Probing the Properties of Polynuclear Superhalogens without Halogen Ligand via ab Initio Calculations: A Case Study on Double‐Bridged [Mg₂(CN)₅]⁻¹ Anions

Abstract

An ab initio study of the superhalogen properties of eighteen binuclear double-bridged [Mg2 (CN)5 ](-1) clusters is reported herein by using various theoretical methods. High-level CCSD(T) results indicate that all the clusters possess strong superhalogen properties owing to their high vertical electron detachment energies (VDEs), which exceed 6.8 eV (highest: 8.15 eV). The outer valence Green's function method provides inaccurate relative VDE values; hence, this method is not suitable for this kind of polynuclear superhalogens. Both the HF and MP2 results are generally consistent with the CCSD(T) level regarding the relative VDE values and-especially interesting-the average values of the HF and MP2 VDEs are extremely close to the CCSD(T) results. The distributions of the extra electrons of the anions are mainly aggregated into the terminal CN units. These distributions are apparently different from those of previously reported triple-bridged isomers and may be the reason for the decreased VDE values of the clusters. In addition, comparisons of the VDEs of binuclear and mononuclear superhalogens as well as studies of the thermodynamic stabilities with respect to the detachment of various CN(-1) ligands are also performed. These results confirm that polynuclear structures with pseudohalogen ligands can be considered as probable new superhalogens with enhanced properties.

Mg3F7: A superhalogen with potential for new nanomaterials design

“…Polynuclear superhalogens (M n X n · k + 1 ), of which the number of central atoms ( n ) is larger than one, take advantage of increasing the number of ligands while maintaining their high stability and, therefore, exploring polynuclear superhalogens has become an essential novel research direction (see Refs. and references cited therein). Examples include magnesia halogens whose electron affinities do not only confirm their superhalogen nature but also reveal a strong relationship with the number of central metal atoms.…”

Electron affinity of modified benzene

“…The utility of superhalogens in the design and synthesis of new materials of technological importance has spurred considerable interest not only in expanding their scope but also in finding ways to enhance their electron affinities. Recent works have shown that superhalogens are not restricted to just a metal atom at the core surrounded by halogen atoms but can be created when the core atom is replaced by a cluster, when the ligands are no longer halogen atoms, and even when none of the constituents are metal or halogen atoms . Equally important, a new class of electronegative clusters called hyperhalogens has emerged where the halogen ligands are replaced by superhalogen ligands, enabling their electron affinities to surpass those of their superhalogen building blocks.…”

Comment on: “Probing the Properties of Polynuclear Superhalogens without Halogen Ligand via ab Initio Calculations: A Case Study on Double‐Bridged [Mg2(CN)5]−1 Anions” by Li et al.

“…On the basis of discrepancies between their Outer Valence Green′s Function (OVGF) and coupled‐cluster singles and doubles plus approximate triples, or CCSD(T), calculations of the vertical detachment energies (VDEs) of six [Mg 2 (CN) 5 ] − isomers, Li et al. asserted that the former method is not suitable for this kind of superhalide . The results of Table and Figure demonstrate that this claim is false.…”

“…Dashed lines are for 2 A“ final states. Previous OVGF results obtained by Li et al with their TZ2 basis set are included for comparison.…”