BIPHENYL-STRAPPED DIPHENYLPORPHYRINS - SYNTHESIS AND SPECTROSCOPIC CHARACTERIZATION OF A SERIES OF PORPHYRINS WITH ETHER-LINKED STRAPS - PRELIMINARY CO BINDING-PROPERTIES OF THEIR IRON(II) DERIVATIVES

The synthesis of a series of meso-5,15-diphenylporphyrins strapped by 2,2'-disubstituted biphenyl units (6H(2), 7H(2), 8H(2)) is described. The biphenyl straps used are linked via their 3,3'-positions by CH2O g roups to ortho-positions of the phenyl rings of the 5,15-diphenylporph yrins. The straps of these porphyrins have their 2,2'-positions occupi ed by H (6H(2)), Me (7H(2)), and OMe (8H(2)). The electronic spectral properties of these strapped porphyrins are given, and their conformat ional properties, which have been studied by H-1 NMR spectroscopy, are described. The synthesis and spectroscopic characterization of severa l iron(II) and iron(III) derivatives of these porphyrins with differen t axial bases are also presented. The X-ray structure of the chloroiro n(III) derivative of the diphenylporphyrin dianion 6 has been determin ed. Violet crystals of composition 6-FeCl . CH3OH . CH2-Cl-2 have been obtained by slow evaporation of CH2Cl2/MeOH solutions of 6-FeCl. Thes e crystals belong to the monoclinic system, space group P2(1)/c, with a = 10.164(3) Angstrom, b = 28.977(9) Angstrom, c = 14.283(4) Angstrom , beta = 106.22(2)degrees and Z = 4. The iron atom of 6-FeCl is five-c oordinate, high-spin. The axial chloride ligand lies opposite to the s trap. The average Fe-N-p bond distance is 2.046(6) Angstrom, and the F e-CI bond length equals 2.234(2) Angstrom. The porphyrin is slightly d omed and ruffled with the iron atom lying at 0.45(1) Angstrom out of t he 4N(p) mean-plane and 0.49(1) Angstrom out of the 24-atom core mean- plane of the porphyrin ring. Ferrous carbonyl adducts of these porphyr ins have been obtained in various solvents in the presence or absence of nitrogenous bases. Their structures have been studied by H-1 NMR an d IR spectroscopy. Two CO stretching vibrations differing by 20 cm(-1) occur in the IR spectra of 6-Fe(CO)(B) (B = py, ImH, NMeIm). The poss ible origin of these two vco bands is discussed.