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Polyphosphate ions encapsulated in oxothiomolybdate rings: synthesis, structure, and behavior in solution
Emmanuel Cadot1, Marie-José Pouet, Chantal Robert-Labarre
1Institut Lavoisier, IREM, UMR CNRS 8637, Université de Versailles Saint Quentin, 45 Avenue des Etats-Unis, 78035 Versailles, France. cadot@chimie.uvsq.fr
Journal of the American Chemical Society
|July 22, 2004
Summary
New cyclic oxothiomolybdates encapsulate polyphosphate ions and halide guests. These complexes exhibit unique structural changes and solution behaviors influenced by halide ion stability and phosphate exchange dynamics.
Area of Science:
- Inorganic Chemistry
- Supramolecular Chemistry
- Materials Science
Background:
- Cyclic oxothiomolybdates are versatile inorganic hosts capable of encapsulating various guest molecules.
- Understanding the interactions between these inorganic frameworks and polyphosphate ions is crucial for designing novel functional materials.
- The influence of guest ions on the structural conformation and stability of these cyclic complexes remains an active area of research.
Purpose of the Study:
- To synthesize and characterize novel cyclic oxothiomolybdates incorporating polyphosphate ions and halide guests.
- To investigate the structural transformations and solution dynamics of these complexes.
- To elucidate the role of halide ions in the supramolecular interactions and conformational changes within the inorganic ring.
Main Methods:
- Synthesis of cyclic oxothiomolybdates in aqueous medium.
- Structural characterization using single-crystal X-ray diffraction.
- Solution behavior analysis via 31P Nuclear Magnetic Resonance (NMR) spectroscopy, including variable temperature and COSY experiments.
- Elemental analysis and infrared spectroscopy for further characterization.
Main Results:
- Isolation and structural determination of three novel cyclic oxothiomolybdates: K(5)[Cl(P(2)O(7)]Mo(12)S(12)O(12)(OH)(12)(H(2)O)(4)].22H(2)O (1), K(6)[(HPO(4))(P(2)O(7))Mo(12)S(12)O(12)(OH)(12)(H(2)O)(2)].19H(2)O (2), and Rb(3)[(H(2)P(3)O(10))Mo(10)S(10)O(10)(OH)(10)].17.5H(2)O (3).
- Compound 1 features a dodecanuclear ring encapsulating a chloride ion and a pyrophosphate group, with the supramolecular interaction maintained in solution.
- Selective substitution of chloride in 1 with a monohydrogenophosphate group leads to compound 2, exhibiting a conformational change to a 'pear-shape'.
- Compound 3, formed with triphosphate, displays a 'heart-shaped' decanuclear ring with a blocked host-guest conformation.
- The stability of supramolecular association with halide guests decreases in the order Cl > Br > I.
- Phosphate exchange is observed in compound 2, while compound 3 shows a conformationally blocked host-guest system.
Conclusions:
- Novel cyclic oxothiomolybdates can be synthesized to encapsulate polyphosphate ions and halide guests, demonstrating tunable structural and dynamic properties.
- The nature of the encapsulated halide ion significantly influences the stability of the supramolecular association and the conformational behavior of the inorganic ring.
- These findings provide insights into the design of complex inorganic host-guest systems with potential applications in molecular recognition and catalysis.
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