Carbolithiation of substituted stilbenes and styrenes with dithianyllithiums

Carbolithiation of a range of substituted stilbenes and styrenes with dithianyllithiums is described, leading to the rapid, efficient and stereocontrolled assembly of highly functionalized dithiane intermediates for acyl-equivalents synthesis.     

Arylethynylacridines: electrochemiluminescence and photophysical properties

Electrogenerated chemiluminescence (ECL) of six new ethyne-based acridine derivatives (1-6) has been studied. The new acridine derivatives were synthesized by cross-coupling of 9-chloroacridine and corresponding donor-substituted phenylethynes under modified Sonogashira conditions. The donor groups were varied in the order of increasing steric hindrance and donor strength at the donor site. The solution phase photophysical properties and ECL of these compounds were studied comparatively in acetonitrile solvent. The UV-Visible spectra of compounds 1-5 exhibit closely the same maxima. Density functional theory (DFT) has been invoked to analyze and understand the unexpected UV-Visible absorption behavior. Compounds with weak electron donors produce excimer ECL irrespective of steric hindrance at the donor site, while the compound with a stronger donor gives rise to ECL that is blue-shifted with respect to its photoluminescence spectrum. All except one of these compounds also exhibit solid state fluorescence which may be useful for solid state devices such as organic light emitting diodes (OLEDs) and as laser dyes. The observed properties are discussed with reference to the structure of the compounds synthesized.     

A boron-containing carbazole dimer: synthesis, photophysical properties and sensing properties

A novel boron-containing π-conjugated compound has been synthesized by the introduction of electron-acceptors (dimesitylboron groups) at the 3,3'-positions of a carbazole dimer (electron-donor). The compound possesses excellent electrochemical properties and high fluorescence quantum yields. In addition, is a sensitive fluorescence sensor with remarkable colour changes and the results could be confirmed through theoretical calculations of the compounds and [(n)Bu(4)N](+)(2)[·(F)(2)](2-). Our studies indicate that could be used as an excellent optoelectronic material in OLED devices and a ratiometric fluorescent chemosensor.     

Dendritic phthalocyanines: synthesis,photophysical properties,and aggregation behavior

This mini-account describes our recent effort to exploit dendritic phthalocyanines, focusing on their photophysical properties and aggregation behavior in water and in microheterogeneous media. Two series of dendritic phthalocyanines have been prepared. The ones with terminal ester functionalities are non-aggregated in common organic solvents, exhibiting an intramolecular singlet-singlet energy transfer from the excited aryl-containing dendrons to the phthalocyanine core. The other series contain terminal carboxylate groups of which the aggregation tendency in water decreases as the size of the dendron increases. The lower-generation analogues are susceptible to surfactants, in particular the cationic n-hexadecyltrimethylammonium bromide (CTAB), and poly(ethylene oxide) (PEO), which are very effective to disrupt the molecular aggregation of phthalocyanines. The interactions have been monitored by absorption and fluorescence spectroscopy together with laser light scattering. The photophysical properties of the dendrimer/PEO complexes have also been studied by transient spectroscopy. To cite this article: D.K.P. Ng, C. R. Chimie 6 (2003).     

Double-lanthanide-binding tags: design, photophysical properties, and NMR applications

Lanthanide-binding tags (LBTs) are peptide sequences of up to 20 encoded amino acids that tightly and selectively complex lanthanide ions and can sensitize terbium (Tb3+) luminescence. On the basis of these properties, it was predicted that increasing the number of bound lanthanides would improve the capabilities of these tags. Therefore, using a structurally well-characterized single-LBT sequence as a starting point, a "double-LBT" (dLBT), which concatenates two lanthanide-binding motifs, was designed. Herein we report the generation of dLBT peptides and luminescence and NMR studies on a dLBT-tagged ubiquitin fusion protein. These lanthanide-bound constructs are shown to be improved luminescent tags with avid lanthanide binding and up to 3-fold greater luminescence intensity. NMR experiments were conducted on the ubiquitin construct, wherein bound paramagnetic lanthanides were used as alignment-inducing agents to gain residual dipolar couplings, which are valuable restraints for macromolecular structure determination. Together, these results indicate that dLBTs will be valuable chemical tools for biophysical applications leading to new approaches for studying the structure, function, and dynamics of proteins.     

Dimeric quinacridone cyclophanes: Synthesis,structures,and photophysical properties

Two novel quinacridone (QA) cyclophanes with intrinsic intramolecular dye-dye interactions have been designed and synthesized.X-ray crystal structures as well as detailed photophysical properties have been well demonstrated.These two dyes have a major advantage that efficient fluorescence quenching can be observed even in their dilute solutions.A comparison of photophysical properties between the dimeric QA cyclophane and its reference monomeric counterpart indicates that the dimerization is predominant for...     

CuI/l-proline-catalyzed selective one-step mono-acylation of styrenes and stilbenes

Vicinal di-oxygenation of styrene-type olefins was achieved with cheaper, less toxic CuI in the presence of l-proline as ligand and NaIO₄ as the oxidant. This approach provides a straightforward and efficient access to mono-acylated diols from both styrene and stilbene derivatives with good to excellent yields and diastereoselectivity.     

New carbazole-containing polyphenylquinoxalines: Synthesis,photophysical, and electroluminescent properties

New carbazole-containing polyphenylquinoxalines combining the electron-transport behavior of quinoxaline with hole-transport and electroluminescent properties of carbazole have been synthesized. The polymers show solubility in organic solvents. Their glass transition temperatures range from 315 to 370°C, and temperatures corresponding to 10% weight loss vary from 510 to 560°C (in air). It has been demonstrated that these polymers exhibit electroluminescent behavior in the 450–750 nm spectral region and offer promise as emitting and electron-hole transport materials for polymeric light-emitting diodes.     

Synthesis and photophysical properties of 2,3,4,5-tetraphenyl-1-n-octyl-1-monophosphole

Russian Chemical Bulletin - A new method for the preparation of 2,3,4,5-tetraphenyl-1-octyl-1-monophosphole was developed. It was shown that the reaction of n-octyl chloride with a mixture of...     

Spectral,luminescent, and photophysical properties of dipyrrolylbenzenes

Dipyrroles with a phenylene bridge, 1,4-bis(pyrrol-2-yl)benzene, 4-(1-vinylpyrrol-2-yl)-1-(pyrrol-2-yl)benzene, and 1,4-bis(1-vinylpyrrol-2-yl)benzene, show intense room-temperature fluorescence in solutions. Analysis of electronic absorption spectra, fluorescence spectra, and results of B3LYP, TD B3LYP, and CIS quantum chemical calculations showed that the introduction of a bulky substituent in position 1 of the pyrrole ring makes the ground-state structures of dipyrrolylbenzenes less planar. Excited-state geometries of all molecules relax to more planar conformations. An increase in the probability of nonradiative transitions has little effect on the quantum yields of fluorescence (Φ_f) of dipyrrolylbenzenes. Even for 1,4-bis(1-vinylpyrrol-2-yl)benzene, where the pyrrole rings deviate from the benzene ring plane by 44°, the fluorescence efficiency remains high enough (Φ_f = 0.7). Substitution at nitrogen atoms has little effect on positions of fluorescence band maxima. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 7, pp. 1433–1438, July, 2008.     

Cobaltacarborane-phthalocyanine conjugates: Syntheses and photophysical properties

Syntheses of two new cobaltacarborane-phthalocyanine conjugates, one anionic (Pc 6) and one zwitterionic (Pc 7), were accomplished via cyclotetramerization of the corresponding cobaltacarborane-substituted phthalonitriles (4 or 5) with excess phthalonitrile in quinoline. X-ray structures of two phthalonitrile precursors (2 and 3) were obtained and are discussed, and the absorption and emission properties of the two cobaltacarborane-phthalocyanine conjugates in several solvents were investigated. The anionic conjugate 6 exists mainly as a monomer in polar organic solvents and has fluorescence quantum yields in the region 0.2-0.3. The zwitterionic conjugate 7 aggregates in solution and displays lower quantum yields ∼0.1 in organic solvents.     

Pyrene-BODIPY-substituted novel water-soluble cyclotriphosphazenes: synthesis,characterization, and photophysical properties

In the present work, pyrene-boron-dipyrromethene (BODIPY)-substituted novel water-soluble cyclotriphosphazene derivatives (6 and 7) were synthesized by click reactions between a cyclotriphosphazene derivative with a hydrophilic glycol side group (2) and BODIPYs (4 and 5). All of the new compounds (2, 6, and 7) were characterized by Fourier-transform infrared and nuclear magnetic resonance spectroscopy, as well as mass spectrometry and elemental analysis. The photophysical properties of the BODIPY-substituted cyclotriphosphazenes (6 and 7) were investigated by UV-Vis and fluorescence emission spectroscopy in water and water/solvent mixtures. It was found that the target compounds were soluble in water and could be potential candidates as water-soluble fluorescent dyes for the desired applications.     

New star-shaped triarylamines: synthesis, mesomorphic behavior, and photophysical properties

A total of 18 compounds 1-6 derived from triphenylamine as core group were prepared and characterized, and their mesomorphic properties were also investigated. Compounds 1-4 and 5,6 were prepared from p,p′,p″-triformyltriphenylamine and p,p′-diformyltriphenylamine with appropriate alkoxyphenylamines. The phase behavior of these mesogenic compounds was characterized and studied by differential scanning calorimetry, polarized optical microscopy, and powder XRD diffraction. Compounds 1-3 exhibited columnar mesophase, however, compounds 4-6 were nonmesogenic. The mesophases observed in compounds 1-3 were found to be side dependent. Compounds 1a, 2a, and 3a appended with one, two, or three side chains exhibited lamellar columnar (Col_L) phases, and compounds 2b and 3b with four or six side chains formed hexagonal columnar (Col_h) phases. The formation of the mesophases, lamellar or columnar mesophases, was probably induced by H-bonding formed between -CH₂NH groups. The oxidation process determined by cyclic voltammetry showed two redox waves, one appeared at 220-255 mV and the other one at 503-677 mV, which gave energy to HOMOs range of 5.02-5.36 eV. The fluorescent properties of the compounds were examined. All λ_max peaks of the absorption and photoluminescence spectra of compounds occurred at ca. 307-392 nm and 368-456 nm, respectively. Compound 4a has a larger red shift due to a better conjugation linked by CC double bonds instead of -CH₂NH in other compounds.     

Highly fluorescent N,N-dimethylaminophenylethynylarenes: synthesis, photophysical properties, and electrochemiluminescence

A new family of aryl-pi-donor-aryl molecules has been synthesized and studied with respect to their photophysical properties and electrogenerated chemiluminscence (ECL) for the first time. Anthracene, phenanthrene, naphthalene, biphenyl, and fluorene were coupled with N,N-dimethylanilino moiety via a C-C triple bond (1-7). Introduction of such a strong electron-donating moiety as N,N-dimethylanilino group through a triple bond imparts new properties to the resultant molecules that are not commonly observed for the parent arenes. All molecules show absorption in the near-visible region and emission totally in the visible region with high fluorescence quantum yields. Bright solid-state photoluminescence has also been noticed for all the compounds in the visible region. 9-Anthryl- and 1-naphthyl- derivatives exhibited blue-shifted electrochemiluminescence (ECL) relative to their photoluminescence because of aggregation. 9-Phenanthryl- and 2-naphthyl- derivatives did not show ECL. 2-Biphenyl derivative showed monomeric ECL while 4-biphenyl counterpart exhibited excimer ECL. No ECL was observed for 2-fluorenyl derivative. The observed electronic properties are discussed with regard to the structure of the molecules. The characteristics of the molecules chosen in the present study open up new prospects and promises for novel tunable organic materials, on the basis of simple extension of conjugation to promote intramolecular communication, for ECL, OLED, and other optoelectronic applications.     

Hexa boron-dipyrromethene cyclotriphosphazenes: synthesis, crystal structure, and photophysical properties

We have synthesized four examples of a cyclotriphosphazene ring appended with six boron-dipyrromethene dyes N(3)P(3)(BODIPY)(6) by adopting two different methods. In method I, 1 equiv of N(3)P(3)Cl(6) was treated with 6 equiv of meso-(o- or m- or p-hydroxyphenyl)boron-dipyrromethene in tetrahydrofuran (THF) in the presence of cesium carbonate. This afforded N(3)P(3)(BODIPY)(6) in yields ranging from 80 to 90%. In method II, we first prepared hexakis(p-formylphenoxy)cyclotriphosphazene N(3)P(3)(CHO)(6) by treating 1 equiv of N(3)P(3)Cl(6) with 6 equiv of 4-hydroxybenzaldehyde in the presence of cesium carbonate in THF. In the second step, N(3)P(3)(CHO)(6) was condensed with excess of pyrrole in the presence of catalytic amount of trifluoroacetic acid (TFA) in CH(2)Cl(2) at room temperature and afforded hexakis(p-phenoxy dipyrromethane)cyclotriphosphazene. In the last step, the hexakis(p-phenoxy dipyrromethane)cyclotriphosphazene was first oxidized with 6 equiv of DDQ in CH(2)Cl(2) at room temperature for 1 h followed by neutralization with triethylamine and further reaction with excess BF(3)·Et(2)O afforded the target N(3)P(3)(BODIPY)(6) in 16% yield. The route II was used only for the synthesis of one target compound whereas the route I was used for the synthesis of all four target compounds. The four compounds were characterized by mass, NMR, absorption, electrochemical, and fluorescence techniques. The crystal structure solved for one of the compounds revealed that the P(3)N(3) ring is slightly puckered and the six substituents were not interacting with each other and attained pseudo-axial and pseudo-equatorial positions. The photophysical studies in five different solvents indicated that the compounds exhibit large Stokes' shifts unlike reference monomeric BODIPYs indicating that the compounds are promising for fluorescence bioassays. The quantum yields and lifetimes of compounds 1-4 depends on the type of BODIPY unit attached to the cyclotriphosphazene ring.     

Asymmetrically tetra-substituted phthalocyanine derivatives: synthesis,photophysical and photochemical properties

Transition Metal Chemistry - The syntheses of highly soluble asymmetrically substituted metal free and zinc phthalocyanine derivatives bearing three 4-(4-(5-phenyl-1,3,4-oxadiazol-2-yl)phenoxy) and...     

Starburst substituted hexaazatriphenylene compounds: synthesis, photophysical and electrochemical properties

Starburst-substituted hexaazatriphenylene compounds have been designed and synthesized by introducing various peripheral aryl substituents to the central heterocyclic core. The effects of various substituent groups on the photophysical and electrochemical properties of the substituted hexaazatriphenylene have been investigated. Significant red-shifts of the absorption peak (from 413 nm to 530 nm) and emission peak (from 432 nm to 700 nm) were observed when the electron-donating ability of the aryl substituents was increased, corresponding to a decrease in the band gap from 2.90 eV to 2.05 eV. Introducing bulky substituents with weak electron-donating ability enhances the fluorescence quantum yield from 23% to 87%. In contrast, incorporating aryl substituents with strong electron-donating ability decreases the fluorescence quantum yield. Also, due to the extended conjugation between the aryl substituents and the hexaazatriphenylene core, the reduction potentials of the compounds were reduced and the LUMO levels were thus increased.     

Axially phenoxy-derivative disubstituted phthalocyanine: synthesis,characterization and photophysical properties

Research on Chemical Intermediates - We report the highly soluble axially disubstituted 4-(methoxymethyl) phenol silicon (IV) (1) phthalocyanine which was synthesized by the reaction of silicon...     

A tetrathiafulvalene-functionalized naphthalene diimide: synthesis, electrochemical and photophysical properties

A tetrathiafulvalene donor has been attached to the naphthalene diimide core via a rigid bridge affording a new planar molecular dyad. Its electronic properties have been studied experimentally by the combination of electrochemistry and UV-vis-NIR spectroscopy. Various electronic excited charge-transfer states are generated in different oxidation states, leading to almost full absorption in the visible to near-IR region with high extinction coefficients. The observed electronic properties are explained on the basis of density-functional-theory. In particular, the oxidized radical species show a strong tendency to undergo aggregation, in which the long-distance attractive interactions overcome the electrostatic repulsions.