"Gating" the pores of a metal oxide based capsule:: After initial cation uptake subsequent cations are found hydrated and supramolecularly fixed above the pores
"Gating" the pores of a metal oxide based capsule:: After initial cation uptake subsequent cations are found hydrated and supramolecularly fixed above the pores
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DOI：
10.1002/anie.200501994
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发表时间：
2006-01-01
影响因子：
16.6
通讯作者：
Berkle, A
中科院分区：
文献类型：
--
作者：
Müller, A;Zhou, YS;Berkle, A
valence sum (BVS) calculations).[7] The release of NH4+ ions from 1a, which occurs during the formation of 2a, was studied by 15N-HSQC NMR (15N-decoupled) spectroscopy. The structure analysis shows that 2a has—as does 1a [3a] and several other related capsules [2]—the “classical” approximate icosahedral {pentagon} 12 {linker} 30 skeleton. This structure can also be easily demonstrated by Raman spectroscopy as 2a shows the characteristic “few-line” spectrum in which the highest intensity band at 876cmÀ1 is assigned to the interesting, totally symmetric Ag breathing vibration of the (large number of) 240 bridging oxygen atoms in the capsule. Remarkably, in 2a, Pr3+ centers are found inside as well as in hydrated form outside the capsule (Figure 1). Each of the five encapsulated Pr3+ ions, which are disordered over 30 equivalent positions forming an icosidodecahedron, is coordinated to a sulfate group that acts as a bidentate ligand to a {Mo2} linker. The coordination sphere of the internal Pr3+ ions is completed by the oxygen atoms of the encapsulated water molecules. In this sense the water molecules, which are formally organized in shells and linked by strong hydrogen bonds,“behave” as polydentate/macrocyclic ligands;[8a] structurally speaking the encapsulated water molecules in 2a form a partially occupied {H2O} 60+ 20 type shell.[8b] Additionally, in this case the {H2O} 60+ 20 shell, together with the Pr positions inside the cavity, form an interesting spherical shell type aggregate; the Pr positions are located a little below/inside the water cage (Figure 2).The important discovery is that in crystals of 2 ten Pr3+ ions are, as a result of a kind of pore closing, found located above the pores, which does not happen with lower Pr3+ ion concentrations; in those cases the Pr3+ ions are only found encapsulated within the cavity (see details in ref.[9] and the Note added in proof ref.[20]). The non-encapsulated Pr3+ ions are found mostly with classical ninefold hydration [10a–d]
