STRUCTURE AND CONFORMATION OF PHOTOSYNTHETIC PIGMENTS AND RELATED-COMPOUNDS .4. 2 CRYSTAL FORMS OF A CHLORIN RHODOCHLORIN-XV DIMETHYL ESTER

Two different crystal forms of the title compound, (2S)-trans-methyl 8-ethenyl-13-ethyl-2,3-dihydro-18-methoxycarbonyl-3,7,12,17-tetramethyl-21H,23H-porphine-2-propionate, were found and investigated by single-crystal X-ray crystallography. Triclinic form: C34H38N4O4.CH2Cl2, M(r) = 647.6, P1BAR, a = 9.879 (4), b = 10.648 (6), c = 16.059 (8) angstrom, alpha = 97.29 (5), beta = 94.24 (4), gamma = 96.97 (4)-degrees, V = 1656.3 (14) angstrom 3 Z = 2, D(x) = 1.300 Mg M-3, A(Mo Kalpha) = 0.7107 angstrom, mu = 0.237 mm-1, F(000) = 680, T = 130 K, R = 0.075 for 3496 reflections with I > 2 sigma(I). This form crystallizes with one methylene chloride of solvation in antiparallel oriented layers, stacked by pi-pi interaction. The solvent molecules are situated between neighboring chlorin molecules in each layer. Orthorhombio form: C34H38N4O4, M(r) 566.7, P2(1)2(1)2, a = 14.892 (6), b = 26.491 (I 1), c = 7.648 (3) angstrom, V = 3017 (2) angstrom3, Z = 4, D(x) = 1.250 Mg M-3, lambda(Mo Kalpha) = 0.7107 angstrom, mu = 0.077 mm-1, F(000) = 1204, T = 130 K, R = 0.067 for 3281 reflections with 1> 3 sigma(I). The molecules in the orthorhombic form are packed by forming dimeric structures held together by interaction of neighboring propionic ester groups. The molecular structures of both forms are' slightly different. In the triclinic form the beta-pyrrole atoms of ring IV deviate by approximately 0.4 angstrom from the plane of the N atoms, while in the orthorhombic form ring I is located 0.2 angstrom above, and ring IV 0. 15 angstrom below the plane.