Manganese(ii) coordination polymers with mixed azide and pyridylbenzoate N-oxide ligands: Structures and magnetism

Two novel Mn(ii) coordination polymers with azide and 4-(4-pyridyl)benzoic acid N-oxide (4,4-Hopybz) were synthesized and structurally and magnetically characterized. They are formulated as {[Mn ₂(4,4-opybz) ₂(N ₃) ₂(H ₂O) ₂] ·H ₂O} _n (1) and {[Mn ₄(4,4-opybz) ₅(N ₃)(H ₂O) ₈](N ₃) ₂·2H ₂O} _n (2). Compound 1 contains 2D coordination layers in which the infinite Mn(ii) chains with alternating (μ-EO-N ₃) ₂(μ-COO) (EO = end-on) and (μ-COO)(μ-O) bridges are interlinked by the backbones of the organic ligands. Compound 2 is a 3D metal-organic framework in which the unique linear tetranuclear clusters with (μ-EO-N ₃)(μ-COO) and (μ-COO)(μ-O) bridges are cross-linked by organic backbones, and it represents a new example of the rare 8-connected self-catenated 3D net with the point symbol 4 ¹⁶·6 ¹². Magnetic analyses on the compounds have been performed in the classical-spin approximation, revealing that all the above-mentioned mixed bridging motifs induce weak antiferromagnetic interactions between Mn(ii) ions.