Ordered arrays generated via metal-initiated self-assembly of terpyridine containing dendrimers and bridging ligands

The interfacial reaction of the terpyridyl-pendant dendrimers (dend-n-tpy; n = 4, 8, 32) and of the bridging ligand 1,4-bis[4,4 "-bis(1,1-dimethylethy l)-2,2':6',2 " terpyridine-4'-yl]benzene (BBDTB) dissolved in CH2Cl2 with a queous Fe2+ or Co2+ gives rise to film formation on highly oriented pyrolyt ic graphite surfaces. Molecularly resolved scanning tunneling microscopy (S TM) images reveal that these films form highly ordered 2-D hexagonal arrays which appear to he composed of one-dimensional polymeric strands with a re peat unit of (tpy-dend-tpy M)(x) in the case of dendrimers or (tpy-bridge-t py-M)(x) in the case of BBDTB (M = Fe2+, Co2+). The extension of the ordere d domains appears to be delimited by terrace width. The dimensions obtained from an analysis of STM images is consistent with the size of the dendrime r or the bridging ligand (obtained from molecular modeling) from which the films are derived. In the case of films derived from dend-n-tpy the orderin g is dependent on the dendrimer generation. In all cases, the films are ele ctrochemically active and exhibit a reversible wave at a formal potential t hat corresponds to the respective [M(tpy)(2)](2+) complex.