Critical Role of CF3 Groups in the Electronic Stabilization of [PdAu24(C≡CC6H3(CF3)2)18]2- as Revealed by Gas-Phase Anion Photoelectron Spectroscopy.

Abstract

The role of alkynyl ligands with electron-withdrawing nature in the stability of metal clusters was investigated by gas-phase anion photoelectron spectroscopy (PES) on heteroleptic cluster anions [PdAu24(C≡CArF)18-x(C≡CPh)x]2- (ArF = 3,5-(CF3)2C6H3). Gas-phase PES on the cluster anions with specific x (= 0-6) revealed that electron binding energies decreased linearly with x, indicating that the electron-withdrawing CF3 substituents on the alkynyl ligand played a critical role in the electronic stabilization of [PdAu24(C≡CArF)18]2-. Density functional theory calculations reproduced the decrease of electron binding energies and rationally explained the ligand effect by a mechanism similar to the modulation of the work function of gold films by organic monolayers.