Crystal Structure of 2-(4-Methylimidazolin-2-yl)phenol: an Another Polymorph

Abstract

The self-assembly of coordination compounds by hydrogenbonding interactions is a promising strategy to construct a supramolecular structure to enable versatile functionalities. We have been focusing on tris-chelate and bis-chelate cobalt complexes with a 2-(2-imidazolinyl)phenolate ligand to control the coordination geometry1 and tune the static and dynamic magnetic properties of a complex.2,3 We previously reported on the synthesis and crystal structure of a methyl substituted analogue of the ligand precursor, (R)-2-(4-methylimidazolin-2yl)phenol, to investigate the effect of a chiral group on the resulting hydrogen-bonded network.4 This compound crystallized from an enantiomerically pure solution to afford the chiral space group P21. In this study, we focused on the crystallization of a racemic mixture of 2-(4-methylimidazolin-2yl)phenol, and report a new chiral polymorph (Fig. 1). The title compound was synthesized using a method modified from that reported in the literature.5 A mixture of methyl salicylate (7.68 g) and a racemic mixture of 1,2-diaminopropane (11.40 g) were heated at 160°C overnight. The unreacted 1,2-diaminopropane was evaporated under atmospheric pressure. After cooling, the title compound was obtained as a pale-yellow residue. The residue was recrystallized from ethanol. The crystal data are included in Table 1. The X-ray crystallographic data was collected on a Bruker smart APEX CCD diffractmeter at –183°C. The integrated and scaled data were empirically corrected with SADABS.6 The initial structure was solved by an intrinsic phasing method with SHELXT-2014,7 and refined using a full-matrix least-squares method on F2 utilizing SHELXL-2014.8 The non-hydrogen atoms were refined anisotropically, and hydrogen atoms were refined using the riding model, except for the N–H atoms. The N–H atoms were located by a difference Fourier map and refined isotropically. The Flack parameter could not be determined reliably because of low Friedel pair coverage. Crystallographic data have been deposited with Cambridge Crystallographic Data 2019 © The Japan Society for Analytical Chemistry