E. COSY principle

Fig. 7.2 Explanation of the E. COSY principle. The E. COSY spectrum can be conceived as a superposition of spectra originating from two...

For the qualitative and quantitative determination of coupling constants, Hartmann-Hahn transfer can be of assistance and also provides a number of new approaches. These approaches are based on Hartmann-Hahn transfer functions or on the efficient transfer of coherence in one subset of the spin system while the polarization of a second subset of spins remains untouched (E.COSY principle). Furthermore, in combination with other experiments, the in-phase multiplets of Hartmann-Hahn experiments can be used as a reference in an iterative fitting of coupling constants in antiphase multiplets. 

Willker and Leibfritz (1992a) introduced an extension of the E.COSY principle that yields additional flexibility. In addition to coherence transfer between the active spins i and j, polarization of spin p, which is passive during is transferred to a spin q, which plays the role of the passive spin during t - Hence, in general, the E.COSY triad is opened up. The two- and three-dimensional JHH-TOCSY experiments for the determination of coupling constants of Willker and Leibfritz (1992a) use a combination of homonuclear TOCSY transfer and two BIRD (bilinear rotation decou-... 

In the absence of a large associated coupling J(A,C), which is a requirement for the successful application of E. COSY or DQ/ZQ methodology, the FIDS (fitting of doublets from singlets) procedure can be applied. The basic principle of this experiment is outlined in Fig. 7.8. 

Similar principle was applied for the simultaneous measurement of one-bond and two-bond couplings. The E.COSY sequence was ext-... 

A more sophisticated IR spectroscopy is 2-D correlation IR spectroscopy. This spectroscopy follows the same measurement principles as 2-D NMR COSY spectroscopy (for details see, e.g., [17, 18]) and results, apart from better resolution, in simplification of complex spectra and enhancement of the spectral resolution by spreading the peaks along the second dimension. Furthermore, assignment of bands can be done and the interaction mechanism determined by analyzing the coupling of bands. 

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