Chiral molecules preferentially form one-handed supramolecular assemblies that reflect the absolute configuration of the molecules. Under specific conditions, however, the opposite-handed supramolecular assemblies are also obtained because of flexibility in the bond length and reversibility of non-covalent interactions. The mechanism of the handedness selectivity or switching phenomenon remains ambiguous, and most phenomena are observed by chance. Here we demonstrate the construction of chiral hydrogen-bonded twofold helical assemblies with controlled handedness in the crystalline state based on crystallographic studies. Detailed investigation of the obtained crystal structures enabled us to clarify the mechanism, and the handedness of the supramolecular chirality was successfully controlled by exploiting achiral factors. This study clearly reveals a connection between molecular chirality and supramolecular chirality in the crystalline state.

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The single-crystal structure of metal-free non-peripheral octahexyl-substituted phthalocyanine (C6PcH 2) has been investigated by single-crystal X-ray structure analysis. Two types of C6PcH 2 single crystal, bulk and needle crystals, were separately grown by controlling the recrystallization conditions. The structures of the two types of crystal were determined, and were found to be completely different, that is, C6PcH 2 exhibits structural polymorphism. It has been clarified that the C6PcH 2 microcrystals in thin films used in previously reported electronic devices have the needle structure.

A crystalline hydrogen-bonded framework with permanent porosity, built by rod-like struts and engineered to bear ultra-fast molecular rotors between two triple bonds, offers the possibility of controlling the rotational rates upon CO adsorption. CO enters the pores from the gas phase and reduces the rotational rates from the extremely fast regime of 10 Hz at 216 K to 10 Hz. The CO-rotor interaction was evident from the H NMR response to the dynamics of the rotors in contact with CO in the crystal structure.