Coordination polymers containing manganese(II)-azido layers connected by dipyridyl-tetrazine and 4,4′-azobis(pyridine) linkers

Abstract

Two new polynuclear manganese (II) complexes [Mn(dptz)(N₃)₂]_n (1) and [Mn(azpy)(N₃)₂]_n (2) (where dptz = dipyridyl-tetrazine and azpy = 4,4′-azobis(pyridine)) have been synthesized by self-assembly of the ligand azide, together with dptz and azpy as secondary spacers. The compounds are characterized by single-crystal X-ray diffraction analyses and variable-temperature magnetic measurements. The structural analyses reveal that in complex 1, which is the first reported Mn (II) complex with the ligand dptz, two μ_1,3 bridging azides connect neighboring manganese ions in a zigzag manner to generate a neutral two-dimensional (2D) sheet which is further connected by the dptz ligands to form a three-dimensional (3D) framework. By contrast, complex 2 contains dimeric [Mn₂(μ_1,1-N₃)₂]²⁺ fragments linked to four identical motifs by means of four single μ_1,3-N₃ bridges, that generates a neutral 2D Mn^II–azide sheet which is further interconnected by azpy ligands to neighboring manganese ions forming an unprecedented 3D network. Variable-temperature (2–300 K) magnetic susceptibility measurements show the presence of predominantly antiferromagnetic coupling for both complexes that has been reproduced with a regular antiferromagnetic S = 5/2 chain (J) with interchain interactions (j) modeled with the molecular field approximation with J = −7.1 cm^–1 and j′ = −0.8 cm^–1 for 1 and J = −4.2 cm^–1 and j′ = 0.1 cm^–1 for 2.