Distyrylbenzene Research Articles

Explicit Modelling of Spectral Bandshapes by a Mixed Quantum-Classical Approach: Solvent Order and Temperature Effects in the Optical Spectra of Distyrylbenzene.

The absorption and emission spectral shapes of a flexible organic probe, the distyrylbenzene (DSB) dye, are simulated accounting for the effect of different environments of increasing complexity, ranging from a homogeneous, low-molecular- weight solvent, to a long-chain alkane, and, eventually, a channel-forming organic matrix. Each embedding is treated explicitly, adopting a mixed quantum-classical approach, the Adiabatic Molecular Dynamics - generalized vertical Hessian (Ad-MD|gVH) model, which allows a direct simulation of the environment-induced constraining effects on the vibronic spectral shapes. In such a theoretical framework, the stiff modes of the dye are described at a quantum level within the harmonic approximation, including Duschinsky mixing effects, while flexible degrees of freedom of the solute (e. g. torsions) and those of the solvent are treated classically by means of molecular dynamics sampling. Such a setup is shown to reproduce the distinct effects exerted by the different environments in varied thermodynamic conditions. Besides allowing for a first-principles rationale on the supramolecular mechanism leading to the experimental spectral features, this result represents the first successful application of the Ad-MD|gVH method to complex embeddings and supports its potential application to other heterogeneous environments, such as for instance, pigment-protein complexes or organic dyes adsorbed into metal-organic frameworks.

Push-Pull Bridged Distyrylbenzene with Highly Bright Solid-State Red-Orange Aggregation-Induced Emission.

Multiple emission colors in solid-state organic fluorophores with the same main skeleton are essential for improving the performance of light-emitting devices/materials. Specifically, emission in the red/near-infrared region is of great importance in the biological field. Previously, we developed di-bridged-distyrylbenzene DBDB[7] with high-brightness solid-state blue and aggregation-induced emissions (AIE) by introducing the bridging structures of a seven-membered ring into the vinylene groups of distyrylbenzene (DSB). Herein, we synthesize MNDBDMeODB[7] (1), which features substituted methoxy and malononitrile groups as donor and acceptor groups, respectively, in DBDB[7]. In solvents more polar than THF, MNDSDMeOB (3), which has the same main skeleton as 1 but without bridges, shows no emission in the solid state, whereas 1 exhibits highly bright red-orange emission in the solid state owing to the suppression of intermolecular electronic interactions by the bridges and the AIE property. We also synthesize MNDSD(EHO)B (2) in which the methoxy groups of 3 are replaced by ethylhexyloxy groups, thus disrupting the crystallinity of the molecule. 2 exhibits positive fluorescence solvatochromism and has a high fluorescence quantum yield in the solid state as a red-emitting DSB derivative. The solid-state emission properties of 1 and 2 will improve the applicability of DSBs and functionalities of light-emitting devices/materials.

Flexible Alkylene Bridges as a Tool To Engineer Crystal Distyrylbenzene Structures Enabling Highly Fluorescent Monomeric Emission.

To design ultrabright fluorescent solid dyes, a crystal engineering strategy that enables monomeric emission by blocking intermolecular electronic interactions is required. We introduced propylene moieties to distyrylbenzene (DSB) as bridges between the phenyl rings either side of its C=C bonds. The bridged DSB derivatives formed compact crystals that emit colors similar to those of the same molecules in dilute solution, with high quantum yields. The introduction of flexible seven‐membered rings to the DSB core produced moderate distortion and steric hindrance in the DSB π‐plane. However, owing to this strategy, it was possible to control the molecular arrangement with almost no decrease in the crystal density, and intermolecular electronic interactions were suppressed. The bridged DSB crystal structure differs from other DSB derivative structures; thus, bridging affords access to novel crystalline systems. This design strategy has important implications in many fields and is more effective than the conventional photofunctional molecular crystal design strategies.

Light emitting, segmented block copolymers containing distyrylbenzene blocks connected through α,ω-nonamethylenedioxy chain spacer for applications in polymer light emitting diodes

Two novel, soluble, semiconducting and light emitting segmented block copolymers, termed as NPPV1 and NPPV2 are synthesized using Horner-Emmons condensation polymerization. The chromophoric groups present in the copolymers are distyrylbenzene (DSB) units substituted with rigid, bulky cyclohexylmethoxy and cyclohexylethoxy groups. The rigid blocks are linked to flexible α,ω-nonamethylenedioxy chain spacer through ether linkage. The structural, morphological, thermal and photo-physical characteristics of the synthesized polymers are studied in detail. Noticeable differences in properties arising through the substituent effects are observed for both the polymers. Detailed studies bring out quite interesting structure-property relationships between the substituents introduced in the synthesized copolymers and their crystalline properties, thermal characteristics, optical properties, photoluminescence emission and fluorescence quantum yield. Polymer light emitting diodes (PLEDs) employing these segmented polymers as emissive layers are assembled and characterized to establish their suitability for lighting applications. Using the architecture, ITO/PEDOT:PSS/NPPV1/LiF-Al, polymer light emitting diodes (PLEDs) are assembled and as the first step of device characterization, their current-voltage characteristics are studied to establish the device behavior and find out the onset voltage. The emission characteristics of the devices are then studied using Ocean Optics USB 2000 spectrometer integrated to a computer using a dedicated program. The assembled devices show Schottky junction like behavior in the current-voltage characteristics and electroluminescence emission in the blue green region with appreciable intensity at the onset voltage of 8.8 V. It is highly desirable to develop polymers showing emission in the high frequency,blue region, using cost-effective synthesis routes. The novel approaches adopted in the synthesis of the monomers and the corresponding copolymers to achieve the anticipated structure-property relationships suitable for the effective designing of polymer light emitting diodes are the highlights of the present work.

Excited state absorption spectra of dissolved and aggregated distyrylbenzene: A TD-DFT state and vibronic analysis.

A time-dependent density functional theory study is performed to reveal the excited state absorption (ESA) features of distyrylbenzene (DSB), a prototype π-conjugated organic oligomer. Starting with a didactic insight to ESA based on simple molecular orbital and configuration considerations, the performance of various density functional theory functionals is tested to reveal the full vibronic ESA features of DSB at short and long probe delay times.

Charge transport in structural-ordering doped organic crystals: The effect of dye-doping concentration and crystal thickness on the mobility

Doped organic crystals with structural-ordering retention expected to the integration of high carrier mobility and high luminescence efficiency could be as promising materials for the high-performance light-emitting devices even the electrically pumped laser. In this work, charge-transport characteristics in doped organic crystals based on distyrylbenzene (DSB) as the host and tetracene (Tc) or pentacene (Pc) as the guest have been discussed in detail, including the effect factors of the guest doping concentration and the crystal thickness by the field-effect transistor (FET) and space-charge limited current (SCLC) methods. In the FETs, the mobilities of doped crystals have the slight decrease compared with that of undoped crystal but all are in the same order of magnitude (∼10−3–10−2cm2/Vs), which is attributed to the structural-ordering retention even when the concentration of guest molecules embedded into the host crystal is up to ∼8%. Different with the lateral-configuration FET transporting the carriers inside several molecular layers of crystal surface, the vertical-configuration diode makes the carriers pass through the crystal body. The mobilities estimated by SCLC for doped and undoped crystals also present the similar variation with the FET’s measurement. More significantly, the mobility increases with the crystal thickness at the same electrical field which indicates the negative influence of interfacial contact between the electrode and the crystal on the injected charges can be further suppressed by means of a relatively thicker crystal. Our primary results showcase that structural-ordering doped organic crystals have the comparable mobilities relative to their host sources, which is promising to extend to other doped crystal systems as well. Considering conveniently controllable properties of high efficiency and color-tunable emission by energy transfer, doped organic crystals are expected to be of interest for high-performance optoelectronic devices; moreover, it is verified that the increase of crystal thickness is beneficial for improving the utilization of injected charges in the vertical-configuration diode.

A highly luminescent organic crystal with the well-balanced charge transport property: The role of cyano-substitution in the terminal phenyl unit of distyrylbenzene

1,4-bis(2-cyano styryl)benzene (2-CSB) crystal with cyano substituent groups introduced to the terminal phenyl rings of distyrylbenzene (DSB) has been prepared and its luminescence efficiency could be as high as ∼55%. Based on the analyses of cyclic voltammetry and crystal structure, cyano substituents not only lower the LUMO level but also result in a change of the packing mode from the herringbone arrangement to the face-to-face slipped π stacking motif. Then field-effect transistors (FETs) based on high-quality 2-CSB crystals grown by the physical vapor transport method have been fabricated and the highest hole and electron mobilities were measured as 0.66 and 0.29 cm2/Vs, which enhanced the corresponding values of DSB crystal by up to one and two orders of magnitude, respectively. 2-CSB crystal simultaneously combined the high luminescence and the well-balanced mobility is expected to be of interest for the fundamental research of organic light-emitting devices.

New Aggregation-Induced Emitters: Tetraphenyldistyrylbenzenes.

The synthesis of five novel distyrylbenzene (DSB) derivatives, featuring a central tetraphenylbenzene core, is reported. The targets show aggregation-induced emission (AIE), which, however, is substituent-dependent. For the pure hydrocarbon and derivatives that do not carry (+M) or (-M) substituents, classic AIE behavior is observed, that is, the DSBs are non-fluorescent in solution, but are highly fluorescent in cold matrices, upon aggregate formation in poor solvents and in the solid, crystalline state. If aldehyde or dibutylamino groups are attached in the para-position of the DSB unit, non-classic AIE-phores result. These are fluorescent both in dilute solution as well as in the solid state. Prolonged irradiation of the targets leads to benzotetraphene derivatives by a double cyclization.

Fabrication and Characterization of Orientation-Controlled Alkoxy- and Cyano-Substituted Distyrylbenzene Derivatives in Thin Film

Distyrylbenzene(DSB) derivatives, trimer of phenylenevinylene, with cyano and alkoxy groups grew epitaxially on the friction-transferred poly(tetrafluoroethylene) (PTFE) layer. DSBs/PTFE double layers indicated the remarkable anisotropic feature in absorption and emission properties.

Amine detection with distyrylbenzenedialdehyde-based Knoevenagel adducts.

Eight acceptor-substituted distyrylbenzene (DSB) derivatives were obtained by postfunctionalization of dialdehyde precursor 1 using Knoevenagel condensation. Solubility in a water/THF 9:1 mixture was achieved through the addition of branched oligoethylene glycol side chains. The acceptor compounds discriminate primary and secondary amines in aqueous solution. The fluorescence responses were analyzed by the multivariate analysis of variance (MANOVA) protocol, a statistical tool. In contrast to 1, the adducts show reactivity toward secondary and aromatic amines. Nitroolefin 2f is the most active dosimeter molecule. Reaction with amines is completed after less than 3 min, and the limit of detection (LOD) is improved by a factor of 10. Propylenediamine can be detected at 75 μM. This is a 10-fold improvement for the detection limit when compared to the detection limit of the starting dialdehyde.

Chelation-Induced Quenching of Two-Photon Absorption of Azacrown Ether Substituted Distyryl Benzene for Metal Ion Sensing.

Imaging of metal ion concentration, distribution, and dynamics can pave the way to diagnose a number of diseases and to identify the normal functioning of the human body. Recently, two-photon microscopy-based imaging of metal ions has become popular due to several favorable factors as compared to fluorescence-based imaging. However, much has to be investigated in order to design probes with large two-photon absorption cross sections and yet with selective binding affinity toward metal ions. In particular, it is crucial to recognize the mechanisms of metal ion-induced changes of the two-photon absorption intensity. The present paper contributes to this effort and reports on the results of extensive studies carried out to define a reliable computational protocol that can account for sampling, solvent, and finite temperature effects for one- and two-photon properties of metal probes, using azacrown ether substituted distyrylbenzene embedded in solvents as a testbed. We employ a selection of theoretical approaches to model the structure of the probe alone and in the presence of Mg(2+) ion in acetonitrile solvent, including static quantum-chemical calculations, rigid- and flexible-body molecular dynamics, and hybrid QM/MM molecular dynamics. For a set of solute-solvent configurations, the one- and the two-photon properties are computed using the recently developed polarizable embedding response approach. It is found that the hybrid QM/MM molecular dynamics based approach is the most successful one among other employed computational strategies, viz. reproduction of the metal ion-induced blue shift in the absorption wavelength and decrease in the two-photon absorption cross section, which actually is in excellent agreement with experimental data. The mechanism for such metal ion-induced changes in the optical properties is put forward using a few-state model. Possible design principles to tune the two-photon absorption properties of probes are also discussed.

ChemInform Abstract: Luminescent Distyrylbenzenes: Tailoring Molecular Structure and Crystalline Morphology

AbstractReview: 119 refs.

Luminescent distyrylbenzenes: tailoring molecular structure and crystalline morphology

The last few years have seen a steady increase in small molecule based conjugated materials, which promise innovative (opto)electronic applications. This requires however a systematic understanding of structure–property relationships, which can only be achieved via libraries of structurally well-defined single crystalline materials based on systematically designed molecular structures. In this feature article, we are presenting structure–property relationships of functionalized distyrylbenzene (DSB), which is one of the most extensively investigated π-conjugated molecular materials. This will provide a general insight into the specific implications of intermolecular arrangements on their solid state optoelectronic properties, discussing H- vs. J-aggregation, herringbone vs. π-stacks, the occurrence of excimers, size effects, and polycrystallinity. The systematic insight into DSB functionalization will then suggest pathways towards targeted molecular design strategies, with special focus on the cyano-vinylene motif (DCS materials) which allows for highly fluorescence solid state samples due to synergetic packing effects promoted by its twist elasticity and secondary bonding interaction. Finally, recent advances in the application of DSB-/DCS-based materials are shortly reviewed.

The Hammett correlation between distyrylbenzene substituents and chemiluminescence efficiency providing various ρ-values for peroxyoxalate chemiluminescence of several oxalates

Abstract Peroxyoxalate chemiluminescence (PO-CL) was investigated using eight oxalates with various phenol moieties and the distyrylbenzene (DSB) fluorophores with various substituents. The ρ -values in the Hammett correlation between the substituent constants (σ p + ) of the DSBs and the singlet chemiexcitation yields ( Φ S ) for the PO-CL reactions varied from −0.50 to −1.01 depending on the oxalate structure, and the reactive oxalates tended to afford the higher absolute ρ -values but with a few exceptions. Based on the CIEEL mechanism, these experimental observations suggest that the aryloxy groups still remain in the 1,2-dioxetanones (DOTs), which are the postulated high-energy intermediates, and control the electronic properties of DOTs as electron-acceptors. The LUMO energies of the DOTs calculated by the ab initio method with a B3LYP/6-31g(d) basis set reveal that the lower the DOT-LUMO energies, the higher the absolute ρ -values were provided for the corresponding oxalates, as predicted by the frontier molecular orbital (FMO) theory. Thus, the chemical species interacting with the DSBs would be not unitary and will be DOTs.

Gas detection by structural variations of fluorescent guest molecules in a flexible porous coordination polymer

The development of a new methodology for visualizing and detecting gases is imperative for various applications. Here, we report a novel strategy in which gas molecules are detected by signals from a reporter guest that can read out a host structural transformation. A composite between a flexible porous coordination polymer and fluorescent reporter distyrylbenzene (DSB) selectively adsorbed CO₂ over other atmospheric gases. This adsorption induced a host transformation, which was accompanied by conformational variations of the included DSB. This read-out process resulted in a critical change in DSB fluorescence at a specific threshold pressure. The composite shows different fluorescence responses to CO₂ and acetylene, compounds that have similar physicochemical properties. Our system showed, for the first time, that fluorescent molecules can detect gases without any chemical interaction or energy transfer. The host-guest coupled transformations play a pivotal role in converting the gas adsorption events into detectable output signals.

High Sensitivity Surface-Enhanced Raman Scattering in Solution Using Engineered Silver Nanosphere Dimers

We describe Raman spectroscopy measurements of distyrylbenzene (DSB) molecules equipped with plasmonic antennae in the form of silver dumbbells in aqueous solution under ambient conditions. A synthetic strategy in which the dithiolated molecule is used as the linker between silver nanospheres ensures that the molecules are attached at the intersphere gap where local fields are maximally enhanced. The measured and calculated enhancement factors are in excellent agreement. The reported method has sufficient sensitivity to also allow for the detection of molecules tethered to single spheres, with 100–1000-fold weaker enhancement. Spectral analysis allows assignment of structures and reveals that in addition to the normal Raman active modes IR active transitions appear in the Raman spectra where field gradients dominate.

Highly Efficient Blue Organic Light-Emitting Devices Based on Improved Guest/Host Combination

We present here a cruciform oligo(phenylenevinlyene) 2,5,2′,5′-tetrastyrylbiphenyl (TSB) exhibits excellent properties as host material for blue emitting guest molecule 1,4-di(4′-N,N-diphenylaminostyryl)benzene (DPA−DSB). TSB, which is constructed by linking two rigid distyrylbenzene (DSB) through the phenyl−phenyl bond, shows good optical and electronic properties e.g. high photoluminescent (PL) efficiency and wide band gap similar to DSB. Meanwhile, the central biphenyl core in TSB, which allows the relatively free rotation of two DSB segments along the biphenyl bond, makes it to be conformational multiformity and relatively flexible. As the result, TSB shows the good film forming property and larger loading ability to the guest molecules. The PL efficiencies of guest−host films of DPA−DSB and TSB arrive at the high level around 70% (68% for the 2 wt % DPA−DSB doped film and 72% for the 8 wt % DPA−DSB doped film), which is approaching the PL efficiency of the guest DPA−DSB in dilute solution (78%), indicating that the host TSB can sufficiently disperse the guest DPA−DSB with little aggregation. The organic light-emitting devices using DPA−DSB (2 wt %) doped TSB as blue emitting layer show the maximum efficiency of 12.2 cd/A (6.2%) and 6.39 lm/W, and the maximum brightness of 17350 cd/m2. Upon further analysis, it has been revealed that the Förster energy transfer and charge trapping are demonstrated to cooperatively work in this doping system.

One- and Two-Photon Absorption and Emission Properties of a Zn(II) Chemosensor

This paper presents the synthesis and two photon-induced absorption (TPA) properties of a functionalized distyrylbenzene (DSB) 1 containing a tetra-azacyclododecane (cyclen) receptor for Zn(II). The influence of Zn(II) on one- and two-photon absorption characteristics of 1 has been investigated in dimethyl sulfoxide. The experiments show that the TPA action spectrum of uncomplexed 1, at 750 nm employing nanosecond-long excitation pulses, is 5 times more intense than that of the complexed form. This moderate contrast between the bound and unbound species confirms, however, the potential of this design scheme for the development of molecular structures with enhanced sensitivity and contrast to be used as Zn(II) sensors through TPA-induced fluorescence microscopy.

Solid-state optical properties of linear polyconjugated molecules: π-stack contra herringbone

The intermolecular arrangement in the solid state and the consequences on the optical and photophysical properties are studied on different derivatives of oligophenylenevinylenes by UV/VIS absorption and angular-resolved polarized fluorescence spectroscopy. Unsubstituted distyrylbenzene (DSB) organizes in a herringbone manner, with the long axes of the molecules oriented in parallel, but the short axes almost perpendicular to each other. Fluorinated distyrylbenzene (F(12)DSB) as well as the DSB:F(12)DSB cocrystals prefer cofacial pi-stacking in the solid state. For all structures, the consequence of the parallel alignment of the transition moments is a strongly blueshifted H-type absorption spectrum and a low radiative rate constant k(F). Significant differences are observed for the emission spectra: the perpendicular arrangement of the short axes in DSB crystals leads to only very weak intermolecular vibronic coupling. Hence the emission spectrum is well structured, very similar to the one in solution. For F(12)DSB and DSB:F(12)DSB, the cofacial arrangement of the adjacent molecules enables strong intermolecular vibronic coupling of adjacent molecules. Thus, an unstructured and strongly redshifted excimerlike emission spectrum is observed. The differences in the electronic nature of the excited states are highlighted by quantum-chemical calculations, revealing the contribution of interchain excitations to the electronic transitions.

Theoretical Studies of Distyrylbenzene and its Optical Properties

The electronic and geometrical properties of distyrylbenzene (DSB) are investigated by using chemistry theoretical calculation methods. Specifically, the excited state properties are studied by performing ab initio correlation interaction singlet (CIS) and time-dependent density functional theory; the ground state and Raman activities are computed by density functional theory with the B3LYP method. Eight conformers of distyrylbenzene are found and they are derived from three isomers which are cis, cis-, cis, trans-, and trans, trans-, respectively. The relative energy shows that each isomer of three types is separated with a large energy barrier, but a small energy difference of each conformer is found if they are in the same type. The transition state also shows the barrier between conformers is lower than isomers. The computed excited transition energies using ZINDO/S based on the optimized geometries at a DFT/B3LYP level with 6–31+G show an excellent agreement with experimental absorption spectra.