Seeding the vertical growth of laterally coherent coordination polymers on the rutile-TiO$_2$(110) surface

Le résumé fourni par la source

Coordination polymers may be synthesized by linear bridging ligands to metal ions with conventional chemistry methods (e.g. in solution). Such complexes can be hardly brought onto a substrate with the chemical, spatial and geometrical homogeneity required for device integration. Instead, we follow an in situ synthesis approach, where the anchoring points are provided by a monolayer of metal(II)-tetraphenylporphyrin (M-TPP, M = Cu, Zn, Co) grown in vacuum on the rutile-TiO$_2$(110) surface. We probed the metal affinity to axial coordination by further deposition of symmetric dipyridyl-naphthalenediimide (DPNDI). By NEXAFS linear polarization dichroism, we show that DPNDI stands up on Zn- and Co-TPP thanks to axial coordination, whereas it lies down on the substrate for Cu-TPP. Calculations for a model pyridine ligand predict strong binding to Zn and Co cations, whose interaction with the O anions underneath is disrupted by surface trans effect. The weaker interactions between pyridine and Cu-TPP are then overcome by the strong attraction between TiO$_2$ and DPNDI. The binding sites exposed by the homeotropic alignment of the ditopic DPNDI ligand on Zn- and Co-TPP are the foundations to grow coordination polymers preserving the lateral coherence of the basal layer.

Ce résumé expose les affirmations des auteurs. BNTIC ne l’interprète pas comme une validation indépendante des résultats.