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Allosteric Guest Binding in Chiral Zirconium(IV) Double Decker Porphyrin Cages.

ABSTRACT: Chiral zirconium(IV) double cage sandwich complex Zr(1)₂ has been synthesized in one step from porphyrin cage H₂1. Zr(1)₂ was obtained as a racemate, which was resolved by HPLC and the enantiomers were isolated in >99.5 % ee. Their absolute configurations were assigned on the basis of X-ray crystallography and circular dichroism spectroscopy. Vibrational circular dichroism (VCD) experiments on the enantiomers of Zr(1)₂ revealed that the chirality around the zirconium center is propagated throughout the whole cage structure. The axial conformational chirality of the double cage complex displayed a VCD fingerprint similar to the one observed previously for a related chiral cage compound with planar and point chirality. Zr(1)₂ shows fluorescence, which is quenched when viologen guests bind in its cavities. The binding of viologen and dihydroxybenzene derivatives in the two cavities of Zr(1)₂ occurs with negative allostery, the cooperativity factors α (=4 K₂/K₁) being as low as 0.0076 for the binding of N,N'-dimethylviologen. These allosteric effects are attributed to a pinching of the second cavity as a result of guest binding in the first cavity.

SUBMITTER: Bruekers JPJ

PROVIDER: S-EPMC7898692 | biostudies-literature | 2021 Jan

REPOSITORIES: biostudies-literature

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Allosteric Guest Binding in Chiral Zirconium(IV) Double Decker Porphyrin Cages.

Bruekers Jeroen P J JPJ Hellinghuizen Matthijs A MA Vanthuyne Nicolas N Tinnemans Paul P Gilissen Pieter J PJ Buma Wybren Jan WJ Naubron Jean-Valère JV Crassous Jeanne J Elemans Johannes A A W JAAW Nolte Roeland J M RJM

European journal of organic chemistry 20210105 4

Chiral zirconium(IV) double cage sandwich complex Zr(1)2 has been synthesized in one step from porphyrin cage H21. Zr(1)2 was obtained as a racemate, which was resolved by HPLC and the enantiomers were isolated in >99.5 % ee. Their absolute configurations were assigned on the basis of X-ray crystallography and circular dichroism spectroscopy. Vibrational circular dichroism (VCD) experiments on the enantiomers of Zr(1)2 revealed tha ...[more]

PMID: 33679232

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Project description:Metalloporphyrin and metallophthalocyanine dyes ligating Hf(IV) and Zr(IV) ions bind to semiconductor oxide surfaces such as TiO(2) via the protruding group IV metal ions. The use of oxophylic metal ions with large ionic radii that protrude from the macrocycle is a unique mode of attaching chromophores to oxide surfaces in the design of dye-sensitized solar cells (DSSCs). Our previous report on the structure and physical properties of ternary complexes wherein the Hf(IV) and Zr(IV) ions are ligated to both a porphyrinoid and to a defect site on a polyoxometalate (POM) represents a model for this new way of binding dyes to oxide surfaces. The Zr(IV) and Hf(IV) complexes of 5,10,15,20-tetraphenylporphyrin (TPP) with two ligated acetates, (TPP)Hf(OAc)(2) and (TPP)Zr(OAc)(2), and the corresponding metallophthalocyanine (Pc) diacetate complexes, (Pc)Hf(OAc)(2) and (Pc)Zr(OAc)(2), were evaluated as novel dyes for the fabrication of dye-sensitized solar cells. Similarly to the ternary complexes with the POM, the oxide surface replaces the acetates to affect binding. In DSSCs the Zr(IV) phthalocyanine dye performs better than the Zr(IV) porphyrin dye, and reaches an overall efficiency of ~ 1.0%. The Hf(IV) dyes are less efficient. The photophysical properties of these complexes in solution suggested energetically favorable injection of electrons into the conduction band of TiO(2) semiconductor nanoparticles, as well as a good band gap match with I(3) (-)/I(-) pair in liquid 1-butyl-3-methyl imidazolium iodide. The combination of blue absorbing TPP with the red absorbing Pc complexes can increase the absorbance of solar light in the device; however, the overall conversion efficiency of DSSCs using TiO(2) nanoparticles treated with a mixture of both Zr(IV) complexes is comparable, but not greater than, the single (Pc)Zr. Thus, surface bound (TPP)Zr increases the absorbance in blue region of the spectra, but at the cost of diminished absorbance in the red in this DSSC architecture.

Dataset Information

Allosteric Guest Binding in Chiral Zirconium(IV) Double Decker Porphyrin Cages.

Publications

Allosteric Guest Binding in Chiral Zirconium(IV) Double Decker Porphyrin Cages.

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