Crystal structures of (E)-1-{3-[(5-fluoro-2-hy-droxy-benzyl-idene)amino]-phen-yl}ethanone and of a fourth polymorph of (E)-1-{3-[(2-hy-droxy-3-meth-oxy-benzyl-idene)amino]-phen-yl}ethanone.

In the mol-ecules of both (E)-1-{3-[(5-fluoro-2-hy-droxy-benzyl-idene)amino]-phen-yl}ethanone, C15H12FNO2, (I), and (E)-1-{3-[(2-hy-droxy-3-meth-oxy-benzyl-idene)amino]-phen-yl}ethanone, C16H15NO3, (II), which crystallizes with Z' = 2 in space group Pca21, there are intra-molecular O-H⋯N hydrogen bonds, and the non-H atoms in each mol-ecule are essentially coplanar. In the crystal of (I), mol-ecules are linked by a single C-H⋯O hydrogen bond to form a C(8) chain, whereas in the crystal of (II), mol-ecules are linked by three C-H⋯O hydrogen bonds to form sheets within which orthogonal C22(16) and C22(17) chains can be identified. Comparisons are made with some related structures.