Competition between hydrogen bonds and halogen bonds: a structural study. (3rd May 2018)

• Record Type: Journal Article
• Authors: Gamekkanda, Janaka C.; Sinha, Abhijeet S.; Desper, John; Đaković, Marijana; Aakeröy, Christer B.
• Is Part Of: New journal of chemistry. Volume 42:Number 13(2018)
• Page Start: 10539
• Page End: 10547
• Publication Date: 2018-05-03
• Subjects: Chemistry -- Periodicals; Chimie -- Périodiques; 540
• DOI: 10.1039/c8nj00537k
• Languages: English
• ISSNs: 1144-0546

Abstract

Abstract : O–H hydrogen-bond donors and R–CC–I halogen-bond donors are close competitors for suitable acceptor sites in solid-state assembly. Abstract : The competition and balance between intermolecular hydrogen bonds (HBs) and halogen bonds (XBs) were explored by co-crystallizing tetra-functionalized (2 × HB (–OH) and 2 × XB (–CC–I)) molecules, trans -1, 4-bis(iodoethynyl)cyclohexane-1, 4-diol (D1 ) and cis -1, 4-bis(iodoethynyl)cyclohexane-1, 4-diol (D2 ), with six ditopic nitrogen based acceptor molecules. The crystal structures of bothD1 andD2 showed non-covalent interactions between HB/XB donors and available acceptor sites (oxygen/triple bond/negative region of iodine). In three co-crystals ofD1 the HB and XB donors act in similar ways as both activated iodine and hydroxyl hydrogen bind to the nitrogen acceptors in the solid state. In contrast, in a co-crystal ofD2, a geometric isomer ofD1, there were only hydrogen bonds to the co-former and the halogen-bond donor interacted with the hydroxyl oxygen atoms ofD2 . A stronger tendency for linear XB interactions (as well as greater van der Waals radii reduction) was observed with nitrogen atoms as acceptors (average reduction = 21%) compared to those involving an oxygen atom as an acceptor (average reduction = 16%). A control molecule, trans -1, 4-diethynylcyclohexane-1, 4-diol (D3 ), which has only HB donors (–OH and –CC–H) was also examined to get a better understanding of the balance between XB and HB intercations. The ethynyl hydrogen atom did not form hydrogen bonds to the nitrogen atoms in acceptors, and only O–H⋯N and –CC–H⋯O hydrogen bonds were observed in these structures.