Activating Room-temperature Phosphorescence Of 1,8-naphthalimide By Doping Into Aromatic Carboxylic Acids Or Aromatic Aldehydes

In recent years,pure organic room-temperature phosphorescent(RTP)materials,which the advantages of long lifetime,high efficiency,low material preparation cost,good biocompatibility and flexible molecular design,have attracted more and more attention.To further improve the phosphorescent lifetime and/or extend the phosphorescent quantum yield of organic phosphorescent materials,organic-organic and organic-polymer RTP materials using the host-guest doping strategies have also been developed rapidly.In this thesis,1,8-Naphthalimide(NI)was selected as the guest,aromatic carboxylic acid or aromatic aldehyde as the host,and the host-guest structure was constructed by simple heating dissolution cooling,which activated the imine room temperature phosphorescence.The relationship between the structure and properties of the host molecule was discussed,and the internal luminescence mechanism and application were explored.The work is mainly studied in detail from the following two parts:Part I:NI@NPA,NI@MOPA,NI@MPA,NI@HPA and NI@CPA were prepared by changing the type of para-substituted groups(-NH₂,-OCH₃,-CH₃,-H,-Cl)of the host mono-aromatic carboxylic acid.The structural characterization and physical properties of NI@MPA,NI@HPA and NI@CPA were investigated.It is shown that they all exhibit a yellow afterglow dominated by the guest phosphorescence emission,and that the energy transfer from the host to the guest and the formation of multiple hydrogen bonding networks are responsible for the observed efficient and long-lived phosphorescence.By changing the host para-substituent group,we found that the stronger the electron absorption of the substituent group,the shorter the distance between the host and guest aromatic ring,the stronger the?-?interaction,and the more intermolecular interactions that make the whole molecular structure more rigid,inhibit the non-radiative decay of the excited molecule.The?E_ST of S₁ and T₁ decreases and ISC increases,thus regulating the luminescence properties.Based on the phosphorescent properties of the doped material NI@HPA,we made a simple inkjet printing application.Part?:three different doping materials NI@CPQ,NI@m CPQ and NI@BPQ were prepared by changing the relative positions(o-,m-,p-)and types(-Cl,-Br)of the main monochlorinated aromatic aldehydes.The study on the structure characterization and photophysical properties of the materials showed that the luminescence properties of the materials were improved significantly by changing the relative positions of the main substituent groups,especially NI@m CPQ.Among them,the best luminescent material is NI@m CPQ,which also exhibits yellow afterglow from the triplet exciton of guest NI at room temperature.The luminescent life is 0.38 s,and the overall luminescent efficiency is up to 31%.However,the mechanism of luminescence needs to be further explored.