Carbazole-Fused Polycyclic Aromatics Enabled by Regioselective Scholl Reactions

The synthesis of new carbazole-fused polycyclic aromatics with interesting geometry and useful properties was explored using Scholl reactions. As found from the Scholl reactions of substrates having two carbazole units linked at different positions through o-phenylene, oxidative coupling of carbazole units occurred in a regioselective manner with new carbon-carbon bonds preferably formed at C3 and C4 in N-alkyl carbazoles. A new N-containing aromatic bowl was characterized by single-crystal X-ray crystallography, and new p-type organic semiconductors exhibited field effect mobility of up to 0.070 cm²  V^-1  s^-1 in solution-processed thin-film transistors.

Synthesis and Chiroptical Properties of Chiral Carbazole-Based BODIPYs

A series of carbazole-based boron dipyrromethenes (BODIPYs) 2 a-g bearing binaphthyl units have been synthesized by the Et₂ AlCl-mediated reaction of the corresponding BODIPY difluorides 1 a-g with 1,1'-binaphthalene-2,2'-diol. Substituents such as halogen, nitrile, and amino groups were tolerated under the reaction conditions, and the reaction of the phenylethynyl-substituted 1 h gave (R,R)-3 h bearing two binaphthyl units. The chiroptical properties of these dyes with different substituents were investigated by UV/Vis, CD, fluorescence, and circularly polarized luminescence (CPL) spectroscopy. The CD spectra showed Cotton effects in the absorption region of the BODIPY moieties. In addition, they showed CPL both in solution and in the solid state. Interestingly, several dyes recorded higher g_lum values in the solid state, probably due to intermolecular interactions. Because (R,R)-3 h recorded relatively low g_lum values, the diastereomer (R,S)-3 h was prepared. The (R,S) diastereomer showed intense CPL, which suggests a synergetic effect of the two binaphthyl groups. Finally, chiral carbazole-based BODIPY dimers have been synthesized for the first time and their chiroptical properties were investigated. They showed redshifted fluorescence and CPL, which reached the near-IR (NIR) region in the solid state.

Synthesis and characterization of organo-soluble polyimides containing phthalazinone and bicarbazole moieties in the main chain

Organo-soluble aromatic polyimides with good comprehensive properties are favorable for insulating layer material applications in flexible copper-clad laminates. A novel aromatic diamine, bis( N-4-amine-phenyl)-3,3′-bicarbazole (BCZDA) was firstly successfully synthesized. The structure of BCZDA was definitely confirmed via Fourier transform infrared and 1H-NMR spectroscopy and elemental analysis. Then a series of soluble polyimides were prepared from BCZDA and the diamine containing phthalazinone moiety as coreactant by one-pot solution copolycondensation with two kinds of anhydrides, 3,3′,4,4′-benzophenonetetracarboxylic dianhydride and 2-bis[4-(3,4- dicarboxyphenoxy) phenyl] propane dianhydride in sulfolane. Experimental results indicated that all the copolyimides having the glass transition temperature in range of 295 to 304 °C exhibited good solubility in N-methyl-2-pyrrolidinone (NMP), m-cresol, and N, N-dimethyl acetamide (DMAc). Their onset temperatures at 5% weight loss were all higher than 505 °C in nitrogen. Their flexible films cast in NMP exhibited good adhesive property (2.32–3.42 N mm−1) to copper foil and had good mechanical properties with the tensile strength of 69.5–79.3 MPa, elongation to break of 16–23% , and tensile modulus of 1.2–1.5 GPa. The copolyimides possessed dielectric constants of 3.08–3.26 (100 kHz) and low water absorption in the range of 0.92–1.06%, indicating that these obtained copolyimides are good candidates for the fields of microelectronics.