Magnetic relaxation in dysprosium and terbium 1D-zigzag coordination chains having only 4,4′-bipyridine as connector

The coordination chain {[Dy(dbm)3bpy]·C7H8}n (1) having only 4,4′-bipyridine as connector has been prepared in high yield and its structural and magnetic properties have been investigated. It is isostructural with the terbium analogue {[Tb(dbm)3bpy]·C7H8}n (2) and features units repeating in a 1D-zigzag fashion, where the metal is octa-coordinated in a distorted square antiprism geometry. Despite the 1D structure, the absence of paramagnetic connectors prevents the direct magnetic intrachain interaction among the lanthanide ions. In zero magnetic field, only a small fraction of the magnetization of 1 displayed slow dynamics with no dependence on temperature. Upon application of a 1 kOe magnetic field, a relaxation process appears, compatible with a mixed Raman/Direct mechanisms. Magnetic dilution in the diamagnetic Y(III)-based analogue revealed that actually two distinct relaxation processes are active for 1, whose temperature dependence can be interpreted again with a mixed Raman/Direct relaxation model. Compound 2 displayed only in-field slow relaxation, compatible with the models employed for 1.