Chapter 4 - Jacobs University

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<strong>Chapter</strong> 7 Pt-containing Polyoxometalate 7.4.2 Solution NMR To complement our solid-state XRD results on 5 with solution studies, we performed 51 V and 195 Pt NMR measurements on 5a redissolved in H 2 O/D 2 O. All NMR spectra were recorded on a 500 MHz JEOL ECX instrument at room temperature using 5-mm tubes. The resonance frequencies used for 51 Vand 195 Pt NMR were 105.155 and 85.951 MHz, respectively, and the chemical shifts are reported with respect to neat VOCl 3 and aqueous 2M K 2 [Pt(CN) 6 ]. All chemical shifts downfield of the references are reported as positive values. The 51 VNMR spectrum exhibits only 3 broad peaks (d= -371.5, -550.3, and -575.1 ppm) with approximate relative intensities 1:2:6 rather than the expected four peaks with relative intensities 1:2:2:5. However, upon heating the solution to 60 o C we observed a splitting of the central, most intense peak (with intensity 6) into two peaks (with intensities 2:5), resulting in exactly the expected spectrum (d = -368.3, -553.0, -556.9, and -571.5 ppm; Figure 7.4). Based on their relative intensities, the largest signal at d = -556.9 ppm can be assigned to the four equivalent vanadium centers (blue, Figure 7.4), and the smallest signal at d = -368.3 ppm corresponds to the unique vanadium atom (red). The situation is somewhat more complicated for the two vanadium centers shown in yellow and green, but we suggest the following 131
<strong>Chapter</strong> 7 Pt-containing Polyoxometalate -360 -370 -380 -390 -400 -410 -420 -430 -440 -450 -460 -470 -480 -490 -500 ppm -360 -370 -380 -390 -400 -410 -420 -430 -440 -450 -460 -470 -480 -490 -500 ppm Figure 7.4 51 V NMR spectrum of 5a redissolved in H 2 O/D 2 O at 293 K (top) and 333 K (bottom). assignment (based exclusively on structural considerations) for the two peaks of equal intensity: d = -553.0 (yellow) and -571.5 ppm (green). Interestingly, the temperature-induced change of the 51 VNMR spectrum is fully reversible. In other words, after allowing the solution of 5 to cool down to room temperature, we observe again the three-line spectrum (Figure 7.4, top). Possible reasons for this phenomenon are a decreasing half width of the NMR signals with increasing 132
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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 1 Introduction 1.5.3 Medici
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Chapter 1 Introduction (17) Evans,
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Chapter 1 Introduction (48) Mizuno,
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Chapter 1 Introduction (84) Isabell
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Chapter 2 were block-diagonal least
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Chapter 2 Experimental 2.2.3 Synthe
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Chapter 2 Experimental 2.2.11 Synth
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Chapter 2 Experimental 2.3Reference
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Chapter 3 The Wheel-Shaped Cu 20 in
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Chapter 3 The Wheel-Shaped Cu 20 3.
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Chapter 3 The Wheel-Shaped Cu 20 Fi
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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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Chapter 9 Unpublished Results 9.2.2
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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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