Unexpected favourable noncovalent interaction between chlorine oxyanions (ClOx−; x  = 1–4) and benzene: Benchmarking DFT and SAPT methods with respect to CCSD(T)

[Display omitted] •A surprisingly favorable interaction is found between benzene and oxyanions.•Binding energies are investigated using ab initio and DFT-D3 calculations.•The DFT functionals are benchmarked with respect to CCSD(T) method.•The present study asserts on the main factors stabilizing the oxyanion–benzene complexes.•The role of different energy components as well as the polarizability of anions on stabilizing anion-π interaction.•5-Interaction energy decomposition analysis for the complexes is performed using SAPT. The noncovalent interaction between chlorine oxyanions, namely: (hypochlorite (ClO−), chlorite (ClO2−), chlorate (ClO3−), and perchlorate (ClO4−), and benzene block is explicitly investigated and analyzed theoretically. The performance of a variety of DFT functionals and their dispersion-corrected DFT-D3 functionals as well as various wavefunction-based SAPT methods for the prediction of noncovalent interaction energies of C6H6–ClOx− (x = 1–4) complexes is justified in comparison with the benchmark CCSD(T)/CBS method. The results showed that benzene can form stable hydrogen-bond complexes of moderate strength with chlorine oxyanions. Moreover, the existence of favorable anion-π interactions between chlorine oxyanions and benzene π-system was demonstrated, which is predominantly attributed to attractive dispersion effects that depend on both the anion polarizability and the binding distance. It is worth mentioning that the origin of the binding energy in the studied complexes was found to be attributed in 68–74% to dispersion interaction. The sSAPT0/aVDZ method is found to perform qualitatively well for the prediction of the variation trends for the interaction energy components, compared to the computationally expensive, though provided the most accurate performance, SAPT2+(CCD)δMP2/aVTZ method. The D3-corrected DFT functionals showed good overall performance, particularly those of M06-2X, TPSS, PBE, and B3LYP.