Unusual Bonding in Platinum Carbido Clusters

Vibrational spectroscopy and density functional theory calculations are used to determine the structures of small gas-phase platinum carbido clusters PtnC(+), n = 3-5. The carbon atom is found to prefer three-coordinate binding sites near the center of the cluster, in contrast to most previously investigated adatoms on transition metal clusters. The Pt3C unit is particularly stable, and binding of the carbon atom also leads to significant rearrangement of the metal framework when compared to the bare clusters.

A novel series of isoreticular metal organic frameworks: realizing metastable structures by liquid phase epitaxy

A novel class of metal organic frameworks (MOFs) has been synthesized from Cu-acetate and dicarboxylic acids using liquid phase epitaxy. The SURMOF-2 isoreticular series exhibits P4 symmetry, for the longest linker a channel-size of 3 × 3 nm² is obtained, one of the largest values reported for any MOF so far. High quality, ab-initio electronic structure calculations confirm the stability of a regular packing of (Cu⁺⁺)₂- carboxylate paddle-wheel planes with P4 symmetry and reveal, that the SURMOF-2 structures are in fact metastable, with a fairly large activation barrier for the transition to the bulk MOF-2 structures exhibiting a lower, twofold (P2 or C2) symmetry. The theoretical calculations also allow identifying the mechanism for the low-temperature epitaxial growth process and to explain, why a synthesis of this highly interesting, new class of high-symmetry, metastable MOFs is not possible using the conventional solvothermal process.