First Ni II –Ln III Coordination Polymers Constructed by Using [Ni(bpca) 2 ] as a Building Block [Hbpca = bis(2‐pyridylcarbonyl)amine]: Synthesis, Crystal Structures and Magnetic Properties

Three new heterobimetallic 1D coordination polymers have been obtained by assembling the [Ni(bpca) 2 ] complex, as a building block, with lanthanide cations: [{Ln(O 2 NO)(H 2 O) 3 }{Ni(bpca) 2 }](NO 3 ) 2 · 3H 2 O (Ln Gd 1 ; Tb 2 ; Dy 3 ). The three compounds are isostructural and their structure consists of infinite cationic chains with Ln III ions connected by [Ni(bpca) 2 ] complexes acting as bridging bis‐bidentate ligands. The charge of the chains is counterbalanced by uncoordinated nitrate ions. The Ln III ions display a coordination number of nine: four oxygen atoms from the carbonyl groups of the bpca ligands belonging to two {Ni(bpca) 2 } moieties, two oxygen atoms from a chelating nitrato ion and three water molecules. The magnetic investigation of the gadolinium derivative 1 revealed very weak intrachain Ni II –Gd III ‐ferromagnetic interactions ( θ = +0.15 K). The weak intrachain‐exchange interactions, as well as the bad magnetic isolation of the chains in the crystals, preclude the single‐chain magnet behaviour of compounds 2 and 3 . The out‐of‐phase, χ ″ , signal observed with compounds 2 and 3 can be ascribed to the magnetic slow relaxation of the lanthanide ions (Tb III , Dy III ).(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)