The nuclear magnetic resonance (NMR) spectra of single-anion bridged, dinuclear copper(II) metallacycles [Cu-2(mu-X)(mu-L)(2)](A)(3) (L-m = m-bis[bis(1-pyrazolyl)-methyl]benzene: X = F-, A = BF4-; X = Cl-, OH-, A = ClO4-; L-m* = m-bis[bis(3,5-dimethyl-1-pyrazoly)methyl]benzene: X = CN-, F-, Cl-, OH-, Br-, A = ClO4-) have relatively sharp H-1 and C-13 NMR resonances with small hyperfine shifts due to the strong antiferromagnetic superexchange interactions between the two S = 1/2 metal centers. The complete assignments of these spectra, except X = CN-, have been made through a series of NMR experiments: H-1-H-1 COSY, H-1-C-13 HSQC, H-1-C-13 HMBC, T-1 measurements and variable-temperature H-1 NMR The T1 measurements accurately determine the Cu center dot center dot center dot H distances in these molecules. In solution, the temperature dependence of the chemical shifts correlate with the population of the paramagnetic triplet (S = 1) and diamagnetic singlet (S = 0) states. This correlation allows the determination of antiferromagnetic exchange coupling constants, -J = (H) over cap -J (S) over cap (1)(S) over cap (2)), in solution for the L. compounds 338(F-), 460(Cl-), 542(OH-), for the L-m* compounds 128(CN-), 329(F-), 717(Cl-), 823(OH-), and 944(Br) cm(-1), respectively. These values are of similar magnitudes to those previously measured in the solid state (-J(solid) = 365, 536, 555, 160, 340, 720, 808, and 945 cm(-1), respectively). This method of using NMR to determine - J values in solution is an accurate and convenient method for complexes with strong antiferromagnetic superexchange interactions. In addition, the similarity between the solution and solid-state -J values of these complexes confirms the information gained from the T1 measurements: the structures are similar in the two states.