Magnetism in Heterobimetallic and Heterotrimetallic Chains Based on the Use of [W V (bipy)(CN) 6 ] – as a Metalloligand

Two new heterobi‐ and trimetallic chains of formula ∞ 1 [{Mn II (pyim) 2 }{(µ‐NC) 2 W V (bipy)(CN) 4 }][W V (bipy)(CN) 6 ] ( 1 ) and ∞ 1 [{Cu II Mn II L}{(µ‐NC) 3 W V (bipy)(CN) 3 }][W V (bipy)(CN) 6 ] · 0.75H 2 O · 2MeCN ( 2 ) were obtained by reacting the cyanido‐based AsPh 4 [W(bipy)(CN) 6 ] heteroleptic complex with the pre‐formed [Mn II (pyim) 2 ] 2+ ( 1 ) and [Cu II Mn II L] 2+ ( 2 ) complexes [bipy = 2,2′‐bipyridine, pyim = 2‐(1 H ‐imidazol‐2‐yl)pyridine and H 2 L = macrocyclic Schiff‐base resulting from the stepwise condensation of 2,6‐diformyl‐ p ‐cresol with ethylenediamine and diethylenetriamine]. The structure of 1 consists of cationic cyanido‐bridged {Mn II W V } chains, assembled from [W V (bipy)(CN) 6 ] – spacers, each one coordinating in a bis‐monodentate fashion, two [Mn II (pyim) 2 ] 2+ nodes, and [W V (bipy)(CN) 6 ] – counteranions. Compound 2 comprises a positively charged 1D coordination polymer, built from [W V (bipy)(CN) 6 ] – cyanido metalloligands that act as tris‐monodentate spacers towards [Cu II Mn II L] 2+ complexes, the entire assembly being neutralized by [W V (bipy)(CN) 6 ] – anions. Each manganese(II) ion in 1 is six‐coordinate in a somewhat distorted octahedral surrounding. Five‐coordinate copper(II) and seven‐coordinate manganese(II) ions exhibiting distorted square pyramidal and monocapped trigonal prism environments respectively, occur in each {Cu II Mn II } node of 2 . The magnetic susceptibility of 1 and 2 investigated down to 1.9 K is characteristic of 1D ferrimagnetic behavior with minima in the χ M T vs. T plots at 35 ( 1 ) and 20 K ( 2 ) ( χ M is the magnetic susceptibility per one Mn II plus two W V ions). The magnetic data of 1 in the whole temperature range were analyzed through a model considering S Mn = 5/2 as a classical spin and S W = 1/2 as a quantum spin, with two interaction parameters J 1 = J (1 – α ) and J 2 = J (1 + α ) {the spin Hamiltonian being defined as H = – J Σ i S W, i [(1 + α ) S Mn, j + (1 – α ) S Mn, i +1 ] + Σ i ( g W S W, i + g Mn S Mn, i ) βH }. The values of the intrachain antiferromagnetic interactions for 1 through this model were –3.0(1) ( J 1 ) and –32.0(1) cm –1 ( J 2 ). The complexity of the spin topology in 2 , a branched chain with four different intrachain antiferromagnetic interactions (double phenoxido bridge between Mn II and Cu II , two single cyanido bridges between Mn II and Cu II , and one single cyanido bridge between Cu II and W V ) precluded any simulation of its magnetic data.