Synthesis and Optical Properties of N→Ga Coordinated Galliumboroxines

Reactions of the N,C,N-chelated organogallium amide LGa(NEt2)2 (1), where L is {2,6-(Me2NCH2)2C6H3}-, with organoboronic acids RB(OH)2 yielded molecular gallium boroxines LGa(O3B2R2) (2: R = OH, 3: R = Ph, 4: R = 4-MeO-C6H4, 5: R = 4-CHO-C6H4, 6: R = Fc), neutral analogues of gallaborates. Molecular structures revealed presence of six-membered central GaB2O3 ring. Film forming properties of 5 allowed the deposition of transparent thin films by spin coating method. The thicknesses, refractive index, energy of the optical gap (Egopt), the activation energy of surface electrical conductivity (Eas) and pre-exponential factor (σ0) of thin layers of 5 were measured and they are close to those found for related oxygen glass. Finally, GBO 5 was also used as additive to printing ink and thin film of 5 was prepared by gravure printing technique.