Dataset Information

?-Octabromo- and ?-Octakis(trifluoromethyl)isocorroles: New Sterically Constrained Macrocyclic Ligands.

ABSTRACT: Presented herein is a study of the acid-induced demetalation of two sterically hindered copper corroles, Cu ?-octabromo-meso-triphenylcorrole (Cu[Br₈TPC]) and ?-octakis(trifluoromethyl)-meso-tris(p-methoxyphenyl)corrole (Cu[(CF₃)₈TpOMePC]). Unlike reductive demetalation, which affords the free-base ?-octabromocorrole, demetalation of Cu[Br₈TPC] under non- reductive conditions (CHCl₃/H₂SO₄) resulted in moderate yields of free-base 5- and 10-hydroxy isocorroles. The isomeric free bases could be complexed to Co^II and Ni^II, affording stable complexes. Only reductive demetalation was found to work for Cu[(CF₃)₈TpOMePC], affording a highly saddled, hydrated corrole, H₃[5-OH,10-H-(CF₃)₈TpOMePC], where the elements of water had added across C₅ and C₁₀. Interaction of this novel free base with Co^II resulted in Co[iso-10-H-[CF₃)₈TpOMePC], a Co^II 10-hydro isocorrole. The new metal complexes were all characterized by single-crystal X-ray diffraction analysis and, despite their sterically hindered nature, were found to exhibit almost perfectly planar isocorrole cores.

SUBMITTER: Thomas KE

PROVIDER: S-EPMC5474668 | biostudies-literature | 2017 Jun

REPOSITORIES: biostudies-literature

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β-Octabromo- and β-Octakis(trifluoromethyl)isocorroles: New Sterically Constrained Macrocyclic Ligands.

Thomas Kolle E KE Beavers Christine M CM Gagnon Kevin J KJ Ghosh Abhik A

ChemistryOpen 20170526 3

Presented herein is a study of the acid-induced demetalation of two sterically hindered copper corroles, Cu β-octabromo-meso-triphenylcorrole (Cu[Br8TPC]) and β-octakis(trifluoromethyl)-meso-tris(p-methoxyphenyl)corrole (Cu[(CF3)8TpOMePC]). Unlike reductive demetalation, which affords the free-base β-octabromocorrole, demetalation of Cu[Br8TPC] under non- reductive conditions (CHCl3/H2SO4) re ...[more]

PMID: 28638773

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Project description:Photosynthetic reaction centers convert excitation energy from absorbed sunlight into chemical potential energy in the form of a charge-separated state. The rates of the electron transfer reactions necessary to achieve long-lived, high-energy charge-separated states with high quantum yields are determined in part by precise control of the electronic coupling among the chromophores, donors, and acceptors and of the reaction energetics. Successful artificial photosynthetic reaction centers for solar energy conversion have similar requirements. Control of electronic coupling in particular necessitates chemical linkages between active component moieties that both mediate coupling and restrict conformational mobility so that only spatial arrangements that promote favorable coupling are populated. Toward this end, we report the synthesis, structure, and photochemical properties of an artificial reaction center containing two porphyrin electron donor moieties and a fullerene electron acceptor in a macrocyclic arrangement involving a ring of 42 atoms. The two porphyrins are closely spaced, in an arrangement reminiscent of that of the special pair in bacterial reaction centers. The molecule is produced by an unusual cyclization reaction that yields mainly a product with C(2) symmetry and trans-2 disubstitution at the fullerene. The macrocycle maintains a rigid, highly constrained structure that was determined by UV-vis spectroscopy, NMR, mass spectrometry, and molecular modeling at the semiempirical PM6 and DFT (B3LYP/6-31G**) levels. Transient absorption results for the macrocycle in 2-methyltetrahydrofuran reveal photoinduced electron transfer from the porphyrin first excited singlet state to the fullerene to form a P(•+)-C(60)(•-)-P charge separated state with a time constant of 1.1 ps. Photoinduced electron transfer to the fullerene excited singlet state to form the same charge-separated state has a time constant of 15 ps. The charge-separated state is formed with a quantum yield of essentially unity and has a lifetime of 2.7 ns. The ultrafast charge separation coupled with charge recombination that is over 2000 times slower is consistent with a very rigid molecular structure having a small reorganization energy for electron transfer, relative to related porphyrin-fullerene molecules.

Dataset Information

?-Octabromo- and ?-Octakis(trifluoromethyl)isocorroles: New Sterically Constrained Macrocyclic Ligands.

Publications

β-Octabromo- and β-Octakis(trifluoromethyl)isocorroles: New Sterically Constrained Macrocyclic Ligands.

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