No abstract

Using the concepts of self-assembly developed for the construction of topologically complex molecules such as [2]-catenanes and rotaxanes, the syntheses of several prophyrin-catenanes are described. The successful insertion of the porphyrin subunit into [2]-catenanes has resulted from the adaptation of previously devised template-directed syntheses based primarily on ?T-r interactions and C-He-0 and C-H-r hydrogen bonding. Several hydroquinolcontaining ether chains were successfully synthesized and subsequently strapped across a porphyrin ring; the X-ray crystal structures of two such molecules which vary in the length of the ether chain are reported. These strapped porphyrins were found to complex paraquat with a parallel orientation of the hydroquinol, paraquat, and porphyrin rings. The complexation of paraquat (K,, = 1955 and 1640 M-I, AGO = -4.5 and -4.4 kcal mol-' for 9 and 11, respectively) by these strapped porphyrins led to their subsequent inclusion, using template-directed self-assembly, into structures which represent the first examples of porphyrin-containing [2]-catenanes. The catenanes were subsequently characterized by FAB-MS and thoroughly examined using dynamic IH NMR. In the case of the hydroquinol-containing catenanes, a dynamic process was observed in solution in which the bipyridinium subunits of the tetracation were exchanged between "inside" and "outside" environments (rotation around the hydroquinol ring axis). The diethylene glycol containing catenanes 14 and 15 were observed to maintain an orientation of the tetracation in which the bipyridinium subunits are parallel to the porphyrin ring. The length of the ether strap in these catenanes influenced the rotation rates of the tetracation macrocycles (50 and 80 times per second for 14 and 15 and 2500 and 1500 times per second for 16 and 17, respectively) at ambient temperature. However, in all the catenanes, the overall orientation of the tetracation, with bipyridinium and porphyrin rings coparallel, is retained in solution. As an extension of the original concepts, an analogous strapped porphyrin containing a naphthoquinol moiety was synthesized and found to complex paraquat with K, = 21 000 M-I and AGO = -5.9 kcal mol-'. The general applicability of the template-directed synthetic procedure developed for porphyrin catenane synthesis was illustrated by the successful isolation of the naphthalenecontaining porphyrin [2]-catenane 23 in 45% yield. Tetracation exchange processes similar to those for the hydroquinol catenanes were observed, along with an additional process which was found to be the decomplexation/complexation of the naphthalene ring in what is termed an "out, turn around, and in again" process similar to that occurring in nonporphyrinic naphthalene [2]-catenanes.

No abstract

The solution optical and NMR spectra of (TPP)MnX (X = F-, NCO, CH3CO2", HCO2", N3", Cl", Br, NO2", NO3", NCS", CN-, I", C104", BF4", B(C6H5)4-) indicate that ionic bonding may be particularly important in manganese tetraphenylporphyrin complexes. A Karplus-Fraenkel equation utilization of 13C NMR spectra for the calculation of electron spin densities at the porphyrin nuclei uncovers an unexpectedly high positive density at the pyrrole -carbon sites. The densities for the acetato, nitrato, and perchlorate complexes are 0.049, 0.056, and 0.063, respectively. Such high densities are unlikely to be covalent in origin, and accordingly an axial ligand dependent mixture of the [Mnn(S = 3/2,4A2)P(S = *l/2,2 2)•"]+ + [Mnm(S = 2,5Ai)P2"]+ electronic states is proposed for the ground valence state of manganese tetraphenylporphyrin complexes. The calculations probably underestimate the -carbon spin densities, so the C2v (d^,^)0 (d^)1 (dxz dyz)2 (dxy)2 (a2(vr))1 (3 ( ))2 [MnnP,-]+ valence state is likely to be the principal ground-state contributor. The electron spin at the -carbon sites dominates the carbon-13 spectroscopy through polarization and correlation. In contrast to previous deductions of negative ( ) density, but in accord with the hyperporphyrin optical spectra, a high positive ( ) density is present at the meso sites. This spin density is effectively undermined by the greater spin at the -carbon location. The phenyl residue NMR reflects an axial ligand dependent balance of spin polarization and positive spin delocalization from the meso position. The

[reaction: see text] A series of diimide-based macrocycles have been prepared using Mitsunobu-mediated alkylation as the macrocyclization step. These macrocycles could not be incorporated into [2]catenanes using previously established building blocks and coupling methodology. However, when one of the macrocycle syntheses was conducted in the presence of a dinaphtho crown ether, catenane formation was achieved. This result is discussed in terms of the ability of the components to establish intermolecular C-H...O hydrogen-bonding contacts.