无机物理方法(核磁共振部分).ppt

The Physical Methods in Inorganic Chemistry  (Fall Term, 2004) (Fall Term, 2005)Department of ChemistryNational Sun Yat-sen University Basic Two-Dimensional Experiments Why multi-dimensional? Resolution Multi-quantum coherences Coherence transfer From 1D to 2D, 3D… A 2D Spectrum 2D FT Typical 2D Lineshapes Resolution Recollecting Chapter 2 Four basic lineshapes A 2D dispersive peak DQF COSY The Advantages of DQF COSY The Disadvantages of DQF COSY There are also disadvantages to the DQF-COSY relative to COSY. First, the sensitivity of DQF is about a factor of two lower than regular COSY. Second, MQ relaxation in 1Hs is very slow, so the experiments require a relatively long d1 relaxation delay. Thus, while a good COSY spectrum could be generated in about 2-4 hours of data accumulation, a good DQF-COSY requires about 16-24 hours to allow complete relaxation during d1. COSY Family COSY COSY-45,COSY-90 R-COSY (LR-COSY) pQF COSY PE-COSY E-COSY MQ COSY TOCSY zCOSY,zzCOSY, J.R.COSY ….. J Coupling Measurement J coupling and peak intensity J coupling and linewidth J coupling and overlap Introduction The availability of other (“hetero”) nuclei than proton for multi-dimensional NMR spectroscopy is extremely useful, particularly, for macromolecules (of synthetic or biological origin) because the connectivity between protons and heteronuclear spins can be established in addition to the homonuclear multi-dimensional spectra. Like homonuclear 2D spectroscopy, the central task in heteronulcear 2D experiments is to select proper coherence pathways so that the desired interaction can be elucidated. Heteronuclear 2D experiments can be more diverse because, e.g., the data acquisition can be carried out on heteronuclei (C-13, N-15 etc) or on protons (inverse detection). Heteronuclear correlation (HETCOR) and its variants Enhanced Heteronuclear Correlation COrrelation via LOng-range Coupling(COLOC) Heteronuclear Multi-Bond Correlation (HMBC) Inverse Detection HSQC Points a