Enhancing electron affinity and tuning band gap in donor-acceptor organic semiconductors by benzothiadiazole directed C-H borylationElectronic supplementary information (ESI) available: Experimental procedures, compound characterisation data, copies of NMR spectra and crystallographic data. CCDC 1050921-1050923, 1050963 and 1062559-1062560. For ESI and crystallographic data in CIF or other electronic format see DOI: 10.1039/c5sc01800e

Electrophilic borylation using BCl 3 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%. Electrophilic borylation using BCl 3 and benzothiadiazole to direct the C-H functionalisation of an adjacent aromatic unit produces fused boracyclic materials with minimally changed HOMO energies but significantly reduced LUMO energies.