AAAA-DDDD quadruple hydrogen-bond arrays featuring NH···N and CH···N hydrogen bonds

J Am Chem Soc. 2013 Jul 3;135(26):9939-43. doi: 10.1021/ja404504m. Epub 2013 Jun 25.

Abstract

The X-ray crystal structure of a previously reported extremely strong quadruple NH···N AAAA-DDDD hydrogen-bond array [5·4] (K(a) = 1.5 × 10(6) M(-1) in CH3CN; K(a) > 3 × 10(12) M(-1) in CH2Cl2) features four short linear hydrogen bonds. Changing the two benzimidazole groups of the DDDD unit to triazole groups replaces two of the NH···N hydrogen bonds with CH···N interactions (complex [5·6]), but only reduces the association constant in CH3CN by 2 orders of magnitude (K(a) = 2.6 × 10(4) M(-1) in CH3CN; K(a) > 1 × 10(7) M(-1) in CH2Cl2). Related complexes without the triazole groups range in K(a) from 18 to 270 M(-1) in CH3CN, suggesting that the CH···N interactions can be considered part of a strong AAAA-DDDD quadruple hydrogen-bonding array. The NH···N/CH···N AAAA-DDDD motif can be repeatedly switched "on" and "off" in CDCl3 through successive additions of acid and base.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Benzimidazoles / chemistry*
  • Crystallography, X-Ray
  • Hydrogen Bonding
  • Models, Molecular
  • Molecular Structure
  • Triazoles / chemistry*

Substances

  • Benzimidazoles
  • Triazoles