FTRZTCz (FPL: 85%; τd: 5.91µs 10 wt% in DPEPO; ΔEST: 0.22 eV), also developed by Lee et al. , is an emitter containing a triazine acceptor with an inductively electron-withdrawing para-fluoro group onto one of the phenyl rings of the TRZ (Figure ). 3,6-di-tertbutylcarbazole groups connected at the ortho positions of the other two phenyl rings complete the donor-acceptor structure. Their placement was to prevent intermolecular interactions, a similar strategy to that used in o-CzTRZ (Figure ). FTRZTCz showed a PL spectrum in toluene with the maximum at 450 nm, which though not directly comparable is similar to the Xu et al. employed diphenylphosphine oxide (PO) as secondary acceptors within a series of The prior examples have implicated an S1 state that has CT character and that the charge transfer process is mediated by a p-conjugated bridging moiety. This type of CT is termed through-bond charge transfer (TBCT). There exists a second CT process that is mediated by p-stacking of the donor and acceptor units, termed through-space charge transfer (TSCT). Distinct from most of the TBCT emitters that feature strong electron coupling through covalent bonds, TSCT emitters possess weaker electronic interaction between donors and acceptors due to the relatively smaller overlap of the frontier molecular orbitals in these systems. The degree of electronic coupling is controlled by the distance and the relative angles between the donor and acceptor groups. For example, an ortho-substitution pattern between the donor and acceptor at the B3LYP functional and 6-31G* basis set. Reproduced with permission. Copyright © 2017, American Chemical Society.