Structural chemistry of metal coordination complexes at high pressure

Abstract

The application of pressures of up to about 10 GPa may induce significant geometric, configurational, conformational and packing changes in molecular solids. This review highlights and describes recent advances in high pressure studies of coordination complexes, many of which have been conducted at synchrotrons or other central facilities. The main focus is on the wide range of geometric changes which occur with pressure. In some cases these changes have associated physical effects, and the review describes materials exhibiting negative linear compressibility, spin cross-over phenomena, magnetism and molecular conduction, as well as detailing the exciting possibilities for future developments in this area of research.

Effects of Internal and External Pressure on the [Fe(PM-PEA)2(NCS)2] Spin-Crossover Compound (with PM-PEA = N-(2′-pyridylmethylene)-4-(phenylethynyl)aniline)

“…Upon further warming, a small bump is observed with a maximum at 90 K, corresponding to the HS* state. It seems that from irradiating the LS 2 state, the HS state reached, HS 2 *, is different from HS 1 * obtained from LS 1 . While HS 2 * relaxes directly to the LS 2 state, HS 1 * relaxes first to LS 1 and then to LS 2 , going through the intermediate HS* (Figure 5).…”

“…The fact that this phenomenon is not observed in the T(LIESST) curves is in favor of a phase transition occurring during the warming. The crystal structure of the photo-induced phase is unknown while the thermally quenched state, HS 1 *, has the same crystal structure than the HS phase at room temperature, HS 1 . The photo-induced HS state is obtained from the LS state, labelled LS 2 , which has a different crystal arrangement from the HS 1 and HS 1 * ones.…”

“…The use of pressure to perturb the electronic structure and the physical properties of metal-coordination compounds is an interesting way for the search towards switching materials [1]. The role of pressure has been studied for many years on spin crossover (SCO) compounds since it has applications in many fields as diverse as biology [2][3][4], geology [5,6], physics and chemistry [7][8][9][10].…”

Probing the structure of framework materials by high pressure and the example of a magnetic, non-porous coordination polymer

“…However, with pressure promoting effects such as magnetic crossover, spin transitions, negative linear compressibility (NLC; for a very recent and elegant review on this subject see Cairns & Goodwin, 2015), changes in proton conductivity, or even phase transitions that generate porous structures, high-pressure crystallographic studies on dense framework materials are markedly on the rise. More generally, coordination compounds are a fascinating class of materials for high-pressure crystallographic studies (Tidey et al, 2014;Moggach & Parsons, 2009). Compared with purely organic compounds, they have an inherent extra degree of flexibility for responding to moderate applied pressures (< 5 GPa), as the geometry at the metal centre can undergo marked changes, whereas other primary bond distances and angles remain largely unaffected.…”

A high-pressure crystallographic and magnetic study of Na5[Mn(l-tart)2]·12H2O (l-tart =l-tartrate)

“…1 This is due to the wide array of structural features that can be modified by the application of hydrostatic pressure, and has been aided by technological developments. 2 In addition, diamond anvil cells (DACs) 3 allow access to a huge range of pressures, spanning atmospheric pressure to tens of gigapascals, offering a much wider window over which to study the physical properties of materials, particularly when compared to variation of temperature.…”