Daul-component Pure Organic Phosphor-escence Materials With Acid Response Based On Donor-accpetor Structure

The research of pure organic room temperature phosphorescence（RTP）materials has always been a hot topic,especially for those stimuli-responsive materials.Pure organic room temperature phosphorescence（RTP）can be achieved by enhancing spin-orbit coupling（SOC）and suppressing non-radiative transitions to promote intersystem crossing（ISC）.Molecules with donor-acceptor structures can generally produce intramolecular charge transfer（TICT）,highly distorted molecular conformation and good solid-state emission properties.More and more researchers have been using donor-acceptor structures to generate pure organic phosphorescence emission.Stimuli-responsive organic phosphorescence materials are those materials that can change their own luminous characteristics such as color,lifetime and intensity under external stimuli such as mechanical force,temperature,p H and light.However,these materials with stimuli responsive properties are mostly limited to pure organic fluorescent materials or phosphorescent materials with relatively short lifetime.Compared with single-component RTP materials with stimuli responsive properties,two-component or even multi-component doped RTP materials have attracted more and more attention.Because for multi-component RTP materials,the luminescent characteristics can be influenced by changing the host,the guest or the host-guest hybrid.Generally speaking,the host matrix generally provides a rigid environment for the guest and improves the phosphorescence of the guest,which limits the responsiveness of multi-component RTP materials to external stimuli.Therefore,it is still necessary to overcome many difficulties to develop a two-component RTP material with stimuli responsive properties.This paper reports a host-guest doped RTP material with strong afterglow and acid response based on the donor-acceptor structure strategy.The doping system consists of two kinds of molecules with donor-acceptor structure,in which Br-BID-Py is the host and NMe₂-BID-Py is the guest.Br-BID-Py（host）and NMe₂-BID-Py（guest）show a small structural difference（the Br atom in the host is replaced by dimethyl imide）,which is beneficial to the energy transfer between them in the solid state and makes the doped system have stronger phosphorescence.In the second chapter,to explore the phosphorescence mechanism of the doping system,the physical properties of pure host（Br-BID-Py）and pure guest（NMe₂-BID-Py）are studied,respectively.The results show that the pure host（Br-BID-Py）emits a weak yellow afterglow,with the single-molecule fluorescence emission at 410 nm,the aggregated fluorescence emission at 460nm,the molecular phosphorescence emission peak at 463 nm and the aggregated phosphorescence emission at 560 nm,while the guest（NMe₂-BID-Py）has no phosphorescence property.Both molecules have acid-responsive properties,and the acid responsive properties of the pure host and guest are explored by X-ray diffraction（XRD）and ¹H NMR.The third chapter mainly reports the properties of the doping system.When the guest（NMe₂-BID-Py）is doped into the host（Br-BID-Py）,it will produce a stronger yellow afterglow,and the afterglow shows a unique thermal activation property.In the solid-state delayed photoluminescence（PL）spectrum,it was found that the emission peaks of the solid afterglow of the doped system are at 463 nm and 560 nm respectively,which indicated that the main emissions of the doped system came from emissions of the host.The enhancement of the emission intensity is due to the fact that the S₁ state of the guest acts as a bridge of energy transfer between the S₁ state and T₁ state of the host.In addition,the doping system inherited the acid stimuli-responsive properties of Br-BID-Py and NMe₂-BID-Py,showing a rare proton-induced afterglow shift.