American Chemical Society
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Exchange Properties of the Three-Dimensional Coordination Compound 1,3,5-Tris(4-ethynylbenzonitrile)benzene·AgO3SCF3

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posted on 1996-07-24, 00:00 authored by Geoffrey B. Gardner, Y.-H. Kiang, Stephen Lee, Anil Asgaonkar, D. Venkataraman
Properties such as guest removal and exchange within a host crystal are investigated for benzene·1,3,5-tris(4-ethynylbenzonitrile)(1)·silver triflate(AgOTf) (polymorph A). The 15 Å × 22 Å channels in the crystal structure are retained through both guest exchange and complete guest removal. The apohost (defined to be a host without guests system) exhibits selectivity for new guests by absorbing aromatic molecules (ranging from 1.5−4 guests per molecule of 1) and not aliphatic molecules from the vapor phase. In solution, guests such as toluene, undecane, and benzyl alcohol are shown to be accomodated typically with two to three guest molecules for every molecule of 1. Guest exchange of nonfunctionalized aliphatic and aromatic molecules make no changes in the original benzene·1· AgOTf adduct orthorhombic cell parameters (11.625(3) Å × 19.110(7) Å × 38.856(15) Å) greater than 0.4 Å for any axis. However, crystals containing alcoholic aromatic molecules can be indexed to the two-dimensional rectangular analog of an orthorhombic cell, with b and c cell axis of 22.0−22.5 Å and 32.8−34.7 Å, respectively. Complete evacuation of the channels by heating also produces a two-dimensional rectangular cell with parameters 22.76(2) Å × 36.32(3) Å. X-ray powder diffraction of all adducts demonstrates the retention of the original three-dimensional ThSi2-type network or, in the case of the alcoholic adduct or apohost systems, the two-dimensional projection of this channel structure. Repeated removal and reintroduction of benzyl alcohol guests is demonstrated to occur with the retention of crystallinity and without the macroscopic reformation of the crystallites.