Halogenation of a twisted non-polar π-system as a tool to modulate phosphorescence at room temperature

Abstract

Twisted π-systems investigation showed a very unusual HAE, influencing independently the ISC and the dual phosphorescence emission, one being very persistent at room temperature and visible by eye in powder.

Halide-containing organic persistent luminescent materials for environmental sensing applications

“…Thus, TTA emission will lead to the loss of triplet excitons, and in most cases, the TTA mechanism is not recommended for the design of OPL materials. 29,34–37 During the radiative process, reducing the nonradiative deactivation process of the triplet excitons is another point to achieve OPL emission, such as nonradiative transitions and external conversion. The nonradiative decay from the first triplet excited state (T 1 ) to ground state (S 0 ) is also regarded as the ISC process and the rate can be described by eqn (2).…”

“…Internal and external heavy-atom effects promote the ISC (or RISC) process and radiative transitions from triplet excited states to ground states, leading to distinct OPL intensity and lifetimes for halogen substituted compounds with different SOC constants. 7,8,29,40–44 It brings great convenience to the OPL molecular design for different environmental sensing application. Generally, iodine-containing OPL materials exhibit high phosphorescence quantum yields with short lifetimes of about several milliseconds, while long emission lifetimes of about hundreds of milliseconds will be realized in chlorine substituted OPL derivatives.…”

“…Even so, efficient ISC processes can occur between two π, π* states with twisted molecular configuration for the non-zero SOC elements induced by the change in the orbital angular momentum. 29 …”

The effect of substituents and molecular aggregation on the room temperature phosphorescence of a twisted π-system

“…7 Thus, several groups have investigated molecular designs and the control of intermolecular interactions to promote ISC and suppress non-radiative decay to obtain organic RTP materials with high quantum yield and long lifetime. 15 The most common strategies are based on the incorporation of heteroatoms with lone pairs, such as O and N. 16 Approaches involving molecular aggregation, 17,18 co-crystallization, 19,20 polymeric systems, 21 host-guest doping systems, 22,23 energy-gap narrowing, 24,25 twisted p systems, 16,26 and structures without lone pairs 27 have also been explored. The inclusion of functional groups has proved to be an important tool for taking full advantage of the El-Sayed rule, promoting an efficient ISC between states with different orbital configurations, populating the triplet states, and adjusting the RTP.…”

Cluster-luminescent polysiloxane nanomaterials: adjustable full-color ultralong room temperature phosphorescence and a highly sensitive response to silver ions

“…[14][15][16] The so-called "clusters" are aggregates formed in space by functional groups through some weak interactions. At present, cluster induced phosphorescence (CIP), even long-lived room temperature phosphorescence (RTP) or afterglow, have been realized through crystal engineering [17][18][19][20] and polymerization induction. 21 However, CIP efficiency is highly dependent on the morphology of the material, requiring high crystal quality (for small molecules) 22,23 or large molecular weight (for polymers).…”