Sorption of small molecule vapours by single crystals of [Pt{4′-(Ph)trpy}(NCS)]SbF6 where trpy = 2,2′:6′,2′′-terpyridine: a porous material with a structure stabilised by extended π–π interactions

Abstract

Treatment of [Pt{4′-(Ph)trpy}Cl]SbF₆ with AgSCN in a metathesis reaction in refluxing acetonitrile affords, after work-up, single crystals of [Pt{4′-(Ph)trpy}(NCS)]SbF₆·CH₃CN, where trpy is 2,2′:6′,2′′-terpyridine. These crystals lose solvent to give single crystals of [Pt{4′-(Ph)trpy}(NCS)]SbF₆ (1). An X-ray crystal structure determination of 1 shows that the SCN⁻ ion is N-bound and that the cation as a whole is approximately planar. Compound 1 is porous with “empty” channels that corkscrew through the crystal: this crystal structure is stabilised by extended π–π interactions between the planar cations. When a single crystal of 1 is exposed to vapours of acetonitrile the vapours are sorbed without loss of single crystallinity, as confirmed by crystal structure determinations of 1 and 1·CH₃33CN using the same single crystal. Similarly, single crystals of 1 sorb vapours of methanol without loss of single crystallinity, as confirmed by a crystal structure determination of 1·CH₃3OH. We also report the crystal structure of 1·(CH₃3)₂2CO; however, in this case the single crystal was grown directly from acetone. Compound 1 and its solvates are all yellow. Nevertheless, there are differences between the emission spectra recorded for 1 and its solvates in the solid state. Thus, whereas 1 exhibits very weak multiple emission from ³MLCT (MLCT = metal-to-ligand charge transfer) and excimeric ³π–π* excited states, 1·CH₃33CN and 1·(CH₃3)₂2CO both exhibit more intense ³MLCT emission; and the emission by 1·CH₃3OH is complicated by the presence of metallophilic interactions in the crystal. We discuss the role of the solvent in causing these differences.