Communication: Coupled-cluster interpretation of the photoelectron spectrum of Au 3−

Recent developments in the general atomic and molecular electronic structure system

A discussion of many of the recently implemented features of GAMESS (General Atomic and Molecular Electronic Structure System) and LibCChem (the C++ CPU/GPU library associated with GAMESS) is presented. These features include fragmentation methods such as the fragment molecular orbital, effective fragment potential and effective fragment molecular orbital methods, hybrid MPI/OpenMP approaches to Hartree-Fock, and resolution of the identity second order perturbation theory. Many new coupled cluster theory methods have been implemented in GAMESS, as have multiple levels of density functional/tight binding theory. The role of accelerators, especially graphical processing units, is discussed in the context of the new features of LibCChem, as it is the associated problem of power consumption as the power of computers increases dramatically. The process by which a complex program suite such as GAMESS is maintained and developed is considered. Future developments are briefly summarized.

A Stable Cyclic (R2 SnAu)3 Anion Having In-Plane σ-Möbius Aromaticity

A cyclic (R₂ SnAu)₃ anion (3^- , R₂ Sn=2,2,5,5-tetrakis(trimethylsilyl)-1-stannacyclopentane-1,1-diyl) has been synthesized as a stable blue salt with K⁺ (THF)₆ through the reaction of stable dialkylstannylene 1 with R'₃ PAuCl (R'=Et, Ph) followed by the reduction with KC₈ . Crystallographic and NMR analysis shows that the six-membered (SnAu)₃ ring of 3^- is planar and highly symmetric with an equal distance of six Au-Sn bonds. A UV/Vis spectrum of 3^- in hexane reveals an intense absorption maximum at 598 nm. While cyclic Au₃ ^- with four valence electrons is known as unstable anti-aromatic anion, 3^- with three divalent tin ligands is stable σ aromatic anion with an unprecedented Möbius orbital array as predicted by the perturbation MO and CCSD analysis of 3^- .

Spin–orbit effects in optical spectra of gold–silver trimers

Photodissociation spectra of cationic gold–silver trimers are analysed using relativistic electronic structure theories paying special attention to the importance of spin–orbit and charge transfer effects.