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

Abstract

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 Ln 3+ 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(C 12H 8N 2)(H 2O) 3} 2Pt(CN) 4](Pt(CN) 4) 2·2C 12H 8N 2·4H 2O ( Ln = Eu ( Eu-1), Tb ( Tb-1), Yb( Yb-1)), [ Ln(DMF) 3(C 12H 8N 2)(H 2O) 2NO 3]Pt(CN) 4 ( Ln = La ( La-2), Eu ( Eu-2), Tb ( Tb-2)), and [ Ln(DMF) 3(C 10H 8N 2)(H 2O) 2NO 3]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(C 12H 8N 2)(H 2O) 3} 2Pt(CN) 4] 2+ complex cations where the two Eu 3+ centers are linked by a trans-bridging Pt(CN) 4 2− anion to form a dimeric lanthanide complex cation. An additional uncoordinated Pt(CN) 4 2− anion balances charge. Eu-2 and Eu-3 consist of zero-dimensional salts with [Eu(DMF) 3(C 12H 8N 2)(H 2O) 2(NO 3)] 2+ or [Eu(DMF) 3(C 10H 8N 2)(H 2O) 2(NO 3)] 2+ complex cations, respectively, and only non-coordinated Pt(CN) 4 2− anions. Photoluminescence measurements illustrate that the Eu 3+ and Tb 3+ compounds for all three structure types display enhanced emission due to intramolecular energy transfer from the coordinated cyclic amines.