Aurophilicity under pressure: a combined crystallographic and in situ spectroscopic study

Abstract

High pressure crystallographic studies on [1,4-C6H4{PPh2(AuCl)}2] (1) reveal the largest pressure-induced contraction of an aurophilic interaction observed for any Au(i) complex; Hirshfeld surface analysis and Raman spectroscopy reveal the presence of several types of intermolecular interaction, which play an important role in the behaviour of 1 as a function of pressure.

Structural Characterization of Aurophilic Gold(I) Iodide under High Pressure

“…Notice that the bulk modulus is similar to that determined from the linear compressibility, indicating that most of the compression of the structure occurs along the layers. In addition, B 0 is very small, comparable to that of rare-gas solids and molecular solids, and 50% smaller than the bulk modulus of the different polymorphs of AgI and CuI. − On the other hand, this B 0 is on the same order of magnitude as that of the aurophilic organometallic solid [1,4-C 6 H 4 {PPh 2 (AuCl)} 2 ], which is 8(13) GPa . Moreover, the pressure derivative of the bulk modulus is much smaller than the typical value for this parameter, which is expected to be near 4 in ionic–covalent solids .…”

“…At ambient pressure, the shortest interatomic distances are those of intralayer Au–I bonds shown in Figure a, which are 2.602 Å, and the Au–I–Au angle in the zigzag chains is 72.42°. Within each layer, the Au atoms form an fcc-like square two-dimensional (2D) network in which the Au–Au distance is equal to = 3.076 Å, which is a typical distance of aurophilic bonds under ambient conditions (Figure a). , We can compare this Au–Au distance with those of other aurophilic structures, e.g., in gold chloride AuCl, 3.22 Å, in organometallic solids like [1,4-C 6 H 4 {PPh 2 (AuCl)} 2 ], 3.6686(5) Å, and in AuEt 2 DTC· x CH 2 Cl 2 , 2.78 Å. , The Au–Au distance in AuI is significantly shorter than in two of these reported above. On one hand, I atoms in each layer form simple square 2D networks at each side of the Au network in which the distance between I atoms is equal to the unit-cell parameter a , i.e., 4.355(3) Å.…”

“…To the best of our knowledge, this is the shortest pressure-induced Au–Au aurophilic distance in an inorganic structure and the largest pressure-induced contraction in the length, around 0.2 Å, of an aurophilic interaction within just 3.3 GPa. Paliwoda et al reported the pressure-induced shortening of aurophilic contacts, from 2.78 to 2.72 Å, in the organometallic gold­(I) diethyldithiocarbamate polymer (organometallic solid) between 0 and 1 GPa, and O’Connor et al published the largest pressure-induced contraction in the length of an aurophilic interaction, 0.613 Å, obtained from 0 to 10.6 GPa in another organometallic compound, [1,4-C 6 H 4 {PPh 2 (AuCl)} 2 ]. , If we do an extrapolation at 10.7 GPa, by using the pressure coefficient of the Au–Au distance (−0.059 Å/GPa), a length contraction of 0.63 Å is calculated, a value that is similar to that obtained by O’Connor et al in the same pressure range for an organometallic compound.…”

“…Currently, the similarity in strength between hydrogen bonding and aurophilic interaction has proven to be a convenient tool in the field of polymer and supramolecular chemistry. To date, the study of the aurophilicity under compression has been very limited. , For this reason, our HP crystallographic study will improve our understanding of the HP behavior of these aurophilic materials, i.e., as the pressure affects the Au–Au interaction that gives rise to aurophilic bonds within inorganic structures.…”

Crystal engineering of aurophilic supramolecular architectures and coordination polymers based on butterfly-like copper–dicyanoaurate complexes: vapochromism, P–T behaviour and multi-metallic cocrystal formation

“…High pressure measurements on gold complexes showing aurophilic interactions have been performed in the past, especially to modulate the luminescence emission or to study polymorphism. [92][93][94][95][96][97] Further investigations have been done on inorganic salts like AuX or M[Au(CN) 2 ] n to study the solid state compressibility of peculiar arrangements of gold atoms. [98][99][100][101] By selecting 1 as a prototype of the supramolecular architectures formed from the dicyanoaurate and metal-gold complexes with a chelating ligand, high pressure and low temperature measurements have been performed.…”