Proton-template synthesis, structure, and characterization of a Robson-type macrocycle with a totally π-conjugated system

pi-Conjugated (1-4) and partially reduced (5) macrocyclic Schiff bases have been obtained by proton-template condensation of 2,6-diformyl-4-R-1-phenol (R-1 = Me, t-Bu) with 1,2-diamino-4,5-R-2-benzene (R-2 = H, Me). The macrocyclic ligands have been characterized by elemental analysis, by IR, H-1 NMR, and C-13 NMR spectroscopy, and by electron impact mass spectrometry. Also, the X-ray crystal structures of 1 and 2 were solved. The crystals were all grown from formic acid. Crystal 1 is triclinic, space group P-1 with a = 867.1(5), b = 916.3(4), and c = 1087.2(3) pm and alpha = 69.62(2), beta = 87.57(3), and gamma = 63.72(4)degrees for Z = 1. Crystal 2 is monoclinic, space group P2(1)/n with a = 632.0(1), b = 1661.5(3), and c = 1658.0(3) and beta = 99.87(3)degrees for Z = 2. Both of the molecules are planar with centers of symmetry. They are protonated twice while being neutralized by two negatively charged perchlorate ions.