title: Force Spectroscopy of Metal-Crown Ether Multivalency: Effect of Local Environments on Energy Landscape and Sensing Kinetics.
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.
authors.affiliation: Department of Chemistry and Center for Emerging Material and Advanced Device, National Taiwan University, 1, Sec. 4, Roosevelt Road, Taipei, 10617 (Taiwan).
authors.forename: Ting-Yang
authors.initials: TY
authors.lastname: Kuo
authors.affiliation: Department of Chemistry and Center for Emerging Material and Advanced Device, National Taiwan University, 1, Sec. 4, Roosevelt Road, Taipei, 10617 (Taiwan).
authors.forename: Wei-Hsiang
authors.initials: WH
authors.lastname: Tseng
authors.affiliation: Department of Chemistry and Center for Emerging Material and Advanced Device, National Taiwan University, 1, Sec. 4, Roosevelt Road, Taipei, 10617 (Taiwan). chhchen@ntu.edu.tw.
authors.forename: Chun-hsien
authors.initials: CH
authors.lastname: Chen
mesh_terms: D056831:Coordination Complexes / Q000737:chemistry; D043844:Crown Ethers / Q000737:chemistry*; D004986:Ether / Q000737:chemistry; D007700:Kinetics; D008670:Metals / Q000737:chemistry*; D018625:Microscopy, Atomic Force; D013816:Thermodynamics
chemical_list: D056831:Coordination Complexes; D043844:Crown Ethers; D008670:Metals; D004986:Ether; C042148:15-crown-5
keywords: crown compounds; ion-molecule reactions; kinetics; molecular recognition; sandwich complexes