Effects of intramolecular hydrogen bonding on the conformation and luminescence properties of dibenzoylpyridine-based thermally activated delayed fluorescence materials

Abstract

The crystal structures show a U shape for 26DAcBPy and 26DPXZBPy and a linear chain conformation for 25DAcBPy; for the first time, we reveal that the conformations are the result of intramolecular hydrogen bonding of these molecules.

Use of Pyrimidine and Pyrazine Bridges as a Design Strategy To Improve the Performance of Thermally Activated Delayed Fluorescence Organic Light Emitting Diodes

“…We hypothesize that the intramolecular hydrogen bonding within the investigated emitters contributes to improvements in both the EQE max and efficiency roll-off as compared to our previously reported pyridine analogues with observations in line with those found in the literature. 31,32 On the other hand, the pDTCz-3DPyS:DPEPO and pDTCz-2DPyS:DPEPO devices show sharp blue EL spectra. While device D1 shows a slightly redshifted λ EL of 461 nm compared to pDTCz-3DPyS:DPEPO (λ EL = 452 nm) and a similar EL maximum to pDTCz-2DPyS:DPEPO (λ EL = 466 nm), its spectrum is broader, reflected by the larger full width at half maximum (FWHM).…”

Molecular Configuration Fixation with C–H···F Hydrogen Bonding for Thermally Activated Delayed Fluorescence Acceleration

“…The 10 wt% doping level is very common especially for green TADF emitters in OLEDs. [32][33][34] Both two devices exhibited the bright green emission character of the dopant (inset of Figure 4A). The higher polarity of o-CzOXD matrix than CBP lead to a bathochromic shift of EL emission by 5 nm for the former based device, however, just inducing a slight change of Commission Internationale de l'E ´clairage (CIE) coordinates.…”

Rational Utilization of Intramolecular Hydrogen Bonds to Achieve Blue TADF with EQEs of Nearly 30% and Single Emissive Layer All-TADF WOLED

“…The similar phenomena were ever observed in other intramolecular hydrogen bond containing compounds . There is no doubt that the existence of strong intramolecular hydrogen bonds will restrict the rotation between the donor and acceptor groups in these molecules and suppress nonradiative processes, thereby favoring the solid-state PLQY and color purity. ,, …”

“…To obtain insights into the molecular structures and further verify the existence of intramolecular hydrogen bonds, single crystals of SON-Cz, SON-PhCz, and SO-Cz were grown from a mixture of dichloromethane and methanol through slow solvent evaporation at room temperature successfully and analyzed by X-ray diffraction study, as shown in Figure 4 32 There is no doubt that the existence of strong intramolecular hydrogen bonds will restrict the rotation between the donor and acceptor groups in these molecules and suppress nonradiative processes, thereby favoring the solid-state PLQY and color purity. 17,31,32 The dihedral angles between the carbazole rings and the pyridine bridge were detected from the crystal structures as S1), verifying the strong conformation difference caused by the intramolecular hydrogen bonds. However, the twisting angles of the carbazole rings in SON-Cz are not as small as those in SON-PhCz, being consistent with the abovementioned relatively longer CH•••N distances.…”

“…Here, the acceptor, that is, the sulfonyl, possesses a twisted tetrahedral configuration, which limits the conjugation of the compound and provides promising features for the construction of blue TADF materials. , The carbazole, 3,6-di- tert -butyl-9 H -carbazole, and 3,6-diphenyl-9 H -carbazole groups were selected as donors for they have high triplet energy levels and weak electron-donating abilities to guarantee weak ICT. In particular, a pyridinyl was deliberately introduced to connect the sulfonyl acceptor and carbazole donors with the expectation to form intramolecular hydrogen bonds between the pyridinyl N atom and the H atoms at 1-position of carbazole rings, so as to realize the high molecular rigidity that generally favors high PLQYs and narrow fluorescence bands. − In this way, three pyridinyl-based TADF materials, SON-Cz, SON- t BuCz, and SON-PhCz were developed. For comparison, a pyridine-free reference molecule 9,9′-(5-tosyl-1,3-phenylene)­bis­(9H-carbazole) (SO-Cz) with phenylene as the linking bridge between donors and acceptor was synthesizes as well.…”