Synthesis and photophysical properties of [3.3](3,9)carbazolophanes

Syn- And anti-[3.3](3,9)carbazolophanes, which are suitable model compounds for sandwich and partial-overlap excimers, respectively, have been synthesized and characterized; the structures of both singlet and triplet carbazole excimer have been described.     

Synthesis, photophysical and photochemical properties of substituted zinc phthalocyanines

The synthesis, photophysical and photochemical properties of the 4-({3,4,5-tris-[2-(2-ethoxyethoxy)ethyloxy]benzyl}oxy) and 4-({3,4,5-tris-[2-(2-ethoxyethoxy)ethyloxy]benzyl}thio) zinc(ii) phthalocyanines are reported for the first time. The new compounds have been characterized by elemental analysis, IR, (1)H and (13)C NMR spectroscopy, electronic spectroscopy and mass spectra. General trends are described for photodegradation, singlet oxygen, fluorescence and triplet excited state quantum yields, and triplet state and fluorescence lifetimes of these compounds in dimethylsulfoxide (DMSO). The fluorescence of the complexes was quenched by benzoquinone (BQ). The effects of the substitution on the photophysical and photochemical parameters of the zinc(II) phthalocyanines (6, 7 and 8) are also reported. Photophysical and photochemical properties of phthalocyanine complexes are very useful for PDT applications. The substituted Zn(II) phthalocyanines showed high triplet and singlet oxygen quantum yields. High singlet oxygen quantum yields are very important for Type II mechanism. Thus, these complexes show potential as Type II photosensitizers.     

Synthesis,structure, and NMR characterization of a novel [3.3] metacyclophane

The synthesis and crystal structure of metacyclophane 2 are reported. The nmr data relevant to conformational properties are also presented.     

Synthesis,photophysical and photochemical properties of tetra- and octa-substituted gallium and indium phthalocyanines

The synthesis, photophysical and photochemical properties of the tetra- and octa-[4-(benzyloxyphenoxy)] substituted gallium(III) and indium(III) phthalocyanines are reported for the first time. The new compounds have been characterized by elemental analysis, IR, ¹H NMR spectroscopy and electronic spectroscopy. General trends are described for quantum yields of photodegredation, fluorescence quantum yields and lifetimes, triplet lifetimes and triplet quantum yields as well as singlet oxygen quantum yields of these compounds in dimethylsulfoxide (DMSO). Substituted indium phthalocyanine complexes (7b–9b) showed much higher quantum yields of triplet state and shorter triplet lifetimes, compared to the substituted GaPc derivatives due to enhanced intersystem crossing (ISC) in the former. The gallium and indium phthalocyanine complexes showed phototransformation during laser irradiation due to ring reduction. The singlet oxygen quantum yields (Φ_Δ), which give an indication of the potential of the complexes as photosensitizers in applications where singlet oxygen is required (Type II mechanism) ranged from 0.51 to 0.94. Thus, these complexes show potential as photodynamic therapy of cancer.     

Synthesis, photophysical and photochemical properties of aryloxy tetra-substituted gallium and indium phthalocyanine derivatives

The synthesis, photophysical and photochemical properties of the tetra-substituted aryloxy gallium(III) and indium(III) phthalocyanines are reported for the first time. General trends are described for photodegradation, singlet oxygen, fluorescence, and triplet quantum yields and triplet lifetimes of these compounds. The introduction of phenoxy and tert-butylphenoxy substituents on the ring resulted in lowering of fluorescence quantum yields and lifetimes, and triplet quantum yields, and an increase of k_IC, k_ISC, and k_F. Photoreduction of the complexes was observed during laser flash photolysis. The singlet oxygen quantum yields (Φ_Δ), which give an indication of the potential of the complexes as photosensitizers in applications where singlet oxygen is required (Type II mechanism) ranged from 0.41 to 0.91. Thus, these complexes show potential as Type II photosensitizers.     

Helically chiral functionalized [6]helicene: Synthesis,optical resolution,and photophysical properties

A short and efficient synthetic pathway leading to a new chiral π-conjugated system is reported. The X-ray structure of the target compound was determined and showed a helical conformation. Its resolution was successfully accomplished, leading to two enantiomers in high optical purity, and their chiroptical properties were examined experimentally. The photophysical properties of the organic material were also evaluated, showing an emission in the visible region, and HOMO and LUMO levels have been estimated experimentally, demonstrating an electrochemical band gap of 2.37 eV.     

Synthesis, photophysical and photochemical properties of poly(oxyethylene)-substituted zinc phthalocyanines

The synthesis, photophysical and photochemical properties of the tetra- and octa-poly(oxyethylene)substituted zinc (II) phthalocyanines are reported for the first time. The new compounds have been characterized by elemental analysis, IR, 1H and 13C NMR spectroscopy, electronic spectroscopy and mass spectra. General trends are described for photodegradation, singlet oxygen, triplet state and fluorescence quantum yields, and triplet and fluorescence lifetimes of these compounds in dimethylsulfoxide (DMSO). Photophysical and photochemical properties of phthalocyanine complexes are very useful for PDT applications. The effects of the substituents on the photophysical and photochemical parameters of the zinc(II) phthalocyanines (3a, 5a and 6a) are also reported. The singlet oxygen quantum yields (Phi(Delta)), which give an indication of the potential of the complexes as photosensitizers in applications where singlet oxygen is required (Type II mechanism) ranged from 0.60 to 0.72. Thus, these complexes show potential as Type II photosensitizers. The fluorescence of the complexes was quenched by benzoquinone (BQ).     

Synthesis and photophysical properties of benzo[c]thiophene,p-phenylene-, triphenylamine-, and pyrene-based vinylenes

An efficient synthesis of benzo[c]thiophenyl/p-phenylenyl/pyrenyl phosphonate esters has been achieved using ZnBr₂-catalyzed Michaelis–Arbuzov reaction of corresponding benzyl alcohol/bromides at room temperature. Horner–Wadsworth–Emmons reaction of the phosphonate esters with aryl/heteroaryl aldehydes in the presence of t-BuOK furnished the vinylenes in good yields. The absorption and emission characteristics of the synthesized vinylenes were also reported.     

Synthesis and photophysical properties of novel pyrimidine-based two-photon absorption chromophores

Three new two-photon absorption chromophores based on a pyrimidine core were synthesized by Aldol condensation in the absence of any organic solvents. Their single-photon spectroscopic characterization as well as their two-photon absorption properties is reported. In addition, strong modulation of single-photon and two-photon fluorescent spectra of these molecules by (de)protonation is also discussed.     

Red-emitting dyes with photophysical and photochemical properties controlled by pH

New unsymmetrical zinc azaphthalocyanines, bearing one substituted aniline as a peripheral substituent, were prepared by using a statistical condensation approach. Both fluorescence and singlet oxygen quantum yields were extremely low in DMF (Φ(F)<0.01, Φ(Δ)<0.02, respectively), but increased after the addition of sulfuric acid, reaching values comparable to controls without aniline substituents (Φ(F)=0.22-0.29, Φ(Δ)=0.40-0.59, respectively). This behavior was attributed to the deactivation of excited states by intramolecular charge transfer from a donor site (aniline), which was blocked after protonation in acidic media. In the protonated form, all of the compounds efficiently emitted light with λ(em) in the region of 662-675 nm. The investigated compounds were anchored to dioleoylphosphatidylcholine (DOPC) unilamellar vesicles and showed response to buffer pH. They were highly fluorescent at low pH values and almost nonfluorescent in neutral solutions. The pK(a) values were determined in DOPC vesicles and ranged between 2.2 and 4.2.     

Synthesis of o-benzoquinones derived from [2.2]- and [3.3]paracyclophanes

Oxidation of [2.2]- and [3.3]paracyclophanols with benzeneseleninic anhydride readily afforded the corresponding cyclophane-o-quinones which showed the intramolecular charge-transfer interactions.     

Synthesis and solvent dependence of the photophysical properties of [60]fullerene-sugar conjugates

A method for the synthesis of optically pure C₆₀ derivatives containing one or two d-galactose or d-glucose units is described. It involves the synthesis of sugar-malonate derivatives followed by a cyclopropanation reaction with C₆₀. The solvent dependence of the photophysical properties of the methano[60]fullerene-sugar derivatives was studied using nanosecond laser flash photolysis coupled with kinetic UV-vis absorption spectroscopy and time-resolved singlet oxygen luminescence measurements. The triplet properties of these fullerenes, including transient absorption spectra, molar absorption coefficients and quantum yield for the photosensitised production of ¹O₂ were determined in toluene, benzonitrile and acetonitrile solutions. The transient absorption spectral profiles are solvent independent although small differences are observed in the transient absorption maximum: 720±5 nm for toluene, 710±5 nm for benzonitrile and 700±5 nm for acetonitrile. Triplet state molar absorption coefficients (ε_T) of C₆₀ derivatives vary from 9456±2090 M⁻¹ cm⁻¹, for compound 10 in toluene, and 15,272±4462 M⁻¹ cm⁻¹, for compound 6 in acetonitrile. Triplet state lifetimes (τ_T) for methano[60]fullerene-sugar derivatives, under our experimental conditions, are similar in toluene or benzonitrile solutions (47.5±1.1 μs≤τ_T≤51.4±2.0 μs) but are lower in acetonitrile solutions (31.8±0.6 μs≤τ_T≤43.0±1.1 μs). Toluene and benzonitrile solutions of C₆₀ derivatives have Φ_Δ close to unity.     

Organosilane polymers: Synthesis and photochemical and photophysical behavior of poly[dimethyl-co-methyl(1-naphthyl)silylene]

A meltable, partially crystalline silane copolymer, PSN, containing dimethylsilylene and methyl(1-naphthyl) silylene units was synthesized and characterized. The polymer has a high molecular weight, is appreciably soluble in common solvents and is photoactive. The emission properties of PSN, under stationary and nonstationary conditions, were studied in dilute THF solution. PSN is the first organosilane polymer showing an intense intramolecular excimer emission in addition to monomer and intramolecular charge transfer (CT) fluorescence. It is shown that the ratio of excimer to monomer fluorescence can be used to monitor the UV induced degradation of the polymer.     

新型双光子吸收化合物的合成、光物理及其在固态分散体系中的性质

通过多步反应制备了三个新型的双光子吸收化合物,测试了它们的光物理性质,发现该系列化合物具有较大的双光子吸收截面,并且随温度降低其双光子吸收截面增大.尤其是化合物TMVDB,其量子效率为0.83,常温时的双光子吸收截面达到1164GM,其双光子吸收截面除以分子量为2.08,表现出了优良的双光子吸收发光性能.进一步将TMVDB掺杂到固体材料中,得到强双光子诱导发光的固体材料.     

Synthesis,characterization, photophysical and electrochemical properties of triazinooxacalix[2]arenes with bisphenol A motif

Oxygen atom bridged calixarene derivatives called oxacalixarenes were synthesized from bisphenol A and cyanuric chloride by aromatic nucleophilic substitution through addition elimination mechanism. All the synthesized oxacalixarenes exhibit strong absorbance band between 225 and 286?nm due to the presence of triazine and phenoxy units. The oxacalixarenes 7 and 10 show strong fluorescence emission and higher λ_em values than all other oxacalixarenes due to the presence of rigid aromatic spacer units such as binol and biphenyl. All the oxacalixarenes exhibit quasi-reversible behaviour and potential shift observed in cyclic voltammetry.     

Photoreaction of a 2,11-diaza[3.3]paracyclophane derivative: formation of octahedrane by photochemical dimerization of benzene

Upon photoirradiation at 300 nm, the title diazaparacyclophane (R = COCF3) provided an octahedrane by the photodimerization of its benzene chromophores. This is the first photochemical formation of octahedrane, namely, via the dimerization of benzene. No octahedrane formation was observed for the photolysis of corresponding carbon-bridged paracyclophane. Thus the nitrogen bridges play an important role in the excited state to afford the octahedrane.     

Structural properties of five- and six-layered [3.3]metacyclophanes

We performed X-ray structural analyses of the five- and six-layered [3.3]metacyclophanes (MCPs) 1 and 2 and the six-layered [3.3]MCP tetraone 3. In the solid state, the MCP moieties of 1, 2, and 3 adopt different conformations from those of the free MCPs in solution. In the five-layered [3.3]MCP 1, all the [3.3]MCP moieties adopt anti (chair/boat) conformations. In the six-layered [3.3]MCP 2, two three-layered [3.3]MCPs are connected by a [3.3]MCP in the anti conformation with completely parallel benzene rings. In the six-layered [3.3]MCP tetraone 3, the outer [3.3]MCP moieties and diones adopt general syn and anti geometries, respectively. However, the inner [3.3]MCP moiety adopts an anti geometry. Based on density functional theory (DFT) calculations, the most stable conformers of 1, 2, and 3 are syn (chair/chair) in the [3.3]MCP moieties and anti (twist boat/twist boat) in the dione moieties.     

Synthesis, structure, and transannular pi-pi interaction of multilayered [3.3]metacyclophanes

The synthesis of a series of three- to six-layered [3.3]metacyclophanes ([3.3]MCPs) 3-6 has been successfully accomplished by the (p-tolylsulfonyl)methyl isocyanide (TosMIC) method as a critical coupling reaction. Their important synthetic intermediates are the two- and three-layered bis(bromomethyl) compounds 11, 17, 21, and tetrakis(bromomethyl) compounds 25 and 28. The structures of the three- to six-layered [3.3]MCPs (3-6) as well as three- to six-layered [3.3]MCP-di- (22-24) and tetraones (26, 27, and 29) as the synthetic intermediates have been elucidated based on the 1H NMR data and X-ray structural analysis. These multilayered cyclophanes are constructed with two different geometries, syn-[3.3]MCP and anti-[3.3]MCP-2,11-dione. In principle, their geometries are maintained in the multilayered [3.3]MCPs, but deformation of the dihedral angle of the two benzene rings of the syn-[3.3]MCP moiety is generally observed. In the four-layered MCP 4, the central [3.3]MCP moiety takes an anti geometry. These data indicate the structural flexibility of the [3.3]MCP moiety. In the electronic spectra, rather simple and structureless absorption curves are observed, and the most significant spectral change is observed for the two to three layers and becomes less effective even if it is more layered. In the charge-transfer (CT) bands of the multilayered [3.3]MCPs with tetracyanoethylene (TCNE), the lambdamax gradually shifts to the longer wavelength region, but the extent of the shift is much smaller as the number of layers increases. In the multilayered [3.3]MCP-di- and tetraones, the anti-[3.3]MCP-dione moiety works as an insulator. Therefore, the CT interaction of the four- and five-layered [3.3]MCPs with one anti-[3.3]MCP-dione moiety (23 and 24) shows the almost comparable magnitude of the interaction with the two- and three-layered [3.3]MCPs (2 and 3), respectively. The tetraones of the three and four-layered MCPs (29 and 26) do not show CT interactions except for the six-layered MCP 27.