Reduction of structural dimensionality through incorporation of auxiliary ligands in lanthanide tetracyanoplatinates

The synthesis of a series of lanthanide tetracyanoplatinates containing the auxiliary ligands 1,10′-phenanthroline (phen) or 2,2′-bipyridine (bpy) have been carried out by reaction of Ln3+ nitrate salts with phen or bpy and potassium tetracyanoplatinate in solvent systems containing dimethylsulfoxide and dimethylformamide. The use of these solvents has lead to the isolation of [{Ln(DMSO)2(C12H8N2)(H2O)3}2Pt(CN)4](Pt(CN)4)2·2C12H8N2·4H2O (Ln = Eu (Eu-1), Tb (Tb-1), Yb(Yb-1)), [Ln(DMF)3(C12H8N2)(H2O)2NO3]Pt(CN)4 (Ln = La (La-2), Eu (Eu-2), Tb (Tb-2)), and [Ln(DMF)3(C10H8N2)(H2O)2NO3]Pt(CN)4 (Ln = La (La-3), Sm (Sm-3), Eu (Eu-3), Tb (Tb-3)) in the form of single crystals. Single-crystal X-ray diffraction has been used to investigate their structural features. The use of DMSO versus DMF as the solvent results in markedly different structural features. Eu-1 contains [{Eu(DMSO)2(C12H8N2)(H2O)3}2Pt(CN)4]2+ complex cations where the two Eu3+ centers are linked by a trans-bridging Pt(CN)42− anion to form a dimeric lanthanide complex cation. An additional uncoordinated Pt(CN)42− anion balances charge. Eu-2 and Eu-3 consist of zero-dimensional salts with [Eu(DMF)3(C12H8N2)(H2O)2(NO3)]2+ or [Eu(DMF)3(C10H8N2)(H2O)2(NO3)]2+ complex cations, respectively, and only non-coordinated Pt(CN)42− anions. Photoluminescence measurements illustrate that the Eu3+ and Tb3+ compounds for all three structure types display enhanced emission due to intramolecular energy transfer from the coordinated cyclic amines.

Graphical abstractThe synthesis and structural characterization of three series of lanthanide tetracyanoplatinates incorporating bidentate amine ligands as auxiliary ligands are presented. All compounds are low-dimensional and lack platinophilic interactions in the solid state. Solid state luminescence properties are discussed for the Eu3+ and Tb3+ compounds.Figure optionsDownload full-size imageDownload as PowerPoint slideHighlights► Synthesis of novel lanthanide tetracyanometallate compounds. ► Auxiliary ligands lead to low-dimensional structures. ► Solid-state structures lack Pt–Pt interactions. ► Sensitization of Eu3+ and Tb3+ luminescence.