A DIBENZOTETRAAZA[14]ANNULENE

The ligand 2,3,6,8,1 1,12,15,17-octamethyl-5,14-dihydro- 5,9,14,18-tetraazadibenzo[b,i]cyclotetradecene (H(2)omtaa, C26H32N4) has a pronounced saddle shape as a result of interactions between the methyl groups and the phenyl rings [the dihedrai angle between the phenyl rings is 139.2(3)degrees]. The overall geometry of H(2)omtaa is very similar to that of H(2)tmtaa (6,8,15,17-tetramethyl-5,14-dihydro-5,9, tetraazadibenzo[b,i]cyclotetradecene, C22H24N4) [Goedken, Pluth, Peng and Bursten (1976). J. Am. Chem. Sec. 98, 8014-8021]. The central cavity in H(2)omtaa has a radius of 1.915 (3) Angstrom (where the radius is defined as half the mean distance between diagonally opposite N atoms), which is significantly smaller than that in a porphyrin (2.04 Angstrom).