Inter- and intra-molecular C-H borylation for the formation of PAHs containing triarylborane and indole units.

Inter-/intra-molecular electrophilic C-H borylation of C4-substituted indoles enables the formation of fused polycyclic aromatic structures containing triarylborane and N-heterocyclic units. These compounds are B-(C)n-N isosteres of carbocyclic PAHs that do not contain B-N bonds and comparison of one pair of BN/CC isosteres reveals that different resonance structures dominate. These compounds are highly sensitive to protodeboronation, of both the chloroborane intermediates and the mesityl protected products, which results in low isolated yields of the latter. Protodeboronation can be utilised productively for a C-H directed, C-H electrophilic borylation to make a previously unknown pinacol boronate ester by selective protodeboronation of the chloroborane intermediate. Intermolecular and double intramolecular electrophilic C-H borylation of a C4-substituted indole leads to a more highly fused structure containing two boracycles which represents a B-(C)n-N analogue of the unknown carbon isostere indeno[1,7ab]perylene.

1,1/1,2 Isomerisation in Lewis base adducts of B2cat2.

Reaction of bis-catecholatodiborane and 1 or 2 equivalents of 1,5-diazabicyclo[4.3.0]non-5-ene or 4-picoline yields Lewis acid-base adducts. Recrystallisation enabled identification of an unexpected isomerisation from the 1,1-isomer to the 1,2-isomer. This observation was probed computationally with significantly different dipole moments calculated for the two effectively isoenergetic isomeric forms.

Enhancing electron affinity and tuning band gap in donor-acceptor organic semiconductors by benzothiadiazole directed C-H borylation.

Electrophilic borylation using BCl3 and benzothiadiazole to direct the C-H functionalisation of an adjacent aromatic unit produces fused boracyclic materials with minimally changed HOMO energy levels but significantly reduced LUMO energy levels. In situ alkylation and arylation at boron using Al(alkyl)3 or Zn(aryl)2 is facile and affords boracycles that possess excellent stability towards protic solvents, including water, and display large bathochromic shifts leading to far red/NIR emission in the solid state with quantum yields of up to 34%. Solution fabricated OLEDs with far red/NIR electroluminescence are reported with EQEs > 0.4%.