Hydrogen-bond tuning of ferromagnetic interactions: Synthesis, structure and magnetic properties of polynuclear copper(ii) complexes incorporating p-block oxo-anions

Robert Patrick Doyle, Miguel Julve, Francesc Lloret, Mark Nieuwenhuyzen, Paul E. Kruger

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Abstract

The reaction of copper(ii) hydroxide with 2,2′-bipyridine (bipy) (1 : 1) in alkaline aqueous solution (pH 14) at room temperature affords the alternating carbonate/hydroxo-bridged copper(ii) polymeric chain compound ([Cu3(bipy)3(µ-OH)2(µ-CO3)2]·11H2O)n, 1, as determined by single-crystal X-ray diffraction. The structure of 1 is built up from two similar centro-symmetric dinuclear [(bipy)Cu(µ-OH)]2cores which link together via bridging carbonate groups to mononuclear [(bipy)Cu] fragments to form the chain. Interdigitation of adjacent chains through π–π interactions, which involve each bipy ligand, forms sheets that are separated by the water molecules of crystallisation. Variable-temperature magnetic susceptibility measurements have shown that 1 behaves as an isolated spin doublet with two non-interacting spin triplets with the magnetic coupling through the bis-µ-hydroxo bridges being strongly ferromagnetic in nature. The hydrothermal reaction of copper(ii) hydroxide, bipy and ammonium hydrogenphosphate (pH 8) yields a dinuclear copper(ii) complex of formula ([Cu2(bipy)2(µ-OH)2(HPO4)(H2O)]·4H2O), 2, as determined by single-crystal X-ray diffraction. The structure of 2 consists of an asymmetric dinuclear bis-µ-hydroxo copper(ii) core with a monodentate hydrogenphosphate dianion coordinating to one copper(ii) atom (above) and a water molecule to the other (below). Intra- and inter-molecular hydrogen bond interactions involving the hydrogenphosphate, water molecules and bis-µ-hydroxo groups link adjacent dinuclear fragments into chains, which interdigitate to form sheets that are separated by the water molecules of crystallisation. The investigation of the magnetic properties of 2 showed that the strength of the ferromagnetic interaction through the bis-µ-hydroxo bridges is influenced by the significant out-of-plane displacement of the hydrogen atom of the hydroxo groups, brought about through hydrogen bonding to the hydrogenphosphate ligand, and yielded the strongest ferromagnetic coupling yet reported for the bis-µ-hydroxo copper(ii) core.

Original languageEnglish (US)
Pages (from-to)2081-2088
Number of pages8
JournalJournal of the Chemical Society. Dalton Transactions
Issue number17
DOIs
StatePublished - Apr 20 2006

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ASJC Scopus subject areas

  • Chemistry(all)

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