Crystal Structure of 1,3-Bis(3,5-dibromosalicylideneamino)-2-propanol

Schiff-base molecules, 1,3-bis(salicylideneamino)-2-propanol (H3salpr), and their substituted derivatives, are potential pentadentate ligands with two phenolato-oxygen, two iminonitrogen, and one central alcoholate-oxygen donor atoms by deprotonation with coordination to metal atoms. It is known that these Schiff-base ligands form a mononuclear copper(II) complex as a tetradentate O, N, N, O-chelate,1 and dinuclear copper(II),2 nickel(II),3 manganese(III),4 and cobalt(III)5 complexes as tridentate O, N, O-chelates. Previously, we reported on the crystal structures of a monosubstituted Schiffbase ligand, 1,3-bis(5-nitrosalicylideneamino)-2-propanol (H3nsalpr) and a disubstituted Schiff-base ligand, 1,3-bis(5chloro-3-methoxysalicylideneamino)-2-propanol (H3cmsalpr). The former has one nitro group at the salicylideneamino ring, whereas the latter has one chloro group and one methoxy group at the salicylideneamino ring. In this study, we prepared 1,3-bis(3,5-dibromosalicylideneamino)-2-propanol (H3dbsalpr), which has two bromo groups at the salicylideneamino ring (Fig. 1), and determined the crystal structure of H3dbsalpr, which has not been elucidated so far. 1,3-Diamino-2-propanol (0.646 g, 7 mmol) and 3,5-dibromosalicylaldehyde (4.00 g, 14 mmol) were dissolved in methanol (50 cm3)–acetonitrile (10 cm3). The solution was refluxed for 3 h, and then left at room temperature. The resulting yellow precipitate was filtered off, washed with methanol, and dried under a vacuum. Yield, 3.98 g (91%). IR (KBr, cm–1): 3235 (ν(OH)), 3055 (ν(CH(phenyl)), 2925 (νasCH2), 2889 (νsCH2), 1632 (νC=N). X-ray quality crystals were grown by recrystallization from acetonitrile. X-ray diffraction data were collected on a Bruker CCD X-ray diffractometer (SMART APEX) using graphite-monochromated Mo-Kα radiation. Crystal data and details concerning the data collection are given in Table 1. The structure was solved by an intrinsic phasing method with SHELXT-2014, and refined by full-matrix least-squares methods with SHELXL-2018. The hydrogen atoms were inserted at their calculated positions, and fixed there with restraints. The hydrogen atoms at the imino groups were also inserted at the calculated positions because it was difficult to locate the hydrogen atoms from the D-Fourier maps including the phenolate oxygen areas. For thermal anisotropic displacement parameters (ADPs) of most of the carbon atoms, enhanced rigid bond restraints were applied. Crystallographic data have been deposited with Cambridge Crystallographic Data Centre (Deposit number CCDC2091176). Copies of the data can be obtained free of charge via http://www.ccdc.cam.ac.uk/conts/retrieving.html (or from the Cambridge Crystallographic Data Centre, 12, Union Road, Cambridge, CB2 1EZ, UK; Fax, +44 1223 336033; e-mail, deposit@ccdc.cam.ac.uk). In the crystal, the asymmetric unit consists of three independent 1,3-bis(3,5-dibromosalicylideneamino)-2-propanol, H3dbsalpr molecules, like in the case for 1,3-bis(salicylideneamino)-2propanol (four independent molecules in the asymmetric unit).8 The asymmetric unit drawn with the thermal ellipsoids is shown in Fig. 2. Selected bond distances and angles are given in 2022 © The Japan Society for Analytical Chemistry