Far-infrared absorption spectra of synthetically-prepared, ligated metal clusters with Au6, Au8, Au9 and Au6Pd metal cores

Abstract

The far infra-red absorption spectra of a series of chemically synthesised, atomically precise phosphinestabilised gold cluster compounds have been recorded using synchrotron light for the first time. Far-IR spectra of the Au 6 (Ph 2 P(CH 2 ) 3 PPh 2 ) 4 (NO 3 ) 2 , Au 8 (PPh 3 ) 8 (NO 3 ) 2 , Au 9 (PPh 3 ) 8 (NO 3 ) 3 , and Pd(PPh 3 ) Au 6 (PPh 3 ) 6 (NO 3 ) 2 clusters reveal a complex series of peaks between 80 and 475 cm À1 , for which all significant peaks can be unambiguously assigned by comparison with Density Functional Theory (DFT) geometry optimisations and frequency calculation. Strong absorptions in all spectra near 420 cm À1 are assigned to the P-Ph 3 stretching vibrations. Distinct peaks within the spectrum of each specific cluster are assigned to the cluster core vibrations: 80.4 and 84.1 cm À1 (Au 6 ) 165.1 and 166.4 cm À1 (Au 8 ), 170.1 and 185.2 cm À1 (Au 9 ), and 158.9, 195.2, and 206.7 cm À1 (Au 6 Pd). The positions of these peaks are similar to those observed to occur for the neutral Au 7 cluster in the gas phase (Science, 2008, 321, 674-676). Au-P stretching vibrations only occur for Au 6 near 420 cm À1 , although they appear near 180 cm À1 for Au 6 Pd and involve gold core vibrations.

Au101–rGO nanocomposite: immobilization of phosphine-protected gold nanoclusters on reduced graphene oxide without aggregation

“…Also, the strongly size-dependent electronic properties of ultra-small metal clusters offer the opportunity to tune their reactivity by choice of appropriate size and composition. 3,4 Furthermore, such clusters are small enough to perform high level DFT calculations, 5,6,7 which are crucial for comprehensive understanding of the catalytic mechanisms needed for the development of superior catalysts. 8 Therefore, size-specific clusters are considered as a platform for investigation of catalysts at the atomic level.…”

Density-functional tight-binding for phosphine-stabilized nanoscale gold clusters

“…Density functional theory (DFT) methods are most oen employed in theoretical investigations, as they are capable to accurately describe electronic, geometrical, and vibrational structure of gold clusters and nanoparticles. [16][17][18][19][20][21][22][23][24][25][26][27][28][29] In particular, the DFT-based simulation of IR, Raman, and UV-vis spectra has been achieved for a range of gold clusters, thus providing useful theoretical ngerprints to distinguish between bonding arrangements and orientations between gold atoms and ligands, and ligandligand interactions within clusters. 23,[30][31][32][33][34] Unfortunately, DFT calculations can become prohibitively expensive with system size, 35 and routine theoretical investigations are limited to moderate system sizes.…”

Nonadiabatic scattering of NO off Au3 clusters: A simple and robust diabatic state manifold generation method for multiconfigurational wavefunctions

“…We used the Modified LANL2DZ basis set by Hay and Wadt that replaces the 60 core electrons of Au atoms by an effective core potential (ECP) obtained from calculations which incorporate relativistic corrections, and contracted Gaussian basis functions for the remaining 19 valence electrons (5s 2 5p 6 5d 10 6s 1 ). This basis set has been widely used in a number of articles for studying properties of gold clusters . Three gold atoms have 57 valence electrons, and a preliminary CAS(7,4) calculation, using Cs symmetry, including the HOMO/LUMO of each symmetry resulted in a 2 E neutral cluster and 1 A 1 cation cluster (labels in C 3 v ).…”