Donor–Acceptor Materials Exhibiting Thermally Activated Delayed Fluorescence Using a Planarized N-Phenylbenzimidazole Acceptor

Abstract

An N-phenylbenzimidazole constrained in a coplanar fashion with a methylene tether (IMAC) was designed and used to prepare a series of emitters exhibiting thermally activated delayed fluorescence (TADF). Four novel TADF emitters using 9,9-dimethylacridine, phenoxazine, phenothiazine, and bis­(di-p-tolylamino)­carbazole as the donor group were designed and synthesized using IMAC as the acceptor. Additionally, two deep-blue fluorescent emitters were prepared with carbazole and tercarbazole as the donor moieties. The twisted conformation between donor and acceptor in these molecules resulted in effective spatial separation of the HOMO and LUMO and small singlet–triplet energy gaps. Crystallographic properties, electronic structures, thermal stabilities, photophysical properties, and energy levels were studied systematically. Ultimately, these findings provide a promising opportunity for the design and synthesis of highly efficient TADF materials based on IMAC derivatives.

Tunable benzothiadiazole-based donor–acceptor materials for two-photon excited fluorescence

“…All reagents were purchased from Sigma-Aldrich or Oakwood Chemical and used as received unless otherwise stated. 4,7-Dibromo-2,1,3-benzothiadiazole, 45 4,7-diphenyl-2,1,3-benzothiadiazole, 46 4,7-bis(4-bromophenyl)-2,1,3-benzothiadiazole, 46 4,7-bis(2-thienyl)-2,1,3-benzothiadiazole, 45 4,7-bis(5-bromothiophen-2-yl)-2,1,3-benzothiadiazole, 47 4,7-bis(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)-2,1,3-benzothiadiazole, 48 9,9-dimethyl-9,10-dihydroacridine, 49 5-methylphenazine, 50 9 0 H-9,3 0 :6 0 ,9 00 -tercarbazole, 51 N3,N3,N6,N6-tetra-ptolyl-9H-carbazole-3,6-diamine, 52 and 2-bromo-4,4,8,8,12,12hexamethyl-8,12-dihydro-4H-benzo [9,1]quinolizino [3,4,5,6,7-defg]acridine 53 were synthesized according to literature methods.…”

Cyclophane Molecules Exhibiting Thermally Activated Delayed Fluorescence: Linking Donor Units to Influence Molecular Conformation

“…[22][23][24][25][26][27][28][29] Molecules exhibiting TADF are generally comprised of donor (D) and acceptor (A) segments, which are electronically decoupled, inducing a high degree of twist between the D-A segments. 30 This results in the formation of intramolecular charge transfer (CT) states, which by interacting with energetically close or degenerate local excited (LE) states facilitate the spin-flip from triplet state to singlet state. Attempts to explain the efficiency of this interconversion mechanism solely by the energy gap between singlet and triplet states did not lead to a conclusive explanation, and second order (vibrational) coupling between the excited states has now been shown to be fundamental to this process.…”

An imidazoacridine-based TADF material as an effective organic photosensitizer for visible-light-promoted [2 + 2] cycloaddition

“…These studies demonstrate that ACR-IMAC is an effective photosensitizer for promoting [2 + 2] cycloadditions and it is comparable to metal-based photosensitizers. Given that the TADF materials presented in Table 1 possess similar triplet state lifetimes, 34 the high performance of ACR-IMAC may suggest a higher ISC rate compared to the others. 11,32 With the identication of ACR-IMAC as an effective photosensitizer, its general use for [2 + 2] cycloaddition was investigated.…”