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Squaric acid as a versatile compound in the design of molecular solids

Authors
  • Serb, Mihaela Diana
Publication Date
Jan 01, 2008
Source
Publikationsserver der RWTH Aachen University
Keywords
Language
English
License
Green
External links

Abstract

Within the scope of this present work the exploitation of the coordination modes of the squarate and also its acid properties were envisaged. In a systematic way, using either a coordinative or a hydrogen-bonding motif, three classes of compounds have been synthesized and characterized by single-crystal X-ray diffraction: 1. Hydrogen-bonded systems based on acid-base reactions of biguanide derivatives (N,N-dimethylbiguanide, N-phenylbiguanide, N-o-tolylbiguanide) and squaric acid. It is envisaged here the correlation between the pH of the media, the p-delocalization and hydrogen bond lengths. The shortest hydrogen bonds are present in very strong acidic media, due to the presence of the [SQH]- ([SQH]- = monohydrogensquarate) together with [BigH3]2+ ([BigH3]2+= biguanidinium). In these ions the p-delocalization is less pronounced than in [SQ]2- ([SQ]2- = squarate dianion) and [BigH2]+, ([BigH2]+ = monohydrogenbiguanidinium) which are present in basic media.2. Squarate complexes of transition metals. A dinuclear Cu(II)-squarate compound and a series of homo- and heteropolynuclear compounds with magnetically interesting cations have been obtained. The coordination modes of the squarate dianion are µ-1,2-bis(monodentate) in the dinuclear compound and µ-1,3-bis(monodentate) in polynuclear compounds.3. Ag(I)-squarate coordination polymers which combine the bridging ability of squarate with the flexibility in the coordination number, donor type and the geometry adopted by the AgI cation.

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