Structure Direction, Solvent Effects, and Anion Influences in Halogen-Bonded Adducts of 2,6-Bis(iodoethynyl)pyridine

Barry, Dawn E.; Hawes, Chris S.; Blasco, Salvador; Gunnlaugsson, Thorfinnur

Abstract

A new divergent and self-complementary halogen bond donor–acceptor molecule 2,6-bis(iodoethynyl)pyridine L has been prepared and structurally characterized, and used to generate a series of extended halogen-bonded adducts with tetrabutylammonium halide salts. The reaction between L and anions such as either bromide or chloride gives the one-dimensional polymeric species {L·TBABr} or {L·TBACl}, respectively, which contains helical strands linked by C–I···X– halogen bonds which partially encapsulate the associated organic cations. Varying the reaction solvent from ethyl acetate to 5:95 methanol/ethyl acetate gives rise to another polymeric phase on combining L with tetrabutylammonium chloride, the one-dimensional looped chain structure {L2·TBACl} in which each chloride ion acts as a four-connected square planar node for halogen bonding interactions originating from L. Similar solvent effects are observed in the discrete macrocyclic species {L·TBAI}-α and {L·TBAI}-β, both consisting of cyclic (L2I2)2– species which vary in their extended structures to adopt different packing modes, resembling those observed in the chloride and bromide adducts. Reaction of L with tetrabutylammonium fluoride in the presence of methanol gives a one-dimensional polymeric assembly {L2·TBAF·MeOH} containing a unique MeOH···F– node in which the strongly hydrogen-bonded anionic species is supported solely by four halogen bonding interactions. Excluding hydrogen bond donors from the reaction mixture affords {L3TBAF2}, an overall two-dimensional polymeric assembly consisting of a mixture of one- and two-dimensional networks based on iodine-fluoride halogen bonds. In all cases, the strong interactions between the iodoethynyl groups and halide anions overcome the tendency for L to form the self-complementary halogen-bonded network, showing that synthetically accessible heterocyclic iodoethynyl compounds present exciting new directions in the structural chemistry field.

Citation

Barry, D. E., Hawes, C. S., Blasco, S., & Gunnlaugsson, T. (2016). Structure Direction, Solvent Effects, and Anion Influences in Halogen-Bonded Adducts of 2,6-Bis(iodoethynyl)pyridine. Crystal Growth and Design, 16(9), 5194-5205. https://doi.org/10.1021/acs.cgd.6b00766

• Journal Article Type: Article
• Online Publication Date: Jul 28, 2016
• Publication Date: Sep 7, 2016
• Deposit Date: Jun 16, 2023
• Journal: Crystal Growth & Design
• Print ISSN: 1528-7483
• Electronic ISSN: 1528-7505
• Publisher: American Chemical Society
• Peer Reviewed: Peer Reviewed
• Volume: 16
• Issue: 9
• Pages: 5194-5205
• DOI: https://doi.org/10.1021/acs.cgd.6b00766
• Keywords: Condensed Matter Physics; General Materials Science; General Chemistry