Heterobimetallic Ln(III)‐Containing Materials Based on One‐Dimensional Aurophilic Chains of Gold(I) Dithiolate Dimers and Their Vapochromic Response to DMF

The synthesis, characterization, X-ray structures and luminescence of a series of lanthanide coordination polymers containing anionic gold(I) iso-maleonitriledithiolate units ([Au2(i-mnt)2]2−; {Au2[S2C=C(CN)2]2}2−) are described. Crystals of (nBu4N)Ln(DMF)8[Au2(i-mnt)2]2 (Ln=Gd, Tb, Eu) contain 1-D aurophilic chains of [Au2(i-mnt)2]2− units and DMF-saturated Ln(III) cations. The Ln=Gd and Tb systems are emissive, with λmax=596 and 625 nm respectively, attributable to the aurophilic chains. The luminescence intensities and emission energies qualitatively correlate to the local concentration of DMF vapour, where emission-quenched (nBu4N)Ln(DMF)5[Au2(i-mnt)2]2 is formed upon sample removal from a DMF atmosphere for 24 hours; the emissive species was regenerated by exposure to fresh DMF vapour. A similar turn-on luminescence effect was also observed when a quenched sample of (nBu4N)Tb(DMF)5[Au2(i-mnt)2]2 powder was exposed to pyridine, resulting in emission with λmax=625 nm. Structure-property correlations show that the emission maximum is influenced not only by the intermolecular Au−Au distances but also by a combination of the Au−Au−Au angles and other geometric factors in the [Au2(i-mnt)2] units.