Creation of photofunctional materials through supramolecular complex formation and host–guest chemistry

Functional dyes can interconvert energies, such as light, heat, and electricity, and they have broad applications in various fields. This review highlights our endeavors in the creation of novel photofunctional materials in solution and solid states via molecular assemblies, linkage, and distortion and the integration of supramolecular complex formation and host–guest chemistry. One approach involves the synthesis of solid-state luminescent materials with the use of cocrystals comprising host molecules with dye backbones and guest molecules derived from aromatic compounds. Cocrystal formation is tuned via intermolecular interactions, such as hydrogen bonding, charge-transfer interactions, π-π stacking, and inclusion phenomena of the crystal engineering approach. This state leads to the emergence of properties such as fluorescence, room-temperature phosphorescence, and the potential for applications in optical sensors. In the second approach, functional dyes comprising multidentate ligands with various elements, which results in photofunctional properties in solution and solid states. This method delves into structural characteristics affected by the distortion and torsional angles of multinuclear complexes and their resulting photophysical properties. Multinuclear complexes encompass helical and axial chirality. Here, we discuss the isolation of enantiomers through optical resolution and their subsequent circular dichroism and circularly polarized luminescence characteristics. The position and nature of substituents considerably affected the ground and excited states of the complexes, which led to the formation of unique photofunctional materials. These methodologies offer insightful and effective avenues for the further improvement of the functionality and device applicability of functional dyes.