Series of Carbazole–Pyrimidine Conjugates: Syntheses and Electronic, Photophysical, and Electrochemical Properties

Abstract

A series of carbazole-pyrimidine conjugates 1-17 were synthesized by Pd-catalyzed cross-coupling, oxidation, and nucleophilic aromatic substitution reactions. In 1-17, the carbazole moieties are connected at the 4,6-positions of the pyrimidine ring either directly or via ethynylene or vinylene spacers, and various electron-donating or electron-withdrawing substituents are introduced at the 2-position of the pyrimidine ring. The effects of structural variations on the electronic, photophysical, and electrochemical properties of 1-17 were comprehensively investigated. Compounds 1-17 exhibit intramolecular charge-transfer (ICT) states, which essentially lead to moderate-to-strong fluorescence emission with large Stokes shifts depending on the solvent polarity. These compounds tend to show significant changes in optical and fluorescence properties upon addition of trifluoroacetic acid. The electron-accepting ability of these compounds can be tuned by both substituents on the pyrimidine moiety and spacers. The ethynylene spacer lowers both the HOMO and LUMO levels, while the vinylene spacer elevates the HOMO level and lowers the LUMO level. The X-ray crystal structures of 3, 6, 11, and 14 are also disclosed.

Charge Transfer Through Dithieno[2,3‐a:3′,2′‐c]phenazine: Effect of Substitution Pattern on the Optoelectronic Properties of Regioisomeric Luminophores

“…[11] Dithieno[2,3-a:3',2'-c]phenazine (DTP), one of the most-popular pyrazine-based acceptor units, [12] possesses three pairs of substitution sites for conjugation extension, at the 2,5-, 8,11-, and 9,10-positions. [13] Incorporating vinyl units at the 9,10-(isomer 4)o r8 ,11-positions (isomer 5)o ft he DTP core led to significantly enhanced ICT interactions and bathochromically shifted absorptiona nd photoluminescence (PL) maxima.S ubstitution at the 8,11-positions was superior to that at the 9,10-positions in enlarging the ICT interactions and expandingt he absorption spectrum, similart o luminophore 2.H owever,u pon incorporating vinyl units at the 2,5-positions of the DTP core, hypsochromically shifted absorption and PL maximaw ere observed fori someric luminophore 6,thus indicating weakened ICT interactions. Herein, we studied the effect of substitution pattern on the optoelectronic properties of regioisomericD -A molecules by designing and synthesizing two series of regioisomeric DTP-based symmetricalD -A-D luminophores (Scheme1).…”

P-169: Light-Blue Thermally Activated Delayed Fluorescent Emitters Realizing a High External Quantum Efficiency of 25%

“…[6] Here, for the donor, we introduced a phenylacridine moiety into the 4,6-position of the PM moiety to induce a twisted structure in the molecule. Three different Ac-RPM derivatives (Ac-HPM, Ac-PPM, and Ac-MPM, where R = H, phenyl, and CH 3 , respectively) were introduced at the 2-position of PM (Figure 1).…”

Theoretical study on photophysical properties of a series of functional pyrimidine‐based organic light‐emitting diodes emitters presenting thermally activated delayed fluorescence

“…Due to strong electron‐donating ability as well as stable and high excited triplet state, phenoxazine, carbazole, and triphenylamine have been reported to act as the D fragments, and electron‐deficient aromatic molecules such as triazine, 4‐benzoylpyridine, and diphenyl sulfone can be used as the A moieties. In addition, pyrimidine has also been proposed as an alternative A unit, owing to its electron‐deficient characteristics and facile functionalization . Very recently, Ganesan et al designed and synthesized a new series of D‐π‐A‐type compounds (see Fig.…”