The synthesis of two new radical-bridged compounds [Co-3(bptz)(3)(dbm)(3)]center dot 2toluene (1) and [Co-4(bptz)(4)(dbm)(4)]center dot 4MeCN (2) (bptz = 3,6-bis(pyridyl)-1,2,4,5-tetrazine; dbm = 1,3-diphenyl-1,3-propanedionate) is reported. The presence of the ligand-centered radical has been confirmed by X-ray crystallography and SQUID magnetometry. These complexes are the first metallacycles bearing nitrogen heterocyclic radicals as bridges. Magnetic studies reveal strong, antiferromagnetic metal center dot center dot center dot radical coupling with coupling 'constants of J = -67.5 and -66.8 cm(-1) for 1 and 2, respectively. DFT calculations further support the strong antiferromagnetic coupling between Co-II ions and bptz radicals and confirm S = 3 and S = 4 spin ground states for 1 and 2, respectively.