Design, Synthesis, and Temperature-Driven Molecular Conformation-Dependent Delayed Fluorescence Characteristics of Dianthrylboron-Based Donor-Acceptor Systems

Propeller shaped triarylamine acid: An ultra-sensitive fluorescence probe for distinguishing propanol isomers and water sensing in organic solvents

The photophysical properties of conformationally flexible (TPA-C) and partially rigidified (Cz-C) triarylamine acids were explored in solid as well as solution state and correlated with the structure. TPA-C and Cz-C exhibited moderate solid-state fluorescence (Φf = 6.2 % (TPA-C) and 5.6 % (Cz-C)) and self-reversible mechanofluorochromism. TPA-C produced fluorescent polymorphs (TPA-C-1 and TPA-C-2) with tunable fluorescence. TPA-C-1 showed unusual carboxylic acid intermolecular interactions whereas TPA-C-2 and Cz-C showed usual carboxylic acid dimer. TPA-C exhibited strong solvent polarity dependent tunable fluorescence (Φf = 0.01 to 0.11 compared to quinine sulphate standard) but Cz-C was non-emissive in the solution state. The dual emissive TPA-C showed highly sensitive fluorescence changes in organic solvents (CH3CN, THF, DMF, EtOH) when trace amount of water was added. In CH3CN, TPA-C showed weak fluorescence at 474 nm and addition of water (1 %) exhibited significant blue shift (λmax = 416 nm). The fluorescence intensity was gradually decreased with blue shifting in DMF, THF and EtOH with water addition. Importantly, TPA-C showed drastically different fluorescence in n-propanol (n-PA) and iso-propanol (IPA). TPA-C in n-PA showed fluorescence at 408 nm that was clearly red shifted to 438 nm with 0.1 % addition of IPA. The limit of detection (LOD) of water in CH3CN, DMF, THF and EtOH by TPA-C revealed 0.02, 0.7, 0.08 and 0.77 %, respectively. The LOD of IPA sensing in n-PA is 0.05 % and indicated the very efficient sensing and distinguishing propanol isomers. Thus, simple triphenylamine acid showed excellent water sensing and propanol isomers discrimination that could be attributed to the twisted intramolecular charge transfer (TICT) formation.

Polymorphism Dependent Cytotoxicity, Cellular Uptake, and Live Cell Imaging Studies on Napthalimide-Vinyl-Phenothiazine Conjugate

Polymorphism-dependent cytotoxicity and cellular uptake of drug molecules have been studied for the past two decades. However, the visualization of polymorph-dependent cellular uptake and cytotoxicity using microscopy imaging techniques has not yet been reported. The luminescent polymorph is an ideal candidate to validate the above hypothesis. Herein, we report the polymorph-dependent cellular uptake, cytotoxicity, and bio-imaging functions of polymorphs 1Y and 1R of a naphthalimide-phenothiazine dyad. These polymorphs show different luminescence colors in the solid state and exhibit aggregation-induced enhanced emission (AIEE) in the DMSO-Water mixture. Bioimaging, cytotoxicity assay, and fluorescence-activated cell sorting (FACS) studies revealed that these polymorphs show different levels of cytotoxicity, cellular uptake, localization, and imaging potential. Detailed photophysical, morphological, and biological studies revealed that the difference in molecular conformation in these polymorphs enables them to form aggregates of different sizes and morphology, which leads to the differential uptake of these into the cells and consequently shows different cytotoxicity and imaging potentials.

Molecular Persistent Room-Temperature Phosphorescence from Tetraarylaminoboranes

Herein, we report the synthesis, molecular structure, and optical features of tetrarylaminoboranes 1 (Mes₂B-N(Ph)(C₁₀H₇)) and 2 (Mes₂B-N(Ph)(C₁₄H₉)). In the solution state, 1 shows aggregation-induced emission enhancement and color switching, while 2 displays emission color switching and aggregation-caused quenching. At 77 K, frozen solutions of 1 show delayed fluorescence (DF) and phosphorescence, whereas 2 display only DF. Pristine solids of 1 and 2 showed delayed fluorescence under ambient conditions; however, crystals of both compounds show no phosphorescence under similar conditions. Polymethyl methacrylate thin films of 1 (1 wt % doping concentration) exhibit persistent room-temperature phosphorescence (pRTP) lasting for ∼0.5 s. In contrast, 2 does not show phosphorescence under similar conditions. Systematic photophysical studies and theoretical (DFT and TD-DFT) calculations are performed on these molecules to rationalize their intriguing optical characteristics.