Axially chiral indolenine derived chromophore dimers and their chiroptical absorption and emission properties

Yamamoto homocoupling of two chiral oxindoles led to the atropo-diastereoselective formation of an axially chiral oxindole dimer. This building block served as the starting material for the syntheses of axially chiral squaraine and merocyanine chromophore dimers. These dimers show pronounced chiroptical properties, this is, outstandingly high ECD signals (Δε up to ca. 1500 M⁻¹ cm⁻¹) as a couplet with positive Cotton effect for the P-configuration around the biaryl axis and a negative Cotton effect for the M-configuration. All investigated dimers also exhibit pronounced circularly polarised emission with anisotropy values of ca. 10⁻³ cgs. Time-dependent density functional calculations were used to analyse the three contributions (local one electron, electric–magnetic coupling, and exciton coupling) to the rotational strength applying the Rosenfeld equation to excitonically coupled chromophores. While the exciton coupling term proves to be the dominant one, the electric–magnetic coupling possesses the same sign and adds significantly to the total rotational strength owing to a favourable geometric arrangement of the two chromophores within the dimer.

From an axially chiral oxindole, squaraine and merocyanine chromophore dimers with pronounced chiroptical properties were prepared.

Selective and efficient detection of picric acid among other nitroaromatics by NIR fluorescent cyanine chemosensors

Designed and synthesized a fluorescent probe composed of a Hemi cyanine dye bearing conjugated N, N-dimethyl amino benzaldehyde based fluorophore C1 and C2 as a new visible and near-infrared chemo dosimeter type sensor on highly sensitive and selective chemosensors. The color change and quenching of the dye emission are selective detections of picric acid at nanomolar concentration is accomplished in water medium without having any interference from other NAC's. The protonation and deprotonation between N,N-dimethylaniline, and N,N-diethyl aniline units will prompt to the changes in the targeted ICT molecules and the emission response can be detected on distinct NAC. The dyes C1 and C2 set out towards NACs was explored in the THF-H₂O medium by UV-vis and fluorescence spectra situated around 560 nm with high molar absorption coefficient. NMR spectroscopic titrations in DMSO‑d₆ for affirming the interface between the picric acid with C1 ¹H NMR was utilized to confirm our proposed mechanism. The as-synthesis of cyanine dyes C1 and C2, involves condensation reaction between (1.0 equiv) of 1,1,2,3-tetramethyl-1H-benzo[e]indol-3-ium iodide 2 with (1.1 equiv.) p-N,N-dimethyl amino benzaldehyde, and catalytic amount of piperidine in ethanol continued by reflux for 7 h under idle states, in this way giving a facile, convenient and minimal effort strategy for detection of picric acid in solution and in contact mode.

Chiral Upconversion Heterodimers for Quantitative Analysis and Bioimaging of Antibiotic-Resistant Bacteria In Vivo

Heterodimers of upconversion nanoparticles (UCNPs) and gold yolk-shell nanoparticles are fabricated for the quantification of polymyxin-B-resistant Escherichia coli. They produce two signals, circular dichroism (CD) and upconversion luminescence (UCL). Interestingly, due to the different affinity of polymyxin B for sensitive and resistant strain, as the concentration of polymyxin B increases, the amount of UCNPs in sensitive bacteria increases sharply, increasing the intracellular UCL signal at a low polymyxin B concentration immobilized on the UCNP. The CD intensity is correspondingly reduced as the amount of UCNPs in solution decreased. Meanwhile, for polymyxin-B-resistant strain, the intracellular UCL increases slowly even in a high polymyxin B concentration, and the CD intensity in solution is also enhanced because of the inefficient entering of UCNP. Therefore, based on the concentration of polymyxin B coupled to the UCNPs, the levels of polymyxin-B-resistant bacteria can be detected with dual signals. Importantly, with 980 nm irradiation, both polymyxin-B-sensitive strains and polymyxin-resistant bacteria used to induce infection in mice are detected with UCL imaging in vivo and treated well with photodynamic therapy. This novel dual-mode heterodimer has potential utility for the advanced surveillance and control of drug-resistant bacteria.

Hydrogen-bonded bent-core blue phase liquid crystal complexes containing various molar ratios of proton acceptors and donors

The molar ratio, alkyl chain length, lateral fluoro-substitution and the chiral center of H-bonded bent-core supramolecules would affect the BP ranges of BPLC complexes. H-bonded bent-core complex PIIIC9/AIIF* (3/7 mol mol⁻¹) displayed the widest BPI range of ΔT_BPI = 12 °C.

Synthesis of Binaphthyl-Based Push-Pull Chromophores with Supramolecularly Polarizable Acceptor Ends

We report on the design and synthesis of new enantiopure binaphthyl derivatives in which electron-donating and electron-withdrawing substituents are placed in direct conjugation, to create push-pull dyes potentially active for NLO applications. The dyes, unprecedentedly, extend theirπ-bridge from the 3,3′ positions of the binaphthyl units and incorporate as acceptors 1,3-dicarbonyl and tetrafluorobenzene units, useful for further supramolecular polarization of the chiral dyes.