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Materials 2010, 3(1), 64-75; doi:10.3390/ma3010064
Article

Coordination of {Mo142} Ring to La3+ Provides Elliptical {Mo134La10} Ring with a Variety of Coordination Modes

1,2
,
1,3
 and
1,4,*
1 Chemical Resources Laboratory, Tokyo Institute of Technology, R1-21, 4259 Nagatsuta, Midori-ku, Yokohama 226–850, Japan 2 Department of Applied Chemistry, College of Engineering, Chubu University, 1200 Matsumoto, Kasugai, Aichi 487–8501, Japan 3 Matsuda Sangyo Co., Ltd., Shinjuku Nomura Building 6th Fl., 1-26-2 Nishishinjuku, Shinjuku-ku, Tokyo 163–0558, Japan 4 (Inc.) MO Device, 2-14-10 Kanaiwa-higashi, Kanazawa 920–0335, Japan
* Author to whom correspondence should be addressed.
Received: 29 November 2009 / Revised: 23 December 2009 / Accepted: 25 December 2009 / Published: 28 December 2009
(This article belongs to the Special Issue Polyoxometalate Compounds)
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Abstract

A28-electron reduced C2h-Mo-blue 34Ǻ outer ring diameter circular ring, [Mo142O429H10(H2O)49(CH3CO2)5(C2H5CO2)]30- (≡{Mo142(CH3CO2)5(C2H5CO2)}) comprising eight carboxylate-coordinated (with disorder) {Mo2} linkers and six defect pockets in two inner rings (four and three for each, respectively), reacts with La3+ in aqueous solutions at pH 3.5 to yield a 28-electron reduced elliptical Ci-Mo-blue ring of formula [Mo134O416H20(H2O)46{La(H2O)5}4{La(H2O)7}4{LaCl2(H2O)5}2]10- (≡{Mo134La10}), isolated as the Na10[Mo134O416H20(H2O)46{La(H2O)5}4{La(H2O)7}4{LaCl2(H2O)5}2]·144 H2O Na+ salt. The elliptical structure of {Mo134La10} showing 36 and 31 Å long and short axes for the outer ring diameters is attributed to four (A-D) modes of LaO9/LaO7Cl2 tricapped-trigonal-prismatic coordination (TTP) geometries. Two different LaO2(H2O)7 and one LaO2(H2O)2Cl2 TTP geometries (as A-C modes) for each of two inner rings result from the coordination of all three defect pockets of the inner ring for {Mo142(CH3CO2)5(C2H5CO2)}, and two LaO4(H2O)5 TTP geometries (as D mode) result from the displacement of two (acetate/propionate-coordinated) binuclear {Mo2} linkers with La3+ in each inner ring. The isothermal titration calorimetry (ITC) of the ring modification from circle to ellipsoid, showing the endothermic reaction of [La3+]/[{Mo142(CH3CO2)5(C2H5CO2)}] = 6/1 with DH = 22 kJ×mol-1, DS = 172 J×K-1×mol-1, DG = −28 kJ×mol-1, and K = 9.9 ´ 104 M-1 at 293 K, leads to the conclusion that the coordination of the defect pockets to La3+ precedes the replacement of the {Mo2} linkers with La3+. 139La- NMR spectrometry of the coordination of {Mo142(CH3CO2)5(C2H5CO2)} ring to La3+ is also discussed.
Keywords: {Mo142}- ring; elliptical {Mo134La10}-ring; Mo-blues molecular design; La3+-coordination geometry; X-ray crystal structure; isothermal titration calorimetry (ITC); 139La-NMR {Mo142}- ring; elliptical {Mo134La10}-ring; Mo-blues molecular design; La3+-coordination geometry; X-ray crystal structure; isothermal titration calorimetry (ITC); 139La-NMR
This is an open access article distributed under the Creative Commons Attribution License (CC BY 3.0).

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Ishikawa, E.; Yano, Y.; Yamase, T. Coordination of {Mo142} Ring to La3+ Provides Elliptical {Mo134La10} Ring with a Variety of Coordination Modes. Materials 2010, 3, 64-75.

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