SYNTHESIS AND CHARACTERIZATION OF A NOVEL SERIES OF BIS-LINKED DIAZA-18-CROWN-6 PORPHYRINS

The synthesis and physicochemical characterization of a novel family o f 'crowned-porphyrins' is presented. The compounds uniquely possess a 5,15-di(2-alkylamidophenyl)etioporphyrin bis-linked to the nitrogens o n opposite sides of a 1,4,10,13-tetraoxa-7,16-diazacyclooctadecane moi ety. The size of the cavity in between the porphyrin and the diaza-18- crown-6 ring has been regulated by varying the length of the alkylamid o linking units. The structures of 5 and 7 bear diacetamido linkers wh ereas 6 is linked via dipropionamido groups. The synthetic pathway pre sented is generalized such that a wide variety of useful porphyrin-bas ed bis-macrocycles can be prepared. Products have been fully character ized by elemental analysis, mass spectrometry, spectrophotometry, H-1 NMR, C-13 NMR and H-1-C-13 heteronuclear correlation NMR spectroscopie s. X-Ray structural data are presented for the free-base porphyrin 6 a nd the Zn-II porphyrin 7. The structural data confirm that the porphyr ins and their diaza-18-crown-6 substituents adopt cofacial orientation s. The size of the cavity between the macrocycles, while demonstrated to accommodate small molecules as shown by the binding of H2O as an ax ial ligand to the central Zn-II ion in the crystal structure of 7, wil l probably not accommodate large ligands or substrates. Moreover, thes e compounds should allow sequential metallations to yield heterobimeta llic species. Therefore, they are ideally suited for study as model sy stems for biologically important heme-dependent phenomena such as xeno n-129 binding to myoglobin or the mimicking of processes related to th e structure and function of cytochrome c oxidase.