Thermodynamics of dehydropolycondensation of 2,3,4,5-tetraphenyl-1,1-diethynyl-1-germacyclopentadiene

Conclusions Using an isothermal calorimeter, equipped with a bomb, we measured the enthalpies of combustion of 2,3,4,5-tetraphenyl-1,1-diethynyl-1-germacyclopentadiene and poly-2,3,4,5-tetraphenyl-1,1-diethynyl-1-germacyclopentadiene, and calculated the thermodynamic parameters for their formation under standard conditions, and also the thermodynamic parameters of the polycondensation process.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 6, pp. 1459–1461, June, 1978.     

Correlation NMR spectroscopy of 1,1-dichloro-2,3,4,5-tetraphenyl-1-germacyclopenta-2,4-diene

Assignment of all of the signals in the¹H and¹³C NMR spectra of 1,1-dichloro-2,3,4,5-tetraphenyl-l-germacyclopenta-2,4-diene has been carried out using two-dimensional NMR spectroscopy. Translated fromIzvestiya Akademii Nauk Seriya Khimicheskaya, No. 3, pp. 623–625, March, 1997.     

2,3,4,5-Tetrahydropyridine 1-oxides. Synthesis and properties (review)

Published data on the synthesis and transformations of 2,3,4,5-tetrahydropyridine 1-oxides are summarized for the first time, classified, and analyzed.A. N. Kosygin Moscow State Textile Academy, Moscow. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 4, pp. 435–481, April, 1998.     

Preparation, reactions and stereochemistry at silicon of (2,3,4,5-tetraphenyl-1-silacyclopentadiene)iron tricarbonyls

Twelve derivatives of (2,3,4,5-tetraphenyl-1-silacyclopentadiene)iron tricarbonyls were prepared. These complexes undergo a variety of substitution at silicon. The exo leaving groups showed enhanced reactivity in such reactions. The stereochemistry of substitution also differs significantly from that established for optically active silanes.     

Diorganostannylenes : III. Formation of dimethylstannylene from 1,1-dimethyl-2,3,4,5-tetraphenyl-1-stannacyclopentadiene and acetylenes

Dimethylstannylene, (CH₃)₂Sn:, was formed transiently in the reaction of 1,1-dimethyl-2,3,4,5-tetraphenyl-1-stannacyclopentadiene (stannole) with dimethyl acetylenedicarboxylate or phenylacetylene. When this reaction was carried out in the presence of n-butyl bromide, dimethylstannylene inserted into the CBr bond of n-butyl bromide to give n-butyldimethyltin bromide in 12% yield, but most of the dimethylstannylene was captured by dimethyl acetylenedicarboxylate to give a complex. The complex was also produced in the photolytic reaction of the dimethyltin polymer, [(CH₃)₂Sn]_m, with dimethyl acetylenedicarboxylate. With phenylacetylene, dimethylstannylene did not give a similar complex, but polymerized to give the dimethyltin polymer.     

Synthesis and photophysical properties of lead phthalocyanines

This work reports on the synthesis and photophysical parameters of tetra-and octa-substituted new lead phthalocyanines. The complexes synthesized are: 1,4-(tetraphenoxyphthalocyaninato)lead (7a), 1,4-(tetra-tert-butylphenoxyphthalocyaninato)lead (7b), 2,3-(tetraphenoxyphthalocyaninato)lead (8a), 2,3-(tetra-tert-butylphenoxyphthalocyaninato)lead (8b), 2,3-octaphenoxyphthalocyaninatolead (9a) 2,3-[octakis(4-t-butylphenoxyphthalocyaninato)]lead (9b). Photophysical properties were studied for these complexes in a dimethylsulfoxide, dimethylformamide, toluene, tetrahydrofuran and chloroform. The fluorescence spectra were different from excitation spectra due to demetallation upon excitation. High triplet quantum yields ranging from 0.70 to 0.88 (in DMSO, DMF and toluene) and low triplet lifetimes (20–50 μs in DMSO, and <10 μs in the rest of the solvents) were observed due to the presence of heavy atom.     

Synthesis and photophysical properties of ferrocene-oligothiophene-fullerene triads

To promote photoinduced charge separation previously observed for the oligothiophene-fullerene dyads (nT-C60), we have designed an additional attachment with a strongly electron-donating ferrocene at the unsubstituted terminal site of the oligothiophene and synthesized two types of the ferrocene-oligothiophene-fullerene triads, Fc-nT-C60 directly linking the ferrocene to the oligothiophene and Fc-tm-nT-C60 inserting a trimethylene spacer between the ferrocene and the oligothiophene. For the central oligothiophene of the triads, a homologous series of quaterthiophene (4T), octithiophene (8T), and duodecithiophene (12T) are systematically examined. The cyclic voltammograms and electronic absorption spectra of Fc-nT-C60 indicate conjugation between the ferrocene and oligothiophene components. The emission spectra of Fc-nT-C60 measured in toluene demonstrate that the fluorescence of the oligothiophene is markedly quenched, as compared to that observed for the dyads nT-C60. This quenching is explained in terms of the involvement of intramolecular electron transfer in the photophysical decay process. The additionally conjugated ferrocene evidently contributes to the stabilization of charge separation states, thus promoting intramolecular electron transfer. This is corroborated by the observation that the emission spectra of the nonconjugated triads Fc-tm-nT-C60 are essentially similar to the corresponding dyads nT-C60.     

Electron density distributions in substituted 2,3,4,5-tetraphenyl-1-germacyclopenta-2,4-dienes studied by NMR spectroscopy

The signals in the¹³C NMR spectra of 2,3,4,5-tetraphenyl-1-germacyclopenta-2,4-dienes (R¹=R²=H, Me,cyclo-C₃H₅, SiMe₃, SnMe₃, R¹=Me, R²=H, Cl) were completely assigned using 2D NMR spectroscopy. The pattern of the variation of the chemical shifts in the¹³C NMR spectra indicates that the effects of substituents R¹ and R² on the heterocycle and on the phenyl groups are of inductive rather than mesomeric origin and include the direct through-space polarization of bonds (field effect). Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 1962–1965, November, 1997.     

Synthesis and photophysical properties of phosphole-cored dendrimers

Phosphole-cored dendrimers having poly(benzyl ether) units through the third generation have been synthesized. The dendrimers display intense blue photoluminescence, the quantum yield increasing with the increasing generation of the dendron units. The optical properties are easily tuned by oxidation of the phosphorus atom of the phosphole ring.     

Synthesis and photophysical properties of phenyl-sulfanylated chlororophyll derivatives

Chlorophyll derivatives that possessed a phenylsulfanyl group at the C3¹- or C3²-position were synthesized and their optical properties were investigated. Methyl 3¹-phenylsulfanyl-mesopyropheophorbide-a was prepared by substitutions of the corresponding C3¹-hydroxy-chlorin, methyl bacteriopheophorbide-d, with thiophenol in the presence of zinc iodide or of the corresponding C3¹-bromo-chlorin with thiophenol. The regioisomeric C3²-phenylsulfanyl-chlorin was obtained by addition of thiophenol to the C3-vinyl group of methyl pyropheophorbide-a in the presence of AIBN. Both the synthetic compounds gave similar electronic absorption and emission spectra in chloroform, but fluorescence quantum yield of the C3¹-sulfanyl-chlorin (0.18) was ca. 30% smaller than those of the C3²-sulfanyl-chlorin (0.25) and the C3-ethyl-chlorin (0.24). These observations were consistent with their fluorescence lifetime data. It is suggested that the heavy atom effect of a sulfur atom at the C3¹-position can tune photophysical properties of the chlorophyll derivatives.     

Synthesis and photophysical properties of nonbenzoid ended fluorophores

A series of pi-conjugated compounds (1-23) were successfully synthesized by the Sonogashira, Suzuki, and Wittig-Horner reactions. The structure-property relationship about photoluminescence based on these synthesized compounds was systematically discussed in detail. In addition, energy gaps between ground and excited states of these compounds, which were in good agreement with the experimental observation, were calculated by the semiempirical parametrized PM3 method. It was revealed that emission efficiency largely depends on molecular structure, aggregation type, and size of nanoaggregates.     

Synthesis and photophysical properties of steroid-linked porphyrin-fullerene hybrids

[structure: see text] The photophysical properties of porphyrin-linked fullerene hybrids have generated significant interest, and a number of these hybrids synthesized by this group and others have been extensively characterized with respect to energy and charge-transfer processes that take place upon photoexcitation. Present studies of steroid-linked dyads demonstrate the extent to which through-bond effects operate in these systems.     

Synthesis and photophysical properties of phenothiazine-labeled conjugated dendrimers

A novel class of conjugated dendrimers bearing phenothiazines as peripheral groups and phenylenevinylene-group as a core has been synthesized through the Wittig-Horner reaction in moderate to good yield.     

Synthesis and photophysical properties of tetrafluorophenyl-modified carbazole oligomers

A series of tetrafluorophenyl-modified oligo(3,6-carbazole ethynylene)s (CfCzCf, CfCz2Cf, CfCz3Cf, (CfCz)2Cf, and Cf2CzCf2) were synthesized by a Pd/Cu-catalyzed Sonogashira coupling reaction and fully characterized. Their photophysical and electronic properties as well as their thermal stabilities were investigated. It is noteworthy that these tetrafluorophenyl modified compounds showed relative thermal stabilities and low-lying HOMO levels ranging from −5.54 to −5.60 eV, which might be the promising candidates for hole-transporting materials in OLEDs.     

Synthesis and photophysical properties of metal anthraquinone phthalocyanine

A novel anthraquinone phthalocyanine Al(Ⅲ) 4 and Co(Ⅱ) 5 were synthesized and characterized by elemental analysis, IR, UV/ vis, 1H NMR, HPLC and MS. The photophysical properties of the two metal complexes were studied and compared by ?uorescence spectrum method.     

Synthesis and photophysical properties of electron-rich perylenediimide-fullerene dyad

An electron-rich perylenediimide-C60 dyad has been prepared to explore a new type of donor-acceptor system. Time-resolved absorption measurements in benzonitrile revealed unambiguous evidence for the formation of a charge-separated state consisting of perylene diimide radical cation and C60 radical anion via photoinduced electron transfer, showing a new class of artificial photosynthetic models in terms of charge separation.     

Synthesis and coordination chemistry of 1-cymantrenyl-2,3,4,5-tetraphenylborole

In this contribution, we report the synthesis of base-free 1-cymantrenyl-2,3,4,5-tetraphenylborole and two of its Lewis base adducts. In addition, the structural characterization and investigation of the photophysical properties are provided.     

Synthesis and photophysical properties of fullerene-phthalocyanine-porphyrin triads and pentads

The synthesis and photophysical properties of several fullerene-phthalocyanine-porphyrin triads (1-3) and pentads (4-6) are described. The three photoactive moieties were covalently connected in an one-step synthesis through 1,3-dipolar cycloaddition to C(60) of the corresponding azomethine ylides generated in situ by condensation reaction of a substituted N-porphyrinylmethylglycine derivative and an appropriated formyl phthalocyanine or a diformyl phthalocyanine derivative, respectively. ZnP-C(60)-ZnPc (3), (ZnP)(2)-ZnPc-(C(60))(2) (6), and (H(2)P)(2)-ZnPc-(C(60))(2) (5) give rise upon excitation of their ZnP or H(2)P components to a sequence of energy and charge-transfer reactions with, however, fundamentally different outcomes. With (ZnP)(2)-ZnPc-(C(60))(2) (6) the major pathway is an highly exothermic charge transfer to afford (ZnP)(ZnP(.+))-ZnPc-(C(60)(.-))(C(60)). The lower singlet excited state energy of H(2)P (i.e., ca. 0.2 eV) and likewise its more anodic oxidation (i.e., ca. 0.2 V) renders the direct charge transfer in (H(2)P)(2)-ZnPc-(C(60))(2) (5) not competitive. Instead, a transduction of singlet excited state energy prevails to form the ZnPc singlet excited state. This triggers then an intramolecular charge transfer reaction to form exclusively (H(2)P)(2)-ZnPc(.+)-(C(60)(.-))(C(60)). A similar sequence is found for ZnP-C(60)-ZnPc (3).     

Synthesis and photophysical properties of N‐styrylazinones

N‐Styrylazinones and 1‐styrylbenzotriazine were synthesized, and their photophysical properties were investigated. (Z)‐ and/or (E)‐N‐Styrylazinones (or azine) 4 were prepared from the corresponding heterocycles 1 and benzaldehyde ( 3 ) by four methods. The absorption maxima of (Z)‐ and/or (E)‐ 4a ‐ 4j were measured in four solvents. Their absorption maxima showed a moderate dependence upon solvents. The absorption maxima of (Z)‐isomers were blue‐shifted as compared the corresponding (E)‐isomers. Emission maxima, fluorescence band half‐widths, 0,0 transition energies, Stokes shifts, and quantum yields of (Z)‐ and/or (E)‐ 4a, 4b, 4d, 4e and 4j were measured in organic solvents. The fluorescence spectra show moderate solvatochroism. The fluorescence properties of N‐styrylheterocycles vary with every heterocycles.     

Synthesis, characterization and photophysical properties of benzidine-based compounds

The N-alkylation of the 3,3′-diaminobenzidine with innocent substituents leads to unusual properties. The emission of the benzidine core can be fine-tuned by subtle modifications, and the N-substitution with benzylic groups results in photoinduced exciplexes with distinct and increased emission. This compound constitutes the first example of intramolecular exciplex containing benzidine unit. We also show that these photoinduced processes could be modulated by proton input, and that the diprotonation of the benzidine core disrupted the intramolecular communication in the excited states with a concomitant inhibition of the ligand-centred fluorescence. Furthermore, upon photo-irradiation at 254 nm, semiquinone imine and quinone diimine systems are produced in CH₂Cl₂ of which the photolysis generates Cl radicals, which rapidly oxidize the tetraamine compounds.