A novel 2D coordination polymer consisting of ferromagnetic Ni(ii) chains with alternating double EO-azide bridges and (EO-azide)bis(carboxylate) triple bridges exhibits solvent-modulated metamagnetism, and the reversible dehydration/hydration processes are accompanied by significant changes in critical temperature, critical field and hysteresis.
By using a neutral inner-salt-type dicarboxylate as coligand, a novel two-dimensional (2D) manganese(II) coordination polymer, [Mn(L)(N(3))]ClO(4) x 1/2 H(2)O (L = 1,3-bis(3-carboxylatopyridinium)propane), was synthesized, and characterized by X-ray crystallography and magnetic measurements. The compound contains uniform Mn(II) chains with simultaneous azide and carboxylate bridges between adjacent Mn(II) ions. The formally negative chains are interlinked by the positively-charged 1,3-bis(pyridinium)propane spacer, and the spiral conformation of the spacer imports intriguing helical features to the resulting 2D network, in which [MnL] helices are connected by sharing metal centers with alternating centro- and C(2)-symmetry. The triple (azide)bis(carboxylate) bridge mediates overall antiferromagnetic coupling with J = -3.0 cm(-1), as a result of the competition between the antiferromagnetic (carboxylate) and ferromagnetic (azide) pathways.
Various zwitterionic carboxylate ligands form MnII coordination polymers with carboxylate and pseudo‐halide bridges mixed in different ways. With mono‐zwitterions, [Mn(N3)2(L1)(H2O)]n and [Mn(N3)2(L2)]n contains 1D chains with (μ‐1,1‐N3)(μ‐1,3‐OCO) and (μ‐1,1‐N3)2(μ‐1,3‐OCO) bridges, respectively. With di‐zwitterions, [Mn(N3)(L3)]n(ClO4)n forms a 2D network based on chains with (μ‐1,1‐N3)(μ‐1,3‐OCO)2 bridges, whereas [Mn2(X)4(L4)]n·2nH2O (X = N3 or NCO) are interpenetrating 3D networks based on chains with (μ‐1,1‐X)2(μ‐1,3‐OCO) bridges. With a tri‐zwitterion, [Mn7(N3)14(OH)2(L5)(H2O)6]n·4nH2O is a 2D network based on a novel chain in which μ‐1,1‐N3‐ and μ‐1,3‐OCO‐bridged trinuclear motifs and μ3‐OH‐ and μ‐1,1‐N3‐bridged tetranuclear motifs are linked by μ‐1,3‐N3 and μ3‐1,1,3‐N3. All compounds exhibit antiferromagnetic interactions, the magnitude of which depends upon the nature and mixing mode of the bridges, and follow the trend (μ‐N3)(μ‐OCO) < (μ‐N3)(μ‐OCO)2 < (μ‐N3)2(μ‐OCO) < (μ‐NCO)2(μ‐OCO).
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