Cu(HCO{sub 2}){sub 2}L{L = pyrazine, 4,4'-bipyridine} : employing the formate anion as a building block in three-dimensional coordination polymers.
The formate anion, HCO{sub 2}{sup -}, has been used infrequently as a building block in molecular magnetic materials. We have synthesized and structurally and magnetically characterized two new Cu(HCO{sub 2}){sub 2}L compounds, where L represents pyrazine (pyz) and 4,4'-bipyridine (bipy). The single crystal structure of Cu(HCO{sub 2}){sub 2}(pyz), 1, has been established by both X-ray (295 K) and neutron diffraction (20 K). The compound consists of tetragonally-elongated CuN{sub 2}O{sub 4} octahedra made up of four bridging formate anions and two neutral pyz ligands. The 3D polymeric network is comprised of 2D Cu(HCO{sub 2}){sub 2} layers that are fused together by the linear pyz spacers, which form Cu-pyz-Cu chains. Cu(HCO{sub 2}){sub 2}(bipy), 2, is chiral and has a more complex framework than 1. The CuO{sub 4}N{sub 2} octahedra align in two unique orientations relative to one another, owing to the 4{sub 1} and 2{sub 1} screw axes that lie along the a and b-axes. The octahedra are connected via four bridging HCO{sub 2}{sup -} anions and two bridging bipy ligands, resulting in a unique 3D scaffold structure. The magnetic behavior of 1 and 2 indicates antiferro- and ferromagnetic interactions, respectively, and the exchange couplings in both 1 and 2 are well reproduced by a 1D spin Hamiltonian. Spin dimer analysis was carried out to evaluate the relative strengths of the various spin exchange paths. It is found that the interaction through HCO{sub 2}{sup -} is comparatively weak, and the strong Cu{sup 2+} spin exchange interactions are mediated by the pyz and bipy ligands via the {sigma}-pathway. A possible reason as to why 2 displays ferromagnetic coupling is proposed.
- Research Organization:
- Argonne National Lab. (ANL), Argonne, IL (United States)
- Sponsoring Organization:
- USDOE Office of Science (SC)
- DOE Contract Number:
- DE-AC02-06CH11357
- OSTI ID:
- 961253
- Report Number(s):
- ANL/MSD/JA-45779; JCDTBI; TRN: US201011%%526
- Journal Information:
- J. Chem. Soc., Dalton Trans., Vol. 14, Issue 2003; ISSN 0300-9246
- Country of Publication:
- United States
- Language:
- ENGLISH
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