A colorimetric and 'OFF-ON' fluorometric chemosensor based on a rhodamine-pyrazole derivative for the detection of Al3+, Fe3+and Cr3+metal ions, and its intracellular application.

The colorimetric and fluorescence responses of a new rhodamine-functionalized probe (E)-2-(((5-chloro-3-methyl-1-phenyl-1H-pyrazol-4-yl)methylene)amino)-3',6'-bis(diethylamino)spiro[isoindoline-1,9'-xanthen]-3-one (RMP) are investigated. RMP has been thoroughly characterized using various spectroscopic tools and single crystal X-ray diffraction. Among different competing cations, it shows highly sensitive colorimetric and "OFF-ON" fluorescence responses towards Al3+, Fe3+and Cr3+metal ions. The spectral shifts are clearly noticeable in the visible region of the absorption spectrum and can be observed with the naked eye. Fluorescence quantum yield, stoichiometric ratio, binding constant and detection limit of RMP towards Al3+, Fe3+and Cr3+metal ions have been calculated. Furthermore, RMP-M3+ complexes are reversible and sensitive to EDTA, which effectively mimics a molecular logic gate. Al3+, Fe3+and Cr3+metal ions have been further applied in intracellular application in model human cells.

A multifunctional basic pH indicator probe for distinguishable detection of Co2+, Cu2+ and Zn2+ with its utility in mitotracking and monitoring cytoplasmic viscosity in apoptotic cells.

Metal ions such as Co2+, Cu2+ and Zn2+ have extensive applications in biological and industrial realms, but the toxicity caused by these ions poses a serious threat to mankind. However, there is no report in the literature on the development of a chemosensor for distinguishable detection of these toxic ions. Addressing this challenge, a multifunctional probe as a basic pH indicator with both colorimetric and fluorescence turn-on responses has been reported. The probe selectively discriminates Co2+, Cu2+ and Zn2+ ions with brown, dark yellow and greenish yellow colors, respectively, in DMF : water (9 : 1 v/v, HEPES 10 mM). Additionally, a fluorescence turn-on response specific to Zn2+ has also been observed. The sensing mechanism has been explored using UV-Vis, fluorescence spectroscopy and 1H NMR titration and confirmed with computational results. The inhibition of CN isomerization and excited state intramolecular proton transfer (ESIPT) along with chelation enhanced fluorescence emission (CHEF) result in fluorescence enhancement with Zn2+. Job's plot and HRMS spectra confirm a 1 : 1 (L : M) stoichiometry between the probe and metal ions. The probe is able to exhibit excellent viscochromism in DMF : glycerol medium. Live cell imaging on SiHa cells has been successfully performed for intra-cellular detection of Zn2+ at basic pH. Furthermore, the probe displays its utility in mitotracking and monitoring cytoplasmic viscosity changes in SiHa cells. It is efficiently used to recognize the apoptosis process by displaying an enhancement in fluorescence intensity from cancerous SiHa cells to apoptotic cells.

A reversible and efficient probe for dual mode recognition of Al3+ and Cu2+ with logic gate behaviour: Crystal structure, theoretical and in-vivo bio-imaging investigations.

This work presents the synthesis, characterization, crystal structure and spectroscopic investigations of isophthalohydrazide based probe. Among various tested metal ions, the probe selectively detects Al3+ and Cu2+ in aqueous ethanol via fluorometric and colorimetric methods, respectively. It displays a fluorescence "turn-on" response with Al3+ and visual colour change from colourless to yellow with Cu2+. Sensing mechanism is explored with UV-Vis, fluorescence spectroscopy and 1H NMR titration, and confirmed with computational results. Suppression of CN isomerization and photo-induced electron transfer (PET) along with chelation enhanced fluorescence emission (CHEF) result in "turn-on" fluorescence with Al3+ while ligand to metal charge transfer (LMCT) accounts for visual colour change with Cu2+. Job's plot and HRMS confirm 1:2 (L:M) stoichiometry. The probe also exhibits efficient reversibility and reproducibility with EDTA which are successfully mimicked with combinatorial logic gate and truth table. Additionally, solid state applications and bio-imaging investigation on gut tissue of Drosophila 3rd instar larvae are performed.