RÉSUMÉ
The realization of a train of molecule-gears working under the tip of a scanning tunneling microscope (STM) requires a stable anchor of each molecule to the metal surface. Such an anchor can be promoted by a radical state of the molecule induced by a dissociation reaction. Our results, rationalized by density functional theory calculations, reveal that such an open radical state at the core of star-shaped pentaphenylcyclopentadiene (PPCP) favors anchoring. Furthermore, to allow the transmission of motion by STM manipulation, the molecule-gears should be equipped with specific groups facilitating the tip-molecule interactions. In our case, a tert-butyl group positioned at one tooth end of the gear benefits both the tip-induced manipulation and the monitoring of rotation. With this optimized molecule, we achieve reproducible and stepwise rotations of the single gears and transmit rotations for up to three interlocked units.
RÉSUMÉ
The electrochemical behavior of stiff dithienylethenes, undergoing double bond isomerization in addition to ring-closure, has been investigated. Electrochromism was observed in almost all cases, with the major pathway being the oxidatively induced cyclization of the open isomers. The influence of the ring size (to lock the reactive antiparallel conformation) as well as substituents (to modulate the redox potential) on the electrocyclization was examined. In the series of derivatives with 6-membered rings, both the E- and the Z-isomer convert to the closed isomer, whereas for the 7-membered rings no cyclization from the E-isomer was observed. For both stiff and normal dithienylethenes bearing benzonitrile substituents an additional and rare reductive electrocyclization was observed. The mechanism underlying both observed electrocyclization pathways has been elucidated.
RÉSUMÉ
The reaction of 3-pentafluoroethyl-4,5,6,7-tetrafluoro-1-H-indazole [3-(C2F5)IndF4]H with Ag2O or [Cu(CH3CN)4]BF4 leads to the formation of two different types of complexes: a trinuclear {[3-(C2F5)IndF4]Ag}3 complex (1) in the case of silver, and an unprecedented type of pentanuclear complex [Et3NH]{Cu5[3-(C2F5)IndF4]6} (2) in the case of copper. When crystallised from Et2O, appears as a dimer with d(10)-d(10) interactions. When crystallized from toluene, affords the [(toluene)(1)(toluene)] adduct, testifying to its strong π-acid properties. The formation and the aggregation pattern of 1 and 2 can be traced to the extended aromaticity and high electron withdrawing properties of the perfluorinated [3-(C2F5)IndF4](-) indazolate.