The chiral structure of 1H-indazoles in the solid state: a crystallographic, vibrational circular dichroism and computational study
J. J. L. González, F. P. Ureña, J. R. A. Moreno, I. Mata, E. Molins, R. M. Claramunt, C. López, I. Alkorta and J. Elguero
New Journal of Chemistry
A survey of the Cambridge Crystallographic Database reveals that there are 17 1H-indazoles forming dimers (7), trimers (4) and catemers or chains (6). Amongst the catemers there is one centrosymmetric compound and five non-centrosymmetric ones that crystallize in chiral helices, either M or P, including indazole itself, whose structure has been determined anew. An explanation will be provided for how an achiral molecule crystallizes in a chiral space group. The second part of the paper is devoted to the use of Vibrational Circular Dichroism (VCD) for determining the absolute configuration of a crystal of indazole. This previously needs the complete assignment of its IR and Raman spectra in solution and in the solid-state based on B3LYP/6-31G(d) calculations of indazole dimers and trimers, which are already chiral.
Vibrational circular dichroism, chiral terpene, limonene, Raman