Structural analysis and photoluminescence properties of low dimensional lanthanide tetracyanometallates

The synthesis of a number of lanthanide tetracyanometallate (TCM) compounds have been carried out by reaction of Ln3+ nitrate salts and potassium tetracyanometallates in solvent systems containing dimethylsulfoxide and water. These reactions result in the isolation of three distinct structure types: (1) monoclinic [Ln(DMSO)4(H2O)3M(CN)4](M(CN)4)0.5·2H2O (Ln = Eu, Tb and M = Pd, Pt), (2) orthorhombic {La(DMSO)3(H2O)2(NO3)M(CN)4}∞·H2O (M = Pd, Pt), and (3) orthorhombic {Ln(DMSO)3(H2O)(NO3)M(CN)4}∞ (Ln = Tb and M = Pd, Pt; Ln = Er, Yb and M = Pt) in the form of single crystals. Single-crystal X-ray diffraction has been used to investigate their structural features. Structure type 1 is a zero dimensional ionic compound with a M/Ln ratio of 1.5:1. It contains coordinated as well as uncoordinated [M(CN)4]2− (M = Pd, Pt) anions and features relatively long platinophilic interactions. Structure types 2 and 3 differ quite drastically from structure type 1, but they are very similar to each other. Both of the latter are one-dimensional in nature due to chains containing linkage of Ln3+ coordination spheres with trans-bridging [M(CN)4]2− anions. These coordination polymers both have a M/Ln ratio of 1:1, a lack of platinophilic interactions, and incorporation of a bidentate NO3− for charge balance. Photoluminescence properties for select Eu3+ and Tb3+ compounds have been investigated. They show characteristic absorption and emission for the Ln3+ ions, but no significant influence of the tetracyanometallate anions.