The spectroscopic, electrochemical and electroluminescent properties of three binuclear Ru(II) complexes with different length of flexible bridges were investigated. The single-layer electroluminescent devices with configuration of indium-tin oxide/Ru complex (similar to 100 nm)/Ga:In were found to give a turn-on voltages as low as 2.3 V, a maximum luminance up to 310 cd/m(2) at a bias voltage of 5.8 V. and low delay times less than 2 s. (C) 2011 Elsevier B.V. All rights reserved.