Self-assembly of Ni(ii) metallacycles (a square and a triangle) supported by tetrazine radical bridges

Abstract

Two Ni(II) molecular metallacycles of [Ni₄(bpz*tz˙⁻)₄(N₃)₄] (1) and [Ni₃(bpz^Phtz˙⁻)₃(pz^Ph(Cl)tz˙⁻)₃]·1.3CH₃OH·9.3H₂O (2) (bpz*tz = 3,6-bis(3,5-dimethyl-pyrazolyl)-1,2,4,5-tetrazine; bpz^Phtz = 3,6-bis(3-phenyl-pyrazolyl)-1,2,4,5-tetrazine; and pz^Ph(Cl)tz = 3-bis(3-phenyl-pyrazolyl)-6-Cl-1,2,4,5-tetrazine) are reported. The single-crystal X-ray diffraction study reveals that 1 displays a square structure while 2 shows a triangle structure due to the steric effect, both bearing tetrazine radical bridges. Furthermore, magnetic studies reveal that the Ni–radical interaction in 1 is strongly ferromagnetic with a coupling constant (J) of 90.8 cm⁻¹ in the 2J formalist, while the overall antiferromagnetic behaviour of 2 is presumably due to the compete ferromagnetic (for the Ni–radical_bridging interaction with J₁ = 95.4 cm⁻¹) and antiferromagnetic (for the Ni–radical_terminal interaction, J₂ = −57.5 cm⁻¹) couplings.