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Issue 31, 2018
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Organic co-crystals of 1,3-bis(4-pyridyl)azulene with a series of hydrogen-bond donors

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The supramolecular interactions between 1,3-bis(4-pyridyl)azulene (azbbpy) as a hydrogen bond acceptor and a variety of aromatic hydrogen-bond donors produced new binary molecular co-crystals and a salt. All crystal structures display extensive and very complex hydrogen bond networks containing both homo- and heterosynthons formed through robust O–H⋯N and OH⋯O hydrogen bonds. The binary co-crystals of azbbpy with 4,4′-biphenol and 4,4′-oxo-bis-benzoic acid in a 1 : 1 ratio revealed that the recognition process differs. While 4,4′-biphenol acts both as a donor and an acceptor of protons, generating a two-dimensional supramolecular network in which azbbpy interacts with only one pyridine moiety, the co-crystallization with 4,4′-oxo-bis-benzoic acid yielded zig-zag chains formed by alternating acid–pyridine supramolecular heterosynthons. Co-crystallization with isophthalic acid yields a 2 : 1 system, 4, as hydrogen-bonded zig-zag supramolecular chains containing a R44(36) graph set organized through strong OH⋯N and weak C–H⋯N hydrogen bonds. Co-crystallization of azbbpy with trimesic acid in different ratios yielded two distinct systems: co-crystal 5 and salt 6. In 5, the trimesic acid molecules are assembled in supramolecular helical chains which are further connected by azbbpy through hydrogen bonding and π–π interactions into a 3D architecture with channels that host water molecules. A complicated supramolecular 3D architecture is also established between trimesic anions and azbbpyH+ cations in crystal 6, resulting in channels filled with disordered solvent molecules. These types of interactions were also evidenced in a quantitative way and confirmed on grounds of the Hirshfeld surface mapped with geometrical parameters that characterize close contacts in co-crystals. The optical properties of these supramolecular systems showed strong absorption bands in the visible region due to the azulene fragment.

Graphical abstract: Organic co-crystals of 1,3-bis(4-pyridyl)azulene with a series of hydrogen-bond donors

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Publication details

The article was received on 08 Jun 2018, accepted on 05 Jul 2018 and first published on 05 Jul 2018

Article type: Paper
DOI: 10.1039/C8CE00945G
Citation: CrystEngComm, 2018,20, 4463-4484

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    Organic co-crystals of 1,3-bis(4-pyridyl)azulene with a series of hydrogen-bond donors

    A. E. Ion, A. Dogaru, S. Shova, A. M. Madalan, O. Akintola, S. Ionescu, M. Voicescu, S. Nica, A. Buchholz, W. Plass and M. Andruh, CrystEngComm, 2018, 20, 4463
    DOI: 10.1039/C8CE00945G

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