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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,*
Received: 29 November 2009; in revised form: 23 December 2009 / Accepted: 25 December 2009 / Published: 28 December 2009
(This article belongs to the Special Issue Polyoxometalate Compounds)
Download PDF [616 KB, uploaded 29 December 2009]
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 which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

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MDPI and ACS Style

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.

AMA Style

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(1):64-75.

Chicago/Turabian Style

Ishikawa, Eri; Yano, Yutaka; Yamase, Toshihiro. 2010. "Coordination of {Mo142} Ring to La3+ Provides Elliptical {Mo134La10} Ring with a Variety of Coordination Modes." Materials 3, no. 1: 64-75.


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