Barbara Morzyk-Ociepa, Ksenia Szmigiel-Bakalarz, Markus Nentwig
Mar 23, 2021
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Journal
Journal of Molecular Structure
Abstract
Abstract The title compound, 1H-indazole-3-carbaldehyde, C8H6N2O (1) is important as it represents a rare example of indazole found in nature. The asymmetric unit of 1 consists of two independent molecules (1A and 1B) which are linked by N—H⋅⋅⋅O hydrogen bonds (N⋅⋅⋅O = 2.8178(15) A and 2.8203(14) A), forming one-dimensional chains. The crystal structure is stabilized by slipped face-to-face π•••π interactions (Cg⋅⋅⋅Cg distances in the range 3.8492(8) – 4.1830(8) A), C=O⋅⋅⋅π interactions (O⋅⋅⋅centroids distances in the range 3.3252(12) – 3.4795(11) A) and weak non-classical C—H⋅⋅⋅N hydrogen bonds (C⋅⋅⋅N = 3.4377(18) A). 3D Hirshfeld surface analysis, 2D fingerprint plots and molecular electrostatic potentials were applied for a detailed investigation of all the interactions participating in the crystal packing. The intermolecular interactions were also confirmed by Natural Bond Orbital (NBO) analysis at the B3LYP and B3LYP-D3 levels using the 6-31++G(d,p) basis set. The energies of the intermolecular interactions (the second-order interaction energies, E2) oscillate between 55.5 kJ•mol−1 and 22.3 kJ•mol−1 for strong N−H⋅⋅⋅O hydrogen bond. The E2 value for the C=O•••π and π•••π interactions are about 4.9 kJ•mol−1 and 3.6 kJ•mol−1, respectively. Moreover, the strength of the hydrogen bonds was evaluated using vibrational spectroscopy (FT-IR and FT-Raman) and DFT calculations at the B3LYP level within the 6-31++G(d,p) basis set. These studies additionally confirm the presence of various intermolecular interactions in the crystal of 1.