SYNTHESIS AND CHARACTERIZATION OF ALL-ALKYL-SUBSTITUTED MONOOXOSAPPHYRIN, DIOXOSAPPHYRIN, AND TRIOXOSAPPHYRIN

The synthesis and characterization of the following heterosapphyrins i s presented: raethyl-2,8,12,13,17,23-hexamethyl-27-oxasapphyrin (5), x aethyl-2,7,18,23-tetramethyl-15,29-dioxasapphyrin (6), and ,8,12,13,17 ,23-hexamethyl-15,27,29-trioxasapphyrin (7). These macrocycles were sy nthesized from the hitherto unknown precursors methyl 3,4-dimethylfura n-2-carboxylate (11) and methyl 4-ethyl-3-methylfuran-2-carboxylate (1 2). Single-crystal X-ray diffraction structures of the bis(hydrochlori c acid) salt (5a) and the bis(trifluoroacetic acid) salt (5b) of 5 and of the bis(hydrochloric acid) salt (6a) of 6 were obtained. These str uctures are compared to those of the parent all-aza sapphyrin 4. In th is context, we report the first solid-state structural analysis of a t rifluoroacetic acid salt of sapphyrin (4b). Crystals of 5a are triclin ic, space group P (1) over bar in a cell of the dimensions a = 11.9686 (13) Angstrom, b = 12.790(2) Angstrom, c = 16.236(2) Angstrom, alpha = 80.924(10)degrees, beta = 88.845(9)degrees, gamma = 80.481(10)degrees , V = 2420.5(5) Angstrom(3), F(000) = 1036, rho = 1.38 g cm(3) with Z = 2. Crystals of 5b are monoclinic, space group P2(1)/c, in a cell of the dimensions a = 9.590(1) Angstrom, b = 33.911(3) Angstrom, c = 13.2 00(1) Angstrom, beta = 94.931(6)degrees, V = 4276.8(6) Angstrom(3), F( 000)= 1904, rho = 1.42 g cm(3), with Z = 4. Crystals of 6a are triclin ic, space group P (1) over bar, in a cell of the dimensions a = 12.827 (3) Angstrom, b = 13.116(3) Angstrom, c = 17.202(7) Angstrom, alpha = 82.89(2)degrees, beta = 82.14(2)degrees, gamma = 80.22(1)degrees, V = 2810(2) Angstrom(3), F(000) = 1184, rho = 136 g cm(3), with Z = 2. Cry stals of 4b are triclinic, space group P (1) over bar, in a cell of th e dimensions a = 11.431(3) Angstrom, b = 11.563(2) Angstrom, c = 16.36 7(4) Angstrom, alpha = 88.07(2)degrees, beta = 75.25(2)degrees, gamma = 86.50(2), V = 2087.8(9) Angstrom(3), F(000)= 872, rho = 1.32, with Z = 2. The monooxasapphyrin salt 5a displays a structure very similar t o that of the parent all-azasapphyrin (4a) in that one chloride anion is bound 1.936 Angstrom above and one chloride anion 1.814 Angstrom be low the plane of the macrocycle. These distances are 1.774 and 1.877 A ngstrom, respectively, for 4a. Almost the same behavior is found for 5 b. Here, the carboxylate anions are bound 1.085 Angstrom above and 1.8 70 Angstrom below the plane of the macrocycle. These distances are 1.3 05 and 1.444 Angstrom, respectively, for 4b. Completely different beha vior is observed in the case of 6a. In this instance, only one chlorid e anion is bound directly with a distance of 1.685 Angstrom above the plane of the macrocycle, while the other chloride anion is well remove d from the dioxasapphyrin and solvated by four chloroform molecules.