Pyrrole proton signal

All the Ru complexes are diamagnetic and display well-revolved NMR spectra. The pyrrolic proton signals are shifted about 0.4 ppm downfield from those of the carbonylruthen-ium(II) precursors. 

Fig. 5.8. H NMR spectra of high spin Fe(lII) porphyrins. (A) Fe TPP-C1 (no substituent at the pyrrole positions). Signal a refers to pyrrole protons signals b, c and d refer to the meta, ortho and para phenyl protons respectively [19]. (B) Fe (protoporphyrin IX)-C1 (see Fig. 5.7A for the ligand). Signals a belong to the methyl groups, signals b and g to the 13,17 a-CH2 and the 3,8 a-CH signals d to the COOH signals e to the 13,17 P-CH2 signals h and i to the 3,8 P-CH cis and p-CH trans respectively [20].

Subjecting 2 or 3 to strongly acidic conditions (e.g. 1 M CF3CO2H or concentrated HQ) leads to rapid demetalation and the production of two isomeric free-base macrocycles 10 and 11 [11, 12]. The structure of 10 was conflrmed by its spectral properties and its remetalation to form the nickel complex 5. On the other hand, the structure of 11 was determined solely by its spectral properties. For instance, the NMR spectrum of 11 demonstrated the presence of a fully unsaturated system. Typical also was the presence of pyrrolic proton signals in the 6-7 ppm range of the NMR spectrum [12]. Compound 11 was very unstable... 

The equivalence of the inner NH protons (Sm = - 2.35) as well as correlation signals with the pyrrolic carbons only (5c = 143.8, 141.6, 139.8 and 136.7) provide evidence for the diaza[18]-annulene tautomer 4a. Two separate NT/ proton signals and cross signals with the a-carbon atoms (5c = 159.3) of the triazole ring are expected, in contrast, for the tetraaza[18]annulene tautomer 4b. 

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