Synthesis, structures and luminescent behaviour of tridentate salicylaldiminato-type borate complexes

Treatment of the ligands 3,5-tBu2-2-(OH)C6H2CHNR [R = 2-(CO2H)C6H4 (1a) and 2-(CO2H)C10H6 (1b)] with trimethylborate, B(OMe)3, in toluene yields, after work-up, the yellow crystalline complexes {[3,5-tBu2-2-(O)C6H2CHNR]B(OMe)} [R = 2-(CO2)C6H4 (2a) and 2-(CO2)C10H6 (2b)], respectively. Further treatment of these complexes with trifluoromethanesulfonic (triflic) acid, CF3SO3H, followed by recrystallisation from tetrahydrofuran (thf) afforded the triflate salts [{3,5-tBu2-2-(O)C6H2CHNR}B(thf)][CF3SO3] [R = 2-(CO2)C6H4 (3a) and 2-(CO2)C10H6 (3b)]. An electroluminescent device was constructed using 2a, which produced orange-green light with broad emission spectra (maximum brightness of 5 cd/m2 being observed at 13 V). Compounds 1a and 2b·2MeCN have been characterised by single crystal X-ray structure determinations.