Bis­[6-amino-3-methyl-5-nitro­so­pyrimidine-2,4(1H,3H)-dionato]­di­aqua­zinc(II) dihydrate, redetermined at 120 K: a three-dimensional hydrogen-bonded framework

The title compound, whose structure has been redetermined at 120 K, contains almost centrosymmetric trans-[Zn(C₅H₅N₄O₃)₂(H₂O)₂]·2H₂O units, together with two uncoordinated water mol­ecules. An extensive series of O—H...O, O—H...N and N—H...O hydrogen bonds gives rise to a three-dimensional framework structure.

The molecular and supramolecular structures of the isomeric compounds 5,7-di­methoxy­imidazo­[1,2-c]­pyrimidine and 7-methoxy-1-methyl­imidazo­[1,2-a]­pyrimidin-5(1H)-one

The supramolecular structures of the isomeric compounds 5,7-di­methoxy­imidazo­[1,2-c]­pyrimidine, C₈H₉N₃O₂, (I), and 7-methoxy-1-methyl­imidazo­[1,2-a]­pyrimidin-5(1H)-one, C₈H₉N₃O₂, (II), are determined by weak C-H...N and C-H...O hydrogen bonds in (I), which generate alternating linked centrosymmetric R₂²(8) and R₂²(10) rings that form a ribbon running parallel to the c axis, and by C-H...O bonds in (II), which link the mol­ecules into sheets comprising centro­symmetric R₂²(10) and R₄⁴(22) rings.

6,6'-Di­methoxy-2,2'-[(1R,2R)-cyclo­hexane-1,2-diyl­bis­(nitrilo­methyl­idyne)]­diphenol: three C-H...O hydrogen bonds generate a three-dimensional framework

Molecules of the title compound, alternatively called (R,R)-N,N'-bis(3-methoxysalicylidene)-trans-cyclohexane-1,2-diamine, C₂₂H₂₆N₂O₄, contain two intramolecular O-H...N hydrogen bonds and adopt a conformation with approximate twofold rotational symmetry. The mol­ecules are linked by three C-H...O hydrogen bonds [H...O = 2.45-2.55 Å, C...O = 3.329 (2)-3.398 (2) Å and C-H...O = 142-172°] into a continuous framework.

2-Benzyl­amino-6-benzyl­oxy­pyrimidin-4(3H)-one: hydrogen-bonded chains of rings linked into sheets by a [pi]-[pi]-stacking interaction

The title compound, C₁₈H₁₇N₃O₂, crystallizes with Z' = 2 in space group P2₁/c, and the two independent mol­ecules are approximate, but not exact, mirror images. The molecular-electronic structure is strongly polarized, and the mol­ecules are linked by paired N-H...O hydrogen bonds [H...O = 2.00-2.23 Å, N...O = 2.798 (3)-2.992 (3) Å and N-H...O = 145-151°] into two independent C(4)C(6)[R₂¹(6)] chains of rings, which are linked into sheets by a single aromatic [pi]-[pi]-stacking interaction.