Porphyrin-fullerene, C60, cocrystallates: influence of C60 on the porphyrin ring conformation.
To examine the influence of fullerene on the macrocyclic ring conformation, crystal structures of a series of cocrystals of 2,3,5,10,12,13,15,20-octaphenylporphyrin, M(TPP)(Ph)(4) (M = 2H, Co(II), Cu(II)), and 2,312,13-tetramethyl-5,7,8,10,15,17,18,20-octaphenyl-porphinato copper(II), CuTPP(Ph)(4)(CH(3))(4), derivatives with fullerene, C(60), were elucidated. Furthermore, crystal structures of the parent porphyrins, M(TPP)(Ph)(4) (M = Co(II), Cu(II)) complexes, were also determined. All the cocrystals revealed one-to-one stoichiometry between the porphyrin and C(60) and were free of lattice solvates. Porphyrin rings in M(TPP)(Ph)(4)·C(60) cocrystals revealed significant distortion with the root-mean-square (rms) value as high as 0.265(2) A which is the average deviation of the 24 atoms core from the least-squares plane. Crystal structures of the parent M(TPP)(Ph)(4) (M = Co(II), Cu(II)) complexes indicated near planarity of the 24-atom core with the root-mean-square deviation value of 0.016(2) A. Molecular packing in the M(TPP)(Ph)(4)·C(60) cocrystals showed essentially one-dimensional chains interconnected by weak interporphyrin and porphyrin-fullerene close contacts. The N(porphyrin)···C(C(60)) shortest distances between the H(2)(TPP)(Ph)(4) (M = 2H, Co(II), Cu(II)) and fullerene in the cocrystals are 3.031(5) A, 3.062(4) A, and 3.059(3) A, respectively. Similarly, close contact M···C distances in the M(TPP)(Ph)(4)·C(60) (M = Co(II), Cu(II)) are 2.761(6) A and 2.886(3) A, respectively. In the Cu(TPP)(Ph)(4)(CH(3))(4)·C(60) cocrystal, the shift of macrocyclic ring toward planarity was evidenced from the rms value of 0.236(2) A relative to that observed in CuTPP(Ph)(4)(CH(3))(4)·CHCl(3) (0.391(2) A). The distortion of the macrocyclic ring in M(TPP)(Ph)(4)·C(60) complexes was examined by normal-coordinate-structure decomposition (NSD) analyses. Their out-of-plane displacement of the core atoms revealed predominant contribution being saddle (∼95-96%) and gentle domed distortions (3-4%). In the case of M(TPP)(Ph)(4)(CH(3))(4)·C(60) cocrystal, it showed mainly saddled (∼83%), minimal ruffled (8%) and domed (8%) distortions of the macrocyclic ring. In-plane displacement on the 24-atom core of the porphyrin in these cocrystallates features generally a varying degree of N-str (B(1g)) and bre (A(1g)) distortions.
Bhyrappa
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Department of Chemistry, Indian Institute of Technology Madras Chennai 600 036, India. byra@iitm.ac.in
Karunanithi
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