Hingeless negative linear compression in the mechanochromic gold complex [(C6F5Au)2(μ-1,4-diisocyanobenzene)

Christopher H Woodall,Simon J Teat,Christian Reber,Andrew Parlett,Lauren E Hatcher,Mourad Intissar,Christine M Beavers,Paul R Raithby,Jeppe Christensen

doi:10.1002/anie.201302825

Abstract

The compression of a crystalline material under hydrostatic pressure always results in a reduction in volume of the solid, with the observed reduction typically occurring in all crystallographic cell parameters.1 However, there are a number of exceptional materials that have been shown to expand in a specific direction upon hydrostatic compression while maintaining a positive volume compression. The phenomenon of uni-or biaxial expansion under compression is known as negative linear compressibility (NLC).1 Rare examples of NLC have attracted attention recently owing to the potential applications in a range of materials, including body armor, artificial muscle actuators, and pressure sensors.2

Highlights

The compression of a crystalline material under hydrostatic pressure always results in a reduction in volume of the solid, with the observed reduction typically occurring in all crystallographic cell parameters.[1]
Ag3[Co(CN)6] exhibits extremely large negative linear compressibility (NLC) at low pressures (À76 TPaÀ1 from ambient to 0.19 GPa) before transforming to a new highpressure phase that displays NLC over a greater pressure range (À5.3 TPaÀ1),[1] while KMn[Ag(CN)2]3, a structural analogue of Ag3[Co(CN)6] has been shown to demonstrate strong persistent NLC (À12 TPaÀ1 from ambient to 2.2 GPa).[2d]. More recently, “giant” NLC has been attributed to a simple zinc gold cyanate complex Zn[Au(CN)2]2
In all these materials the observation of large NLC is attributed to specific structural motifs where covalent bonds act as hinges allowing the material to behave in a manner that mimics a wine-rack or trellis.[1,2b,d] In molecular complexes, the largest NLC effect has been reported by Shepherd et al in the spin crossover complex [Fe(dpp)2(NCS)2]·py.[4]

Summary

Introduction

The compression of a crystalline material under hydrostatic pressure always results in a reduction in volume of the solid, with the observed reduction typically occurring in all crystallographic cell parameters.[1]. The compound displays a remarkably large NLC effect parallel to the crystallographic c-axis that is the largest of any other material ever reported (À42(5)TPaÀ1 between ambient and

Results

Conclusion