Integrating 31P DOSY NMR Spectroscopy and Molecular Mechanics as a Powerful Tool for Unraveling the Chemical Structures of Polyoxomolybdate‐Based Amphiphilic Nanohybrids in Aqueous Solution. Issue 18 (11th April 2014)

• Record Type: Journal Article
• Authors: Shestakova , Pavletta; Absillis, Gregory; Martin‐Martinez, Francisco J.; De Proft, Frank; Willem, Rudolph; Parac‐Vogt, Tatjana N.
• Is Part Of: Chemistry. Volume 20:Issue 18(2014)
• Page Start: 5258
• Page End: 5270
• Publication Date: 2014-04-11
• Subjects: Chemistry -- Periodicals; 540
• DOI: 10.1002/chem.201304969
• Languages: English
• ISSNs: 0947-6539

Abstract

<abstract abstract-type="main" xml:lang="en"> <title>Abstract</title> <p>Novel organic–inorganic hybrids of various sizes were generated by reaction of 1, 8‐octanediphosphonic acid (ODP) and (NH<sub>4</sub>)<sub>6</sub>Mo<sub>7</sub>O<sub>24</sub> in aqueous solution. The formation of rodlike hybrids with variable numbers of covalently bound ODP and polyoxomolybdate (POM) units can be tuned as a function of increasing (NH<sub>4</sub>)<sub>6</sub>Mo<sub>7</sub>O<sub>24</sub> concentration at fixed ODP concentration. The chemical structure of the ODP/POM hybrids was characterized by <sup>1</sup>H, <sup>31</sup>P, and <sup>95</sup>Mo NMR spectroscopy. Heteronuclear <sup>31</sup>P DOSY (diffusion‐ ordered NMR spectroscopy) and molecular mechanics (MM) calculations were applied to determine the size and shape of the nanosized hybrids generated at various ODP/POM ratios. For this purpose, the structures of ODP/POM hybrids with variable numbers of ODP and POM units were optimized by MM and then approximated as cylinder‐shaped objects by using a recently described mathematical algorithm. The thus‐obtained cylinder length and diameter were further used to calculate the expected diffusion coefficients of the ODP/POM hybrids. Comparison of the calculated and experimentally determined diffusion coefficients led to the most probable ODP/POM hybrid length for each sample composition. The <sup>31</sup>P DOSY results show that the length of the hybrids increases with increasing POM concentration and reaches a maximum corresponding to an average of 8 ODP/7 POM units per chain at a sample composition of 20 m<sc>M</sc> ODP and 14 m<sc>M</sc> POM. With excess POM, above the latter concentration, the formation of shorter‐chain hybrids terminated by Mo<sub>7</sub> clusters at one or both ends was evidenced on further increasing the POM concentration. The results demonstrate that the combination of <sup>31</sup>P DOSY and MM, although virtually unexplored in POM chemistry, is a powerful innovative strategy for the detailed characterization of nanosized organic–inorganic POM‐based hybrids in solution.</p> </abstract>