Origin of structure and stability of M@C18 (M = Cu, Ag, and Au) complexes with D9h point group.

Abstract

Theoretical predictions and recent experimental studies lead to the discovery of an exciting new member of the carbon allotrope family polyynic cyclo[18]carbon (C18 ). Present investigation aims to probe the structure, stability, and properties of coinage metal (M)@C18 complexes using density functional theory (DFT) calculations. The DFT results unequivocally show that even Cu@C18 , Ag@C18 , and Au@C18 complexes substantially preserve the ground state polyynic structure of C18 . It is also worth to mention that only Au@C18 is a stable D9h structure, however the symmetry is distorted in the case of Cu@C18 and Ag@C18 . Due to computational limitations, in this investigation the M@C18 complexes were scrutinized using the C2v sub abelian group of D9h . The highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) of D9h conformers are a singlet a1 and two same value singlets a1 ⊕ b1 generated from doublet e, respectively. The non-covalent interaction index (NCI), quantum theory of atoms in molecule (QTAIM), and energy decomposition analysis (EDA) vividly explains the interaction between a coinage metal atom and C18 ring. It is found from the results that the stability of Cu@C18 Ag@C18 , and Au@C18 is governed by the attractive electrostatic, orbital and dispersion interaction.