Stilbazolium Derivatives Research Articles

Investigation on the growth, structural, HOMO–LUMO and optical studies of 1-ethyl-2-[2-(4-hydroxy-phenyl)-vinyl]-pyridinium iodide (HSPI) – a new stilbazolium derivative for third-order NLO applications

The organic third-order non-linear optical crystal HSPI, a new derivative of the stilbazolium family, was successfully synthesized and the optical quality single crystal was grown by a slow evaporation technique for the first time.

Supramolecular Discotic Columnar Liquid Crystals Built through Single Hydrogen Bonding between Carboxylic Acid and Pyridine Moieties

New self-assembled discotic columnar liquid crystals were prepared via single hydrogen bonding between the core molecule of 1,3,5-cyclohexanetricarboxylic acid and the peripheral units of stilbazole derivatives. The hydrogen-bonded liquid crystals exhibited rectangular columnar and hexagonal columnar mesophases depending on the number of alkyl chains in three arms of the discotic mesogen through dipole-dipole interactions between carbonyl groups along the column axis. The intermolecular hydrogen bonding between carboxylic acid and pyridine moieties provides an effortless methodology to prepare the ordered columnar liquid crystals for electronic applications.

Preparation and Photoluminescent Properties of Hydrogen-bonded Discotic Liquid Crystals

Photoluminescent discotic liquid crystals (DLCs) have been prepared through intermolecular hydrogen bonding between core and peripheral units. 1,3,5-Trihydroxybenzene was employed as core molecule and peripheral stilbazole derivatives containing linearly conjugated moieties were complexed to form hydrogen-bonded DLCs. Their structures, mesophases, and optical properties were investigated. The complexation of core and peripherals made some discotic complexes form photoluminescent DLCs. The prepared luminescent DLCs exhibited columnar mesophases with strong blue or sea green photoluminescence. These findings may contribute to the development of luminescent supramolecular liquid crystals for emitting materials in light emitting devices.

Synthesis, growth, structural and HOMO and LUMO, MEP analysis of a new stilbazolium derivative crystal: A enhanced third-order NLO properties with a high laser-induced damage threshold for NLO applications

A new organic third-order nonlinear optical crystal from stilbazolium family 2-[2-(4-methoxy-phenyl) vinyl]-1-methyl-pyridinium tetrafluoroborate (4MSTB) has been synthesized and grown by slow evaporation method for the first time. The grown crystal structure was confirmed by single crystal X-ray diffraction analysis, and it is revealed that the grown crystal crystallized in a triclinic crystal system with centrosymmetric space group P1¯. The HOMO and LUMO energies were calculated for the grown crystal explains charge transfer takes place within the molecule and confirms the suitability of the title crystal for NLO applications. The presence of various vibration modes of expected functional groups was identified by FT-IR analysis. The transmittance ability of the grown crystal was also analyzed by using UV–Vis–NIR spectral studies and shows that the crystal has no absorption of light in the entire Vis–NIR region. The thermal stability of the title crystal has been investigated by TGA/DTA studies and revealed that the material was thermally stable up to the melting point, 193°C. The hardness number, Meyer index, yield strength, and elastic stiffness constant has been estimated for the grown 4MSTB crystal using Vickers microhardness tester. Photoluminescence excitation studies showed green emission radiation occurred at 517nm. The dielectric properties of the grown crystal have been analyzed as a function of temperature over a wide range of frequency (50Hz–5MHz) by using LCR meter. The result of ac electrical conductivity of 4MSTB was found to be 5.25×10−5 (Ωm)−1. The laser damage threshold (LDT) energy for the grown crystal has been measured by using a Q-switched Nd:YAG laser as a source in single-shot mode (1064nm, 10Hz, 420mJ). The result of LDT indicates that grown title crystal has excellent resistance to laser radiation than those of known some inorganic NLO materials. The chemical etching studies were carried out to assess the perfection of the grown crystals. Its third-order nonlinear optical properties were investigated by Z-scan technique and proved that the 4MSTB crystal possesses two-photon absorptions (TPA) and the self-defocusing effect. The second-order molecular hyperpolarizability (γ) value at 632.8nm is calculated to be 3.555×10−34esu. The photoconductivity study of 4MSTB reveals that the negative photoconducting nature. The obtained all the results in the present work are making a 4MSTB promising candidate for the possible applications in optical switches, optical power limiter, and non-linear optical applications.

Concerted mitigation of O···H and C(π)···H interactions prospects sixfold gain in optical nonlinearity of ionic stilbazolium derivatives.

DAST (4-dimethylamino-N-methyl-4-stilbazolium tosylate) is the most commercially successful organic nonlinear optical (NLO) material for frequency-doubling, integrated optics, and THz wave applications. Its success is predicated on its high optical nonlinearity with concurrent sufficient thermal stability. Many chemical derivatives of DAST have therefore been developed to optimize their properties; yet, to date, none have surpassed the overall superiority of DAST for NLO photonic applications. This is perhaps because DAST is an ionic salt wherein its NLO-active cation is influenced by multiple types of subtle intermolecular forces that are hard to quantify, thus, making difficult the molecular engineering of better functioning DAST derivatives. Here, we establish a model parameter, ηinter, that isolates the influence of intermolecular interactions on second-order optical nonlinearity in DAST and its derivatives, using second-harmonic generation (SHG) as a qualifier; by systematically mapping intercorrelations of all possible pairs of intermolecular interactions to ηinter, we uncover a relationship between concerted intermolecular interactions and SHG output. This correlation reveals that a sixfold gain in the intrinsic second-order NLO performance of DAST is possible, by eliminating the identified interactions. This prediction offers the first opportunity to systematically design next-generation DAST-based photonic device nanotechnology to realize such a prospect.

Neutron crystal structure analysis of stilbazolium derivatives for terahertz-wave generation

The refined crystal structure of stilbazolium derivatives was determined by neutron diffraction. The interatomic distances between the cation and the anion increased when the 4-position of the benzenesulfonate counteranion had a larger atom. The absorption coefficients of the 4-halobenzenesulfonate stilbazolium derivatives in the THz region became lower.

Bulk crystal growth and nonlinear optical characterization of a stilbazolium derivative crystal: 4-[2-(3,4-dimethoxyphenyl)ethenyl]-l methylpyridinium tetraphenylborate (DSTPB) for NLO device fabrication

The search for organic crystals with highly efficient nonlinear optical (NLO) properties with a high surface laser damage threshold (LDT) has become more of a demand in the frontier areas of optical switching and communications applications.

Investigation on third order nonlinear optical, electrical and surface properties of organic stilbazolium crystal of 4-N,N-dimethylamino-N′-methylstilbazolium p-methoxybenzenesulfonate

The third order nonlinear optical, electric and dielectric properties of an organic stilbazolium derivative of 4-N,N-dimethylamino-N′-methylstilbazolium p-methoxybenzenesulfonate (DSMOS) crystal are reported. The nonlinear refractive index (n2), two photon absorption coefficient (β) and third order optical susceptibility χ(3) have been measured by Z-scan technique using Gaussian beam from the Nd:YAG laser at 1064nm. The results show a large negative nonlinear refractive index (n2=−1.122×10−9cm2/W) with a molecular two photon absorption coefficient β value of 3.625×10−6cm/W. The low dielectric constant observed in the high frequency region indicates the suitability of the sample for electro-optic applications. The surface features are also investigated by atomic force microscopy (AFM).

Terahertz-wave generation from 4-dimethylamino-N′-methyl-4′-stilbazolium p-bromobenzenesulfonate crystal: Effect of halogen substitution in a counter benzenesulfonate of stilbazolium derivatives

We have developed a technique to grow 4-dimethylamino-N′-methyl-4′-stilbazolium p-bromobenzenesulfonate (DASB) with a halogen (bromine) substituent in the anion for THz-wave generation. The bulky DASB single crystals, typically measuring 3×3×0.2mm3, are grown from a methanol solution by the slow-cooling method over a 5-week period. Compared with 4-dimethylamino-N′-methyl-4′-stilbazolium tosylate (DAST), the DASB crystal showed high transmittance at around 3THz and in the region above 100THz. Using the difference frequency generation process, we can obtain a broadband THz-wave between 2 and 25THz from a DASB crystal. Moreover, the output THz-wave power between 2.5 and 5.5THz generated from DASB is high, confirming that halogen substitution in the anion of stilbazolium derivatives enables efficient THz-wave generation in the region between 2.5 and 5.5THz.

Investigation of synthesis, crystal structure and third-order NLO properties of a new stilbazolium derivative crystal: a promising material for nonlinear optical devices

A new organic stilbazolium derivative crystal 2-[2-(3-hydroxy-4-methoxy-phenyl)-vinyl]-1-methyl-pyridinium naphthalene-2-sulfonate dehydrate (C25H23NO5S·2H2O) (VSNS) was synthesized successfully.

Engineering of Acentric Stilbazolium Salts with Large Second-Order Optical Nonlinearity and Enhanced Environmental Stability

A series of organic nonlinear optical (NLO) materials based on the stilbazolium derivatives of 4-N,N-dimethylamino-4′-N′-methyl-stilbazolium tosylate (DAST) were synthesized, and the single crystals were grown from the solutions. Single-crystal structure determinations and Kurtz powder tests reveal that replacement of the p-toluenesulfonate anion in the DAST crystal, forming 4-N,N-dimethylamino-4′-N′-methyl-stilbazolium 4-aminotoluene-3-sulfonate (1) and 4-N,N-dimethylamino-4′-N′-methyl-stilbazolium p-chlorobenzenesulfonate (2), constructs new acentric crystals with quite a large powder second-harmonic generation (SHG) of more than 3 orders of magnitude larger than that of urea around 2.0 μm, whereas the other two complexes show their centrosymmetric structures without any SHG effects. A possible estimation of the molecular first hyperpolarizabilities βijk performed on 2 further confirms its origin of its enhanced NLO merits. Furthermore, both 1 and 2 exhibit even higher environmental stabilities, includi...

Self-assembled discotic nematic liquid crystals formed by simple hydrogen bonding between phenol and pyridine moieties

New discotic nematic liquid crystals have been prepared through intermolecular hydrogen bonding between the core of 1,3,5-trihydroxybenzene (phloroglucinol, PG) or 1,3,5-tris(4-hydroxyphenyl)benzene (THPB) and the peripheral molecules of stilbazole derivatives. The various nematic phases formed by new hydrogen bonding building blocks were investigated by differential scanning calorimetry, polarising optical microscopy and X-ray diffraction. The first discotic complexes of PG and trans-4-alkoxy-4′-stilbazoles exhibited nematic columnar (NC) and hexagonal columnar phases depending on the length of alkyl chains, which were considered as the basic discotic structure. Several structural variations on the building blocks were attempted to examine their effects on the liquid crystalline properties of discotic complexes. The nematic lateral phase (NL) with enhanced intercolumnar order was observed for the complexes of PG and trans-4-cyanoalkoxy-4′ stilbazoles due probably to the strong dipole interactions between cyano groups at the end of alkoxy chains. By introducing the nonlinear structure in three arms of supramolecular discotic mesogen, a discotic nematic phase (ND) was observed for the complex of THPB and trans-4-octyloxy-4 -stilbazole. The single hydrogen bonding between phenol and pyridine moieties in this study provides a simple and effective method for preparing the rarely found discotic nematic liquid crystals.

Quantum Chemical Evaluation of Ionic Nonlinear Optical Chromophores and Crystals Considering the Counteranion Effects

The direction and the magnitude of the first hyperpolarizability are investigated by the finite field (FF) method for organic nonlinear optical ionic chromophores and crystals with an isotropic counteranion, either a point charge or hexafluorophosphate. Simple model compound 4-aminopyridinium and DAPSH (N,N-dimethylamino-N′-phenyl-4-stilbazolium hexafluorophosphate) crystal with the highest quadratic optical nonlinearities measured to date in organic crystals, as well as stilbazolium derivatives having heteroaromatic and/or bulky aromatic rings, are investigated. Calculations indicate that the extrinsic isotropic point-charges or anions almost have no effect on the direction of the intrinsic first hyperpolarizability of the cation chromophores, and induce a limited increase of the magnitude smaller than ∼15% due to their asymmetric distribution with respect to the pyridinium nitrogen atom. This finding enables one to simply approximate the first hyperpolarizability of ionic crystalline systems having 1D i...

Star-shaped supramolecular liquid crystals formed by hydrogen bonding between phloroglucinol and stilbazole derivatives with different molecular shapes

Three types of the stilbazole derivative, 4-(4-alkoxybenzoyloxy)-4′-stilbazole (nSz), 4-(3,4-dialkoxybenzoyloxy)-4′-stilbazole (nDSz), and 4-(3,4,5-trialkoxybenzoyloxy)-4′-stilbazole (nTSz), were synthesised and complexed via hydrogen bonding with phloroglucinol (PG) to build liquid crystals, and their mesomorphic properties were investigated. In PG/nSz complexes, a wider mesomorphic range was observed than in nSz. The types of observed mesophases were nematic (n = 6, 8) and smectic phases (n = 10, 12). PG/nDSz and PG/nTSz complexes showed mesophases which were not observed for the non-complexed components. Monotropic nematic phases were observed for the PG/nDSz complexes, and PG/nTSz complexes exhibited hexagonal columnar structures. Based on the X-ray diffraction data, schematic models for the molecular arrangement were proposed for the smectic, nematic and hexagonal columnar phases of the complexes.

The two-photon absorption property of stilbazolium derivative with A–π–D–π–A structure: Influence by counter-anion and aggregation

This paper reported two stilbazolium derivatives with differdent counter-anion (OPVBr and OPVOH). The two stilbazolium derivatives have a quadrupoles (A–π–D–π–A) structure, in which pyridinium cation was used as electron-accept group and dibutoxy benzene as electron-donor group. Their linear optical properties were investigated through UV–vis and fluorescence spectral analysis. Two-photon laser induced fluorescence measurements have shown that OPVOH have a small TPA cross section (35 GM), while OPVBr have a large TPA cross section (904 GM). The TPA cross-sections value of OPVBr is increased with the concentration increasing due to the enhancement of intermolecular π–π stacking interaction.

Anion influenced self-assembly of stilbazolium derivative and acid-sensitive property of its corresponding gel

Two stilbazolium derivatives with different counter-anions (Br− and OH− ) have been designed and synthesised. Different counter-anions cause different aggregation properties. The reason of this difference was investigated through concentration- and temperature-dependent 1H NMR and IR spectra. When the counter-anion is OH− , the stilbazolium derivative exhibits pronounced aggregation properties. The scanning electron microscope images of xerogels show the characteristic gelation morphologies of 3D fibrous network structures. X-ray diffraction and fluorescence spectroscopy studies have been carried out, and provide more information to define the molecular packing model in gelation states. Finally, the acid-sensing abilities of the xerogel film were studied.

Fluorescent and photooptical properties of H-bonded LC composites based on stilbazole derivative

A novel series of H-bonded LC (smectic and nematic) composites and “model” mixtures without hydrogen bonding based on the stilbazole derivative were prepared. As the matrices of the composites following polymers were synthesized: smectic homopolymer containing p-oxybenzoic groups, nematic copolymer containing p-oxybenzoic and methoxyphenylbenzoic side groups, and nematic homopolymer with methoxyphenylbenzoate groups. The spectral properties of composite films were studied in detail. Significant differences in the fluorescence spectra of H-bonded LC composites and “model” mixtures were revealed. Mechanism of the processes occurring in the films of the LC composites under the action of the UV light was proposed. The mechanism includes a reversible proton transfer involved in the H-bonds formation. It was found that in the oriented films of the nematic composite degree of fluorescence polarization is higher than in the films of a similar mixture without H-bonding. The effect of linearly polarized light on the optical properties of the composite films was studied. It was shown that the highest values of the photoinduced dichroism are achieved in nematic liquid crystals composites. It was revealed that for the irradiated LC composites annealing leads to decease of dichroism values (degree of polarized emission drops to zero), whereas for “model” LC mixture without hydrogen bonding a significant increase in these parameters was found.

Theoretical study of solvent effect on the structure, first electronic excited state, and nonlinear optical properties of substituted stilbazolium cations

AbstractMolecular structure, first excited state properties and charge distribution of a series of substituted stilbazolium cations in different media are theoretically investigated. First static hyperpolarizability (β0) of considered compounds is studied by both finite‐field and two‐state model methods. In contrast to the recent theoretical studies, in present contribution the mutually consistent description of solvent polarity dependence of β0 calculated by both employed approaches is achieved. It is shown that the ground‐to‐excited state intramolecular charge‐transfer is significantly affected by the solvent that provides the hyperpolarizability variation. Taking into account both solvent polarity and substituent effect the peculiarities of β0 behavior of stilbazolium derivatives are re‐examined. The effect of molecular geometry on the calculated electronic excitation properties is investigated. © 2010 Wiley Periodicals, Inc. Int J Quantum Chem, 2011

Non-covalent dendrimer-based liquid crystalline complexes: Synthesis and characterization

The synthesis and structural characterization of dendritic macromolecules based on 3,5-dihydroxybenzoic acid are described. The molecular structures and purity of all new compounds were confirmed by 1H NMR, 13C NMR spectroscopy and elemental analysis. The dendritic non-covalent liquid crystalline complexes were prepared through the formation of hydrogen bonds between different generation of dendritic acids (proton donor) and stilbazole derivative containing bipyridyl units (proton acceptor). We found that, the hydrogen-bonded dendritic liquid crystals supramolecules (G1–2py, G2–2py and G3–2py) exhibits nematic and semectic phase. The polarizing optical microscopy (POM) and differential scanning calorimetry (DSC) were used for investigation of the liquid crystalline properties of the hydrogen-bonded dendritic supramolecular complexes.

Bulk Crystal Growth of Stilbazolium Derivatives for Terahertz Waves Generation

The two stilbazolium derivatives, 4-dimethylamino-N-methyl-4-stilbazolium tosylate (DAST) and 4-dimethylamino-N-methyl-4-stilbazolium p-chlorobenzenesulfonate (DASC), are organic ionic nonlinear optical materials that have a tendency to form bulk crystals when grown in a mixed solvent of methanol and acetonitrile. We observed the generation of broadband high-power terahertz (THz) waves from the bulk crystals of DASC. DASC crystals have superior transmission characteristics in the THz band than DAST crystals, and it is expected that the THz waves generated using DASC crystals will have higher power than those generated using DAST crystals.