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Force Spectroscopy of Metal–Crown Ether Multivalency: Effect of Local Environments on Energy Landscape and Sensing Kinetics
Author(s) -
Kuo TingYang,
Tseng WeiHsiang,
Chen Chunhsien
Publication year - 2015
Publication title -
angewandte chemie international edition
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 5.831
H-Index - 550
eISSN - 1521-3773
pISSN - 1433-7851
DOI - 10.1002/anie.201503948
Subject(s) - force spectroscopy , dissociation (chemistry) , atomic force microscopy , chemistry , molecule , alkali metal , energy landscape , kinetic energy , bond dissociation energy , carboxylate , spectroscopy , crown ether , metal , kinetics , computational chemistry , analytical chemistry (journal) , chemical physics , nanotechnology , materials science , ion , stereochemistry , physics , organic chemistry , biochemistry , quantum mechanics
Abstract Sandwich complexation involving alkali or alkaline‐earth metals, multivalency, and effects associated with local environments is widely encountered in biological and synthetic systems yet the mechanic properties remain unexplored. Herein, AFM (atomic force microscopy)‐based single‐molecule force spectroscopy is employed to investigate a classical model of M n+ [15C5] 2 , a metal cation hosted jointly by two 15‐crown‐5 moieties immobilized on both the substrate and the AFM tip. Factors reportedly promoting the recognition performance are examined. The rupture force required to break apart M n+ [15C5] 2 is found to be in the order of tens of pico‐Newton, e.g., f β =31 pN for K + [15C5] 2 . The presence of a second functional group, carboxylate, confers K + [15C5] 2 with a longer lifetime (from 13 to 16 ms), faster association (from 0.4 to 1.3×10 6 M −1 s −1 ), and slower dissociation (from 77 to 62 s −1 ). The effect of local environments is significant on association yet less critical on dissociation pathways.