The synthesis spectroscopic magnetic and structural characterization of three new dinuclear copper(II) carboxylates are described. All compounds exhibit the typical dinuclear paddle-wheel type structure, consisting of two copper(II) ions in square-pyramidal geometry bridged by four carboxylate anions in the xy plane and O- or N-donor ligands at the apex. [tetrakis(diphenyl acetato- μ- O, O′)bis(acetonitrile- N dicopper(II)tetrakis(acetonitrile) ( 1, C nhCu 2N 2O 8, crystallizes in the triclinic space group P 1 (No.2) with a=10.8941(17) b=11.140), c=13.346(3) A ̊ , α=69.9271(17), β=78.658(16), γ=86.819(14)°= Z=1, R=0.0438 and R w =0.0479 for 5188 observed reflections. The −2 J value of this compounds is 330(17)cm −1, the triplet state exhibiting a rhombic zero-field splitting with D=0.353(11 cm 1 and E=0.0022(2) cm −1, with g=2.03(1), g=2.05(1) and g=2.34(1). The compound [tetrakis(diphenylacetato- μ- O, O′)bis(acetone-O)dicopper(II)] ( 2). C 62H 50Cu 2O 10 crystallizes in the triclinic space group Pt (No. 2). The cell dimensions are a=10.8722(6), b=11.4003(8), c=11.6856(10) A ̊ , α=94.216(6), β=104.859(6), γ=111.193(5)°, Z=1, R1=0.0325 and wR2=0.0795 . The −2 J value is 303(15) cm 1, the triplet state exhibiting a rhombic zero-field splitting with D=0.345(10)cm −1 and E=0.0004cm 1, with g 1=2.06(1), g 1=2.33(1) and g 1=2.33(1). The dinuclear compound [tetrakis(1-phenyl-1-carboxylato- μ- O, O′- cyclopentane)bis(ethanol- O)dicopper(II)] bis(ethanol) (3). C 56H 76Cu 2O 12, crystallizes in the triclinic space group P 1 (No. 2). The cell dimensions for 3 are a=10.1013(6), b=11.6013(6), c=12.7596(5) A ̊ , α=64.908(4), β=70.116(4), γ=83.079(5)°, Z=1, R=0.0311 and R w =0.0253 . The structure forms an extended chain by hydrogen bonding from the axial ethanol, via a lattice ethanol to a carboxylate oxygen of another dicopper unit. The relatively small −2 J value of this compound is 284(14) cm −1, the triplet state exhibiting a rhombic zero-field splitting with [ D]=0.346(10) cm 1 and relatively large [ E]=0.0058 cm 1, g 1=2.04, g 1=2.04 and g 1=2.33, A 1=0.065cm −1.