Jump to main content
Jump to site search

Issue 28, 2011
Previous Article Next Article

Hydrogen bonding and chemical shift assignments in carbazole functionalized isocyanides from solid-state NMR and first-principles calculations

Author affiliations

Abstract

Carbazole functionalized polyisocyanides are known to exhibit excellent electronic properties (E. Schwartz, et al., Chemistry of Materials, 2010, 22, 2597). The functionalities and properties of such materials crucially depend on the organization and stability of the polymer structure. We combine solid-state Nuclear Magnetic Resonance (NMR) experiments with first-principles calculations of isotropic chemical shifts, within the recently developed converse approach, to rationalize the origin of isotropic chemical shifts in the crystalline monomer L-isocyanoalanine 2-(9H-carbazol-9-yl) ethyl amide (monomer 1) and thereby gain insight into the structural organization of its polymer (polymer 2). The use of state-of-the-art solid-state NMR experiments combined with Density Functional Theory (DFT) based calculations allows an unambiguous assignment of all proton and carbon resonances of the monomer. We were able to identify the structure stabilising interactions in the crystal and understand the influence of the molecular packing in the crystal structure on the chemical shift data observed in the NMR spectra. Here the Nuclear Independent Chemical Shift (NICS) approach allows discriminating between ‘physical’ interactions amongst neighboring molecules such as ring-current effects and ‘chemical’ interactions such as hydrogen bonding. This analysis reveals that the isocyanide monomer is stabilized by multiple hydrogen bonds such as a bifurcated hydrogen bond involving –N–H, –C–H and O[double bond, length as m-dash]C– moieties and Ar–H⋯C[triple bond, length as m-dash]N– hydrogen bonding (Ar = aromatic group). Based on the geometrical arrangement it is postulated that the carbazole units are involved in the weak σ–π interactions giving rise to a Herringbone packing of the molecules. The chemical shift analysis of the polymer spectra readily establishes the existence of N–H⋯O[double bond, length as m-dash]C hydrogen bonds despite the limited resolution exhibited by the polymer spectra. It is also elucidated that the relative arrangement of the carbazole units in the polymer differs significantly from that of the monomer.

Graphical abstract: Hydrogen bonding and chemical shift assignments in carbazole functionalized isocyanides from solid-state NMR and first-principles calculations

Back to tab navigation

Supplementary files

Publication details

The article was received on 04 Feb 2011, accepted on 28 Apr 2011 and first published on 15 Jun 2011


Article type: Paper
DOI: 10.1039/C1CP20304E
Citation: Phys. Chem. Chem. Phys., 2011,13, 13082-13095
  •   Request permissions

    Hydrogen bonding and chemical shift assignments in carbazole functionalized isocyanides from solid-state NMR and first-principles calculations

    C. M. Gowda, F. Vasconcelos, E. Schwartz, E. R. H. van Eck, M. Marsman, J. J. L. M. Cornelissen, A. E. Rowan, G. A. de Wijs and A. P. M. Kentgens, Phys. Chem. Chem. Phys., 2011, 13, 13082
    DOI: 10.1039/C1CP20304E

Search articles by author

Spotlight

Advertisements