Synthesis of symmetrical tetraaryltetranaphtho[2,3]porphyrins

[GRAPHICS] A new method of synthesis of meso-tetraaryltetranaphtho[2,3]porphyrins (Ar4TNP) has been developed. Ar(4)TNPs with peripheral functional groups are obtained by oxidative aromatization of meso-tetraarylporphyrins in which pyrrole units are fused with either octahydro- or dihydronaphthalene moieties. These precursor porphyrins are synthesized in four to five steps from readily available starting materials, such as naphthalene or 1,4-benzoquinone. The pathway originating in dihydronaphthalene, i.e., the "dialine" route, was found to be superior to the alternative "octaline" route in that it (1) enables the shortening of the overall reaction sequence, (2) has a broader scope in terms of the peripheral substitution in Ar(4)TNPs, and (3) affords higher yields of the target porphyrins. Pd complexes of the synthesized Ar(4)TNPs exhibit remarkably strong absorption bands at 710-720 nm (epsilon similar to 200 000 M-1 cm(-1)) and phosphoresce at room temperature with moderate quantum yields (phi = 2-3%, lambda(max) = 900-1000 nm). The absorption maxima of naphthoporphyrins substituted with eight methoxy groups (Ar4TNP(OMe)(8)) were found to be about 15-20 nm red shifted compared to the corresponding maxima of unsubstituted Ar(4)TNPs. The X-ray crystallographic data suggest that these spectral shifts are caused not by the differences in nonplanar distortions of the macrocycles but by the purely electronic effects of the substituents.