Six-Component Molecular Solids: ABC[D1–(x+y)ExFy]2

A strategy has been developed to achieve six-component molecular solids. The first part of the protocol involves the design and development of a family of stoichiometric quaternary cocrystals. It relies on the idea that when a molecule is in two distinct crystallographic environments in a lower-order cocrystal it becomes susceptible to substitution by a new molecule at the site where it is more weakly bound, if it is enthalpically advantageous to do so. Accordingly, a binary cocrystal acts as a stepping stone to a ternary, and so on. However, the subject system ran into a synthetic dead end at the level of quaternary cocrystals, in that no further crystallographic inequivalences could be found. This necessitated the development of the second part of the protocol, which exploits the shape-size similarities of 2-chloro-, 2-bromo-, and 2-methylresorcinols (CRES, BRES, and MRES respectively) and circumvents this synthetic dead end to achieve several five-and six-component solids, wherein the fifth and sixth components are incorporated in a solid solution fashion at the site of the fourth component.本研究开发了一种可制备六组分分子固体的合成策略。该方案的第一部分旨在设计并构建一系列化学计量比明确的四组分共晶体（cocrystal）家族，其核心逻辑基于以下原理：当某一分子在低阶共晶体中处于两种截然不同的晶体学环境时，若新分子的取代在焓变上有利，则该分子结合较弱的位点将更易被新分子取代。据此，二元共晶体可作为构建三元共晶体的阶梯，依此类推即可逐步提升共晶体的组分数。但本研究的目标体系在四组分共晶体阶段遭遇了合成瓶颈：此时已无法找到更多的晶体学不等价位点。这一问题推动了方案第二部分的开发：该部分利用2-氯间苯二酚（2-chlororesorcinol）、2-溴间苯二酚（2-bromoresorcinol）与2-甲基间苯二酚（2-methylresorcinol）之间的形状与尺寸相似性，规避了上述合成瓶颈，成功制备出多种五组分与六组分分子固体。其中第五组分与第六组分以固溶体（solid solution）的形式占据第四组分的晶体位点。