Electrochemically activated coordenative assembly of a triruthenium cluster metallopolymer

A general strategy for electrochemically induced assembly of coordination metallopolymers is demonstrated using the tritopic bridging [Ru3(μ3O)(CH3COO)6(pytpy)3]+ cluster complex, where pytpy is the 4′-(4-pyridyl)-2,2′:6′,2″-terpyridine ligand, and iron(III) ions. The concept of such an electrochemically induced coordinative assembly was proven exploring the large difference in the [Fe(pytpy)2] complex formation constants depending on the iron ion oxidation state. Much more stable bridging complexes are formed in the presence of Fe(II) in contrast to Fe(III) ions. The build-up of electrochemically active films on FTO electrodes was confirmed by the growth of the corresponding voltammetric peaks concomitantly with the rise of typical triruthenium cluster and [Fe(pytpy)2]2+ complex absorption bands. The metallopolymer was constituted by agglomerates of more or less fused tape like structures, exhibiting large voids and pinholes, as revealed by SEM and AFM images. The adhesion/deposition on FTO was improved by functionalizing the surface with TES-tpy and HOOC-tpy, which increased the surface coverage up to 80%, as estimated by impedance spectroscopy.

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► A general strategy for electrochemically induced coordinative assembly of metallopolymers was demonstrated.
► The concept was proven using FeCl3 and the tritopic bridging [Ru3(μ3O)(CH3COO)6(pytpy)3]+ complex by exploiting the large difference in the formation constants of the [Fe(pytpy)2]3+/2+ complex as a function of the oxidation states (III/II).
► The porous clickable {[Fe(pytpy)2]n[Ru3(μ3O)(CH3COO)6]m}(2n+m)+ metallopolymer films are constituted by agglomerates of tape like structures, as confirmed by MEV and AFM.