ABSTRACT
Mono- and binuclear metal-organic compounds bearing long alkyl chains were synthesized and studied at the liquid/graphite interface using scanning tunneling microscopy. Two different lamellar surface patterns as well as a star like structure were obtained driven by van der Waals interactions of the alkyl chains and weak hydrogen bonds of the phenoxy moieties. In the case of the star like structure solvent molecules (1,2,4-trichlorobenzene) are supposed to play an important role for the stabilization of the created pattern. Magnetic investigation of the bulk material by a superconducting quantum interference device magnetometer revealed magnetic moments up to 1.7 mu(B) (NiCo) and most likely antiferromagnetic coupling between the two metals within a single complex. The presented two-dimensional crystallization of the binuclear complexes may provide an easy access to new designable materials in molecular electronics.
ABSTRACT
The two-dimensional nanopatterning of a series of neutral alkoxy/alkyl-functionalised bis(salicylaldehydato)/bis(aldiminato)copper(II) and -palladium(II) complexes at a liquid/solid (highly oriented pyrolytic graphite, HOPG) interface has been studied by scanning tunnelling microscopy (STM). The relative metal-metal distances were tuned stepwise in two dimensions by ligand design. Exchange of the carbonyl O-atom for NH or N-alkyl units effects different intermolecular interactions such as weak hydrogen bonds and steric effects that determine, together with the van der Waals forces between the alkyl chains, the relative arrangements of the complexes. Further variation of the length and position of the alkoxy side chains as well as the exchange of CuII for PdII affords an absolute fine-tuning of the surface structures. Highly resolved STM images of the resultant highly ordered adlayers allow us to establish detailed models of the molecular 2D arrays and to classify them into three basic chiral pattern types. Homochirality within the individual domains is induced by the highly regular deposition of the prochiral complexes from the same enantiotopic face. In the case of the C12 O-substituted bis(salicylaldiminato) (NH) Cu(II) complex Cu5, a secondary structure occurs as a racemic mixture of two chiral surface species deposited in a distinct alternating order.
ABSTRACT
The order of self-assembled monolayers of Cu(II) salicylic aldehyde and aldimine complexes has been gradually changed by ligand substitution and the resulting nanostructures have been studied at the graphite/liquid interface using scanning tunneling microscopy.
