Cobalt salen functionalised polycrystalline gold surfaces

The ability of N,N′-ethylene-bis(4-dodecyloxysalicylideneiminato)Co(II) (4) and literature known N,N′-ethylene-bis(3,5-di-t-butylsalicylideneiminato)Co(II) (5) to coordinate molecular oxygen was studied using ultraviolet–visible spectroscopy. For a comparison, the study was complemented with the archetype Co(II) salen (salen = N,N′-ethylene-bis(salicylideneamine)) complex. Especially 4, bearing long alkoxy chain substituents, coordinates dioxygen efficiently and reversibly, and therefore is an attractive candidate for further development of functional surfaces e.g. towards molecular level dioxygen sensors. In this respect, complexes 4 and 5 were attached on two different 4-pyridinethiol pre-treated polycrystalline Au surfaces. The changes in surface morphology after pyridinethiol and the complex treatment were studied with atomic force microscopy (AFM) measurements. Accordingly, with this method fairly smooth surfaces bearing cobalt(II) salen complexes can be prepared. In addition, the AFM results were complemented by X-ray reflection, cyclic voltammetry and wettability studies.