Generation of a series of Bn fused oligo-naphthalenes (n = 1 to 3) from a B1-polycyclic aromatic hydrocarbon.

A series of Bn-PAHs have been prepared by functionalisation of a B1-PAH, leading to the first only boron doped B3-PAH to the best of our knowledge. These Bn-PAHs represent the first three members of a series of {B-Mes} fused oligo-naphthalenes and trends in key properties of this series have been elucidated.

A modular route to boron doped PAHs by combining borylative cyclisation and electrophilic C-H borylation.

Heteroatom doping into polyaromatic hydrocarbons (PAHs) is a powerful approach for modifying key physical properties, however, there are extremely few modular routes that enable facile formation of B-, B2- and B,N-(specifically not containing direct B-N bonds) doped PAHs despite the growing importance of these materials. Sequential, one pot borylative cyclisation/intramolecular electrophilic C-H borylation of naphthyl-alkynes provides a simple new route to access novel B-, B,N- and B2-doped (PAHs). The initial products, dihydronaphthalene/dihydroquinoline B-mesityl PAHs, were reacted with [Ph3C][BF4]/pyridyl base to form the oxidised B-, and B,N-doped PAHs. However, for B-triisopropylphenyl (Trip) PAH congeners oxidation has to be performed prior to Trip installation due to preferential oxidation of an isopropylaryl moiety to the styrene. This alternative sequence enables access to Trip-B-PAHs and to structurally constrained B and B2-PAHs. Analysis of the solid state structures and optoelectronic properties of these PAHs confirm that frontier orbital energies, extended packing structures, Stokes shift and quantum yields all can be rationally modified using this methodology. The simplicity of this synthetic approach makes it a powerful tool for rapidly generating novel bench stable boron doped PAHs, which is important for facilitating further structure-property relationship studies and the wider utilisation of these materials in optoelectronic applications.

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.

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%.