Synthesis and Magneto‐Structural Study of Distorted Octahedral Co II Complexes with Picolinamide and Azide ( μ 1,1 )‐Bridge

Two compounds [Co 2 (pa) 2 ( μ 1,1 ‐N 3 ) 2 ]n ( 1 ) and [Co 4 (pa) 6 ( μ 1,1 ‐N 3 ) 6 ] ( 2 ), (pa=picolinamide) were obtained and studied by electronic and magnetic spectroscopies. 1 is a polymer and 2 is a tetramer of mixed‐valence Co II/III . The N 3 − anions act as bridges between cobalt ions in the μ 1,1 coordination mode. UV‐Vis spectrum analysis showed the octahedral distortion of the compounds. ESR solution spectra revealed a low‐spin ground state, s =1/2 ( d z 2 ) for Co II . The energy gap was J>k T between levels, S = 0 to S = ± 1 , of 2 ; consequently, its transition would not be observed. 1 showed zero‐field splitting of the excited level S = ± 1with D ∼0.31 cm −1 . Hyperfine ( 59 Co, I =7/2) and superhyperfine ( 14 N, I =1) couplings were observed. Magnetic susceptibility studies (3–300 K) revealed antiferromagnetic exchange interactions in 1 and 2 with exchange coupling constants, J 1 =−108 cm −1 and J 2 =−20 cm −1 , g =2 and s = 1 / 2 , for the Co(2)‐Co(2) magnetic exchange pathways.