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

Abstract

Two new heterobi‐ and trimetallic chains of formula ∞1[{MnII(pyim)2}{(µ‐NC)2WV(bipy)(CN)4}][WV(bipy)(CN)6] (1) and ∞1[{CuIIMnIIL}{(µ‐NC)3WV(bipy)(CN)3}][WV(bipy)(CN)6]·0.75H2O·2MeCN (2) were obtained by reacting the cyanido‐based AsPh4[W(bipy)(CN)6] heteroleptic complex with the pre‐formed [MnII(pyim)2]2+ (1) and [CuIIMnIIL]2+ (2) complexes [bipy = 2,2′‐bipyridine, pyim = 2‐(1H‐imidazol‐2‐yl)pyridine and H2L = 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 {MnIIWV} chains, assembled from [WV(bipy)(CN)6]– spacers, each one coordinating in a bis‐monodentate fashion, two [MnII(pyim)2]2+ nodes, and [WV(bipy)(CN)6]– counteranions. Compound 2 comprises a positively charged 1D coordination polymer, built from [WV(bipy)(CN)6]– cyanido metalloligands that act as tris‐monodentate spacers towards [CuIIMnIIL]2+ complexes, the entire assembly being neutralized by [WV(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 {CuIIMnII} 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 χMT vs. T plots at 35 (1) and 20 K (2) (χM is the magnetic susceptibility per one MnII plus two WV ions). The magnetic data of 1 in the whole temperature range were analyzed through a model considering SMn = 5/2 as a classical spin and SW = 1/2 as a quantum spin, with two interaction parameters J1 = J(1 – α) and J2 = J(1 + α) {the spin Hamiltonian being defined as H = –JΣiSW,i[(1 + α)SMn,j + (1 – α)SMn,i+1] + Σi(gWSW,i + gMnSMn,i)βH}. The values of the intrachain antiferromagnetic interactions for 1 through this model were –3.0(1) (J1) and –32.0(1) cm–1 (J2). The complexity of the spin topology in 2, a branched chain with four different intrachain antiferromagnetic interactions (double phenoxido bridge between MnII and CuII, two single cyanido bridges between MnII and CuII, and one single cyanido bridge between CuII and WV) precluded any simulation of its magnetic data.