Porphycenes crystalline

In (87BBPC941), Limbach made a major contribution to understanding crystalline and amorphous environments using compounds that in the gas phase show symmetric double minimum potentials. Several compounds were used to illustrate the periodic (crystal) and random (glass) distortions of the potential surface, among them H2P and porphycene. Tlie seminal paper on the tautomerism of porphyrins in the solid state is that of Limbach... 

As mentioned earlier, the poor solubility and crystallinity characteristics of the metal complexes derived from porphycene 3.2 inspired the synthesis of a number of P-alkyl-substituted analogs. Not surprisingly, these P-substituted systems showed metal coordination properties similar to those of their unsubstituted counterpart. For instance, the 2,7,12,17-tetrapropylporphycene 3.20 has been shown to form stable complexes with Co(II), Ni(II), Cu(II), Pd(II), and Pt(II) (i.e., 3.63-... 

In porphycene, the rates, barriers and the overall tautomerization mechanism seem to be completely different. Comparison of the reaction for 1 and 2 in the crystalline state was performed using i N CPMAS NMR (Fig. 8.5) [40, 68]. At elevated temperatures both molecules reveal only one peak, characteristic of a rapid inner hydrogen exchange. For porphyrin, lowering of the temperature from 356 to 192 K leads to line broadening and, finally, to the separation of =N- and NH... 

M., Ermer, O, and Vogel, E. (1987) N-CPMAS-NMR study of the problem of NH tautomerism in crystalline porphin and porphycene. Angew. Chem. Int Ed. Engl, 26, 934-936. 

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