Hydrogen and Halogen Bond Mediated Coordination Polymers of Chloro-Substituted Pyrazin-2-Amine Copper(I) Bromide Complexes

Aaron Mailman, Rakesh Puttreddy, Manu Lahtinen, Noora Svahn, Kari Rissanen

Research output: Contribution to journalArticleScientificpeer-review

Abstract

A new class of six mono- (1; 3-Cl-, 2; 5-Cl-, 3; 6-Cl-) and di-(4; 3,6-Cl, 5; 5,6-Cl-, 6; 3,5-Cl-) chloro-substituted pyrazin-2-amine ligands (1-6) form complexes with copper (I) bromide, to give 1D and 2D coordination polymers through a combination of halogen and hydrogen bonding that were characterized by X-ray diffraction analysis. These Cu(I) complexes were prepared indirectly from the ligands and CuBr2 via an in situ redox process in moderate to high yields. Four of the pyrazine ligands, 1, 4-6 were found to favor a monodentate mode of coordination to one Cu-I ion. The absence of a C6-chloro substituent in ligands 1, 2 and 6 supported N1-Cu coordination over the alternative N4-Cu coordination mode evidenced for ligands 4 and 5. These monodentate systems afforded predominantly hydrogen bond (HB) networks containing a catenated (mu(3)-bromo)-Cu-I 'staircase' motif, with a network of 'cooperative' halogen bonds (XB), leading to infinite polymeric structures. Alternatively, ligands 2 and 3 preferred a mu(2)-N,N' bridging mode leading to three different polymeric structures. These adopt the (mu(3)-bromo)-Cu-I 'staircase' motif observed in the monodentate ligands, a unique single (mu(2)-bromo)-Cu-I chain, or a discrete Cu2Br2 rhomboid (mu(2)-bromo)-Cu-I dimer. Two main HB patterns afforded by self-complimentary dimerization of the amino pyrazines described by the graph set notation R-2(2)(8) and non-cyclic intermolecular N-H center dot center dot center dot N' or N-H center dot center dot center dot Br-Cu leading to infinite polymeric structures are discussed. The cooperative halogen bonding between C-Cl center dot center dot center dot Cl-C and the C-Cl center dot center dot center dot Br-Cu XB contacts are less than the sum of the van der Waals radii of participating atoms, with the latter ranging from 3.4178(14) to 3.582(15) angstrom. In all cases, the mode of coordination and pyrazine ring substituents affect the pattern of HBs and XBs in these supramolecular structures.

Original languageEnglish
Pages (from-to)700-713
Number of pages14
JournalChemistry
Volume2
Issue number3
DOIs
Publication statusPublished - Sep 2020
Publication typeA1 Journal article-refereed

Keywords

  • hydrogen bond
  • halogen bond
  • pyrazine
  • chloropyrazine
  • chloropyrazin-2-amine
  • copper halide
  • CRYSTAL-STRUCTURES
  • ACID
  • LIGANDS
  • PHOTOLUMINESCENCE
  • INHIBITORS
  • CHEMISTRY
  • POTENT
  • ANION

Publication forum classification

  • Publication forum level 1

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