Dataset Information

A Rare Low-Spin CoIV Bis(?-silyldiamide) with High Thermal Stability: Steric Enforcement of a Doublet Configuration.

ABSTRACT: Attempted preparation of a chelated CoII ?-silylamide resulted in the unprecedented disproportionation to Co0 and a spirocyclic cobalt(IV) bis(?-silyldiamide): [Co[(Nt Bu)2 SiMe2 ]2 ] (1). Compound?1 exhibited a room-temperature magnetic moment of 1.8?B.M. and a solid-state axial EPR spectrum diagnostic of a rare S= 1/2 configuration for tetrahedral CoIV . Ab initio semicanonical coupled-cluster calculations (DLPNO-CCSD(T)) revealed the doublet state was clearly preferred (-27?kcal?mol-1 ) over higher spin configurations only for the bulky tert-butyl-substituted analogue. Unlike other CoIV complexes, 1 had remarkable thermal stability, and was demonstrated to form a stable self-limiting monolayer in preliminary atomic layer deposition (ALD) surface saturation experiments. The ease of synthesis and high stability make 1 an attractive starting point to investigate otherwise inaccessible CoIV intermediates and for synthesizing new materials.

SUBMITTER: Zanders D

PROVIDER: S-EPMC7496428 | biostudies-literature | 2020 Aug

REPOSITORIES: biostudies-literature

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A Rare Low-Spin CoIV Bis(β-silyldiamide) with High Thermal Stability: Steric Enforcement of a Doublet Configuration.

Zanders David D Bačić Goran G Leckie Dominique D Odegbesan Oluwadamilola O Rawson Jeremy J Masuda Jason D JD Devi Anjana A Barry Seán T ST

Angewandte Chemie (International ed. in English) 20200608 33

Attempted preparation of a chelated CoII β-silylamide resulted in the unprecedented disproportionation to Co0 and a spirocyclic cobalt(IV) bis(β-silyldiamide): [Co[(Nt Bu)2 SiMe2 ]2 ] (1). Compound 1 exhibited a room-temperature magnetic moment of 1.8 B.M. and a solid-state axial EPR spectrum diagnostic of a rare S= 1 / 2 configuration for tetrahedral CoIV . Ab initio semicanonical coupled-cluster calculations (DLPNO-C ...[more]

PMID: 32369235

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Project description:In this work, electron paramagnetic resonance (EPR) spectroscopy and X-ray crystallography were used to examine the origins of EPR line shapes from spin-labels at the protein-lipid interface on the β-barrel membrane protein BtuB. Two atomic-resolution structures were obtained for the methanethiosulfonate spin-label derivatized to cysteines on the membrane-facing surface of BtuB. At one of these sites, position 156, the label side chain resides in a pocket formed by neighboring residues; however, it extends from the protein surface and yields a single-component EPR spectrum in the crystal that results primarily from fast rotation about the fourth and fifth bonds linking the spin-label to the protein backbone. In lipid bilayers, site 156 yields a multicomponent spectrum resulting from different rotameric states of the labeled side chain. Moreover, changes in the lipid environment, such as variations in bilayer thickness, modulate the EPR spectrum by modulating label rotamer populations. At a second site, position 371, the labeled side chain interacts with a pocket on the protein surface, leading to a highly immobilized single-component EPR spectrum that is not sensitive to hydrocarbon thickness. This spectrum is similar to that seen at other sites that are deep in the hydrocarbon, such as position 170. This work indicates that the rotameric states of spin-labels on exposed hydrocarbon sites are sensitive to the environment at the protein-hydrocarbon interface, and that this environment may modulate weak interactions between the labeled side chain and the protein surface. In the case of BtuB, lipid acyl chain packing is not symmetric around the β-barrel, and EPR spectra from labeled hydrocarbon-facing sites in BtuB may reflect this asymmetry. In addition to facilitating the interpretation of EPR spectra of membrane proteins, these results have important implications for the use of long-range distance restraints in protein structure refinement that are obtained from spin-labels.

Dataset Information

A Rare Low-Spin CoIV Bis(?-silyldiamide) with High Thermal Stability: Steric Enforcement of a Doublet Configuration.

Publications

A Rare Low-Spin Co<sup>IV</sup> Bis(β-silyldiamide) with High Thermal Stability: Steric Enforcement of a Doublet Configuration.

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