A NOVEL SERIES OF STRAPPED PORPHYRINS - COMPARISON OF THE MOLECULAR-STRUCTURES OF 4 2,2'-SUBSTITUTED BIPHENYL STRAPPED MESO-DIPHENYLPORPHYRINS

The crystal and molecular structures of four metal-free 2,2'-disubstit uted biphenyl strapped diphenylporphyrins are reported. The 2,2'-subst ituents of the biphenyl straps are nitro (1a), ethoxy, (1b), methyl (2 a) and methoxy (2b) groups. The covalent links between the 3,3'-positi ons of the biphenyl straps and the o-positions of the meso-phenyl ring s of the diphenylporphyrins are amido (-C(O)-NH-) groups in 1a and 1b, and ether (-CH2 - O-) moieties in 2a and 2b. In all these strapped po rphyrins, the 2,2'-substituents are oriented toward the porphyrin core s and are in Van-der-Waals contact with each other and with porphyrin- core atoms. The heights of the cavities lying between the straps and t he mean planes in the porphyrin have similar values in 1a and 1b, and in 2a and 2b, the corresponding mean values being 5.207(5) Angstrom (1 a, 1b) and 5.293(4) Angstrom (2a, 2b). These figures indicate that in the metal-free porphyrins the amido or ether links introduce similar c avity heights. Strong hydrogen bonds occur in Ib between the NH groups of the amido links and the oxygen atoms of the 2,2'-ethoxy substituen ts of the strap. Crystal data: \[NHCO - (2,2'-(NO2)(2) - BPh) - COHN] H2DPP\. 3CHCl(3) (H2DPP=5,15-diphenylporphyrin) (1a . 3CHCl(3)), tricl inic, P ($) over bar 1, a=15.529 (4), b=14.096 (4), c=12.740 (3) Angst rom, alpha=105.98 (2), beta=99.57 (2), gamma=102.21 (2)degrees, Z=2; \ [NHCO - (2,2'-(OC2H5)(2)-BPh) - NHCO] H2DPP\. CHCl3 (1b . CHCl3), tric linic P ($) over bar 1, a=13.811(4), b=15761(5), c=10.258(3) Angstrom, alpha=98.11(2), beta=97.86(2), gamma=98.28(2 degrees), Z=2; \[OCH2-(2 ,2'-(CH3)(2) -BPh)-CH2O]H2DPP\ (2a), triclinic, P ($) over bar 1, a=13 .545(4), b=14.511(4), c=12.488(3) Angstrom, alpha=114.43 (2), beta=99. 52 (2), gamma=115.84 (2)degrees, Z=2; and \[OCH2 - (2,2'-(OCH3)(2) - B Ph) - CH2O] Etio(II) - H2DPP\ (2b) (Etio(II)-H2DPP=2, 8, 12, 13-tetrae thyl-3, 7, 13, 17-tetramethyl-5, 15-diphenylporphyrin), triclinic, P ( $) over bar 1, a=14.559(4), b=14.669(4), c=12.459(3) Angstrom, alpha=9 4.96(2), beta=103.48(2), gamma=107.95 (2)degrees, Z=2.