Bromine‐Substituted Fluorene: Molecular Structure, Br–Br Interactions, Room‐Temperature Phosphorescence, and Tricolor Triboluminescence

Abstract

Organic tribophosphorescence materials are rarely reported and the introduction of Br atoms mayb eapractical way to design such materials.H ere four bromine-substituted fluorene-based derivatives are presented and BrFlu À CBr, having fluorescence-phosphorescence dual-emission induced not only by UV light but also by mechanical stimulus,manifests the highest phosphorescence efficiency of 4.56 %upon photoirradiation. During the grinding process,t hree different triboluminescent spectra were identified. Upon introduction of am echanical stimulus,t he triboluminescence emission is cyan, whereas after an extended period it changed to blue.After removing the mechanical stimulus,g reen-white phosphorescent emission was observed. Careful research on single-crystal structures and theoretical calculations demonstrate that strong Br···Br interactions are vital to facilitate spin-orbit coupling and promote intersystem crossing, thus generating the unique properties.

Polymorphism-Dependent Dynamic Ultralong Organic Phosphorescence

“…Notably, crystallization is essential to such phenomenon, implying the importance of molecular stacking on dynamic UOP. Moreover, molecular stacking has been proved to be effective in manipulating luminescent properties of organic materials in solid state [49][50][51][52]. Therefore, it is urgent to provide an insight from molecular stacking to understanding the inherent mechanism in dynamic UOP.…”

Utilizing d–pπ Bonds for Ultralong Organic Phosphorescence

“…[8] In this regard, the development of organic phosphorescent substances with efficient UOP needs to satisfy at least the following two factors: i) incorporating functional groups such as carbonyls,h eavy atoms,a swell as heteroatoms (N,S ,P ,e tc. )t op romote ISC through SOC enhancement; [9] ii)constructing arigid environment to suppress the non-radiative decay of triplet excitons by as eries of feasible approaches such as crystallization, [10] hydrogen bonding, [11] halogen bonding, [12] self-assembly, [13] H-aggregation, [14] hydrogen-bonded organic aromatic frameworks (HOAFs), [15] etc.T hrough the tremendous efforts of scientists,m any organic phosphorescent substances with ultralong lifetimes have been developed along with the proposed mechanism. [16] Among those,m ost work focuses on creating amore rigid external environment to suppress the non-radiative pathways and thereby prolong the phosphorescence lifetime,while less attention was paid to the engineering of the intrinsic molecular structure.H ence,aconcise yet efficient chemical strategy to prolong the lifetime is attractive and practical.…”

AIE-active two-photon fluorescent nanoprobe with NIR-II light excitability for highly efficient deep brain vasculature imaging

“…Therefore, the extra photo-stability or better anti-photobleaching capability of AIETP under 1040 nm two-photon laser irradiation could be attributed to the insertion of -Br substitution in the structural feature (Scheme 1 ) which is indispensable for efficient long-term bioimaging studies. Probably, compared to the heavy-atom effect induced by the introduction of 'Br' atom that enables the spin-orbit coupling to promote the intersystem crossing between singlet and triplet states, the inter molecular halogen bonding (Br···Br interaction) might have played more significant role to facilitate the partial restriction of nonradiative decay to ensure better photostability of AIETP 34 . Additionaly, AIETP NPs also revealed better resistance to the photobleaching compared to the commercial fluorescent dyes such as Evans blue and Alexa 647 upon 1040 nm continuous two-photon laser irradiation ( Figure S27 , Supporting Information ), which again reiterated the high photo-stability of AIETP NPs.…”