Abstract
In the title metal-organic framework, [Fe(C4H3BrN2)2{Cu(CN)2}2] n , the FeII cation is located on an inversion center and has a slightly elongated octa-hedral coordination environment [FeN6], ligated by two pyrazine N atoms of symmetry-related bridging 2-bromo-pyrazine mol-ecules in the axial positions and by four N atoms of pairs of symmetry-related cyanido groups in the equatorial positions. The CuI center has a fourfold coordination environment [CuC3N], with an almost perfect trigonal-pyramidal geometry, formed by three cyanido C atoms and an N atom of a bridging 2-bromo-pyrazine mol-ecule. Copper(I) centers related by a twofold rotation axis are bridged by two carbon atoms from a pair of μ-CN groups, resulting in Cu2(CN)2 units. Each Cu2(CN)2 unit is linked to six FeII cations via a pair of linear CN units, the pair of μ-CN groups and two bridging 2-bromo-pyrazine ligands, resulting in the formation of a metal-organic framework, which is additionally stabilized by the short Cu⋯Cu contacts of 2.4450 (7) Å.
Highlights
The rational design and synthesis of cyanide-based coordination materials is of key interest today
The Hofmann clathrate analogues of the general formula [MA(L)x{MB(CN)y}] constitute another prominent example of bimetallic cyanometallates (Hofmann & Kuspert, 1897), which are famous for their switchable magnetic properties (Munoz & Real, 2011)
The deviation from an ideal octahedron of the FeII center can be described by the octahedral distortion parameter Æ|90 À | = 23.36, where is a cis-N— Fe—N angle
Summary
The rational design and synthesis of cyanide-based coordination materials is of key interest today. Prussian blue analogues form networks with general formula AMA[MB(CN)6] (A = alkali metal ion, MA and MB = transition metal ions) (Keggin & Miles, 1936) These complexes have a cubic structure in which the metallic centers are bridged in an MA—C N—MB fashion, forming threedimensional frameworks. Another class of heterometallic cyanide coordination compounds that has attracted much attention is represented by f–d complexes composed of lanthanide(III) ions and dblock cyanometallates. This type of materials has been shown to have exceptional photoluminescent properties (Chorazy et al, 2017). We describe the crystal structure of a new Hofmann clathrate analogue of general formula [Fe(Brpz)2{Cu(CN)2}2]n
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