Two-stage metal ion sensing by through-space and through-bond charge transfer

Abstract

A highly selective colorimetric and ratiometric “two-stage”/“off-on” type fluorescent probe with the ability to exclude other heavy and transition metal ions has been designed and synthesized. Low concentration of Fe3+...

Exploring binding chemistry of alkali/alkaline earth cations in solution through modulation of intramolecular charge-transfer in an excited ambidentate organic fluorophore

“…This phenomenon has been described for a high CT-fluorophore having a coordination donor-group. 37–41 Curiously, this type of fluorescence response in 3k generated a dye–metal adduct with an emission spectrum similar to that found for the low CT 3g (Fig. 1A), which reflects the pivotal role of the methoxy moiety in the origin of the ICT in this type of chemical system.…”

“…). 37–42 Meanwhile, the combined LE-state enhancement and CT-state decay was derived from the interaction of the AM cations with the donor-group [ 3k(MeO) -cation], which blocked the ICT upon excitation, favoring an enrichment of the LE-state (route 2, Fig. 3).…”

“…In the search for convenient analytical strategies, fluorometry and the occurrence of specific fluorescence mechanisms [chelation enhancement fluorescence (CHEF), chelation enhancement quenching (CHEQ), depletion of metal–ligand charge-transfer (MLCT), fluorescence resonance energy transfer (FRET) or modulation of intramolecular charge-transfer (ICT)], which are highly sensitive to the presence of metal cations, offer a great opportunity to recognize M–L monoligation in solution. 31–43 Recent reports have demonstrated that the ICT process can be modulated upon metal-binding (Ca 2+ , Zn 2+ or Cd 2+ ) by specific interactions with (A)- and (D)-groups upon excitation, leading to distinguished spectral changes including simultaneous CT-decay and LE-enhancement by interaction with (D)-group and CT-enhancement by interaction with (A)-group (Chart 1A–D). 37–41 ICT is a photophysical process that involves electron transfer (ET) upon excitation from a donor group (D) to an acceptor group (A) through a π-conjugated linker.…”

“…31–43 Recent reports have demonstrated that the ICT process can be modulated upon metal-binding (Ca 2+ , Zn 2+ or Cd 2+ ) by specific interactions with (A)- and (D)-groups upon excitation, leading to distinguished spectral changes including simultaneous CT-decay and LE-enhancement by interaction with (D)-group and CT-enhancement by interaction with (A)-group (Chart 1A–D). 37–41 ICT is a photophysical process that involves electron transfer (ET) upon excitation from a donor group (D) to an acceptor group (A) through a π-conjugated linker. This process generates an anomalous emission band called the charge-transfer (CT) state, which is an excited state derived from a local excited (LE) state (normal emission).…”

Detection of Heavy Metal Ions by Ratiometric Photoelectric Sensor

“…Yin et al 50 synthesized a chemical probe to detect Fe 3+ . When the concentration was higher than 6 nM, Fe 3+ would combine with the pyridyl group of the probe, and the ICT effect was enhanced.…”