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, C15 H12 FNO2 , (I), and ( E )-1-{3-[(2-hy-droxy-3-meth-oxy-benzyl-idene)amino]-phen-yl}ethanone, C16 H15 NO3 , (II), which crystallizes with Z ' = 2 in space group Pca 21 , 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 C 2 2 (16) and C 2 2 (17) chains can be identified. Comparisons are made with some related structures.