Supramolecular Tessellations by a Rigid Naphthalene Diimide Triangle

Tessellation
of organic polygons though [π···π]
and charge-transfer (CT) interactions offers a unique opportunity
to construct supramolecular organic electronic materials with 2D topologies.
Our approach to exploring the 3D topology of 2D tessellations of a
naphthalene diimide-based molecular triangle (NDI-Δ) reveals that the 2D molecular arrangement is sensitive to the identity
of the solvent and solute concentrations. Utilization of nonhalogenated
solvents, combined with careful tailoring of the concentrations, results
in NDI-Δ self-assembling though [π···π]
interactions into 2D honeycomb triangular and hexagonal tiling patterns.
Cocrystallization of NDI-Δ with tetrathiafulvalene
(TTF) leads systematically to the formation of 2D tessellations
as a result of superstructure-directing CT interactions. Different
solvents lead to different packing arrangements. Using MeCN, CHCl3, and CH2Cl2, we identified three sets
of cocrystals, namely CT-A, CT-B, and CT-C, respectively. Solvent modulation plays a critical role
in controlling not only the NDI-Δ:TTF stoichiometric ratios and the molecular arrangements in the crystal
superstructures, but also prevents the inclusion of TTF guests inside the cavities of NDI-Δ. Confinement
of TTF inside the NDI-Δ cavities in
the CT-A superstructure enhances the CT character with
the observation of a broad absorption band in the NIR region. In the CT-B superstructure, the CHCl3 lattice molecules
establish a set of [Cl···Cl] and [Cl···S]
intermolecular interactions, leading to the formation of a hexagonal
grid of solvent in which NDI-Δ forms a triangular
grid. In the CT-C superstructure, three TTF molecules self-assemble, forming a supramolecular isosceles triangle TTF-Δ, which tiles in a plane alongside the NDI-Δ, producing a 3 + 3 honeycomb tiling pattern of the two different
polygons. Solid-state spectroscopic investigations on CT-C revealed the existence of an absorption band at 2500 nm, which on
the basis of TDDFT calculations, was attributed to the mixed-valence
character between two TTF•+ radical cations and one neutral TTF molecule.

通过[π···π]和电荷转移（CT）相互作用对有机多边形的镶嵌处理，为构建具有二维拓扑结构的超分子有机电子材料提供了独特机遇。我们探索基于萘二酰亚胺分子三角形（NDI-Δ）二维镶嵌的3D拓扑结构的方法表明，二维分子排列对溶剂的种类和溶质浓度极为敏感。使用非卤代溶剂并结合对浓度的精心调控，NDI-Δ能够通过[π···π]相互作用实现自组装，形成二维蜂窝状三角形和六边形镶嵌图案。NDI-Δ与四硫富瓦伦（TTF）的共晶化系统性地导致由超结构导向的CT相互作用引起的二维镶嵌的形成。不同的溶剂导致不同的堆积排列。使用甲腈（MeCN）、三氯甲烷（CHCl3）和二氯甲烷（CH2Cl2），我们分别识别出CT-A、CT-B和CT-C三种共晶体。溶剂调节在控制NDI-Δ:TTF化学计量比和晶体超结构中的分子排列方面发挥着关键作用，并防止TTF客体分子嵌入NDI-Δ的空腔中。在CT-A超结构中，TTF被限制在NDI-Δ空腔内，增强了CT特性，并在近红外区域观察到宽吸收带。在CT-B超结构中，CHCl3晶格分子形成一系列[Cl···Cl]和[Cl···S]分子间相互作用，导致溶剂形成六边形网格，其中NDI-Δ形成三角形网格。在CT-C超结构中，三个TTF分子自组装，形成一个超分子等腰三角形TTF-Δ，与NDI-Δ在同一平面上镶嵌，产生两种不同多边形的3+3蜂窝镶嵌图案。对CT-C进行的固态光谱研究揭示了2500 nm处的吸收带的存在，根据TDDFT计算，这一吸收带归因于两个TTF•+自由基阳离子与一个中性TTF分子的混合价态特性。