Magneto-structural variety of new 3d–4f–4(5)d heterotrimetallic complexes†
Abstract
Three families of heterotrimetallic chains (type 1–type 3), with different topologies, have been obtained by reacting the 3d–4f complexes, [{Cu(L1)}xLn(NO3)3] with x = 1 or 2, formed in situ by the reaction of Schiff-base bi-compartmental [CuII(L1)] complexes and lanthanide(III) salts, with (NHBu3)3[M(CN)8] (M = MoV, WV). For type 1 series of compounds, 1-D coordination polymers, with the general formula [{Cu2(valpn)2Ln}{M(CN)8}]·nH2O·mCH3CN (where H2valpn = 1,3-propanediylbis(2-iminomethylene-6-methoxy-phenol), result from the association of trinuclear {CuII2LnIII} moieties and [MV(CN)8]3− anions acting as tri-connecting spacers [Ln = La (1), Ce (2), Eu (3), Tb (4), Ho (5), M = Mo; Ln = Tb (6), Ho (7), M = W; m = 0, n = 1.5 (7) and 2 (1–4, 6); n = 1, m = 1 (5)]. The type 2 family has the general formula [{Cu(valdp)Ln(H2O)4}{M(CN)8}]·2H2O·CH3CN (where H2valdp = 1,2-propanediylbis(2-iminomethylene-6-methoxy-phenol)) and also consists of heterotrimetallic chains involving binuclear {CuIILnIII} units linked to [M(CN)8]3− anions coordinating through two cyano groups [Ln = Gd (8), Tb (9), Dy (10); M = Mo; Ln = La (11), Gd (12), Tb (13), Dy (14); M = W]. With large LnIII ions (LaIII and PrIII), the type 3 family of heterotrimetallic compounds are assembled: [{Cu2(valdp)2Ln(H2O)4}{Mo(CN)8}]·nCH3OH·mCH3CN, n, m = 0, Ln = La (15); n = m = 1, Pr (16), in which the trinuclear {CuII2LnIII} nodes are connected to [MoV(CN)8]3− anions that act as tetra-connecting spacers. For TbIII derivatives of the type 1 (compounds 4 and 6), the DC magnetic properties indicate a predominant ferromagnetic CuII–TbIII interaction, while the AC magnetic susceptibility (in the presence of a static magnetic field, HDC = 3000 Oe) emphasize the slow relaxation of the magnetization (Ueff/kB = 20.55 K and τ0 = 5.5 × 10−7 s for compound 4, Ueff/kBT = 15.1 K and τ0 = 1.5 × 10−7 s for compound 6). A predominant ferromagnetic CuII–LnIII interaction was also observed in the type 2 series (compounds 8–10 and 12–14) as a result of the magnetic coupling between copper(II) and lanthanide(III) ions via the phenoxo-bridge. The magnetic behavior for the LaIII derivatives reveals that weak ferromagnetic interactions are also operative between the CuII and the 4d/5d centers.