Triphenylamine Functionalized Unsymmetrical Quinoxalines

Accelerated Intramolecular Charge Transfer in Tetracyanobutadiene- and Expanded Tetracyanobutadiene-Incorporated Asymmetric Triphenylamine-Quinoxaline Push-Pull Conjugates

The excited-state properties of an asymmetric triphenylamine-quinoxaline push-pull system wherein triphenylamine and quinoxaline take up the roles of an electron donor and acceptor, respectively, are initially investigated. Further, in order to improve the push-pull effect, powerful electron acceptors, viz., 1,1,4,4-tetracyanobutadiene (TCBD) and cyclohexa-2,5-diene-1,4-diylidene-expanded tetracyanobutadiene (also known as expanded-TCBD or exTCBD), have been introduced into the triphenylamine-quinoxaline molecular framework using a catalyst-free [2 + 2] cycloaddition-retroelectrocyclization reaction. The presence of these electron acceptors caused strong ground-state polarization extending the absorption well into the near-IR region accompanied by strong fluorescence quenching due to intramolecular charge transfer (CT). Systematic studies were performed using a suite of spectral, electrochemical, computational, and pump-probe spectroscopic techniques to unravel the intramolecular CT mechanism and to probe the role of TCBD and exTCBD in promoting excited-state CT and separation events. Faster CT in exTCBD-derived compared to that in TCBD-derived push-pull systems has been witnessed in polar benzonitrile.

Palladium-Catalyzed Cross-Coupling Reactions of Borylated Alkenes for the Stereoselective Synthesis of Tetrasubstituted Double Bond

The stereoselective formation of tetrasubstituted alkenes remains one of the key goals of modern organic synthesis. In addition to other methods, the stereoselective synthesis of tetrasubstituted alkenes can be achieved by means of cross-coupling reactions of electrophilic and nucleophilic alkene templates. The use of electrophilic templates for the stereoselective synthesis of tetrasubstituted alkenes has previously been described. Therefore, the present review summarizes the procedures available for the stereoselective preparation of tetrasubstituted alkenes using stable and isolable nucleophilic templates.

Temperature-sensitive emission of dialkylaminostyrylhetarene dyes and their incorporation into phospholipid aggregates: Applicability for thermal sensing and cellular uptake behavior

A series of dialkylaminostyrylhetarene dyes constructed from electron-rich and electron-deficient moieties of various structures connected via vinylene π-bridges are introduced as temperature-sensitive luminophores. The temperature dependent emission of the dyes in the acidified dichloromethane solutions derives from temperature-induced shift of the equilibrium between neutral and protonated forms of the dyes. The heating-induced blue shift and intensification of emission of neutral form of the dyes make them a promising basis for development of nanoparticles exhibiting temperature-sensitivity in aqueous solutions at pH typical of biological liquids. Hydrophobicity-driven incorporation of the water insoluble dyes into L-α-phosphatidylcholine(PC)-based bilayers allows to obtain water dispersible dye-PC aggregates, and to follow their emission in the aqueous solutions. Structure of the dyes has strong impact on the efficacy of the dyes incorporation into the PC-based bilayers, temperature sensitivity of emission of the dye-PC aggregates and its reversibility under the heating/cooling cycles. This enables structural optimization of the dyes in order to obtain the dye-PC species demonstrating maximal temperature dependence and reversibility of their luminescence in aqueous solutions. The selected leader exhibits low cytotoxicity exemplified for M-HeLa and Chang Liver cell lines, while the efficient cell internalization of the dye, manifested in the staining of the cell cytoplasm, opens further opportunities for biosensing applications.

Phenothiazine and phenothiazine-5,5-dioxide based push-pull Derivatives: Synthesis, photophysical, electrochemical and computational Studies

A set of phenothiazine (PTZ) and phenothiazine-5,5-dioxide based π-conjugated push–pull chromophores PTZ 1–6 were designed and synthesized by the Pd-catalyzed Sonogashira cross-coupling and [2+2] cycloaddition retroelectrocyclic ring opening reaction in...