Structural and bonding properties of AlnC4−/0 (n = 2–4) clusters: Anion photoelectron spectroscopy and theoretical calculations

Abstract

We measured the photoelectron spectra of AlnC4− (n=2-4) clusters by using size-selected anion photoelectron spectroscopy. The structures of AlnC4−/0 (n = 2–4) clusters were explored with quantum chemistry calculations and were determined by comparing the theoretical results with the experimental spectra. It is found that the most stable structure of Al2C4− anion is a C2v symmetry planar structure with two Al atoms interacting with two C2 units. In addition, Al2C4− anion also has a D∞h symmetry linear structure with two Al atoms located at the two ends of a C4 chain, which is slightly higher in energy than the planar structure. The most stable structure of neutral Al2C4 has a D∞h symmetry linear structure. The most stable structure of Al3C4− anion is a planar structure with three Al atoms interacting with two C2 units. Whereas neutral Al3C4 cluster has a C2v symmetric V-shaped bent structure. The global minima structures of both Al4C4− and neutral Al4C4 are C2h symmetry planar structures with four Al atoms interacting with the ends of two C2 units. Adaptive natural density partitioning analyses of AlnC4− (n=2−4) clusters show that the interactions between the Al atoms and C2 units have both σ and π characters.