Halochromic isoquinoline attached mechanochromic triphenylamine, N-phenyl-N-(4-(quinolin-2-yl)phenyl)benzenamine (PQPBA) and tris(4-(quinolin-2-yl)phenyl)amine (TQPA), smart fluorescent materials exhibit thermo/mechanochromism and tunable solid state fluorescence and their unusual halochromic response in PMMA matrix have been used for fabricating rewritable and self-erasable fluorescent platforms. PQPBA and TQPA showed strong fluorescence in solution (Φ = 0.9290 (PQPBA) and 0.9160 (TQPA)) and moderate solid state fluorescence (Φ = 20 (PQPBA) and 17% (TQPA). Interestingly, they exhibited a rare temperature (0-100 °C) dependent positive fluorescence enhancement via activating radiative vibrational transition. The deaggregation of PQPBA and TQPA in PMMA polymer matrix lead to the enhancement of fluorescence intensity strongly and fabricated strong blue fluorescent thin films (Φ = 58% (PQPBA) and 54% (TQPA). The halochromic isoquinoline has been exploited for demonstrating reversible off-on fluorescence switching by acid (TFA (trifluoroacetic acid)/HCl) and base (NH) treatment in both solids as well as PMMA thin films. Importantly, rewritable and self-erasable fluorescent platform has been achieved by make use of unusual fluorescence responses of PQPBA/TQPA with TFA/HCl after exposing NH. Single crystal and powder X-ray diffraction (PXRD) studies provided the insight on the solid-state fluorescence and external stimuli-induced fluorescence changes.

Tin(IV) porphyrin scaffolds having long-chain (C 8 and C 16 ) alkoxyphenyl group at one meso position were synthesized with axial dichloro and dihydroxo ligands. Modifications with respect to the alkoxy chain length and the axial ligands were investigated using UV−vis and fluorescence spectroscopy as well as cyclic voltammetry. Significantly higher molar absorption coefficients were noted with dichloro axial ligands whereas higher fluorescence quantum yields were observed for C 8 alkoxy chain substituents. Electrochemical redox data revealed that the porphyrin ring became difficult to reduce consequent to the presence of electron donating alkoxy chain. Evaluation of the aggregation behavior in different organic solvents and DMF-water mixture has been carried out. The singlet oxygen production and photostability data are supportive of their suitability for antibacterial photodynamic therapy. The antibacterial studies carried out in Gram negative (E. coli) and Gram positive (B. subtilis) bacteria using agar well diffusion and LB broth assay revealed selective toxicity in B. Subtilis cells. Fluorescence microscopy and competitive DNA binding studies with Hoechst 33342 revealed DNA binding at the minor groove which was further substantiated with molecular docking studies.

The unsymmetrical phosphorus ylide, Ph 2 PCH 2 CH 2 PPh 2 @C(H)C(O)Ph is shown to react with Hg(II) halides to form polymeric products with the composition {HgX 2 [PPh 2 CH 2 CH 2 PPh 2 C(H)C(O)Ph]} n , where X = Cl (1), Br (2), I (3). The complexes have been characterized by elemental analysis, IR, 1 H, 31 P NMR spectra as well as by ESI mass spectra. In product 1 the ylide exhibits a P, C-bridging mode of coordination, while in 2 and 3 it shows a monodentate P-coordination with the dangling ylide. The structure of complex 3 has been characterized crystallographically. The monomeric -Hg-I-Hg-bridging in 3 leads to a zig-zag polymeric chain in which mercury assumes a distorted tetrahedral geometry.

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