TY - JOUR
T1 - The Peculiar H-Bonding Network of 4-Methylcatechol: A Coupled Diffraction and In Silico Study
AU - Lopresti, Mattia
AU - Palin, Luca
AU - Calegari, Giovanni
AU - MILANESIO, Marco
PY - 2024
Y1 - 2024
N2 - The crystal structure of 4-methylcatechol (4MEC) has, to date, never been solved, despite its very simple chemical formula C7O2H8 and the many possible applications envisaged for this molecule. In this work, this gap is filled and the structure of 4MEC is obtained by combining X-ray powder diffraction and first principle calculations to carefully locate hydrogen atoms. Two molecules are present in the asymmetric unit. Hirshfeld analysis confirmed the reliability of the solved structure, since the two molecules show rather different environments and H-bond interactions of different directionality and strength. The packing is characterised by a peculiar hydrogen bond network with hydroxyl nests formed by two adjacent octagonal frameworks. It is noteworthy that the observed short contacts suggest strong inter-molecular interactions, further confirmed by strong inter-crystalline aggregation observed by microscopic images, indicating the growth, in many crystallization attempts, of single aggregates taller than half a centimetre and, often, with spherical shapes. These peculiarities are induced by the presence of methyl group in 4MEC, since the parent compound catechol, despite its chemical similarity, shows a standard layered packing alternating hydrophobic and polar layers. Finally, the complexity and peculiarity of the packing and crystal growth features explain why a single crystal could not be obtained for a standard structural analysis.
AB - The crystal structure of 4-methylcatechol (4MEC) has, to date, never been solved, despite its very simple chemical formula C7O2H8 and the many possible applications envisaged for this molecule. In this work, this gap is filled and the structure of 4MEC is obtained by combining X-ray powder diffraction and first principle calculations to carefully locate hydrogen atoms. Two molecules are present in the asymmetric unit. Hirshfeld analysis confirmed the reliability of the solved structure, since the two molecules show rather different environments and H-bond interactions of different directionality and strength. The packing is characterised by a peculiar hydrogen bond network with hydroxyl nests formed by two adjacent octagonal frameworks. It is noteworthy that the observed short contacts suggest strong inter-molecular interactions, further confirmed by strong inter-crystalline aggregation observed by microscopic images, indicating the growth, in many crystallization attempts, of single aggregates taller than half a centimetre and, often, with spherical shapes. These peculiarities are induced by the presence of methyl group in 4MEC, since the parent compound catechol, despite its chemical similarity, shows a standard layered packing alternating hydrophobic and polar layers. Finally, the complexity and peculiarity of the packing and crystal growth features explain why a single crystal could not be obtained for a standard structural analysis.
KW - Hirshfeld surface
KW - X-ray powder diffraction
KW - antioxidant
KW - crystal structure
KW - first principle calculation
KW - hydrogen bond
KW - octagonal H-bond nests
KW - Hirshfeld surface
KW - X-ray powder diffraction
KW - antioxidant
KW - crystal structure
KW - first principle calculation
KW - hydrogen bond
KW - octagonal H-bond nests
UR - https://iris.uniupo.it/handle/11579/178642
U2 - 10.3390/molecules29102173
DO - 10.3390/molecules29102173
M3 - Article
SN - 1420-3049
VL - 29
SP - 2173
JO - Molecules
JF - Molecules
IS - 10
ER -