The 1:1 mixture of Co(Brhfpip)(2) and D1py(2) gave isomeric diazocobalt complexes, 1 and 2, formulated by [Co(Brhfpip)(2)(D1py(2))](n). Complexes 1 and 2 have zigzag and linear chain structures by the cis and trans coordination of pyridine units in D1py(2), respectively. After irradiation of microcrystalline samples, the generated carbene interacted with the cobalt ion to form ferromagnetic chains, lc and 2c. Those isomeric chains exhibited slow magnetic relaxation with U-eff = 93 and 87 K and H-c = 20 and 13 kOe at 1.9 K for 1c and 2c, respectively.