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

• Published in: CrystEngComm 2018, Vol.2 (31), p.4463-4484
• Main Authors: Ion, Adrian E, Dogaru, Andreea, Shova, Sergiu, Madalan, Augustin M, Akintola, Oluseun, Ionescu, Sorana, Voicescu, Mariana, Nica, Simona, Buchholz, Axel, Plass, Winfried, Andruh, Marius
• Format: Article
• Language: English
• Subjects: Absorption spectra; Acids; Architecture; Azulene; Benzoic acid; Bonding strength; Chains; Channels; Crystal structure; Crystallization; Crystals; Hydrogen bonding; Hydrogen bonds; Optical properties; Trimesic acid; Water chemistry
• ISSN: 1466-8033; 1466-8033
• DOI: 10.1039/c8ce00945g

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 R 4 4 (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. 1,3-Bis(4-pyridyl)azulene has been employed as a hydrogen bond acceptor to construct two-component organic cocrystals.