Multicomponent Molecular Puzzles for Photofunction Design: Emission Color Variation in Lewis Acid–Base Pair Crystals Coupled with Guest-to-Host Charge Transfer Excitation

Simple yet ubiquitous
multimolecular assembly systems with color-tunable
emissions are realized by cooperative electron donor–acceptor
interactions, such as the boron–nitrogen (B–N) dative
bond as a Lewis acid–base pair and charge transfer (CT) interactions.
These are ternary-component systems consisting of a naphthalenediimide
derivative (NDI), tris­(pentafluorophenyl)­borane (TPFB), and aromatic
molecules (guest) with an NDI:TPFB:guest ratio of 1:2:2. The crystal
shows guest-dependent color-tunable emissions such as deep blue to
orange when a guest molecule of benzene is replaced with other π-conjugated
systems. A good correlation between the emission wavelength and ionization
potential of the guest and electronic structure calculations indicated
that the emission is due to the CT transition from the guest to the
NDI. The present study suggests that a rational solution of multcomponent
molecular puzzles would be useful for obtaining novel photofunctional
solid-state systems.