Nano-engineering lattice dimensionality for a soft matter organic functional material.

A high performing electro-optic (EO) chromophore with covalently attached coumarin-based pendant groups exhibits intermolecular correlation of coumarin units through molecular dynamics (MD) simulations. Unique, orthogonal molecular orientations of the chromophore and coumarin units are also evident when investigated optically. Such molecular orientation translates to reduced lattice dimensionality of the bulk C1 soft matter material system, leading to increased acentric order and EO activity.

Solution-based synthesis of crystalline silicon from liquid silane through laser and chemical annealing.

We report a solution process for the synthesis of crystalline silicon from the liquid silane precursor cyclohexasilane (Si(6)H(12)). Polysilane films were crystallized through thermal and laser annealing, with plasma hydrogenation at atmospheric pressure generating further structural changes in the films. The evolution from amorphous to microcrystalline is characterized using scanning electron microscopy (SEM), atomic force microscopy (AFM), Raman spectroscopy and impedance spectroscopy.

Rational enhancement of second-order nonlinearity: bis-(4-methoxyphenyl)hetero-aryl-amino donor-based chromophores: design, synthesis, and electrooptic activity.

Two new highly hyperpolarizable chromophores, based on N,N- bis-(4-methoxyphenyl) aryl-amino donors and phenyl-trifluoromethyl-tricyanofuran (CF3-Ph-TCF) acceptor linked together via pi-conjugation through 2,5-divinylenethienyl moieties as the bridge, have been designed and synthesized successfully for the first time. The aryl moieties on the donor side of the chromophore molecules were varied as to be thiophene and 1-n-hexylpyrrole. The linear and nonlinear optical (NLO) properties of all compounds were evaluated in addition to recording relevant thermal and electrochemical data.

Electronic polarization reversal and excited state intramolecular charge transfer in donor/acceptor ethynylpyrenes.

An attempt to tune the electronic properties of pyrene (Py) by coupling it with a strong electron donor (-PhNMe2, DMA)/acceptor (anthronitrile, AN) through an ethynyl bridge has been undertaken. A moderate electron donor (iPrOPh-, IPP)/acceptor (2-quinolinyl, 2Q) has also been incorporated, and all four molecules were studied with reference to a neutral molecule, namely, 1-phenylethynylpyrene (PhEPy). All the arylethynylpyrenes (ArEPy's) have been thoroughly characterized, and their electronic properties were studied by absorption and emission spectral properties of these ArEPy's.

Efficient emission from charge recombination during the pulse radiolysis of electrochemical luminescent substituted quinolines with donor-acceptor character.

Efficient emission from various donor-acceptor quinolines with an ethynyl linkage (PnQ), which are known as efficient electrogenerated chemiluminescent molecules, was observed with time-resolved fluorescence measurement during the pulse radiolysis in benzene. On the basis of the transient absorption and emission measurements, and steady-state measurements, the formation of PnQ in the singlet excited state can be interpreted by charge recombination between the PnQ radical cation and the PnQ radical anion which are generated initially from the radiolytic reaction in benzene. The strong electronic coupling between the donor and acceptor through conjugation is responsible for the efficient emission during the pulse radiolysis of PnQ in benzene.

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.

Structure-property relationships in conjugated donor-acceptor molecules based on cyanoanthracene: computational and experimental studies.

[reaction: see text] Two series of pi-conjugated bipolar compounds, namely, 9-phenyl-10-anthronitriles (PAN series) and 9-phenylethynyl-10-anthronitriles (PEAN series), having inherent redox centers have been synthesized and their electronic absorption, fluorescence emission, and electrochemical behavior have been studied. Electrochemiluminescence of these molecules bearing weak, strong, and spin-polarized donors is also studied. The observed electronic properties are explained with the help of results obtained from density functional theory (DFT- B3LYP/6-31G) calculations.

Efficient emission from charge recombination during the pulse radiolysis of electrochemical luminescent donor-acceptor molecules with an ethynyl linkage.

Efficient monomer and excimer emission from various donor-acceptor substituted phenylethynes (PE), which are known as efficient electrogenerated chemiluminescent molecules, was observed with time-resolved fluorescence measurement during the pulse radiolysis in benzene. On the basis of the transient absorption and emission measurements, and steady-state measurements, the formation of PE in the singlet excited state (1PE*) and the excimer (1PE2*) can be interpreted by the charge recombination between the PE radical cation (PE.+) and the PE radical anion (PE.

Synthesis, electronic properties, and electrochemiluminescence of donor-substituted phenylethynylanthronitriles.

A new series of pi-conjugated donor-acceptor compounds (1-6) with inherent redox centers have been prepared and studied with respect to their electronic properties. The photophysical characteristics of these compounds have been studied in relation to their structures. Cyclic voltammetry and UV-vis spectroelectrochemistry were used to probe the ground-state electronic properties of the neutral and charged species.

Donor-substituted phenyl-pi-chromones: electrochemiluminescence and intriguing electronic properties.

Phenylethynylchromones bearing different donor groups at the phenyl moiety have been prepared and their photophysical and electrogenerated chemiluminescence (ECL) properties have been studied with respect to their structural features. Intriguingly, the presence and variation of donor groups do not much influence the absorption spectra, which can be compared with the spectrum of unsubstituted chromone, whereas the photoluminescence (PL) spectra show pronounced changes. Density functional theory (DFT) calculations indicate enhancement of HOMO energy levels upon increasing the donor strength.

Synthesis and electrogenerated chemiluminescence of donor-substituted phenylethynylcoumarins.

Two series of donor-bearing phenylethynylcoumarins have been synthesized, and their photophysical properties have been evaluated. Chemiluminescence was observed through the annihilation of their electrogenerated radical ions and was found to be only slightly affected by the presence of various donor groups on the phenyl moiety linked through the C-C triple bond. The overall properties of the two series of compounds are discussed with respect to their structures.

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.

Synthesis and electrogenerated chemiluminescence of donor-substituted phenylquinolinylethynes and phenylisoquinolinylethynes: effect of positional isomerism.

In furtherance of our research on the design, synthesis and study of electrogenerated chemiluminescence (ECL) of new donor substituted phenylquinolinylethynes, we report here more new series with the aim of studying the effect of positional isomerism on their overall photophysical properties with a special focus on ECL. For this study we have chosen 2-, 3-, and 4-(p-substituted phenyl)ethynylquinolines, and 1- and 4-(p-substituted phenyl)ethynylisoquinolines. These ethynes were synthesized in good yields by modified Sonogashira coupling of the corresponding terminal alkyne with the respective haloquinolines.

First synthesis and electrogenerated chemiluminescence of novel p-substituted phenyl-2-quinolinylethynes.

A series of p-substituted phenyl-2-quinolinylethynes as blue-green emitters were synthesized using a modified Sonogashira coupling reaction and their electrogenerated chemiluminescence properties are reported.

Sonogashira coupling reaction with diminished homocoupling.

[reaction: see text] The side product from homocoupling reaction of two terminal acetylenes in the Sonogashira reaction can be reduced to about 2% using an atmosphere of hydrogen gas diluted with nitrogen or argon. Terminal arylethynes, diarylethynes, and a few new arylpyridylethynes with donor substituents have been synthesized in very good yields. Comparative control experiments suggest that the homocoupling yield is determined by concentration of both catalyst and oxygen.