CoII, MnII and CuII-directed coordination polymers with mixed tetrazolate–dicarboxylate heterobridges exhibiting spin-canted, spin-frustrated antiferromagnetism and a slight spin-flop transition

Abstract

Three new paramagnetic ion-directed coordination frameworks, {[Co₄(H₂O)₂(μ₃-OH)₂(atz)₂(nip)₂]·3H₂O}_n (1), {[Mn₄(H₂O)₂(μ₃-OH)₂(atz)₂(nip)₂]·H₂O·MeOH}_n (2) and {[Cu₂(H₂O)(μ₃-OH)(atz)(nip)]·2H₂O}_n (3), were, respectively, obtained by solvo-/hydrothermal reactions of 5-amino-1H-tetrazole (Hatz), 5-nitroisophathalic acid (H₂nip) with an inorganic Co^II, Mn^II or Cu^II salt. The former two complexes are two-dimensional (2D) covalent layers built from butterfly-shaped tetranuclear M₄(μ₃-OH)₂ clusters and double atz⁻ and nip²⁻ linkers. Whereas complex 3 is a 3D framework with scarcely observed corner-sharing Cu₃(μ₃-OH) Δ-chains extended by nip²⁻ linkages, in which the anionic atz⁻ ligand acts as a reinforcement to consolidate the Δ-chain. Magnetically, due to the interplay of the anisotropy of spin carrier and magnetic exchange interactions from the adjacent spin carriers, the complexes exhibit spin-canted antiferromagnetism with a Néel temperature lower than 2.0 K for 1 and an antiferromagnetic ordering with a slight field-induced spin-flop transition for 2. In contrast, complex 3 with a local Kagomé sublattice displays spin-frustrated antiferromagnetic behavior with magnetic ordering at 16.0 K.