Conformational Dynamics of Monomer‐ versus Dimer‐like Features in a Naphthalenediimide‐Based Conjugated Cyclophane

Room-Temperature Phosphorescence Emitters Exhibiting Red to Near-Infrared Emission Derived from Intermolecular Charge-Transfer Triplet States of Naphthalenediimide-Halobenzoate Triad Molecules

Room-temperature phosphorescence (RTP) emitters have attracted significant attention. However, purely organic RTP emitters in red to near-infrared region have not been properly investigated. In this study, a series of naphthalenediimide-halobenzoate-linked molecules are synthesized, one of which exhibits efficient RTP properties, showing red to near-infrared emission in solid and aqueous dispersion. Spectroscopic studies and single-crystal X-ray diffraction analysis have shown that the difference in the stacking modes of compounds affects the optical properties, and the formation of intermolecular charge-transfer complexes of naphthalenediimide-halobenzoate moiety results in a bathochromic shift of absorption and RTP properties. The time-dependent density functional theory calculations showed that the formation of charge-transfer triplet states and the external heavy atom effect of the halogen atom enhance the intersystem crossing between excited singlet and triplet states.

Discrete π Stack of a Tweezer-Shaped Naphthalenediimide-Anthracene Conjugate

The design and synthesis of a tweezer-shaped naphthalenediimide (NDI)-anthracene conjugate (2NDI) are reported. In the structure of the closed form (π_NDI ⋅⋅⋅π_NDI stack) of 2NDI, which was elucidated by single-crystal XRD, the existence of C-H⋅⋅⋅O hydrogen bonding involving the nearest carbonyl oxygen atom of an NDI unit was suggested. The tunability of π_NDI ⋅⋅⋅π_NDI interactions was studied by means of UV/Vis absorption, fluorescence and NMR spectroscopy and molecular modelling. This revealed that the π_NDI ⋅⋅⋅π_NDI interactions in 2NDI affect the absorption and emission properties depending on the temperature. Furthermore, in polar solvents, 2NDI prefers the stronger π_NDI ⋅⋅⋅π_NDI stack, whereas the π_NDI ⋅⋅⋅π_NDI interaction is diminished in nonpolar solvents. Importantly, the conformational variations of 2NDI can be reversibly switched by variation in temperature, and this suggests potential application for fluorogenic molecular switches upon temperature changes.

Quantitative Supramolecular Heterodimerization for Efficient Energy Transfer

The challenge of quantitatively forming self-assembled heterodimers without other equilibrium by-products is overcome through self-sorting favored by the introduction of designed shape-complementary moieties. Such a supramolecular strategy based on cucurbit[8]uril-directed dimerization is further applied to generate hetero-chromophore dimers quantitatively, leading to efficient energy transfer (>85 %) upon photoexcitation.