Integration of the 1,2,3‐Triazole “Click” Motif as a Potent Signalling Element in Metal Ion Responsive Fluorescent Probes

Abstract

In a systematic approach we synthesized a new series of fluorescent probes incorporating donor-acceptor (D-A) substituted 1,2,3-triazoles as conjugative π-linkers between the alkali metal ion receptor N-phenylaza-[18]crown-6 and different fluorophoric groups with different electron-acceptor properties (4-naphthalimide, meso-phenyl-BODIPY and 9-anthracene) and investigated their performance in organic and aqueous environments (physiological conditions). In the charge-transfer (CT) type probes 1, 2 and 7, the fluorescence is almost completely quenched by intramolecular CT (ICT) processes involving charge-separated states. In the presence of Na(+) and K(+) ICT is interrupted, which resulted in a lighting-up of the fluorescence in acetonitrile. Among the investigated fluoroionophores, compound 7, which contains a 9-anthracenyl moiety as the electron-accepting fluorophore, is the only probe which retains light-up features in water and works as a highly K(+)/Na(+)-selective probe under simulated physiological conditions. Virtually decoupled BODIPY-based 6 and photoinduced electron transfer (PET) type probes 3-5, where the 10-substituted anthracen-9-yl fluorophores are connected to the 1,2,3-triazole through a methylene spacer, show strong ion-induced fluorescence enhancement in acetonitrile, but not under physiological conditions. Electrochemical studies and theoretical calculations were used to assess and support the underlying mechanisms for the new ICT and PET 1,2,3-triazole fluoroionophores.

Substitution Pattern Reverses the Fluorescence Response of Coumarin Glycoligands upon Coordination with Silver (I)

“…This is similar to a chelation mode recently described between a triazolyl coumarin-based chemo-probe and a heavy metal36, as well as to some other simulated motifs including constrained glycoligands in complex with heavy metals3738. In contrast, as only the triazole groups are in coordination with silver, the FL quenching of DT3 could be possibly ascribed to a heavy metal effect1539.…”

A Ratiometric Fluorescent Probe for K+ in Water Based on a Phenylaza‐18‐Crown‐6 Lariat Ether

“…[7e] In a furtherr eport, we explored aK + -responsive fluorescent probe, which consists of ap henylaza-18-crown-6 ionophore and an anthracene unit as al ocally excited (LE) fluorophore, which are connected by a1 ,2,3-triazole moiety in af ully p-conjugated fashion (Scheme 1, fluorescent probe 3). [8] In addition, 3 exhibits aw eakly emissive charget ransfer (CT) state (S1) at 539 nm and al ocally excited (LE) state (S2) at 415 nm in CH 3 CN. In the presence of K + ,t he CT is decreased and energeticallys hifted upwards andt he LE state becomes the dominating fluorescent state (S1).…”

“…[10] Furthermore, we found for the 1,2,3-triazol p-linked fluorescent probe 3 av ery low fluorescent CT state in acetonitrile and water. [8] However,B ag and Kundu showed ad ual emission behaviorf or the 1,2,3-triazol p-linked pyrene derivative 4 (Scheme 1) in dioxane/water mixtures. [11a-c] Even af luorescent CT state in polar solvents is observed when ad imethylaniline unit is p-linked via a1 ,2,3-triazol-1,4-diyl unit with ab enzene moiety.…”

“…Fluorescent probe 1 showeda high K + -induced fluorescencee nhancement (FE) by af actor of 7.7 of the anthracenic emission and ad issociation constant (K d )v alue of 38 mm in water.F urther,f or 2 + K + ,w e observed ad uale mission behavior at 405 and 505 nm.K + increasest he fluorescencei ntensityo f2 at 405 nm by a factor of approximately 4.6 and K + decreases the fluorescence intensity at 505 nm by af actor of about 4.8. Fluorescent probe 2 + K + exhibited a K d value of approximately 8mm in Na + -free solutionsa nd in combined K + /Na + solution as imilar K d value of about 9mm was found, reflecting the highK + /Na + selectivityo f2 in water.T herefore, 2 is a promising fluorescent tool to measure ratiometrically and selectively physiologically relevant K + levels.[a] Dr.Scheme1.Studied fluorescent probes 1 and 2 and reference compounds 3 [8] and 4. [11] Chem.E ur.…”

Donor–acceptor–acceptor (D–A–A) type 1,8-naphthalimides as non-fullerene small molecule acceptors for bulk heterojunction solar cells

“…20,21 The Sonogashira cross-coupling reactions of compound 1 with 4-bromotriphenylamine 2 resulted in compound 3 (Scheme 1). 21,22 The naphthalimide based small molecules SM1 and SM2 were synthesized by the [2 + 2] cycloaddition–retroelectrocyclization reaction of compound 3 with tetracyanoethylene (TCNE) and 7,7,8,8-tetracyanoquinodimethane (TCNQ).…”