Halogen-Bonded, Eight-fold PtS-Type Interpenetrated Supramolecular Network. A Study toward Redundant and Cross-Bar Supramolecular Nanowire Crystal

Making crystalline organic conducting nanowires will allow three-dimensional nanoscale wiring, owing to their periodic arrangement in the solid state. In order to find new motifs for insulation sheaths in a crystal, new large and rigid spacer molecules containing iodine atoms have been successfully synthesized. One novel nonplanar aromatic tecton with an extended skeleton, 2,2′,4,4′,6,6′-hexafluoro-3,3′,5,5′-tetrakis((4-(iodoethynyl)phenyl)ethynyl)biphenyl (1) has formed halogen-bonded supramolecular self-assemblies in the presence of halide anions. Bis(propylenedithio)tetrathiafulvalene (PT), a precursor of organic conductors, was electrochemically oxidized to the cation radical state as Cl– or Br– salt and cocrystallized with this neutral iodinated tecton 1 to form multicomponent supramolecular self-assembled isostructural crystalline salts PT(1)X (X = Cl, Br). X-ray structure analysis, conductivity, and magnetic susceptibility measurements were performed on these ternary salts. Owing to the pseudotetrahedral symmetry of the tecton, an eight-fold interpenetrated PtS-type network of class Ia has been identified and some clues for future developments of cross-bar nanowire monocrystals have been obtained. In these layer-by-layer type crystals, the fully oxidized PT molecules adopt a rare purely two-dimensional S = 1/2 Heisenberg square lattice type organization with weak antiferromagnetic interactions.

制备结晶有机导电纳米线可实现三维纳米级布线，这得益于其在固态下的周期性有序排列。为发掘晶体中绝缘护套的新型构造基元，研究人员成功合成了含碘原子的新型大体积刚性间隔分子。一种带有扩展骨架的新型非平面芳香构造模块（nonplanar aromatic tecton）——2,2′,4,4′,6,6′-六氟-3,3′,5,5′-四((4-碘乙炔基)苯基)乙炔基联苯(1)，在卤化物阴离子存在下可形成卤键驱动的超分子自组装体。双(丙二硫基)四硫富瓦烯（Bis(propylenedithio)tetrathiafulvalene, PT）作为有机导体的前驱体，经电化学氧化为阳离子自由基态，并以氯化物或溴化物盐的形式与该中性碘化构造模块1共结晶，得到多组分超分子自组装的同构结晶盐PT(1)X（X=Cl、Br）。针对这些三元盐，研究人员开展了X射线结构分析、电导率与磁化率测试。得益于该构造模块的假四面体对称性，研究人员确认其形成了Ia类八重互穿PtS型网络，并为交叉杆型纳米线单晶的后续研发提供了若干线索。在这类逐层排布的晶体中，完全氧化的PT分子呈现出罕见的纯二维S=1/2海森堡正方形晶格排布，且伴随弱反铁磁相互作用。