3D NMR spectrum

Both NMR and molecular computations are greatly enhanced by interactive scientific visualization. High speed 2D and 3D color graphics can provide the investigator with nearly instantaneous feedback. (No table of numbers can show us molecular shapes, or allow us to get perspective on a complex 2D or 3D NMR spectrum). 

Figure 9. Slices corresponding to flJ3 planes (a-c) from the HCF triple resonance 3D-NMR spectrum (d) of poly(1-chloro-l-fluoroethylene) (PCFE) at the shifts of the three F resonances. (Reproducedfrom reference 10. Copyright 1997 American Chemical Society.)...

Similarly, H/ C/ Si triple resonance 3D-NMR was used to study the structure of poly(l-phenyl-l-silabutane) (PPSB).f72 In this polymer, stereogenic centers are present at the Si atoms. While the H ID NMR spectrum only revealed two sets of resonances fix)m protons a and 3 to Si (Figure 10a), the ID Si NMR spectrum exhibited three peaks from mm, mr/rm and rr stereosequences (Figure 10c). As with PCFE, a H- C- Si chemical shift correlated 3D-NMR spectrum (Figure 11) permitted assignment of the resonances from the three triad steieosequences. 

Slices from the 3D NMR spectrum, at the shifts of each of the unique Si atoms are shown in Figures llb-d. As with PCFE discussed above, examination of the correlations from methylene groups p to Si reveals the same types of single and double correlations for r and m methylenes. It thus became possible to assign the sets of resonances ( H, and Si) to mm, mr/rm and rr triads structures. Similar techniques have also been used to study the structures of small oligomers of poly(dimethylsiloxane).(73)... 

Figure 13. Slices from the HCSi 3D NMR spectrum of carbosilane dendrimer using coherence transfer delays based on (a c) Jch Jcsu and (d f) Jqh and Jcsv (Reproducedfrom reference 14. Copyright 1999 American Chemical Society.)...

Figure 17, Illustration of the HCP 3D-NMR spectrum of phosphorus-containing chain-end structures formed through styrene polymerization initiated by diphenylphosphinyl radical (Reproducedfrom reference 19. Copyright 2001 American Chemical Society.)...

Figure 11.12 The H/ C/ Si 3D NMR spectra of a first generation carbo-sUicone dendrimer. (a) 3D projection of the one-bond C-Si H/ C/ Si 3D NMR spectrum (b-c) slices at different Si chemical shifts from the one-bond C-Si H/ C/ Si 3D NMR spectrum (b) //, slice at = 9.39 and slice at = -9.80 (d) 3D projection ofthe multiple-bond C-Si H/ C/+Si 3D NMR spectrum (e-f) //j slices at different Si chemical shifts from the two-bond C-Si H/ C/ Si 3D NMR spectrum (e)//, slice at 8 = 9.39 and (f) slice at 29Si= -9.80. Reproduced with permission from [71] Copyright (1999) American Chemical Society.

The low resolution H/ C/ F/ 3D-NMR spectrum of PCFE is shown in Figure 8.16 fifs correlations) slices at the three different F chemical shifts are shown in... 

Figure 8.16 H/i3(2/i9p 3D-NMR spectrum of PCFE with flf3 slices at different F resonance frequencies ...

Figure 58 Selected slices taken from the H correlated 3D-NMR spectrum of PCFE showing k planes at F chemical shifts of (a) mm, (b) mr/rm, and (c) rrCF-centered triads. Reprinted with permission from Li, L Rinaldi, P. L. Macromolecules 29,4808. Copyright 1996 American Chemical Society.

Plots of the projections and slices from the H/ G/ Si 3D-NMR spectra of the Gi dendrimer are shown in Figure 70. Spectra labeled a-c are those from the 3D-NMR spectrum collected with delays optimized for one-bond G-Si couplings these plots contain information about H-G-Si atomic connectivities. The spectrum in Figure 70(a) is the projection of the 3D data onto the/i//3 plane ( Si vs. chemical shifts). In this... 

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