We have observed reversible light-induced mechanical switching for individual organic molecules bound to a metal surface. Scanning tunneling microscopy (STM) was used to image the features of individual azobenzene molecules on Au(111) before and after reversibly cycling their mechanical structure between trans and cis states using light. Azobenzene molecules were engineered to increase their surface photomechanical activity by attaching varying numbers of tert-butyl (TB) ligands ("legs") to the azobenzene phenyl rings. STM images show that increasing the number of TB legs "lifts" the azobenzene molecules from the substrate, thereby increasing molecular photomechanical activity by decreasing molecule-surface coupling.
A new thermally cross-linkable copolymer containing reactive benzocyclobutene (BCB) units and the well-known hole-transporting moiety N,N′-bis(3-methylphenyl)-N,N′-diphenylbenzidine) (TPD) was synthesized and characterized. Thermal annealing of spun-cast films of the copolymer, followed by crosslinking at 200 °C, led to insoluble polymer films with a smooth surface. Green emitting fluorescent OLEDs were fabricated using the new cross-linkable polymer and compared with conventionally prepared devices. Using the thermally cross-linked copolymer as a hole-transporting layer, solution processed multilayer light emitting diodes were prepared that exhibited high performance with 10.4% external quantum efficiency at a brightness of 350 cd/m 2 .
The scandium-catalyzed intramolecular hydroamination of alkynes and alkenes is reported. Complex structure/catalyst activity investigations resulted
in the identification of a highly catalytically active
cationic, β-diketiminato scandium complex.
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