Mitochondria-Targeted Luminescent Organotin(IV) Complexes: Synthesis, Photophysical Characterization, and Live Cell Imaging

Five fluorescent ONO donor-based organotin(IV) complexes, [Sn^IV(L^1-5)Ph₂] (1-5), were synthesized by the one-pot reaction method and fully characterized spectroscopically including the single-crystal X-ray diffraction studies of 2-4. Detailed photophysical characterization of all compounds was performed. All the compounds exhibited high luminescent properties with a quantum yield of 17-53%. Additionally, the results of cellular permeability analysis suggest that they are lipophilic and easily absorbed by cells. Confocal microscopy was used to examine the live cell imaging capability of 1-5, and the results show that the compounds are mostly internalized in mitochondria and exhibit negligible cytotoxicity at imaging concentration. Also, 1-5 exhibited high photostability as compared to the commercial dye and can be used in long-term real-time tracking of cell organelles. Also, it is found that the probes (1-5) are highly tolerable during the changes in mitochondrial morphology. Thus, this kind of low-toxic organotin-based fluorescent probe can assist in imaging of mitochondria within living cells and tracking changes in their morphology.

Solvent-Regulated Fluorimetric Differentiation of Al3+ and Zn2+ Using an AIE-Active Single Sensor

The absence of d-orbital electrons or presence of full-filled d-orbital electrons in metal ions is a well-known Achilles' heel problem for the detection of these metal ions by a simple UV-visible study. For this reason, detection of metal ions such as Al³⁺ with no d-orbital electrons or Zn²⁺ with filled d-orbital electrons is a challenging task. Herein, we report a 2-naphthol-based fluorescent probe [1-((E)-((E)-(5-bromo-2-hydroxybenzylidene)hydrazono)methyl)naphthalen-2-ol] (H₂L) that has been used to sense and discriminate Al³⁺ and Zn²⁺ via solvent regulation. The probe exhibits excellent selectivity and swift sensitivity toward Al³⁺ in MeOH-water (9:1, v/v) and toward Zn²⁺ in dimethyl sulfoxide (DMSO)-water (9:1, v/v) among various metal ions. The respective detection limit is found to be 9.78 and 3.65 μM. The sensing mechanism is attributed to multiple processes, viz., the inhibition of photo-induced electron transfer (PET) along with the introduction of chelation-enhanced emission (CHEF) and excited-state intramolecular proton transfer (ESIPT) inhibition, which are experimentally well verified by UV-vis absorption spectroscopy, emission spectroscopy, and NMR spectroscopy. The probe shows aggregation-induced emissive (AIE) response in ≥70% aqueous media as well as in the solid state. The experimental results are well corroborated by time-resolved photoluminescence (TRPL) and density functional theory (DFT) calculations. An advanced-level OR-AND-NOT logic gate has been constructed from a different chemical combinational input and emission output. The reversible recognition of both Al³⁺ in MeOH-water (9:1, v/v) and Zn²⁺ in DMSO-water (9:1, v/v) is also ascertained in the presence of Na₂EDTA, enabling the construction of a molecular memory device. The probe H₂L also detects intracellular Al³⁺/Zn²⁺ ions in Hela cells. Altogether, our fundamental findings will pave the way for designing and synthesis of unique chemosensors that could be used for cell imaging studies as well as constructing molecular logic gates.

Green synthesis of fluorescent Schiff bases: chemo-photophysical characterization, X-ray structures, and their bioimaging

Two Schiff bases have been prepared by mechano- and ultrasound-assisted synthesis and their structures were elucidated by X-ray diffraction. One of them showed good fluorescent cell staining in vitro and low cytotoxicity.

Indigo-Based Acceptor Type Small Molecules: Synthesis, Electrochemical and Optoelectronic Characterizations

In this paper, we report design and synthesis of novel low bandgap small molecules, indigo-benzimidazole (Tyr-3) and indigo-schiff base (Tyr-4) type acceptors. In these structures, tert-butoxycarbonyl (t-BOC) group has been attached to indigo nitrogen atom in order to increase the solubility. UV-vis absorption spectra of Tyr-3 and Tyr-4 dyes exhibit wide absorption bands ranging from 350 to 600 nm, indicating the relatively low bandgap giving around 2.07 eV for each. Excitation of both Tyr-3 and Tyr-4 dyes at 485 nm displays characteristic emission features of indigo moiety and also intramolecular charge transfer complex (ICT) related with their subunits. Besides increasing fluorescence quantum yields as compared to model compound, biexponential decay times for fluorescence life times were also obtained for Tyr-3 and Tyr-4 dyes. Their appropriate energy levels along with low HOMO levels are desired for light harvesting acceptors for organic solar cells when blended with poly[N-9'-heptadecanyl-2,7-carbazole-alt-5,5-(4,7-di-2-thienyl-2',1',3'-benzothiadiazole] (PCDTBT) as donor polymer. Photovoltaic behavior of the synthesized dyes were examined in bulk heterojunction concept and achieved photovoltaic conversion efficiencies were discussed.

Self-reversible mechanochromism and aggregation induced emission in neutral triarylmethanes and their application in water sensing

Neutral triarylmethanes exhibit intramolecular exciplex formation, self-reversible mechanochromism, and aggregation induced/viscosity-dependent emission and sense water in organic solvents.

Dynamic fluorescence quenching by 2,4,6-trinitrophenol in the voids of an aggregation induced emission based fluorescent probe

PY-DNSfollows dynamic fluorescence quenching with TNP to elicit a linear change in fluorescence quenching over eight orders of concentration of TNP (10⁻¹³–10⁻⁵M).