Synthesis and characterisation of luminescent fluorinated organoboron compounds

Abstract

The reaction of 8-hydroxyquinoline (HQ) with B(C₆F₅)₃ leads to the formation of the zwitterionic compound (C₆F₅)₃BQH (1), involving a proton migration from O to N. Compound 1 can be converted thermally to (C₆F₅)₂BQ (2), which can also be prepared from (C₆F₅)₂BCl and HQ. The reaction of HQ with (C₆F₅)B(OC₆F₅)₂ generates initially (C₆F₅)(OC₆F₅)BQ (3), which easily hydrolyses to give the diboron compound ((C₆F₅)BQ)₂O (4). Compounds 1, 2 and 4 have been fully characterised, including X-ray analysis. The spectroscopic properties of these compounds, including photoluminescence (PL) have been investigated and compared with the non-fluorinated luminescent boron compound (C₆H₅)₂BQ and also with AlQ₃. The changes in luminescent behaviour upon fluorination of these boron quinolinate compounds have been rationalised using computational studies.