Structure and energetics of the anisole–Arn (n = 1, 2, 3) complexes: high-resolution resonant two-photon and threshold ionization experiments, and quantum chemical calculations

Abstract

We present a concerted experimental and theoretical study of the anisole⋯Ar_n complexes with n = 1–3. Experimentally, anisole was seeded into a pulsed supersonic argon jet producing a molecular beam. Resonant two-photon, two-colour ionisation (R2PI) spectra of anisole⋯Ar_n complexes with n = 1–3 were obtained. Also, the photodissociation of the (1 : 1) cluster was probed synchronously by – Zero Electron Kinetic Energy Photoelectron Spectroscopy (ZEKE) – and – Mass Resolved Threshold Ionization (MATI) – measuring electrons and ions obtained from pulsed field ionization of high-n Rydberg states upon two-colour laser excitation. The experimental results are compared to quantum chemical calculations at the DFT-D3 (B-LYP/def2-QZVP level with Grimme's D3 dispersion correction) level. Structure and energetics due to microsolvation effects by the direct interaction of the argon atoms with the π-system were evaluated. The experimental binding energy of the 1 : 1 cluster is finally compared to computational results; in the S₀ ground state the theoretical value based on the “gold standard” CCSD(T)/CBS calculations lies within the error bars of the observed value. In the excited state the agreement between theory and experiment is not so spectacular but relative values of observed dissociation energies (D₀) in the ground and excited states and of calculated ones agree well.