Benzothiazolium-π-thiazole-dicyanomethanides: new nonlinear optical chromophores

Design and Photonics of Merocyanine Dyes

Merocyanines, thanks to their easily adjustable electronic structure, appear to be the most versatile and promising functional dyes. Their D-π-A framework offers ample opportunities for custom design through variations in both donor/acceptor end-groups and the π-conjugated polymethine chain, and leads to a broad range of practical properties, including noticeable solvatochromism, high polarizability/hyperpolarizabilities, and the ability to sensitize various physicochemical processes. Accordingly, merocyanines are applied and extensively studied in various fields, such as light-converting materials for optoelectronics, nonlinear optics, optical storage, solar cells, fluorescent probes, and antitumor agents in photodynamic therapy. This review encompasses both classical and novel more important publications on the structure-property relationships in merocyanines, with particular emphasis on the results by A.  I. Kiprianov and his followers in Institute of Organic Chemistry in Kyiv, Ukraine.

Novel Thiazole Based Styryl Dyes with Benzimidazole Unit - Synthesis, Photophysical and TD-DFT Studies

Three new Y-shaped styryl dyes were designed and synthesized from thiazole carbaldehyde with different active methylene compounds as acceptor moieties. All the dyes were characterized by IR, ¹HNMR, MS/LCMS/HRMS. Spectroscopic properties and non-linear optical properties styryl derivatives were analyzed and the effect of change in solvent polarity on their absorption and emissive properties has been investigated. The dye with (1-phenylethylidene) propanedinitrile unit shows red shift absorption/emission profile among all the dyes. Density Functional Theory and Time Dependent-Density Functional Theory computations have been used for comparative study with the experimental data and also to understand the structural, molecular, electronic and photophysical parameters of the styryl dyes. The computational method was also employed to investigate the nonlinear optical properties of the styryl dyes in different organic solvent. The unsubstituted benzimidazolyl thiazole styryl dyes possess good non-linear optical properties.

Highly emissive, naked-eye solvatochromic probe based on styryl tetrahydrodibenzo[a,i]phenanthridine for acidochromic applications

A new series of 5-styryl tetrahydrodibenzo[a,i]phenanthridines was readily synthesized from β-tetralone, ammonium acetate and cinnamaldehydes and successfully applied to quantitatively detect pH in biological fluids and acid impurities in solvents.

Benzothiazoles with tunable electron-withdrawing strength and reverse polarity: a route to triphenylamine-based chromophores with enhanced two-photon absorption

A series of dipolar and octupolar triphenylamine-derived dyes containing a benzothiazole positioned in the matched or mismatched fashion have been designed and synthesized via palladium-catalyzed Sonogashira cross-coupling reactions. Linear and nonlinear optical properties of the designed molecules were tuned by an additional electron-withdrawing group (EWG) and by changing the relative positions of the donor and acceptor substituents on the heterocyclic ring. This allowed us to examine the effect of positional isomerism and extend the structure-property relationships useful in the engineering of novel heteroaromatic-based systems with enhanced two-photon absorption (TPA). The TPA cross-sections (δ(TPA)) in the target compounds dramatically increased with the branching of the triphenylamine core and with the strength of the auxiliary acceptor. In addition, a change from the commonly used polarity in push-pull benzothiazoles to a reverse one has been revealed as a particularly useful strategy (regioisomeric control) for enhancing TPA cross-sections and shifting the absorption and emission maxima to longer wavelengths. The maximum TPA cross-sections of the star-shaped three-branched triphenylamines are ∼500-2300 GM in the near-infrared region (740-810 nm); thereby the molecular weight normalized δ(TPA)/MW values of the best performing dyes within the series (2.0-2.4 GM·g(-1)·mol) are comparable to those of the most efficient TPA chromophores reported to date. The large TPA cross-sections combined with high emission quantum yields and large Stokes shifts make these compounds excellent candidates for various TPA applications, including two-photon fluorescence microscopy.