At least since the discovery of graphene and the subsequent finding of a plethora of other 2D materials, it is well anticipated that the dimensionality of a material may constitute a functional parameter. In this paper, we discuss zero-field 53Cr nuclear magnetic resonance (NMR) measured in the magnetically ordered state and 35Cl nuclear quadruple resonance (NQR) data derived in the paramagnetic state of the two-dimensional van der Waals material CrCl3, comparing the results for a bulk single crystal and a nanocrystal. In particular, we apply these spectroscopic methods to monitor the evolution of local environments in the single crystal across the structural phase transition and compare the structural and magnetic properties of a bulk single crystal and nanocrystal sample at low temperatures. The actual structural transition is reported to be of first order, where a certain hysteresis is to be expected. However, we see that both the high- and low-temperature phases coexist in both sample types across the full temperature range (300 K-1.5 K) albeit with different phase fractions. This coexistence of phases in different sample types originates in a kinetic arrest where the arrested structural domains are related to defects and stacking faults. Such defects are to a large part found in the nanocrystal but to a smaller extent in the bulk single crystal. These frozen-in phases have further consequences: The critical exponent beta, derived by fitting the 53Cr NMR data, is considered to denote the dimensionality of magnetic interactions. Here, the values differ considerably for both sample types. Probably, the difference in beta arises from the specific domain structure of kinetically arrested phases and, in turn, from an altered interlayer magnetic exchange mediated by magnetic moments related to frozen-in domains that are related to defects and stacking faults,with their number being much higher in the nanocrystal. These findings may, in part, explain the different magnetic properties reported for different samples as their individual defect landscape determines the kinetically arrested phase fraction in CrCl3. Hence, the structure-property relation in CrCl3 is even more complex than anticipated.

1.1. Besides the prosthetic groups, disulfide, sulfhydryl and basic groups in the protein component of catalase are active centers for the reaction with H2O2. The disulfide and sulfhydryl groups behave as a redox system acting upon H2O2. The basic groups interact with the prosthetic groups. This influences the binding strength of the peroxide, which is combined with the Fe+ of the prosthetic group. It is discussed which groups in the protein component could be responsible for the heme-protein interaction.2.2. The actual activity of catalase may be derived from the measured activity-pH relationship by elimination of the five intermediate equilibria. These are: the dissociation of peroxide, the dissociation of catalase hydroxide, the dissociation of catalase peroxide, the pH dependence of the redox potential and the pH dependence of latent sulfhydryl groups. The actual catalase activity is pH dependent because of heme-protein interaction.3.3. With the help of these results the fundamental mechanism of the catalatic reaction may be explained. The oxidation of peroxide to oxygen by the disulfide bridges of catalase is the rate-determining process, the peroxide being combined with the Fe of the heme group. The reaction velocity depends upon the size of the catalase redox potential and the strength of the heme-protein interaction. Values for the magnitude of these quantities are presented

1.1. The amperometrically titratable disulfide and sulfhydryl content of beef-liver catalase is not constant. It changes with enzyme activity, pH and after the action of weak oxidizing agents. As a rule, the ratio disulfide: sulfhydryl increases with increasing enzyme activity. With variation of pH latent sulfhydryl groups are released, and free sulfhydryl groups are masked. The pK of this equilibrium reaction is 7.18. Through the action of oxidizing agents, some sulfhydryl groups can be oxidized to disulfide groups.2.2. When the sulfhydryl groups of catalase are blocked by Hg2+ or C6H5Hg+ a loss of enzyme activity occurs. The loss of activity with increasing Hg2+ or C6H5Hg+ concentration may be represented as an equilibrium curve. The change of activity on blocking the prosthetic groups with azide can be expressed in the same way.3.3. The dissociation of the proton from the sulfhydryl group was followed by electrometric titration. The dissociation constant was found to be 2.00 · 10−9 M (at 0°).

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Angewandte ChemieVolume 75, Issue 6 p. 302-302 Versammlungsberichte Änderung des Diamagnetismus bei der Bildung organischer Salze und Additionsverbindungen B. Stemminger, B. Stemminger BerlinSearch for more papers by this authorW. Haberditzl, W. Haberditzl BerlinSearch for more papers by this authorR. Havemann, R. Havemann BerlinSearch for more papers by this author B. Stemminger, B. Stemminger BerlinSearch for more papers by this authorW. Haberditzl, W. Haberditzl BerlinSearch for more papers by this authorR. Havemann, R. Havemann BerlinSearch for more papers by this author First published: 21. März 1963 https://doi.org/10.1002/ange.19630750625AboutPDF ToolsRequest permissionAdd to favorites ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat No abstract is available for this article. Volume75, Issue621. März 1963Pages 302-302 This is the German version of Angewandte Chemie. Note for articles published since 1962: Do not cite this version alone. Take me to the International Edition version with citable page numbers, DOI, and citation export. We apologize for the inconvenience. RelatedInformation

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Article Magnetochemische Untersuchungen an Porphyrin- und Phthalocyanin-Schwermetall-Komplexen was published on January 1, 1962 in the journal Zeitschrift für Physikalische Chemie (volume 218O, issue 1).

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