Premium
Molecular Shuttles Based on Tetrathiafulvalene Units and 1,5‐Dioxynaphthalene Ring Systems
Author(s) -
Kang Seogshin,
Vig Scott A.,
Tseng HsianRong,
Stoddart J. Fraser
Publication year - 2004
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.200305725
Subject(s) - tetrathiafulvalene , chemistry , ring (chemistry) , rotaxane , terphenyl , crystallography , linker , molecule , molecular machine , conjugated system , stereochemistry , nanotechnology , supramolecular chemistry , polymer , organic chemistry , materials science , computer science , operating system
Six different degenerate [2]rotaxanes were synthesized and characterized. The rotaxanes contained either two tetrathiafulvalene (TTF) units or two 1,5‐dioxynaphthalene (DNP) ring systems, both of which serve as recognition sites for a cyclobis(paraquat‐ p ‐phenylene) (CBPQT 4+ ) ring. Three different spacer units were incorporated into the dumbbell components of the [2]rotaxanes between the recognition sites. They include a polyether chain, a terphenyl unit, and a diphenyl ether linker, all of which were investigated in order to probe the effect of the spacers on the rate of the shuttling process. Data from dynamic 1 H NMR spectroscopy revealed a relatively small difference in the Δ G ≠ values for the shuttling process in the [2]rotaxanes containing the three different spacers, in contrast to a large difference between the TTF‐containing rotaxanes (18 kcal mol −1 ) and the DNP‐containing rotaxanes (15 kcal mol −1 ). This 3 kcal mol −1 difference is predominantly a result of a ground‐state effect, reflecting the much stronger binding of TTF units to the CBPQT 4+ ring in comparison with DNP ring systems. An examination of the enthalpic (Δ H ≠ ) and entropic (Δ S ≠ ) components for the shuttling process in the DNP‐containing rotaxanes revealed significant differences between the three spacers, a property which could be important in designing new molecules for incorporation into molecular electronic and nanoelectromechanical (NEMs) devices.