A Highly K⁺‐Selective Two‐Photon Fluorescent Probe

Abstract

A highly K(+)-selective two-photon fluorescent probe for the in vitro monitoring of physiological K(+) levels in the range of 1-100 mM is reported. The two-photon excited fluorescence (TPEF) probe shows a fluorescence enhancement (FE) by a factor of about three in the presence of 160 mM K(+), independently of one-photon (OP, 430 nm) or two-photon (TP, 860 nm) excitation and comparable K(+)-induced FEs in the presence of competitive Na(+) ions. The estimated dissociation constant (Kd ) values in Na(+)-free solutions (Kd (OP) =(28±5) mM and Kd (TP)=(36±6) mM) and in combined K(+)/Na(+) solutions (Kd (OP) =(38±8) mM and Kd (TP)=(46±25) mM) reflecting the high K(+)/Na(+) selectivity of the fluorescent probe. The TP absorption cross-section (σ2PA ) of the TPEF probe+160 mM K(+) is 26 GM at 860 nm. Therefore, the TPEF probe is a suitable tool for the in vitro determination of K(+).

A Highly K+‐Selective Fluorescent Probe – Tuning the K+‐Complex Stability and the K+/Na+ Selectivity by Varying the Lariat‐Alkoxy Unit of a Phenylaza[18]crown‐6 Ionophore

“…ϕ F and λ max were slightly influenced by the introduction of different alkoxy groups on the ortho position of the aniline moiety. The low ϕ F of 4 , 5 and 6 are caused by a photoinduced electron transfer (PET)– across a virtual spacer, as already observed for the 1,2,3‐triazol‐fluoroionophores 1 , 2 and 3 ,…”

1,2,3‐Triazol‐1,4‐diyl‐Fluoroionophores for Zn2+, Mg2+ and Ca2+ based on Fluorescence Intensity Enhancements in Water

“…These φ f values are low, caused by a PET process from the aniline unit to the coumarin moiety, which quenches the fluorescence. Further, similar low φ f values were also found for a set of π ‐conjugated 1,2,3‐triazol‐1,4‐diyl–fluoroionophores [11a–e,12a−c] . Herein, the regioisomeric triazole linkage in Zn1 is responsible for a better fluorescence quenching than in Zn3 .…”

“…In a further study, they developed selective fluorescent probes for K + by using the highly K + /Na + selective ionophore the N ‐(o‐2‐methoxyethoxy)phenylaza‐18‐crown‐6 (cf. K1 and K2 , Scheme 2) [11a–e] and for Na + by using the highly Na + /K + selective ionophore the N ‐(o‐methoxyphenyl)aza‐15‐crown‐5 (cf. Na1 and Na2 , Scheme 2).…”

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

“…Recently, we developed highly K + ‐selective PET fluoroionophores to exclusively determine K + by fluorescence intensity enhancements,– when excited by a one‐photon– or two‐photon process and by fluorescence lifetime changes . In a further report, we explored a K + ‐responsive fluorescent probe, which consists of a phenylaza‐18‐crown‐6 ionophore and an anthracene unit as a locally excited (LE) fluorophore, which are connected by a 1,2,3‐triazole moiety in a fully π‐conjugated fashion (Scheme , fluorescent probe 3 ) .…”