Seeding the vertical growth of laterally coherent coordination polymers on the rutile-TiO 2 (110) surface

• Published in: Nanoscale 2024-07, Vol.16 (27), p.13071-13078
• Main Authors: Schio, Luca, Bavdek, Gregor, Grazioli, Cesare, Obersnù, Claudia, Cossaro, Albano, Goldoni, Andrea, Calloni, Alberto, Bossi, Alberto, Bussetti, Gianlorenzo, Orbelli Biroli, Alessio, Vittadini, Andrea, Floreano, Luca
• Format: Article
• Language: English
• ISSN: 2040-3364; 2040-3372
• DOI: 10.1039/d4nr01309c

Coordination polymers may be synthesized by linear bridging ligands to metal ions with conventional chemistry methods ( 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 synthesis approach, where the anchoring points are provided by a monolayer of metal(II)-tetraphenylporphyrin (M-TPP, M = Cu, Zn, Co) grown in on the rutile-TiO (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 effect. The weaker interactions between pyridine and Cu-TPP are then overcome by the strong attraction between TiO 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.