Conformations and rotational barriers of di‐ and tetraarylporphyrins; a computational and experimental study

Schrijvers, R.; Dijk, M. van; Sanders, Georgine M.; Sudhölter, Ernst J. R.

doi:10.1002/recl.19941130703

Cited by 14 publications

(7 citation statements)

References 16 publications

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“…The suspension was stirred under a positive pressure of hydrogen gas for 21 h. The solvent was distilled under reduced pressure, and the residue dissolved in a mixture of water and dichloromethane. (15). Metallic sodium (0.23 g, 0.010 mol) was dissolved in 500 mL of benzyl alcohol, and 23 g (0.10 mol) of 14 was added.…”

Section: Methodsmentioning

confidence: 99%

“…For steric reasons, this is not the case. In the solid state, the dihedral angle between the plane of the porphyrin and the plane of the aryl group is usually between 60° and 90°. − Calculations and NMR studies in solution , have estimated the angle to be about 45°. At angles between 0° and 90°, conjugation between the two π-electron systems would be partial.…”

Section: Introductionmentioning

confidence: 99%

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Aryl Ring Rotation in Porphyrins. A Carbon-13 NMR Spin−Lattice Relaxation Time Study

et al. 1997

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Overall tumbling and internal rotational motions in porphyrins bearing meso aryl substituents and, in some cases, flanking alkyl groups at the β-pyrrolic positions have been determined using 13 C spin-lattice relaxation time measurements. In deuteriochloroform solution at 303 K, the overall reorientation of all three porphyrins investigated occurs with diffusion coefficients of ∼1 × 10 9 s -1 . In porphyrins with only hydrogen at the β-pyrrolic positions, the meso phenyl rings undergo rotations about their single bonds to the porphyrin with diffusion coefficients of ∼4 × 10 9 s -1 . Introduction of methyl substituents at the β-pyrrolic positions adjacent to the phenyl rings reduces these motions, but only to ∼1 × 10 9 s -1 . Thus, significant internal motions are present in both types of molecules. These motions occur on the time scale of many photoinduced electron and energy transfer processes in porphyrins covalently linked to electron or energy donors or acceptors through meso aryl groups. Thus, the internal librational motions may affect rates of photoinduced electron and energy transfer, even in relatively "rigid" molecular constructs.

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Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Aryl Ring Rotation in Porphyrins. A Carbon-13 NMR Spin−Lattice Relaxation Time Study

et al. 1997

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“…In porphyrins with unsubstituted “β-pyrrolic” peripheral positions ( cf. structure 3 ), these aryl rings make angles ≥45° but <90° with the mean porphyrin plane. − Thus, conjugation between the ring and the macrocycle π-electron system can play a role in the donor−acceptor electronic interaction, which in turn affects the electron-transfer rate . A number of investigators have attempted to limit this conjugative interaction by placing alkyl groups at the β-pyrrolic positions ( cf.…”

Section: Introductionmentioning

confidence: 99%

Structural Effects on Photoinduced Electron Transfer in Carotenoid−Porphyrin−Quinone Triads

et al. 1997

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meso-Polyarylporphyrins are often used as components of molecules that mimic photosynthetic reaction centers by carrying out photoinduced electron-transfer reactions. Studies of these systems have raised questions concerning the role of alkyl substituents at the "β-pyrrolic" positions on the porphyrin periphery in limiting π-π overlap between the macrocycle and the aryl rings. The degree of overlap affects electronic coupling and, therefore, the rates of electron-transfer reactions. There is also evidence that when the linkages joining porphyrins to electron-acceptor or -donor moieties contain amide bonds, the sense of the amide linkage may strongly affect electron-transfer rate constants. In this study, three carotenoid-porphyrin-quinone molecular triads and various model compounds have been prepared, and electron-transfer has been studied using timeresolved emission and absorption techniques. The results show that steric hindrance due to methyl groups at the β-pyrrolic positions reduces electron-transfer rate constants by a factor of ∼ 1 / 5 . In addition, amidecontaining donor-acceptor linkages having the nitrogen atom attached to the porphyrin meso-aryl ring demonstrate electron-transfer rate constants ∼30 times larger than those for similar linkages with the amide reversed, after correction for thermodynamic effects.

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“…21 Due to this wide versatility, both theoretical and experimental studies have addressed the underlying factors that influence the rotation of these aryl rings. [22][23][24][25][26][27][28][29][30][31][32][33][34][35][36][37] Unsymmetric substitution of the meso aryl ring can result in atropisomers, which arise from differing orientations of the aryl substituents above or below the porphyrin plane. Models have indicated that deformation of the porphyrin core from a planar configuration is required in order for these interacting substituents to pass one another in the transition state.…”

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confidence: 99%

Synthesis, characterization, and atropisomerism of iron complexes containing the tetrakis(2-chloro-6-fluorophenyl)porphyrinate ligand

et al. 2015

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Iron complexes of the meso-(tetraaryl)porphyrin, 5,10,15,20-tetrakis(2-chloro-6-fluorophenyl)porphine (H2ClFTPP) are reported. This unique ligand affords the opportunity to study atropisomerism in a porphyrin system containing similar substituents in the 2 and 6 positions of the meso-aryl rings. The atropisomerism displayed by the iron porphyrinates is observed to be a function of both the oxidation state of the metal and the nature of the axial ligand. In the case of iron(iii) porphyrinates, a single atropisomer is favored, whereas with the iron(ii) porphyrinate a statistical distribution of all possible atropisomers is observed. Variable temperature studies with the iron(ii) porphyrinate demonstrate that the distribution of atropisomers is maintained even at elevated temperatures. The results are discussed in the context of atropisomerism with other meso-(tetraaryl)porphyrins.

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Conformations and rotational barriers of di‐ and tetraarylporphyrins; a computational and experimental study

Cited by 14 publications

References 16 publications

Aryl Ring Rotation in Porphyrins. A Carbon-13 NMR Spin−Lattice Relaxation Time Study

Aryl Ring Rotation in Porphyrins. A Carbon-13 NMR Spin−Lattice Relaxation Time Study

Structural Effects on Photoinduced Electron Transfer in Carotenoid−Porphyrin−Quinone Triads

Synthesis, characterization, and atropisomerism of iron complexes containing the tetrakis(2-chloro-6-fluorophenyl)porphyrinate ligand

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