Blue-emitting carbon- and nitrogen-bridged poly(ladder-type tetraphenylene)s

An efficient synthesis has been developed toward two new poly(ladder-type tetraphenylene)s, either with one nitrogen at the bridge-head position or all carbon-bridged, both of which were blue emitters. The two polymers exhibited very narrow emission centered around 445 nm, where the human eye is most sensitive. Polymer light-emitting diodes prepared under inert atmosphere in the standard configuration (indium tin oxide/poly(3,4-ethylenedioxythiophene): polystyrenesulfonic acid/polymer/Ca/Al) demonstrated very high luminance values, typically over 600-900 cd/m(2) at a bias of 10-15 V for the two polymers. The nitrogen-bridged poly(ladder-type tetraphenylene) demonstrated a lower electroluminescence onset voltage and was found to be more stable toward oxidative degradation compared to the all-carbon-bridged analogue, which undergoes oxidative degradation as evidenced by the appearance of a new emission maximum around 575 nm.