Magneto-structural versatility of copper(II)-3-phenylpropionate coordination polymers with N-donor coligands

A novel series of copper(II) coordination polymers [Cu-2(O2CC8H9)(4)(pyz)](n) (1), [Cu-2(O2CC8H9)(4)(dps)](n) (2), {[Cu(O2CC8H9)(2)(dps)(H2O)]center dot H2O}(n) (3), {[NaCu(O2CC8H9)(2)(bpm)(NO3)]center dot H2O}(n) (4), and [Cu-4(O2CC8H9)(6)-(OH)(2)(bpp)(2)](n) (5) [O2CC8H9- = 3-phenylpropionate anion, pyz = pyrazine, dps = di(4-pyridyl)sulfide, bpm = 2,2'-bipyrimidine, and bpp = 1,3-bis(4-pyridyl)propane] have been synthesized and magneto-structurally investigated. Compounds 1 and 2 belong to a large group of copper(II) carboxylates where bis-monodentate pyz (1) and dps (2) ligands connect the paddle-wheel [Cu-2(II)(mu-O2CC8H9)(4)] units leading to alternating copper(II) chains. The structure of 3 consists of uniform chains of trans-[Cu-II(O2CC8H9)(2)] units linked by the bis-monodentate dps ligand. Compound 4 consists of heterobimetallic chains where [(Na2Cu2II)-Cu-I(mu-O2CC8H9)(4)(NO3)(2)] units are doubly bridged by bis-bidentate bpm ligands. Compound 5 is also a chain compound whose structure is made up by tetranuclear [Cu-4(II)(mu(3)-OH)(2)(mu-O2CC8H9)(4)(O2CC8H9)(2)] units which are doubly bridged by bis-monodentate bpp ligands. The magnetic properties were investigated in the temperature range 1.8-300 K. Strong antiferromagnetic interactions across the quadruple syn-syn carboxylate are observed in 1 and 2 [J = -378 (1) and -348 cm(-1) (2)] whereas a weak ferromagnetic coupling through the double out-of-plane oxo(carboxylate) bridge occurs in 4 [J = +2.66 cm(-1)], the spin Hamiltonian being defined as H = -JS(1).S-2 with S-1 = S-2 = S-Cu = 1/2. A quasi Curie law is observed for 3 (theta = -0.36 cm(-1)), the bis-monodentate dps ligand being a very poor mediator of magnetic interactions. The analysis of the magnetic properties of 5 is quite complex because of the presence of two crystallographically independent tetracopper(II) units with single-mu-hydroxo, di-mu-hydroxo, mu(3)-hydroxo and single-mu-hydroxo plus double syn, syn carboxylate bridges in each one. The nature and values of the magnetic couplings for 5 obtained by fitting (intermediate, strong and weak antiferromagnetic interactions for the three former exchange pathways respectively, and intermediate ferromagnetic interactions for the latter one) were substantiated by DFT type calculations.