Two M^II tetranuclear complexes bridged only by azido, Mn₄(N₃)_7.3Cl_0.7L₄ (1) and Co₄(N₃)₈L₄ (2) in which the four M^II ions are precisely coplanar bridged only by six azido anions, were obtained by using 4,5-diazafluoren-9-one (L) as a corner ligand. Magnetic studies indicate that ferromagnetic coupling was conducted by the azido anions between M^II ions. At low temperature, 1 exhibits a large magnetocaloric effect and 2 shows field-induced multiple magnetic relaxations.