Synthesis of tris(4-amino-2,6-dimethylphenyl)borane and facile extension of its π-conjugated system by utilizing the reactivity of the amino groups

An Azide‐Substituted Triarylborane: A Key Compound for the Facile Synthesis of Fluorescent Triarylboranes Bearing Triazole Moieties as Connectable π‐Conjugated System Linkages

“…This was notable because the fluorescence of triarylboranes bearing an extended π‐conjugated system through the reactivity of amino groups can be achieved using triazole π‐linkages. This was in contrast to previously reported triarylboranes with imine or azo π‐linkages, which did not emit fluorescence . The solvent effects in the fluorescence spectra depended on the substituent at the molecular periphery (Table S1).…”

“…In the UV/Vis spectra, compounds 3a – e , 4a , and 4b exhibited absorption maxima at 345–365 nm in chloroform, which were assigned to the π–π* transition (Table , Figures S1 and S2). The π–π* absorption maxima were redshifted and the molar absorption coefficients were higher compared with those of trimesitylborane ( λ max = 331 nm, ε = 1.6 × 10 4 cm –1 m –1 in methylcyclohexane or isooctane) and tris(4‐bromo‐2,6‐dimethylphenyl)borane ( λ max = 334 nm, ε = 1.8 × 10 4 cm –1 m –1 in chloroform), which have smaller π‐conjugated systems. The changes in the absorption maxima wavelengths and molar absorption coefficients between trimesitylborane and compound 3a were comparable to those between tris(2,3,5,6‐tetramethylphenyl)borane ( λ max = 327 nm, ε = 1.4 × 10 4 cm –1 m –1 in THF) and tris(2,3,5,6‐tetramethyl‐1,1′;4′,1′′‐terphenyl‐4‐yl)borane ( λ max = 333 nm, ε = 2.9 × 10 4 cm –1 m –1 in THF), showing that the triazole ring was as well‐conjugated as a benzene ring.…”

“…Examples of triarylboranes bearing an extended π‐conjugated system with CH=N or N=N π‐linking moieties have been reported , . For three‐fold symmetric triarylboranes, we have reported a facile extension of the π‐conjugated system of an amino‐substituted triarylborane 1 through the formation of nitrogen‐containing double bond π‐linking moieties (Scheme ) …”

Highly Stable, Readily Reducible, Fluorescent, Trifluoromethylated 9‐Borafluorenes

“…Thus, three‐coordinate boranes can be employed as π‐acceptors, single‐electron or electron‐pair acceptors. Such boranes have been used in linear and non‐linear optical materials, anion sensors, frustrated Lewis pairs (FLPs), as well as in organic light‐emitting diodes (OLEDs) . There are numerous examples, both aromatic and antiaromatic, of boron‐containing conjugated cyclic π‐systems .…”

Electronically Driven Regioselective Iridium‐Catalyzed C−H Borylation of Donor‐π‐Acceptor Chromophores Containing Triarylboron Acceptors

“…The relevance of boron in these systems is due to the empty p z ‐orbital on boron that can act as an electron acceptor (A) in conjugated systems. Based on this, potential applications of three‐coordinate boron have been investigated, such as for linear and non‐linear optics, bioimaging, sensors, frustrated Lewis pairs (FLPs), and organic light‐emitting diodes (OLEDs) . The drawback of the employment of three‐coordinate boron in conjugated systems, however, is their inherent reactivity towards nucleophiles, such as water, due to the empty p z ‐orbital.…”