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Abstract Doping of polycyclic aromatic hydrocarbons (PAHs) with boron and/or nitrogen is emerging as a powerful tool to tailor the electronic structure and photophysical properties. AsN‐doped analogues of anthracene,N,N‐dihydrophenazines play important roles as redox mediators, battery materials, luminophores, and photoredox catalysts. Although benzannulation has been used successfully as a structural constraint to control the excited state properties, fusion of the N‐aryl groups to the phenazine backbone has rarely been explored. Herein, we report the first examples of dihydrophenazines, in which the N‐aryl groups are fused to the phenazine backbone via B←N Lewis pair formation. This results in structural rigidification, locking the molecules in a bent conformation, while also modulating the electronic structure through molecular polarization. B─N fusion inBNPz1−BNPz3induces a quinoid resonance structure with significant C─N(py) double bond character and reduces the antiaromatic character of the central pyrazine ring. Borylation also lowers the HOMO/LUMO (highest occupied/lowest unoccupied molecular orbital) energies and engenders bathochromic shifts in the emission. Further rigidification in the solid state gives rise to enhanced emission quantum yields, consistent with aggregation‐induced emission enhancement (AIEE) observed upon water addition to solutions in tetrahydrofuran (THF). The demonstrated structural control and fine‐tuning of optoelectronic properties are of great significance to potential applications as emissive materials and in photocatalysis. 

Abstract Acenes are attractive as building blocks for low gap organic materials with applications, for example, in organic light emitting diodes, solar cells, bioimaging and diagnostics. Previously, we have shown that modification of dipyridylanthracene via B–N Lewis pair fusion (BDPA) strongly redshifts the emission, while facilitating self‐sensitized reactivity toward O₂to reversibly generate the corresponding endoperoxides. Herein, we report on the further expansion of the π‐system of BDPA to a vinyl‐substituted monomer, vinylene‐bridged dimer, and a polymer with an average of 20 chromophores. The extension of π‐conjugation results in largely reduced band gaps of 1.8 eV for the dimer and 1.7 eV for the polymer, the latter giving rise to NIR emission with a maximum at 731 nm and an appreciable quantum yield of 7 %. Electrochemical and computational studies reveal efficient delocalization of the lowest unoccupied molecular orbital (LUMO) along the pyridyl‐anthracene‐pyridyl axis, which results in effective electronic communication between BDPA units, selectively lowers the LUMO, and ultimately narrows the band gap. Time‐resolved emission and transient absorption (TA) measurements offer insights into the pertinent photophysical processes. Extension of π‐conjugation also slows down the self‐sensitized formation of endoperoxides, while significantly accelerating the thermal release of singlet oxygen to regenerate the parent acenes. 

Abstract Main‐chain boron‐containing π‐conjugated polymers are attractive for organic electronic, sensing, and imaging applications. Alternating terthiophene‐borane polymers were prepared and the effects of regioisomeric attachment of the conjugated linker and variations in the electronic effect of the pendent aryl groups (2,4,6‐tri‐tert‐butylphenyl, Mes*; 2,4,6‐tris(trifluoromethyl)phenyl, FMes) examined. Pd₂dba₃/P(t‐Bu)₃‐catalyzed Stille polymerization of arylbis(2‐thienyl)borane and arylbis(3‐thienylborane) with 2,5‐bis(trimethylstannyl)thiophene at 120 °C gave polymers with appreciable molecular weight but MALDI‐TOF MS analyses showed evidence of unusually prominent homocoupling. These defects could be suppressed by using brominated rather than iodinated monomers, more hindered 2,5‐bis(tri‐n‐butylstannyl)thiophene as comonomer, and Pd₂dba₃/P(o‐tol)₃as the catalyst at 100 °C. Under these conditions, macrocyclic species withn=3–10 repeating units formed preferentially according to MALDI‐TOF MS analyses. Photophysical studies revealed a prominent effect of the regiochemistry and the nature of the pendent aryl groups on the absorption and emission, giving rise to orange, yellow‐green, blue‐green, and blue emissive materials respectively. The electronic effects were rationalized through DFT calculations on bis(terthiophene) model systems.