T. Schwartze, J. Riemer, H.-J. Holdt
A Ratiometric Fluorescent Probe for K+ in Water Based on a Phenylaza-18-Crown-6 Lariat Ether
Chemistry - A European Journal 2018, 24, 10116-10121
DOI: 10.1002/chem.201802306
This work presents two molecular fluorescent probes 1 and 2 for the selective determination of physiologically relevant K+ levels in water based on a highly K+/Na+ selective building block, the o-(2-methoxyethoxy)phenylaza-18-crown-6-lariat ether unit. Fluorescent probe 1 showed high K+-induced fluorescence enhancement (FE) by a factor of 7.7 of the anthracenic emission and a dissociation constant (Kd) value of 38 mm in water.Further, for 2 + K+ , we observed adualemission behavior at 405 and 505 nm. K+ increases the fluorescence intensity of 2 at 405 nm by a factor of approximately 4.6 and K+ decreases the fluorescence intensity at 505 nm by a factor of about 4.8. Fluorescent probe 2 + K+ exhibited a Kd value of approximately 8 mm in Na+-free solutions and in combined K+/Na+ solution a similar Kd value of about 9 mm was found, reflecting the high K+/Na+ selectivity of 2 in water.Therefore, 2 is a promising fluorescent tool to measure ratiometrically and selectively physiologically relevant K+ levels.
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