Published: March 08, 2011 r2011 American Chemical Society 2701 dx.doi.org/10.1021/jo2000447 | J. Org. Chem. 2011, 76, 2701–2715 ARTICLE pubs.acs.org/joc Synthesis and Properties of Conjugated Oligoyne-Centered π-Extended Tetrathiafulvalene Analogues and Related Macromolecular Systems Guang Chen, † Ilias Mahmud, † Louise N. Dawe, † Lee M. Daniels, ‡ and Yuming Zhao* ,† † Department of Chemistry, Memorial University of Newfoundland, St. John’s, Newfoundland A1B 3X7, Canada ‡ Rigaku Americas Corporation, 9009 New Trails Drive, The Woodlands, Texas 77381, United States b S Supporting Information ’ INTRODUCTION Tetrathiafulvalene (TTF) as an important organic electron donor has found extensive uses in modern materials science. 1,2 Ever since the seminal work by Wudl and co-workers on the electrical conductivity of [TTF] •þ Cl  in the early 1970s, 3,4 an enormous array of TTF variants has been synthesized and appli- ed as useful building blocks in the construction of advanced molecular/supramolecular materials and devices, ranging from organic conductors and superconductors, 58 magnets, 79 mo- lecular switches and sensors, 1012 molecular machines, 13,14 organic optoelectronics, 15,16 and plastic solar cells, 15,17,18 just to name a few. In the development of functional TTF derivatives, the strategy of increasing the π-conjugation of the TTF back- bone has been widely employed to generate the so-called π- extended tetrathiafulvalene analogues (exTTFs), 11,15,19,20 In current TTF chemistry, insertion of various π-conjugated spacers such as quinoid, 2124 vinylogous, 2527 arylene, 28 and acetylene bridges 29,30 between the two dithiole rings of TTF has been proven effective at tuning the properties and functions of exTTF derivatives to be applicable for device applications, such as enhanced electron-donating ability, increased solid-state or- dering and dimensionality, as well as controlled multistage redox activities. Conjugated oligoynes or polyynes constitute a class of quasi- one-dimensional conjugated carbon chains and have been ex- tensively investigated as versatile scaffoldings for functional carbon-rich materials, owing to their rich optoelectronic and electromagnetic properties and unique solid-state reactivities. 3139 For instance, the nonlinear optical susceptibil- ities of oligoynes were found to increase exponentially with increasing number of acetylenic repeat units, 40,41 while topo- chemical polymerization of oligoynes tended to result in highly conjugated polymer networks 37,4250 and ordered carbon-based nanomaterials. 5154 Moreover, the “wire-like” sp carbon chains (spCCs) of conjugated oligoynes or polyynes are the substruc- tures of an intriguing carbon allotropecarbyne, 55,56 while debates over the nature of electronic delocalization in spCCs have galvanized both experimental and theoretical invest- igations. 5763 In particular, synthetic endeavors aiming at exten- sion and functionalization of conjugated oligoynes have been actively undertaken in recent years in order to realize suitable models for unraveling the mystical characteristics of carbyne and related polyyne materials. 6370 Received: January 12, 2011 ABSTRACT: Alkynyl-substituted phenyldithiafulvenes have been found to act as versatile building blocks for the construc- tion of π-conjugated molecular rods, shape-persistent macro- cycles (SPMs), and conducting polymers. Through Cu(I)- catalyzed alkynyl homocoupling, a series of linear-shaped π- extended tetrathiafulvalene analogues (exTTFs) carrying con- jugated oligoynes (ranging from diyne to hexayne) as the central π-bridge were readily prepared. The solid-state proper- ties and reactivities of diyne- and tetrayne-centered exTTFs were characterized by X-ray crystallography and differential scanning calorimetry (DSC), while the electronic properties of the oligoyne-exTTFs were elucidated by UVvis absorption spectroscopy and density functional theory (DFT) calculations. Cyclic voltammetric analysis showed that the terminal phenyldithiafulvene groups of the oligyne-exTTFs could undergo oxidative coupling to form tetrathiafulvalene vinylogue (TTFV)-linked polymer wires. Through a different synthetic route involving oxidative dimerization and Pd/Cu-catalyzed alkynyl homocoupling, the acetylenic phenyldithiafulvene precursors led to shape-persistent macrocycles where the formation of trimeric macrocycles was particularly favored due to the small ring strain incurred. Finally, spectroelectrochemical studies on these oligoyne and TTF hybrid materials disclosed electrochromic and molecular redox- controlled switching properties applicable to molecular electronic and optoelectronic devices.