Multicolor Photoluminescence Including White-Light Emission by a Single Host–Guest Complex

Abstract

Achieving multicolor photoluminescence especially white-light emission under mild conditions based on a single fluorescent compound is a great challenge. Herein, we report a novel colorful-emission host-guest complex BPCY, which is composed of a two-arm fluorescent guest molecule (BPC) and γ-cyclodextrin (γ-CD) as the host molecule. BPC bears a unique asymmetrical donor-acceptor-donor (D1-A +~D 2) type structure, where D1, A + , D2 stand for the binaphthol electron donor, pyridinium electron acceptor, and coumarin electron donor, respectively. The luminescence property of BPC shows dual-sensitivity, i.e. toward the excitation wavelength and the cyclodextrin host molecule. Under certain conditions the complex shows three different emission wavelengths allowing the realization of multicolor photoluminescence, including red (R), green (G), blue (B) and the various intermediate colors by orthogonally modulating these two stimuli. In this way, nearly pure white-light emission with CIE coordinates (0.33, 0.34) could be generated. A combination of structural, spectroscopic, and computational simulation studies revealed the occurrence of synergetic mechanistic processes for the stimuli-responsive multicolor luminescence of the BPCY complex, namely host-enhanced intramolecular charge-transfer (ICT) and host-induced restriction of intramolecular rotation (RIR). This new supramolecular complex with superior multicolor emission abilities may find wide applications in the fields of information processing and display media. Furthermore the molecular design rationale presented here may provide a new design strategy for the development of high performance optical materials using a single supramolecular platform.

Highly Emissive Organic Single‐Molecule White Emitters by Engineering o‐Carborane‐Based Luminophores

“…Zuschriften the white emitters,t he f abs of 3-f has reached 67 %, which is higher than the known organic single-molecule white emitters (that is,the reported largest f abs = 47 %). [3,4] 3-ph-me and 3-cl afford 50 %a nd 17 %, respectively. 3-ph-me adopts ac rossstacking aggregate,w hich also promotes f abs owing to ap rogressive transition from the lowest excited state (Figure 2c).…”

“…[2] This approach, however, encounters many thorny problems,such as spectral instability, bad color reproducibility and fabrication complexity. [3] The best strategy to solve these problems is to develop singlemolecule white emitters.T od ate,h owever, few strategies enable single-molecule luminophores to emit white light efficiently in the solid state. [4] Tw oc rucial issues have determined such slow research progress.O no ne hand, to achieve white-light emission requires precise manipulation of excited state of emitters through arational molecular design, which is very difficult to realize.Onthe other hand, restricted by both the broad band gap [5] and the aggregation-caused quenching (ACQ) effect, [6] theluminous efficiency in the solid state is usually low.Therefore,the design of ahighly emissive solid-state white emitter still remains abig challenge.…”

“…To the best of our knowledge,t his is the highest value among the single-molecule white-light emitters in the solid state. [3,4] The o-carborane-based luminophores were synthesized through aS uzuki coupling reaction in yields of 41-61 % (Supporting Information, Scheme S1). Their structures were firmly identified by 1 H, 13 C, 11 BNMR spectroscopy and mass spectrometry (see the Supporting Information).…”

Enhanced Solution and Solid‐State Emission and Tunable White‐Light Emission Harvested by Supramolecular Approaches

“…As described in Kasha's rule, followed by the majority of luminophores, photons that produce luminescence (fluorescence or phosphorescence) in appreciable yield can only be emitted from the lowest excited state of a given multiplicity, which means that it is very difficult for a single organic compound to emit either two or three colors of luminescence to cover the entire visible spectra from 400 to 700 nm . Certain methods have been developed to generate white‐light emission, among which the most common strategy is to combine several components with different fluorescent emissions into a single system to cover the whole visible spectrum . Single‐molecule luminogens with white‐light emission have been synthesized by embedding different luminophores into a single molecule through covalent bonds, the occurrence of white‐light emission being afforded by Förster resonance energy transfer (FRET), excited‐state intramolecular proton transfer (ESIPT), and/or twisted intramolecular charge transfer (TICT)…”

Cyclodextrin Rotaxane with Switchable Pirouetting

“…10 CD-based rotaxanes are normally obtained by a two-step process of CD threading, followed by in-situ stoppering in water. The initial CD threading process is driven by the hydrophobic effect and is disfavored by high temperature.…”