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.

通过对有机多边形的镶嵌，尤其是通过π···π相互作用和电荷转移（CT）相互作用，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的机遇。本课题组在探索基于萘二酰亚胺分子三角形（NDI-Δ）二维镶嵌的3D拓扑结构时发现，二维分子排列对溶剂的种类和溶剂质的浓度极为敏感。采用非卤化溶剂，并精心调整浓度，可促使NDI-Δ通过π···π相互作用自我组装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）的共结晶，由于超结构导向的CT相互作用，系统性地导致二维镶嵌的形成。不同的溶剂会导致不同的堆积排列。使用甲腈（MeCN）、氯仿（CHCl3）和二氯甲烷（CH2Cl2），我们分别鉴定出CT-A、CT-B和CT-C三组共晶体。溶剂调控在控制NDI-Δ:TTF的化学计量比以及晶体超结构中的分子排列方面起着至关重要的作用，并且还能防止TTF分子被包含在NDI-Δ的空腔中。在CT-A超结构中，TTF被限制在NDI-Δ的空腔内，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晶格分子建立了一系列[Cl···Cl]和[Cl···S]分子间相互作用，形成了一个溶剂的六角网格，其中NDI-Δ形成三角形网格。在CT-C超结构中，三个TTF分子自我组装，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的固态光谱研究揭示了在2500 nm处的吸收带的存在，根据TDDFT计算，这一吸收带可归因于两个TTF•+自由基阳离子与一个中性TTF分子之间的混合价态特性。