Effects of the Dendrimer Cage on O2 Binding of Dendritic Cobalt(II) Porphyrins

Doorslaer, Sabine Van; Zingg, Adrien; Schweiger, Arthur; Diederich, François

doi:10.1002/1439-7641(20020816)3:8<659::aid-cphc659>3.0.co;2-g

Cited by 27 publications

(19 citation statements)

References 18 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…At X-band frequency, the whole spectrum is ∼20 mT wide. Its appearance resembles many X-band spectra of oxygenated forms of related cobalt complexes and cobaloximes (see, e.g., refs , , ). A well-resolved hyperfine structure is visible around g y , although the hyperfine structure around g x is not resolved.…”

Section: Resultssupporting

confidence: 56%

“…This is in contrast to vitamin B 12 complexes, in which the hyperfine structure at low field is typically well resolved. 61,64,65 The number of lines could only be reproduced in the spectral simulation by the assumption of significant hyperfine interaction of one phosphorus nucleus and one cobalt nucleus, both being very similar in magnitude, around 35 MHz. The presence of substantial 31 P hyperfine interaction was confirmed by additional experiments.…”

Section: ■ Results and Discussionmentioning

confidence: 99%

See 1 more Smart Citation

The Hydrogen Catalyst Cobaloxime: A Multifrequency EPR and DFT Study of Cobaloxime’s Electronic Structure

et al. 2012

View full text Add to dashboard Cite

Solar fuels research aims to mimic photosynthesis and devise integrated systems that can capture, convert, and store solar energy in the form of high-energy molecular bonds. Molecular hydrogen is generally considered an ideal solar fuel as its combustion is essentially pollution-free. Cobaloximes rank among the most promising earth-abundant catalysts for the reduction of protons to molecular hydrogen. We have used multifrequency EPR spectroscopy at X-band, Q-band, and D-band combined with DFT calculations to reveal electronic structure and establish correlations between structure, surroundings and catalytic activity of these complexes. To assess the strength and nature of ligand cobalt interactions, the BF2-capped cobaloxime, Co(dmgBF2)2, was studied in a variety of different solvents with a range of polarities and stoichiometric amounts of potential ligands to the cobalt ion. This allows the differentiation of labile and strongly coordinating axial ligands for the Co(II) complex. Labile, or weakly coordinating, ligands like methanol result in larger g-tensor anisotropy than strongly coordinating ligands like pyridine. Additionally, a coordination number effect is seen for the strongly coordinating ligands with both singly-ligated LCo(dmgBF2)2 and doubly-ligated L2Co(dmgBF2)2. The presence of two strongly coordinating axial ligands leads to the smallest g-tensor anisotropy. The relevance of the strength of the axial ligand(s) to the catalytic efficiency of Co(dmgBF2)2 is discussed. Finally, the influence of molecular oxygen and formation of Co(III) superoxide radicals LCo(dmgBF2)2O2• is studied. The experimental results are compared with a comprehensive set of DFT calculations on Co(dmgBF2)2 model systems with various axial ligands. Comparison with experimental values for the “key” magnetic parameters like g-tensor and 59Co hyperfine coupling tensor allows the determination of the conformation of the axially ligated Co(dmgBF2)2 complexes. The data presented here are vital for understanding the influence of solvent and ligand coordination on the catalytic efficiency of cobaloximes.

show abstract

Section: Resultssupporting

confidence: 56%

Section: ■ Results and Discussionmentioning

confidence: 99%

The Hydrogen Catalyst Cobaloxime: A Multifrequency EPR and DFT Study of Cobaloxime’s Electronic Structure

et al. 2012

View full text Add to dashboard Cite

show abstract

“…We and others have sought to prepare several types of redox-active core dendrimers to study these various phenomena. These include illustrating the effect of dendrimer architecture on rate and driving force for electron transfer, ,,, comparison of structural features in dendrimer isomers, and illustration of the behaviors of several types of redox active cores in dendrimers including Fe 4 S 4 , Mo 6 Cl 8 , Re 6 Se 8 , − ferrocene, − and porphyrins. − …”

Section: Introductionmentioning

confidence: 99%

Synthetic Approaches to an Isostructural Series of Redox-Active, Metal Tris(bipyridine) Core Dendrimers

Hong

Gorman

2003

J. Org. Chem.

View full text Add to dashboard Cite

Several types of six-armed, metal tris(bipyridine) core dendrimers were synthesized. Bis-4,4'-alkoxy bipyridine dendrons were prepared and employed to make tris(bipyridine) dendrimers. Although the ruthenium-centered and iron-centered dendrimers displayed quasi-reversible cyclic voltammetry, the analogous cobalt-centered complex did not. The synthesis of 4,4'-disubstituted bipyridines containing -CH(2)OR groups proceeded in low yield. The reactions of the dicarbanion of 4,4'-dimethyl bipyridine prepared with LDA and mesylate, triflate, and bromide groups were found to result in no or poor yields of carbon-carbon bond formation. Use of KDA in place of LDA resulted in much higher yields of dendritic bipyridines.

show abstract

“…The cage effect, therefore, was extensively applied in studies on radical reaction mechanism [13] , determination of rate constant [2] , stabilization of labile species [14] , chiral molecular recognition [15] , encapsulation of nonpolar molecules (e.g., He, H 2 and O 2 ) [16,17] , molecular reactor [3,18] , and so on.…”

Section: Introductionmentioning

confidence: 99%

The cage effect on assembly of cyclic-bis-(zinc porphyrin) with 5,15-dipyridylporphyrin

Zhou

Zhu

Zheng

2009

Sci. China Ser. B-Chem.

View full text Add to dashboard Cite

An inclusion complex of cyclic bis(zinc porphyrin) 1 with 5,15-dipyridylporphyrin derivative 3 has been designed and constructed. The complex formation is induced by Zn-N coordination, and is robust (K assoc ~ 10 6 L/mol) due to the presence of the cage effect of cyclic bis(zinc porphyrin). The cage-like complex as an entity is stable enough, and also convenient to achieve relative movement between the bis(zinc porphyrin) host and the dipyridylporphyrin guest connected by Zn-N coordination. The characteristics of these assemblies have been demonstrated by 1 H NMR, UV-vis, and fluorescence spectra. The results show its potential applications as a molecular gyroscope in molecular machines.cage effect, cyclic bis(zinc porphyrin), assembly, template-directed synthesis

show abstract

Effects of the Dendrimer Cage on O2 Binding of Dendritic Cobalt(II) Porphyrins

Cited by 27 publications

References 18 publications

The Hydrogen Catalyst Cobaloxime: A Multifrequency EPR and DFT Study of Cobaloxime’s Electronic Structure

The Hydrogen Catalyst Cobaloxime: A Multifrequency EPR and DFT Study of Cobaloxime’s Electronic Structure

Synthetic Approaches to an Isostructural Series of Redox-Active, Metal Tris(bipyridine) Core Dendrimers

The cage effect on assembly of cyclic-bis-(zinc porphyrin) with 5,15-dipyridylporphyrin

Contact Info

Product

Resources

About