Lithol Red : a systematic structural study on salts of a sulfonated azo pigment

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Kennedy, Alan and Stewart, Heather and Eremin, Katherine and Stenger, Jens (2012) Lithol Red : a systematic structural study on salts of a sulfonated azo pigment. Chemistry - A European Journal, 18 (10). pp. 3064-3069. ISSN 1521-3765 (https://doi.org/10.1002/chem.201103027)

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Abstract

The first systematic series of single-crystal diffraction structures of azo lake pigments is presented (Lithol Red with cations=MgII, CaII, SrII, BaII, NaI and CdII) and includes the only known structures of non-Ca examples of these pigments. It is shown that these commercially and culturally important species show structural behaviour that can be predicted from a database of structures of related sulfonated azo dyes, a database that was specifically constructed for this purpose. Examples of the successful structural predictions from the prior understanding of the model compounds are that 1) the Mg salt is a solvent-separated ion pair, whereas the heavier alkaline-earth elements Ca, Sr and Ba form contact ion pairs, namely, low-dimensional coordination complexes; 2) all of the Lithol Red anions exist as the hydrazone tautomer and have planar geometries; and 3) the commonly observed packing mode of alternating inorganic layers and organic bilayers is as expected for an ortho-sulfonated azo species with a planar anion geometry. However, the literature database of dye structures has no predictive use for organic solvate structures, such as that of the observed Na Lithol Red DMF solvate. Interestingly, the Cd salt is isostructural with the Mg salt and not with the Ca salt. It is also observed that linked eight-membered [MOSO]2 rings are the basic coordination motif for all of the known structures of Ca, Sr and Ba salts of sulfonated azo pigments in which competing carboxylate groups are absent.

ORCID iDs

Kennedy, Alan ORCID logoORCID: https://orcid.org/0000-0003-3652-6015, Stewart, Heather, Eremin, Katherine and Stenger, Jens;
  • Item type:Article
    ID code:39751
    Dates:
    Date
    Event
    5 March 2012
    Published
    Notes:Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
    Subjects:Science > Chemistry
    Department:Faculty of Science > Pure and Applied Chemistry
    Depositing user: Pure Administrator
    Date deposited:17 May 2012 14:26
    Last modified:11 Nov 2024 10:08
    URI:https://strathprints.strath.ac.uk/id/eprint/39751
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