-5 the emission is red-shifted with a tremendously decreased intensity, fluorination at C-6 causes a blue-shift with a significantly increased intensity, and fluorination at C-7 has a minor effect on both the colour and intensity of Alq3's emission.     

Synthesis of bicyclopyrroles with various substituents at the bridging positions

Bicyclopyrroles are important synthetic equivalents of isoindoles, which are difficult to synthesize. Using bicyclopyrrole as a starting material, functional organic materials such as benzopyrromethene and benzoporphyrin can be synthesized. However, there are few reports on introducing substituents into bridging positions in bicyclopyrrole. By combining various reactions, we successfully obtained bicyclopyrroles with various substituents at the bridging positions.