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Marc Schmidtmann

Publications and source records attributed to Marc Schmidtmann.

13 recordsLinked to original sources
PubMed2005

A small cavity with reactive internal shell atoms spanned by four {As(W/V)9}-type building blocks allows host-guest chemistry under confined conditions.

The reaction of [H2As(III)W18O60]7- with VO2+ and SO4(2-) ions in aqueous solution leads to a V(IV)/V(V) mixed-valence cluster anion containing the {As4M40O140}-type cryptand which has a high formation tendency. An important result is that it exhibits a new type of reactive internal cavity shell. The correspondingly obtained compound Na(NH4)20[{(V(IV)O(H2O))(V(IV)O)2(SO4)2}{(As(III)W9O33)2(As(III)W7.5V(V)1.5O31)2(WO2)4}] x 40 H2O (1), which can also be synthesized from a precursor with the preorganized cryptand, was characterized by elemental and thermogravimetric analyses (determination of crystal water content), redox titrations (determination of the number of V(IV) centers), electronic absorption as well as vibrational spectra, single-crystal X-ray structure analysis (including bond valence sum calculations), and magnetic susceptibility measurements. The relatively small central cavity--formed by the linking of four {AsM9}-type lacunary units (M = W/V) by four WO6 octahedra--allows positioning of a variety of cationic as well as anionic "guests" under confined conditions according to a new approach: replacement of some of the W by V atoms leads to high reactivity of the internal cavity shell as a result of relatively weak VO bonds compared to the WO bonds. This allows an interesting "encapsulation chemistry" with new options. In the present case the cavity contains besides an arrangement of three V(IV) centers, two sulfate groups that replace O atoms of the {AsM9} units as well as an interesting hydrogen bond situation.

Journal Article↗
PubMed2004

En route to coordination chemistry under confined conditions in a porous capsule: Pr3+ with different coordination shells.

The highly charged nanocontainer capsule of the type [pentagon]12[linker]30 identical with [(Mo)Mo5O21(H2O)6]12[Mo2O4(SO4)]30 with 20 nanosized pores and channels allows the entrance of cations like Pr3+: the latter are positioned at two different sites and have two different coordination shells, corresponding to a coordination chemistry under confined conditions; a fascinating aspect is that capsule encapsulated water shells fixed by hydrogen bonds act formally as polydentate ligands.

Journal Article↗
PubMed2003

Synergetic activation of "silent receptor" sites leading to a new type of inclusion complex: integration of a 64-membered ring comprising K+ and SO4(2-) ions into a molybdenum oxide-based nanoobject.

The new type of inclusion species [Mo(VI)114Mo(V)32O429(H2O)50(KSO4)16]30- comprising 16 encapsulated K+ and SO4(2-) ions shows an unusual 64-membered [K(SO4)]16 ring integrated into a wheel-shaped type nanocluster host; it is formed by a synergetically induced functional complementarity and represents a text-book example of a very complex non-biological material.

Chemical Phenomena↗
PubMed2002

Heterobinuclear complexes as building blocks in designing extended structures.

The heterobinuclear complex [CuPrL(NO(3))(3)] has been used as a building block for the construction of a two-dimensional coordination polymer with the formula [CuPrL(NO(3)(2)(IN)], 1 (L(2-) = the dianion of the compartmental Schiff-base ligand obtained from the 2:1 condensation of 3-methoxysalicylaldehyde with 1,3-propanediamine; IN(-) = the isonicotinate ion). The heterobinuclear units, [CuPrL(NO(3))(2)](+), are connected through the unsymmetrical exo-bidentate ligands, IN(-), leading to a unique extended structure. Crystal data for compound 1: FW, 790.94; monoclinic, space group P2(1)/n, a = 11.2837(3) A, b = 14.7785(4) A, c = 16.9745(4) A, beta = 100.427(1) degrees; V = 2783.86(12) A(3); Z = 4; R1 = 0.0210, wR2 = 0.0562 [I > 2sigma(I)].

Journal Article↗
PubMed2002

Urea as 'deus ex machina' in giant molybdenum blue type cluster synthesis: an unusual hybrid compound with perspectives for related nano, supramolecular and extended structures.

The reaction of an aqueous solution of ammonium heptamolybdate with sodium dithionite and urea--a glue and cluster hydration shell destructing agent corresponding to its role in inclusion compound chemistry--at low pH value results in the formation of nanosized ring shaped molybdenum-oxide based clusters which in a short time get linked to chains.

Journal Article↗
PubMed2001

"Nanoobjects" by Self-Assembly Concomitant with Modifications under Alterable Boundary Conditions: Incorporation of Paramagnetic Metal Centers (Cu(2+)) in Ring-Shaped Molybdenum-Oxide Based Clusters The authors thank Prof. D. Gatteschi, University of Florence (Italy), for helping with the interpretation of the ESR spectrum, and Dipl.-Chem. A. Berkle and Dr. J. Hockemeyer, University of Bielefeld (Germany), for their collaboration. C. R. thanks the Alexander von Humboldt Foundation for her fellowship. Financial support by the Deutsche Forschungsgemeinschaft and the Fonds der Chemischen Industrie is gratefully acknowledged.

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Journal Article↗