Nickel(II) Chain with Alternating End-On/End-to-End Single Azido Bridges: A Combined Structural, Magnetic, and Theoretical Study

The reaction of a tridentate Schiff base LH (L-:  1,1,1-trifluoro-7-(dimethylamino)-4-methyl-5-aza-3-hepten-2-onato)
with a Ni(II) salt in the presence of azide salt has led to a new alternating end-on (EO)/end-to-end (EE) azido-bridged Ni(II) chain of formula {[Ni2(μ1,1-N3)(μ1,3-N3)(L)2(MeOH)2]}n. Its originality lies in the presence of single EE
and EO coordination modes for the azide. It crystallizes in the C2/c space group, a = 21.570(7) Å, b = 10.79(1)
Å, c = 16.154(5) Å, β = 120.81(2)°, Z = 4. The chain can be viewed as {Ni2(N3)(L)2(MeOH)2}+ dimeric units
linked to each other in a zigzag pattern by the other azide. Magnetic susceptibility and magnetization measurements
have been performed and revealed that the chain can magnetically be depicted as isolated {Ni2(N3)} units exhibiting
antiferromagnetic interaction (JAF ∼ −37 cm-1). Ab initio calculations confirmed the efficient magnetic coupling
through the EE bridge and vanishingly small EO {Ni2(μ1,1-N3)} interactions.