Crystal packing in the structures of diethanolamine derivatives

Four distinct hydrogen-bonding topologies were observed in the structures of six diethanolamine ligands. These compounds are (1R*, 2R*)-2-[(2-hydroxyethyl)(methyl)amino]-1,2-diphenylethanol, C(17)H(21)NO(2), (I), 1-[(2S)-2-(hydroxydiphenylmethyl)pyrrolidin-1-yl]-2-methylpropan-2-ol, C(21)H(27)NO(2), (II), 2-[(2hydroxyethyl)(methyl)amino]-1,1-diphenylethanol, C(17)H(21)NO(2), (III), 1-{(2-hydroxy-2-methylpropyl)[(1S)-1-phenylethyl]amino}-2-methylpropan-2-ol, C(16)H(27)NO(2), (IV), 1-{[(2R)--2hydroxy-2-phenylethyl][(1S)-1-phenylethyl] amino}-2-methylpropan-2-ol, C(20)H(27)NO(2), (V), and (1R*, 2S*)-2-[(2-hydroxyethyl)( methyl) amino]-1,2-diphenylethanol, C(17)H(21)NO(2), (VI). In each compound, all 'active' hydroxy H atoms are engaged in hydrogen bonding, but the N atoms are not involved in intermolecular hydrogen bonding. In the structures of (I), (II) and (IV)-(VI), molecules are linked into chains by intermolecular O-H center dot center dot center dot O interactions. These chains are organized in such a way as to hide the hydrophilic groups inside, and so the outer surfaces of the chains are hydrophobic. The structure of (VI) contains two distinct non-equivalent systems of intermolecular O-H center dot center dot center dot O hydrogen bonds formed by disordered hydroxy H atoms.