Supramolecule-Originated Emission: A Room-Temperature Phosphorescence 2D Ionic H‑Bond Network from Nonemissive Aliphatic Derivatives

Supramolecular
materials exhibiting unique functions unavailable
from their individual components are attracting great attention. Here,
we report a novel supramolecule emission strategy, where the emission
originated from a two-dimensional (2D) ionic hydrogen bond (H-bond)
supramolecular network. High-quality crystals were obtained by rapid
self-assembly of liquid aliphatic amine and ketone. The 2D ionic H-bonding
network was characterized by single-crystal X-ray diffraction (XRD)
that shows a planar electron system similar to aromatic species. First-principles
calculations demonstrated that the charge-separated transition process
and high spin–orbital coupling constants of the rigid supramolecular
structure contribute to the enhanced singlet–triplet intersystem
crossing process. The emission could be well regulated via the substituents
of either the enol or amine part, and a maximum quantum efficiency
of 26% was realized. The emission system demonstrated stable room-temperature
phosphorescence (RTP), which is even hard to obtain for aromatic species,
and the lifetime reached 0.45 s with an 8% luminescence quantum yield.
For application, with liquid amine and enol as ink, high-quality RTP
patterns can be fabricated by computer-controlled precision printing.
Our findings will surely bring completely fresh thinking for photoluminescence
and other functions purely originated by the supramolecular structure.