title: Tracking "apolar" NMe4+ ions within two polyoxothiomolybdates that have the same pores: smaller clathrate and larger highly porous clusters in action.
abstract: Two nanosized polyoxothiometalates were synthesized based on linking oxomolybdate building blocks with {Mo2O2S2}(2+) groups. Remarkably, both compounds are formed selectively primarily upon changing the related concentrations in a logical way; they exhibit common structural features based on the same {Mo9O6S3}-type pores, which result in connections between {Mo6O21} pentagons and {Mo2O2S2}(2+) linkers. Whereas the much larger spherical Mo132-type Keplerate contains twenty pores, the smaller Mo63 -type cluster remarkably contains only two. The two compounds and a similar Keplerate exhibit interesting supramolecular properties related to interactions with the unusual predominantly apolar NMe4(+) cations. Structural characterization of the Mo63 -type compound reveals in the solid state a clathrate-like species that contains four NMe4(+) cations embedded in two types of structurally well-adapted pockets. Related NMR spectroscopic investigations in solution using NMe4(+) as the NMR spectroscopic probe are in agreement with the solid-state description. (1)H NMR spectroscopic experiments (1D variable-temperature, 2D total correlation spectroscopy (TOCSY), exchange spectroscopy (EXSY), and diffusion-ordered spectroscopy (DOSY)) feature firmly immobilized and mobile NMe4(+) ions in relationship with the type of host-guest arrangements. The use of the (1)H NMR DOSY spectroscopic methodology has been successfully applied to track the interactions of the NMe4(+) cations with the {Mo9O6S3} pores of a sulfurated Keplerate, thereby allowing the first quantitative analysis of this type of plugging process. The stability constant K=(210±20) mol(-1)  L is discussed related to the character of the process.
authors: Nikolaev Institute of Inorganic Chemistry, Siberian Branch of the Russian Academy of Sciences, Novosibirsk 630090 (Russia).
authors: Vladimir S
authors: VS
authors: Korenev
authors: Antoine G
authors: AG
authors: Boulay
authors: Mohamed
authors: M
authors: Haouas
authors: Fatma
authors: F
authors: Bannani
authors: Vladimir P
authors: VP
authors: Fedin
authors: Maxim N
authors: MN
authors: Sokolov
authors: Emmanuel
authors: E
authors: Terazzi
authors: Somenath
authors: S
authors: Garai
authors: Achim
authors: A
authors: Müller
authors: Francis
authors: F
authors: Taulelle
authors: Jérôme
authors: J
authors: Marrot
authors: Nathalie
authors: N
authors: Leclerc
authors: Sébastien
authors: S
authors: Floquet
authors: Emmanuel
authors: E
authors: Cadot
keywords: NMR spectroscopy; molybdenum; polyoxometalates; supramolecular chemistry; thiometalates