title: Neutral and anionic guests and their effect on the formation of pseudorotaxanes by using a flexible tetracationic imidazolium macrocycle.
abstract: The ability to control and direct molecular assembly has important implications in the design of environmentally responsive materials. Reported here is the use of competitive neutral- and anionic-guest recognition to control the formation, disruption, replacement-based construction and higher-order assembly properties of pseudorotaxane structures involving a large, cationic tetraimidazolium receptor. In particular, we showed that the chloride anion (as the tetrabutylammonium (TBA(+)) salt) serves to replace directly the 2,6-naphthalene dicarboxylate dianion from the preformed complex, involving this dianion. In contrast, the addition of the nitrate anion (as the TBA(+) salt) serves to effect displacement of a pre-bound 2,6-naphthalene dicarboxylate dianion in a stepwise manner allowing for stabilization of a so-called "outside"-binding mode under appropriate conditions. We have also found that by using biphenyl-3,4,3',4'-tetraamine as the guest, a 1D-donor-acceptor-donor coordination polymer can be stabilized, whereas the addition of 6-amino-naphthalene-2-sulfonate anion to the pre-formed complex between the tetraimidazolium receptor and the 2,6-naphthalene dicarboxylate dianion produces a new pseudorotaxane complex. This guest-based competition and subsequent molecular translocation is supported by solution-state NMR spectroscopic studies as well as solid-state single-crystal X-ray structural analyses. The results described herein provide initial evidence that guest competition can be used to control molecular "switching" and substrate binding within an appropriately designed anion receptor.
authors.affiliation: Department of Chemistry and Biochemistry, The University of Texas at Austin, 1 University Station, A5300, Austin, TX 78712-0165, USA. hanyuangong@mail.ruc.edu.cn
authors.forename: Han-Yuan
authors.initials: HY
authors.lastname: Gong
authors.forename: Brett M
authors.initials: BM
authors.lastname: Rambo
authors.forename: Vincent M
authors.initials: VM
authors.lastname: Lynch
authors.forename: Karin M
authors.initials: KM
authors.lastname: Keller
authors.forename: Jonathan L
authors.initials: JL
authors.lastname: Sessler