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Cooperative Binding of Metal Cations to a Spiropyran‐Conjugated Calix[4]arene
Author(s) -
Lee Minhe,
Cho Daeheum,
Kim Inwon,
Lee Juhyen,
Lee Jin Yong,
Satheeshkumar Chinnadurai,
Song Changsik
Publication year - 2017
Publication title -
chemistryselect
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.437
H-Index - 34
ISSN - 2365-6549
DOI - 10.1002/slct.201700222
Subject(s) - spiropyran , chemistry , divalent , metal , cooperative binding , stoichiometry , molecule , cooperativity , metal ions in aqueous solution , crystallography , density functional theory , conjugated system , inorganic chemistry , binding site , computational chemistry , organic chemistry , polymer , biochemistry
Cooperative binding occurs frequently in biological systems, but is less exploited in synthetic receptor molecules. We synthesized a bis(spiropyran)‐conjugated calix[4]arene ( bSPTC ) through a 1,2,3‐triazole linker and found cooperativity in bindings of a series of divalent metal cations (Ca 2+ , Mg 2+ , Cd 2+ , Co 2+ , Fe 2+ , Hg 2+ , Ni 2+ , and Zn 2+ ). UV‐vis absorption spectroscopy and principle component analysis were used to differentiate the recognized metal cations. The binding stoichiometry was determined by various continuation methods, which indicated that bSPTC has two binding ratios, 1:1 for Zn 2+ and 1:2 for all other metal cations. Importantly, positive cooperativity was suggested for the 1:2 stoichiometry of bSPTC to Mg 2+ ions from the sigmoidal saturation curve and Hill equation analysis. Density functional theory (DFT) calculations imply that the first binding of Mg 2+ to one spiropyran destabilizes the second spiropyran, which facilitates binding of a second Mg 2+ .