SQ—SQ experiment for determination of relative signs of small nJ(29Si,13C) couplings in a wide variety of silicon compounds

✍ Scribed by Vratislav Blechta; Jan Schraml

• Publisher: John Wiley and Sons
• Year: 2009
• Tongue: English
• Weight: 155 KB
• Volume: 47
• Category: Article
• ISSN: 0749-1581
• DOI: 10.1002/mrc.2505

✦ Synopsis

Abstract

A modification of double quantum–zero quantum (DQ—ZQ) experiment termed single‐quantum–single‐quantum (SQ—SQ) experiment is proposed for the determination of relative signs and magnitudes of coupling constants. The modification replaces the multiple‐quantum evolution period by two synchronously incremented single‐quantum periods. Similarly to DQ—ZQ experiment, the sequence requires only two coupling constants that share one nucleus, the one to be measured and a reference one. This allows application to a larger variety of molecular fragments than traditional 2D sequences producing E.COSY or TROSY pattern. The SQ—SQ experiment eliminates the effects of some other couplings during t~1~, thereby simplifying the 2D pattern and increasing the signal intensity in comparison with DQ—ZQ experiment.

The presented sequence is particularly designed for the determination of silicon–carbon coupling constants across several bonds at natural abundance using silicon–hydrogen couplings as the sign reference. The signs of silicon–carbon couplings across two and three bonds in dimethyl(phenoxy)silane which cannot be detected by traditional methods and which have not yet been determined are established by the SQ—SQ method here: ^2^J(Si,C) = +2.2 Hz and ^3^J(Si,C) = −1.7 Hz. Copyright © 2009 John Wiley & Sons, Ltd.