Polymerization of Heteroleptic Amphiphilic Osmium(II) Complexes at the Air/Water Interface: Attempts Toward Nanoarchitectonics in Form of Molecular Textiles

The controlled construction of interwoven molecular architectures via metal coordination represents a promising strategy for the development of ordered, interwoven, two-dimensional (2D) materials. Here, we report a bottom-up approach to probe the relationship between molecular symmetry and interfacial 2D polymerization behavior. Two amphiphilic heteroleptic osmium(II) terpyridine complexes were designed that incorporate aldehyde and amine functionalities, asymmetric complex (1), capable of forming two imine bonds, and a symmetric analog with four reactive sites (2). Langmuir-Blodgett isotherms, Brewster angle microscopy confirmed monolayer formation. In noncontact atomic force microscopy images 1 produced discrete oligomeric aggregates, while 2 yielded extended, chain-like polymeric structures with high surface coverage. X-ray photoelectronic spectroscopy measurements supported the presence of polymers as a product of imine condensation. Density functional theory calculations of 1 and its dimer and tetramer were performed to assess the stability of motifs relevant to the supramolecular structures observed. Comparison of the oligomers indicates a slight thermodynamic preference for chain-like growth over crosslinking. ... mehrAlthough these calculations are limited, the intrinsic bias toward linear linkages is consistent with atomic force microscopy data. Together, these results suggest polymer formation through imine condensation on the water-air interface, yielding kinetically favored chain formation and expanded 2D connectivity.