Multiple ion (Al3+, Cr3+, Fe3+, and Cu2+) sensing using a cell-compatible rhodamine-phenolphthalein-derived Schiff-base probe

Tuning ESIPT-coupled luminescence by expanding π-conjugation of a proton acceptor moiety in ESIPT-capable zinc(ii) complexes with 1-hydroxy-1H-imidazole-based ligands

“…The ESIPT photoreaction is extremely sensitive to the media surrounding the molecules of ESIPT-fluorophores. The reaction is affected by such factors as the nature of solvents, [42][43][44][45] acidity and basicity of media, 46,47 protonation/ deprotonation, [48][49][50][51] the presence of metal ions, 52,53 packing in the solid state, 54,55 etc. The formation of hydrogen bonds between the proton-donating group of an ESIPT-fluorophore and neighbouring molecules can break the intramolecular hydrogen bond and result in the emission of the normal form only.…”

Structure–metal ion selectivity of rhodamine-based chemosensors

“…Erdemir et al reported a bisphenol A incorporated rhodamine dye (80) for the identification of Zn 2+ in acetonitrile and Hg 2+ in CH 3 CN-water (8/2, v/v, HEPES, pH 7.0). 94 Hg 2+ induced the opening of the spirolactam ring which resulted in high fluorescence at 580 nm. On the other hand, Zn 2+ could not open the ring of the compound and gave fluorescence at 468 nm.…”

“…A reaction between phenolphthaleindialdehyde and rhodamine B hydrazide afforded compound 78 (Scheme 13) which could detect multiple cations in CH 3 OH–water (9 : 1, v/v, HEPES buffer, pH 7.2). 94 It displayed a significant absorbance increase at 555 nm in the presence Cu 2+ and Fe 3+ and high fluorescence at ∼585 nm with Al 3+ and Cr 3+ although the last couple of cations showed pink coloration. All the cations induced ring opening and complexation via amide oxygen, azomethine nitrogen and phenolic oxygen atoms.…”

First 1-hydroxy-1H-imidazole-based ESIPT emitter with an O–H⋯O intramolecular hydrogen bond: ESIPT-triggered TICT and speciation in solution

“…The ESIPT photoreaction in ESIPT-capable molecules depends strongly on the nature of media, [35][36][37][38][39][40][41][42][43][44][45][46][47][48][49][50] on substituents introduced in the core of an ESIPT-capable molecule and on the degree of p-conjugation between different moieties of the molecule. [51][52][53][54][55][56][57][58][59][60][61][62][63][64][65][66][67][68][69] These factors affect the electronic structure of the molecule and can induce barriers between the normal and tautomeric forms on the potential energy surfaces (PESs) in the excited state, causing partial or even full frustration of the proton transfer.…”