Oligoethylene chains terminated by ferrocenyl end groups:: Synthesis, structural properties, and two-dimensional self-assembly on surfaces

A series of unsaturated long-chain-bridged diferrocenes Fc-(CH2)(n)CH=CH-(CH2)(n)-Fc (4a-e) was synthesized by means of olefin metathesis. Subsequent catalytic hydrogenation furnished the saturated alpha,omega-bis-ferrrocenyl oligoethylene products Fc-(CH2)(m)-Fc (5). Members of both series formed highly ordered laminar structures at the highly oriented pyrolytic graphite (HOPG) solid/liquid interface or on the Ag(110) surface, which were characterized by STM. Details of the structural features of these ordered physisorbed surface assemblies of 4 and 5 were analyzed by comparison with DFT calculations on model systems and with the characteristic packing modes of these systems in the crystal.