Vapor-phase π–π molecular recognition: a fast and solvent-free strategy towards the formation of co-crystalline hollow microtube with 1D optical waveguide and up-conversion emission

Abstract

Molecular self-assemblies based on a solution system and solid-state reaction have been largely developed and achieved great success during last few decades; however, the knowledge on the molecular recognition and potential formation of orderly molecular hybrids in the vapor phase is quite limited and examples are still rare. Herein, we confirmed that the molecular recognition organized by intermolecular π–π interaction can be achieved based on a facile vapor deposition process. Through a continuous heating–cooling process of the self-assembled units (such as dibenzothiophene and tetracyanobenzene), the obtained co-crystalline hybrids present an orderly one-dimensional (1D) hollow tubular structure, which also features a high fluorescence quantum yield (47%), optical waveguide, and two-photon emission properties. A combination of crystal morphology prediction and experimental observation deduced that the 1D micro-sized tubular co-crystals were formed based on a growth mechanism of random aggregation. Moreover, this strategy based on vapor-phase molecular recognition can be further extended to the construction of other 1D co-crystal systems. Therefore, this study supplies a facile and environmentally friendly way to prepare high-quality 1D co-crystals towards potential photonic and photofunctional applications.