Exohedral M-C-60 and M-2-C-60 (M = Pt, Pd) systems as tunable-gap building blocks for nanoarchitecture and nanocatalysis

Transition metal-fullerenes complexes with metal atoms bound on the external surface of C-60 are promising building blocks for next-generation fuel cells and catalysts. Yet, at variance with endohedral M@C-60, they have received a limited attention. By resorting to first principles simulations, we elucidate structural and electronic properties for the Pd-C-60, Pt-C-60, PtPd-C-60, Pd-2-C-60, and Pt-2-C-60 complexes. The most stable structures feature the metal atom located above a high electron density site, namely, the pi bond between two adjacent hexagons (pi-66 bond). When two metal atoms are added, the most stable configuration is those in which metal atoms still stand on p-66 bonds but tends to clusterize. The electronic structure, rationalized in terms of localized Wannier functions, provides a clear picture of the underlying interactions responsible for the stability or instability of the complexes, showing a strict relationship between structure and electronic gap

On the trail of molecular hydrophilicity and hydrophobicity at aqueous interfaces

Uncovering microscopic hydrophilicity and hydrophobicity at heterogeneous aqueous interfaces is essential as it dictates physical and chemical properties such as wetting, electrical double layer, reactivity. Here, we combine density functional theory-based MD simulations (DFT-MD) and both theoretical and experimental SFG spectroscopy to explore how the interfacial water responds in contact with self-assembled monolayers (SAM) of tunable hydrophilicity. We introduce a microscopic metric to track the transition from hydrophobic to hydrophilic interfaces, which combines a structural descriptor based on the preferential orientation within the water network in the topmost binding interfacial layer (BIL) and spectroscopic fingerprints of H-bonded and dangling OH groups of water pointing towards the surface carried by BIL-resolved SFG spectra. This metric builds a bridge between molecular descriptors of hydrophilicity/hydrophobicity and spectroscopically measured quantities, and provides a recipe to quantitatively or qualitatively interpret experimental SFG signals