Backbone-controlled LUMO energy induces intramolecular C–H activation inortho-bis-9-borafluorene-substituted phenyl ando-carboranyl compounds leading to novel 9,10-diboraanthracene derivatives

Abstract

The backbone linker for two ortho-bis-(9-borafluorene)s influences the LUMO at the boron centers and the reactivity of the respective compounds.

Facile Construction of New Hybrid Conjugation via Boron Cage Extension

“…As such, carboranes have been utilized as important building blocks to construct functional molecules − and tunable pharmacophores (especially for Boron Neutron Capture Therapy (BNCT) drugs). − Among these studies, carboranes are generally treated as an “appended” structural unit. However, it would be more interesting and distinct if carborane-embedded polycyclic systems would be developed with carborane playing a central role. − In such a way, the carborane together with the extended part can serve as a new and united structural skeleton. So far, such a “cage extension strategy” to construct boron cluster-cored polycyclics is much less established in contrast to the classical extension of 2D aromatic rings.…”

The Effect of Carborane Substituents on the Lewis Acidity of Boranes

“…71 Marder and co-workers synthesized a bis(ortho-carboranyl)-(para-tolyl)-borane (4) that could be reduced and isolated as the corresponding radical anion due to the low energy of its lowest unoccupied molecular orbital (LUMO). 72 Marder, Braunschweig, and co-workers reported the monoand bis-borafluorene ortho-carboranyl species 5 and 6 73,74 that are both susceptible to endocyclic B−C bond cleavage or insertion to access heterocycles, 75 which are, in many cases, similar to 9-borafluorenes with B-aryl or B-halo substitutions. 50,51,76−87 Carboranes are considered to be 3D analogues of benzene, so accordingly, carborane that contains analogues of fluorene and anthracene have been targeted.…”

“…Marder, Braunschweig, and co-workers reported the mono- and bis-borafluorene ortho -carboranyl species 5 and 6 , that are both susceptible to endocyclic B–C bond cleavage or insertion to access heterocycles, which are, in many cases, similar to 9-borafluorenes with B-aryl or B-halo substitutions. ,,− Carboranes are considered to be 3D analogues of benzene, so accordingly, carborane that contains analogues of fluorene and anthracene have been targeted. The Ye and Dobrovetsky groups, along with our group, have reported bis- ortho -carboranyl-borane analogues of a 9-borafluorene with various substitutions on boron ( 7 ).…”

High radiative efficiency based on intramolecular charge transfer in a 9,9′-bianthracene-ortho-carboranyl luminophore

“…11,12 The three-dimensional functional group o-carborane exhibits high thermal/electrochemical stability. [13][14][15] In addition, it can lead to intramolecular charge transfer (ICT) derived from its strong electron-withdrawing property via the high polarizability of its σ-aromaticity for the ten boron atoms in a cluster, 16,17 when assembled with a conjugated π-aromatic fluorophore. Such an ICT feature results in the formation of an electronic donor (D, π-aromatic group)acceptor (A, o-carborane) dyad system.…”