N-aryl-2-(trifluoromethyl)benzo[b][1,8]naphthyridin-4(1H)-one as convenient platform to design high photostable and long-lived dyad fluorophore with potential application in live-cell imaging

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

“…1A–C). 43 Detailed information on the photophysical properties of these three fluorophores can be found in Table S1 (ESI†). This comparison was important to study the role of the ICT and the relevance of an extra coordination point along the D–A chain, which allowed us to obtain more information on the binding ability of the AM cations.…”

“…All three N 1 -aryl-2-(trifluoromethyl)-benzo[ b ][1,8]naphthyridin-4(1 H )-ones, 3g , 3i and 3k , were previously prepared by our group following a synthetic strategy of successive steps. 57,58 The fluorescent profile of both p K a -probes were previously studied by our group 43 and some key photophysical properties are listed in Table S1 (ESI†). All the alkali and alkaline inorganic salts in chloride form were purchased from commercial sources ( e.g.…”

“…Previously, we found that B3LYP/6-31G(d,p) gave good estimations for structural parameters of the N 1 -aryl-2-(trifluoromethyl)benzo[ b ][1,8]naphthyridin-4(1 H )-ones, as a convenient approach for providing reasonably results for intermolecular interactions. 43,65 This study was focused on fluorophore 3k . The geometries of ambidentate ligand 3k and corresponding complexes were optimized in the gas phase.…”

“…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.…”