Magneto-structural variety of new 3d-4f-4(5)d heterotrimetallic complexes
Résumé
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)2LnM(CN)8][middle dot]nH2O[middle dot]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)4M(CN)8][middle dot]2H2O[middle dot]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)4Mo(CN)8][middle dot]nCH3OH[middle dot]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 [small tau]0 = 5.5 [times] 10-7 s for compound 4, Ueff/kBT = 15.1 K and [small tau]0 = 1.5 [times] 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.