Triptycene 1,2-Quinones and Quinols: Permeable Crystalline Redox-Active Molecular Solids.

Suitably designed quinones and quinols are promising modules for the programmed construction of ordered redox-active molecular solids. To explore this potential, we have synthesized compounds 1-4, in which multiple 1,2-benzoquinone and 1,2-quinol units are attached to a triptycene core. The resulting molecules have topologies that disfavor efficient packing, and structural studies show that they crystallize to form open networks held together by characteristic attractive intermolecular forces, including O-H···O hydrogen bonds, C-H···O interactions, π-stacking, and dipolar interactions. Remarkably, the resulting solids are permeable and can undergo reversible redox reactions without loss of crystallinity. Our work may thereby help lead to the design of robust carbon-based batteries with electrodes derived from quinones, quinols, and other redox-active molecules abundantly produced by nature.

Predictably Ordered Open Hydrogen-Bonded Networks Built from Indeno[1,2-b]fluorenes.

Predictably ordered materials can be constructed by a modular strategy in which properly designed molecular components are positioned in space by reliable interactions. In principle, this approach can be used to control the arrangement of adjacent systems of π-conjugation, thereby creating molecular materials with valuable optoelectronic properties. To explore this possibility, we have synthesized compounds in which 2,4-diamino-1,3,5-triazinyl groups are attached to derivatives of 6,12-dihydroindeno[1,2-b]fluorene to produce molecules with well-defined cruciform topologies, extended π-conjugated aromatic cores, and an ability to form multiple hydrogen bonds. These compounds crystallize to form robust open hydrogen-bonded networks with parallel indenofluorenyl cores, significant volume (64-70%) available for accommodating guests, and characteristic luminescence. Our results will help permit the rational design of complex new molecular materials in which multiple optoelectronically active components are arranged in productive ways.

Molecular Organization of 2,1,3-Benzothiadiazoles in the Solid State.

Derivatives of 2,1,3-benzothiadiazole (1) are widely used in many areas of science and are particularly valuable as components of active layers in various thin-film optoelectronic devices. Even more effective benzothiadiazoles are likely to result if a deeper understanding of their preferred patterns of molecular association can be acquired. To provide new insight, we have analyzed the structures of compounds in which multiple benzothiadiazole units are attached to well-defined planar and nonplanar molecular cores. Our results show that molecular organization can be controlled in complex structures by using directional S···N bonding of benzothiadiazole units and other characteristic interactions. Moreover, the observed structures are distinctly different from those of analogous arenes. Replacing benzene rings in arenes by thiadiazoles thereby provides a strategy for making new compounds with extended systems of π-conjugation and unique patterns of molecular organization, including the ability to co-crystallize with the fullerenes C60 and C70.

Synthesis of Salts of 1,2,5,6- and 1,4,5,8-Naphthalenetetramine.

1,2,5,6-Naphthalenetetramine (1a), its 1,4,5,8-isomer (2a), and their salts are valuable precursors for synthesizing nitrogen-containing arenes and other targets of interest. We describe how salts of tetramines 1a and 2a can be made from simple protected derivatives of 1,5-naphthalenediamine (2d) by sequences of regioselective dinitration, deprotection, and reduction. Various shortcomings of previously reported syntheses of tetramines 1a and 2a can thereby be avoided. In addition, we report structural studies that may help clarify the mechanism of nitration and resolve an earlier controversy about the regioselectivity observed in nitrations of derivatives of 1,5-naphthalenediamine (2d).