Chapter 4 - Jacobs University

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<strong>Chapter</strong> 7 Pt-containing Polyoxometalate temperature and/or downfield shift of the NMR signals with increasing temperature (by about 3 ppm). In addition, the fact that two molecules of 5 form hydrogen-bonded dimers in the solid state (Figure 7.5) could also be important. It is possible that the NMR spectrum at 293 K actually corresponds to the weakly bound dimer assembly, whereas heating to 333 K breaks them apart, resulting in monomeric 5. . It must be remembered that the 51 VNMR experiments take several hours. We plan to investigate the thermodynamic stability of the dimer assembly in the future by using appropriate techniques (e.g. size exclusion chromatography, ultracentrifugation, cryo-mass spectrometry). Figure 7.5 Dimer formation of 5 in the solid state via hydrogen bonding. Already more than 30 years ago Pope and O’Donnell investigated the decavanadate ion V 10 by 51 VNMR spectroscopy in solution, and they discovered that the chemical shifts are pH dependent. 17 Since then also other groups have engaged in 51 Vand 17 7a, 18 O NMR studies of V 10 but to our knowledge no study on the temperature dependence of the chemical shifts has been 133
<strong>Chapter</strong> 7 Pt-containing Polyoxometalate reported for V 10 . Our results above show that such a study could be interesting, in particular for derivatives of V 10 with different degrees of protonation. Next, we performed 195 Pt NMR measurements on 5a redissolved in H 2 O/D 2 O. This technique had only been applied once before in POM chemistry for [α-SiPtW 11 O 50 ] 6- , but no signal was observed. 19 We located the expected singlet for 5 at d = 3832 ppm (Figure 7.6). The corresponding 195 Pt NMR signal for the precursor Na 2 [Pt(OH) 6 ] appeared significantly more upfield (3295 ppm). The combination of 51 V and 195 Pt NMR is fully consistent with the solidstate structure of 5 and hence provides unequivocal evidence for the presence of this polyanion also in solution. Importantly, this is the first report ever on the successful use of 195 Pt NMR in POM chemistry. 3500 3400 3300 3200 3100 ppm 4000 3900 3800 3700 3600 ppm Figure 7.6 Platinum-195 NMR spectrum of Na 5 [H 2 PtV 9 O 28 ]×21H 2 O (5a) and of the precursor Na 2 [Pt(OH) 6 ] (insert) in H 2 O/D 2 O at 293 K (reference is H 2 PtCl 6 which appears at 0 ppm). 134
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Synthesis, Structure and Properties
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"The greatest book of philosophy, w
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system, space group I4/m, unit cell
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Acknowledgements The accomplishment
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teaching, and Professor Maravanji S
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2.1.2 Single crystal X-ray diffract
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5.5 Conclusion…………………
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9.1.6.1 Results and discussion…
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9.3.5 Synthesis of K 12 [Hf 4 (µ 2
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Crespo………………………
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Figure 5.4 ORTEP view of the asymme
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Figure 9.6 31 P NMR of 7a in H 2 O/
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Figure 9.34 TGA spectrum of 17a…
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Figure 9.62 FTIR spectrum of 23a…
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Table 9.6 Crystal data and structur
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Chapter 1 Introduction heteropolyan
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Chapter 1 Introduction 1.3 Structur
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Chapter 1 Introduction C) Keggin a-
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Chapter 1 Introduction shows no suc
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Chapter 1 Introduction α-[P 2 W 18
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Chapter 1 Introduction Figure 1.7 B
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Chapter 1 Introduction [P 2 W 18 O
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Chapter 3 The Wheel-Shaped Cu 20 3.
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Chapter 3 The Wheel-Shaped Cu 20 Cu
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Chapter 3 The Wheel-Shaped Cu 20 20
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Chapter 4 16-Iron Metal Center Nano
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Curriculum Vitae SIB SANKAR MAL Dep
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EDUCATION PhD Jacobs University (20
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POSTER, ORAL PRESENTATION 1. Poster
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6. “Two Iron-Containing Tungstoge
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Appendix
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Appendix
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