We herein present the synthesis and X-ray structures of five copper(II) complexes of formulae [Cu(bpca)(CF₃SO₃)(H₂O)]·H₂O (1), [Cu(bpca)(Phpr)(H₂O)]·3/2H₂O (2), {[Cu(bpca)]₂[Cu(opba)(H₂O)]}·H₂O (3), {[Cu(bpca)]₂(H₂opba)}₂·6H₂O (4) and [Cu(bpca)(EtH₂opba)]_n (5), where bpca = bis(2-pyridylcarbonyl)amidate, Phpr = 3-phenylpropionate, CF₃SO₃ ⁻ = triflate (anion of the trifluoromethanesulphonic acid), H₄opba = N,N′-1,2-phenylenebis(oxamic acid), and EtH₃opba = monoethyl ester derivative of the H₄opba. 1 and 2 are mononuclear copper(II) complexes where the copper atom is five-coordinate in distorted square pyramidal surroundings with a tridentate bpca and a water molecule (1)/carboxylate oxygen (2) building the basal plane and a triflate oxygen (1)/water molecule (2) filling the apical position. 3 is a neutral tricopper(II) complex where the [Cu(opba)(H₂O)]²⁻ unit acts as a bis-bidentate ligand toward two peripheral [Cu(bpca)]⁺ fragments. The three crystallographically independent copper(II) ions in 3 are five-coordinate with two nitrogen and two oxygen atoms (inner copper atom)/three bpca-nitrogen and an oxamate oxygen (outer copper atom) building the basal plane plus a water molecule (inner copper)/an oxamate oxygen (outer copper) in the apical position (inner copper atom) of somewhat distorted square pyramidal surroundings. 4 is a centrosymmetric tetracopper(II) compound where four [Cu(bpca)]⁺ fragments are assembled by two H₂opba²⁻ groups adopting an unusual bidentate/bis-monodentate bridging mode. The two crystallographically independent copper(II) ions in 4 are also five-coordinate having the three bpca-nitrogens in basal positions, the other two sites of the distorted square pyramid being filled by two oxygens of either a bidentate oxamate (at one copper centre) or two bis-monodentate oxamates (at the other copper atom). 5 is a zigzag chain of [Cu(bpca)(H₂O)]⁺ units which are connected through the EtH₂opba⁻ ligand adopting a bidentate/monodentate bridging mode across the monodeprotonated oxamate group. Each copper(II) ion in 5 is six-coordinate in an elongated octahedral CuN₃O₃ chromophore. The magnetic properties of 3–5 were investigated in the temperature range 1.9–300 K. 3 exhibits an intermediate intramolecular antiferromagnetic interaction [J = −65.8(2) cm⁻¹ with the Hamiltonian H = −J(S Cu₁ ·S Cu₂ + S Cu₂ ·S Cu₃ )] which leads to a low-lying spin doublet at low temperatures. A weak antiferromagnetic coupling between the inner copper(II) ions occurs in 4 [J = −2.36(2) cm⁻¹, H = −JS₁·S₂)] and a very small intrachain antiferromagnetic interaction is observed in 5 [J = −0.17(1) cm⁻¹ with H = −J∑_iS_i·S_i+1]. These values are analyzed by means of simple orbital symmetry considerations and compared with those previously reported for parent systems.

A novel series of copper(II) coordination polymers [Cu₂(O₂CC₈H₉)₄(pyz)]_n (1), [Cu₂(O₂CC₈H₉)₄(dps)]_n (2), {[Cu(O₂CC₈H₉)₂(dps)(H₂O)]·H₂O}_n (3), {[NaCu(O₂CC₈H₉)₂(bpm)(NO₃)]·H₂O}_n (4), and [Cu₄(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^II ₂(μ-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 [Na^I ₂Cu^II ₂(μ-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^II ₄(μ₃-OH)₂(μ-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 = −JS₁·S₂ with S₁ = S₂ = S_Cu = 1/2. A quasi Curie law is observed for 3 (θ = −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-μ-hydroxo, di-μ-hydroxo, μ₃-hydroxo and single-μ-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.