Control of dimensionality and topology in nickel and cobalt coordination polymers containing adamantane-based dicarboxylate and long-spanning dipyridyl ligands

Abstract

Hydrothermal reaction of a metal nitrate, an adamantane-based dicarboxylic acid, and a long-spanning dipyridyl ligand produced six coordination polymers that were structurally characterized by single-crystal X-ray diffraction. [Ni2(adc)2(μ-H2O)(4-bpfh)2]n (1, adc=1,3-adamantanedicarboxylate, 4-bpfh=bis(4-pyridylformyl)homopiperazine) displays 1D coordination polymer ribbons based on [Ni2(OCO)2(μ-H2O)] dimeric units. {[Ni(adc)(4-bpfp)2(H2O)2]·H2O}n (2, 4-bpfp=bis(4-pyridylformyl)piperazine) shows a simple stacked (4,4) layer structure. {[Ni2(adc)2(3-bpmp)2(H2O)2]·15H2O}n (3, 3-bpmp=bis(3-pyridylmethyl)piperazine) also possesses stacked (4,4) grids, but with two different types of infinite water tapes in the interlamellar regions. {[Ni2(adc)2(4-bpmp)2(H2O)2]·3H2O}n (4, 4-bpmp=bis(4-pyridylmethyl)piperazine) again exhibits (4,4) layers, but with two-fold 2D+2D→2D parallel interpenetration. [Co(adc)(4-bpmp)]n (5) displays carboxylate bridged {Co2(OCO)2} cluster units pillared by adc and 4-bpmp ligands into an 8-connected 42464bcu topology. Use of the longer 1,3-adamantanediacetate (ada) ligand afforded {[Ni2(ada)2(4-bpmp)2(H2O)]·2H2O}n (6), which possesses dinuclear {Ni2(OCO)2(μ-H2O)} cluster units linked into [Ni2(ada)2(H2O)] ribbons, further connected by 4-bpmp ligands into a rare 6-connected self-penetrated 4867msw net. Variable temperature magnetic studies were undertaken in cases where dimeric units were evident; antiferromagnetic coupling was observed for 1 and 5, while ferromagnetic coupling with low temperature spin canting was observed for 6. Thermal properties of all new materials were also investigated.