Aggregation-induced new functions: structure-property relationships in molecular crystals

Abstract

Molecular crystals, as ordered aggregates of organic molecules, exhibit unique photophysical properties distinct from their monomeric counterparts. Rooted in the emerging framework of aggregate science, this review highlights how collective behaviors (such as arising from intermolecular interactions, symmetry breaking, and crystalline packing) fundamentally reshape excited-state dynamics and energy conversion pathways. We examine recent advances in crystal engineering and cocrystal strategies that enable tunable room-temperature phosphorescence, radical emission, near-infrared luminescence, and efficient photothermal conversion. Through case studies of lone-pair interactions, radical stabilization, and donor-acceptor cocrystals, we elucidate how molecular assemblies can activate new optoelectronic functions inaccessible to isolated molecules. By bridging structure-property relationships across the molecular-to-crysta, this review offers a unified perspective on the role of aggregation in functional material design. Looking ahead, aggregate science will continue to guide the discovery of next-generation materials by integrating structural precision, dynamic responsiveness, and multiscale energy manipulation in condensed molecular systems.