Tetranuclear Ru₂Ln₂ complexes of heavier lanthanides (Gd, Tb, Dy, Ho, Lu) with [RuNO(NO₂)₄OH]²⁻ anion, combining SMM properties and photoswitchable Ru-NO group

Five new heterometallic complexes with a {Ln[RuNO(µ-NO₂)₄(µ₃-OH)]₂Ln} (Ln = Gd, Tb, Dy, Ho, Lu) core were prepared by the reaction of Na₂[RuNO(NO₂)₄OH] with lanthanide nitrates. Investigation of magnetic properties showed that magnetic interactions between lanthanide ions become apparent at temperatures lower than 40–50 K, while at temperatures higher than 100 K the dependencies of magnetic susceptibility of the complexes are well explained by the presence of two non-interacting paramagnetic centres. Frequency dependencies of magnetic susceptibility for the dysprosium complex in the temperature range 10–30 K revealed single molecule magnet (SMM) properties with a thermally activated slow magnetic relaxation process. The anisotropy barrier is 89.4 cm⁻¹ (112 K) and τ₀ = 7.6 × 10⁻⁷ s. Irradiation of the Dy₂Ru₂ complex with blue light (443 nm) at 80 K resulted in the formation of nitrosyl linkage isomers of the RuNO fragment; the T_d of reverse isomerisation is 195 K.