title: Structural characterization of modular supramolecular architectures in solution.
abstract: Structures of modular supramolecular architectures consisting of a hexameric, diphenylethyne-linked porphyrin macrocyclic array and the corresponding host-guest complex formed by inclusion of a tripyridyl guest molecule were characterized in solution using high-angle X-ray scattering. Scattering measurements made to 6 A resolution coupled with pair distance function (PDF) analyses demonstrated that (1) the porphyrin architectures are not rigid but are distributed across a conformational ensemble with a mean diameter that is 1.5 A shorter than the diameter of a symmetric, energy-minimized model structure, (2) the conformational envelope has limits of 3 A positional dispersion and full rotational freedom for all six porphyrin groups, and (3) insertion of the tripyridyl guest molecule expands the diameter of the host conformer by 0.6 A and decreases the configurational dispersion by approximately 2-fold. These results validate the molecular design, provide a new measure of conformational ensembles in solution that cannot be obtained by other techniques, and establish a structural basis for understanding the photophysical and guest-hosting functions of the hexameric porphyrin architectures in liquids.
authors.affiliation: Chemistry Division, Argonne National Laboratory, Argonne, Illinois 60439, USA. tiede@anl.gov
authors.forename: David M
authors.initials: DM
authors.lastname: Tiede
authors.forename: Ruitian
authors.initials: R
authors.lastname: Zhang
authors.forename: Lin X
authors.initials: LX
authors.lastname: Chen
authors.forename: Lianhe
authors.initials: L
authors.lastname: Yu
authors.forename: Jonathan S
authors.initials: JS
authors.lastname: Lindsey