Intermolecular Potential Energy Surfaces and Bound State Calculations of Rg–CuF (Rg = Ar, Kr, Xe): Insights into the Nature of Noble Gas–Metal Bonding

Abstract

High-precision two-dimensional intermolecular potential energy surfaces (PESs) for Rg–CuF (Rg = Ar, Kr, Xe) were constructed at the coupled-cluster singles and doubles with non-iterative triples [CCSD(T)] level by employing aug-cc-pVXZ (X = D, T, Q) basis sets, and the energies were extrapolated to the complete basis set (CBS) limit. All three complexes exhibit a consistent topological pattern: the global minimum corresponds to a collinear Rg–Cu–F configuration, and the local minimum corresponds to an anti-linear Rg–F–Cu configuration. As the atomic number of noble gas increases, the Rg–Cu equilibrium distance lengthens while the binding strength remarkably enhances. Bound state calculations were performed based on these PESs to yield rotational levels, which can be used to derive the intermolecular vibrational frequencies, molecular structures and spectroscopic parameters for all primary isotopologues. The predicted rotational constants B are in excellent agreement with the experimental observations, attaining a sub-MHz accuracy at the AVTZ level for Kr–CuF and at the CBS limit for Ar–CuF and Xe–CuF. Vibrational wavefunction analysis reveals that the intermolecular vibrational modes of Kr–CuF and Xe–CuF are highly localized, consistent with the pronounced molecular rigidity observed experimentally. Isotopic effect analysis reveals a well-defined linear relationship between the changes in the rotational constant B and the intermolecular vibrational frequency in relation to the reduced mass of the complex, which provides a reliable basis for predicting spectroscopic parameters of unobserved isotopologues. Symmetry-adapted perturbation theory (SAPT) energy decomposition further demonstrates that the Rg–Cu interaction is dominated by induction forces, with significant contributions from dispersion and electrostatics, and exhibits notable charge transfer character. This polarization and orbital overlap transcend the conventional van der Waals picture and reveal a partially covalent nature in noble gas transition metal interactions.