The building block approach to extended solids: 3,5-pyrazoledicarboxylate coordination compounds of increasing dimensionality

Abstract

A series of M(II) complexes with the ligand 3,5-pyrazoledicarboxylic acid (H₃dcp) has been synthesised mainly via hydrothermal reactions and their structures have been characterised. Simple mononuclear [Ni(Hdcp)(H₂O)₄] (1), Na₂(μ-H₂O)₂(H₂O)₈[Ni(Hdcp)₂(H₂O)₂] (2), [M(H₂dcp)₂(H₂O)₂]·2H₂O [M = Co (3), Zn (4) and Cu (5)] and dinuclear (Et₃NH)₂[Cu₂(dcp)₂(H₂O)₂] (9) building blocks have been isolated and subsequently linked into 1-D chains [Mn(Hdcp)(H₂O)₂]_∞ (6), [{Mn(H₂O)₄}{Mn(Hdcp)₂(H₂O)₂}·4H₂O]_∞ (7), [Ni₂(Hdcp)₂(μ-H₂O)₂(H₂O)₂]_∞ (8), [{Ni(H₂O)₄}{Ni₂(dcp)₂(H₂O)₄}]_∞ (11), or 3-D arrays [{Na₂(μ-H₂O)₂}{Cu₂(dcp)₂}]_∞ (10), [Cu₃(dcp)₂(H₂O)₄]_∞ (12), utilising novel bridging modes of the H₃dcp ligand. In the unprecedented 1-D Ni(II) chain 8, rarely reported double aqua-bridges link the Ni(II) ions to form an inter-linked double stranded chain. The magnetic properties of these compounds have been measured and reveal a variety of antiferromagnetic coupling behaviours induced by the ligand bridging modes.