Xanthene-bridged cofacial bisporphyrins

The synthesis and characterization of cofacial bisporphyrins juxtaposed by xanthene-bridged pillars are presented. The one-pot preparation of the xant hene dialdehyde avoids the lengthy bridge synthesis accompanying other cofa cial porphyrin systems, thus allowing for the facile preparation of homobim etallic zinc (10), copper (11), and nickel (12) complexes. The cofacial ori entation of the two porphyrin macrocycles was confirmed by X-ray crystallog raphy. Structural data are provided for bisporphyrins 10-12: 10 (C79H82N8OZ n2), triclinic, space group P (1) over bar, a = 11.2671(2) Angstrom, b = 14 .9809(2) Angstrom, c = 20.4852(2) Angstrom, alpha = 101.6680(10)degrees, be ta = 100.8890(10)degrees, gamma = 101.8060(10)degrees, Z = 2; 11 (C79H82N8O Cu2), triclinic, space group P (1) over bar, a = 11.21410(10) Angstrom, b = 14.9539(5) Angstrom, c = 20.6915(7) Angstrom, alpha = 101.810(2)degrees, b eta = 101.044(2)degrees, gamma = 101.722(2)degrees Z = 2: 12 (C79H82N8ONi2) , monoclinic, space group C2/c, a = 24.1671(4) Angstrom, b = 10.669 Angstro m, c = 50.5080(9) Angstrom, beta = 99.553(2)degrees Z = 8. Exciton interact ions between the porphyrin rings are apparent in electronic spectra, consis tent with the cofacial superstructure. The combination of structural and sp ectroscopic data provides a basis for the design of additional metal deriva tives for the activation of dioxygen and other small molecules.