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Solvent‐dependent ground‐state distributions in a donor–acceptor redox‐active bistable [2]catenane
Author(s) -
Wang Cheng,
Cao Dennis,
Fahrenbach Albert C.,
Fang Lei,
Olson Mark A.,
Friedman Douglas C.,
Basu Subhadeep,
Dey Sanjeev K.,
Botros Youssry Y.,
Stoddart J. Fraser
Publication year - 2012
Publication title -
journal of physical organic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.325
H-Index - 66
eISSN - 1099-1395
pISSN - 0894-3230
DOI - 10.1002/poc.1960
Subject(s) - chemistry , ground state , catenane , ring (chemistry) , acceptor , solvent , crystallography , molecule , organic chemistry , physics , quantum mechanics , condensed matter physics
The solvent dependency of the ground‐state distribution as well as the electrochemical switching behavior in a redox‐active bistable donor–acceptor [2]catenane, containing bisthiotetrathiafulvalene (STTFS) and 1,5‐dioxynaphthalene (DNP) recognition sites incorporated within a macrocyclic polyether encircled by the cyclobis(paraquat‐ p ‐phenylene) (CBPQT 4+ ) ring, has been investigated. There are two translational isomers: (i) the ground‐state co‐conformation (GSCC) in which the CBPQT 4+ ring encircles the STTFS unit and (ii) the metastable‐state co‐conformation (MSCC) in which the CBPQT 4+ ring encircles the DNP unit. 1 H NMR spectroscopy indicates that the ground‐state distribution of GSCC to MSCC varies from approximately 1:1 in MeCN to 7:1 in MeCN : H 2 O (1:1, v/v) at 283 K. The reversible electrochemical switching behavior of the [2]catenane was confirmed by 1 H NMR and UV−Vis spectroscopies, as well as by cyclic voltammetry (CV). Additionally, variable scan‐rate CV studies were compared with simulated CV data and show that the ground‐state distribution of GSCC to MSCC is about 30:1 in MeCN : H 2 O (1:1, v/v) at 298 K. With the assistance of isothermal titration calorimetry of model compounds, it was found that the changing ground‐state distribution in differing solvent systems is driven entropically rather than enthalpically. Copyright © 2012 John Wiley & Sons, Ltd.