SYNTHESIS AND STRUCTURE OF A 5,15-BIS(4-PYRIDYL)PURPURIN

Base catalyzed cyclization of a 5,15-di(4-pyridyl)octaalkylporphyrin-5 -acrylate 6 yields smoothly the corresponding purpurin 2. Quaternizati on with methyl iodide yielded the corresponding cationic N,N'-dimethyl pyridiniumpurpurin 3; X-ray crystallography of purpurin 2, the first p urpurin to be studied crystallographically, shows the two p-alkyl grou ps on the saturated ring of the purpurin have a syn configuration, and the macrocycle to have a slight saddle shape with a mean deviation of 0.230 Angstrom from the least-squares plane calculated for the core a toms.