The synthesis and characterization of octasubstituted cyclooctatetraenes (COTs) as well as their use as electron transporting materials in organic LEDs are reported. Tetraaryl-tetraarylethynyl-cyclooctatetrenes[C8Ar4(C=CAr)(4)] were prepared from diaryldiynes with a RuH2(CO)(PPh3)(3) catalyst in good yield (40-80%). Octaaryl-cyclooctatraenes were prepared from diarylacetylenes by treatment with lithium and iodine in 50% yield. Cyclic voltametry indicates that these COTs are reduced in sequential one-electron steps. C8Ar4(C=CAr)(4) and C8Ar8 are thermally stable to sublimation and have wide optical energy gaps [lambda(max)(emission) = 392-412 nm] making them good candidates for use in organic LEDs. These octasubstituted COTs have been used as electron transport layers in single heterostructure organic LEDs, i.e. ITO/NPD 400 Angstrom/octasubstituted COT 400 Angstrom/Mg-Ag (TTO = indium-tin oxide, NPD = N,N'-diphenyl-N,N'-dinaphthylbenzidine). External quantum efficiencies of 0.1-0.2% (photons/electrons) were observed, with turn-on voltages of ca. 6 V. The emission from this device comes exclusively from the NPD hole transporting layer, with lambda(max) of 435 nm. Doping the NPD layer with 1% perylene leads to an increased quantum efficiency of 0.6% and an electroluminescence spectrum indicative of emission solely from the perylene dopant, confirming exclusive emission from the NPD hole transporting layer.