Correlation between molecular structure and optical properties for the bis(2-(2-hydroxyphenyl)benzothiazolate) complexes

A series of methyl-substituted bis(2-(hydroxyphenyl)benzothiazolate)zinc derivatives [Zn(n-MeBTZ)2, n = 3 (1a), 4 (1b), 5 (1c)] were synthesized to investigate the correlation between molecular structures and optical properties. The results indicate that the blue-emitting (λmax = 470 nm) complex 1b is monomer with a higher PL quantum efficiency than complexes 1, 1a, 1c. Two green-emitting (λmax = 507 nm and 499 nm) complexes 1a and 1c have special bi-molecular structures. The molecular structure for Zn(BTZ)2 (complex 1) is dimer. Bilayer organic light-emitting devices were fabricated by using these complexes as emitting layer. The maximum emission wavelengths of the devices are in the range of 501–553 nm. The devices show turn-on voltages at 9.2, 12.7, 2.3 and 10.7 V for complex 1, 1a, 1b, and 1c, respectively. In particular, the device with complex 1b shows a higher brightness than the other complexes under the same conditions.