Supramolecular structures of five 5-(arylmethylene)-1,3-dimethylpyrimidine-2,4,6(1H,3H,5H)-triones: isolated molecules, hydrogen-bonded chains and chains of fused hydrogen-bonded rings

In each of the five title compounds, namely 5-benzylidene-1,3-dimethylpyrimidine-2,4,6(1H,3H,5H)-trione, C13H12N2O3, (I), 5-(3-methoxybenzylidene)-1,3-dimethylpyrimidine-2,4,6(1H,-3H,-5H)-trione, C14H14N2O4, (II), 5-(4-methoxybenzylidene)-1,3-dimethylpyrimidine-2,4,6(1H,3H,5H)-trione, C14H14N2O4, (III), 5-[4-(dimethylamino)benzylidene]-1,3-dimethylpyrimidine-2,4,6(1H,3H,5H)-trione, C15H17N3O3, (IV), and 5-(3,5-di-tert-butyl-4-hydroxybenzylidene)-1,3-dimethylpyrimidine-2,4,6(1H,3H,5H)-trione, C21H28N2O4, (V), which crystallizes with Z' = 2 in PT, there is a very wide C-C-C angle at the methine C atom linking the two rings, ranging from 137.1 (2)° in (I) to 139.14 (14)° in (III). There is evidence for intramolecular charge separation in (IV) and, to a lesser degree, in (III). The molecules of (I)-(III) are linked by pairs of C-H••• O hydrogen bonds into chains of edge-fused rings, with alternating R-2(2)(14) and R-2(2)(16) rings in (I), alternating R-2(2)(14) and R-4(4)(20) rings in (II), with two types of R-2(2)(16) rings alternating in (111). The molecules in (IV) are linked by a single C-H••• O hydrogen bond into simple C(8) chains, but there are no direction-specific intermolecular interactions in M.