The Daily Bulletin

Please join the Chemistry and Physics departments for the seminar "Tessellation of Shape-Persistent Donor-Acceptor Cyclophanes for the Creation of Two-Dimensional Porous Materials," presented by Fulbright alumnus M. Mustafa Cetin, '08, on Thursday, November 8, from 12:15 to 1:30 p.m. in Science and Mathematics Complex 173. Dr. Cetin is currently a postdoctoral fellow in the Department of Chemistry at Northwestern University.

Abstract
Porous two-dimensional (2-D) networks of polygons with uniform or heterogeneous morphologies have attracted much attention over the last three decades. The concept of tessellation, which refers to the closely fitted arrangement of shapes in a repeated pattern, has been employed in the construction of beautiful crystalline porous 2-D frameworks through the judicious choice of polygon-like macrocyclic building blocks whose edges and vertices fit snugly together to form an extended, stackable array. While the construction of covalent organic frameworks (COFs) requires the introduction of covalent bonds between organic subunits, the preparation of 2-D networks, in contrast, makes use of non-covalent bonding for assembly. The resulting structure is a tiled network consisting of shape-persistent polygons held together by dispersive forces. In the present work, a series of donor-acceptor (D–A)-based cyclophanes of different shapes, sizes, and symmetries has been prepared by introduction of both viologen (acceptor) and 2,6- or 2,7-naphthalene (donor) subunit functionalities into molecular rings resembling simple polygons. The resulting cyclophanes were either "box–like" or "truncated-hexagon-like" in shape. All cyclophanes based on the 2,6-naphthalene subunit are highly symmetrical and establish a favorable network of D–A interactions, resulting in a 2-D network that exhibits uniform pores. When the 2,7-naphthalene subunit is used, the resulting cyclophane has a "truncated-hexagon-like" structure that is chiral and exhibits dual pores in its 2-D network. The solid-phase packing of the cyclophanes can be tuned by co-crystallization with a strong donor such as tetrathiafulvalene (TTF). In the presence of TTF, one of two cyclophane structures can result: "box-like" or "hexagon-like." The "box-like" motif results in either a 1-D charge-transfer (CT) mixed stack characterized by interactions between viologen and TTF, or a host-guest complex. On the other hand, the "hexagon-like" motif generates a well-ordered and uniform tubular structure where CT interactions between viologen and TTF propagate in two dimensions. In the course of these investigations, we have uncovered design rules for the creation of “programmable” building blocks that result in well-defined crystal habits. Spectroscopic properties of these cyclophanes and their corresponding co-crystals have also been determined in both solution and the solid state.