Encapsulation of Cyanometalates by a Tris-macrocyclic Ligand Tricopper(II) Complex: Syntheses, Structural Variation, and Magnetic Exchange Coupling Pathways
✍ Scribed by Mihail Atanasov; Peter Comba; Yaroslaw D. Lampeka; Gerald Linti; Thomas Malcherek; Ronald Miletich; Alexander I. Prikhod'ko; Hans Pritzkow
- Publisher
- John Wiley and Sons
- Year
- 2006
- Tongue
- English
- Weight
- 572 KB
- Volume
- 12
- Category
- Article
- ISSN
- 0947-6539
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✦ Synopsis
Abstract
The reaction of [M(CN)~6~]^3−^ (M=Cr^3+^, Mn^3+^, Fe^3+^, Co^3+^) and [M(CN)~8~]^4−/3−^ (M=Mo^4+/5+^, W^4+/5+^) with the trinuclear copper(II) complex of 1,3,5‐triazine‐2,4,6‐triyltris[3‐(1,3,5,8,12‐pentaazacyclotetradecane)] ([Cu~3~(L)]^6+^) leads to partially encapsulated cyanometalates. With hexacyanometalate(III) complexes, [Cu~3~(L)]^6+^ forms the isostructural host–guest complexes [{[Cu~3~(L)(OH~2~)~2~][M(CN)~6~]~2~}{M(CN)~6~}]⋅[M(CN)~6~]⋅30 H~2~O with one bridging, two partially encapsulated, and one isolated [M(CN)~6~]^3−^ unit. The octacyanometalates of Mo^4+/5+^ and W^4+/5+^ are encapsulated by two tris‐macrocyclic host units. Due to the stability of the +IV oxidation state of Mo and W, only assemblies with [M(CN)~8~]^4−^ were obtained. The Mo^4+^ and W^4+^ complexes were crystallized in two different structural forms: {Cu~3~(L)(OH~2~)}~2~{Mo(CN)~8~}~8~⋅15 H~2~O with a structural motif that involves isolated spherical [{Cu~3~(L)(OH~2~)}~2~{M(CN)~8~}]^8+^ ions and a “string‐of‐pearls” type of structure {[Cu~3~(L)]~2~[M(CN)~8~]}{M(CN)~8~}~4~⋅ 20 H~2~O, with [M(CN)~8~]^4−^ ions that bridge the encapsulated octacyanometalates in a two‐dimensional network. The magnetic exchange coupling between the various paramagnetic centers is characterized by temperature‐dependent magnetic susceptibility and field‐dependent magnetization data. Exchange between the Cu⋅⋅⋅Cu pairs in the [Cu~3~(L)]^6+^ “ligand” is weakly antiferromagnetic. Ferromagnetic interactions are observed in the cyanometalate assemblies with Cr^3+^, exchange coupling of Mn^3+^ and Fe^3+^ is very small, and the octacoordinate Mo^4+^ and W^4+^ systems have a closed‐shell ground state.