(E)-1-[(2,4,6-Tri­bromo­phen­yl)diazen­yl]naphthalen-2-ol

The title azo mol­ecule, C₁₆H₉Br₃N₂O, adopts a trans conformation with respect to the azo N=N double bond. An intra­molecular O—H...N hydrogen bond forms an S(6) ring motif. The dihedral angle between the naphthalene ring system and the benzene ring is 33.80 (16)°. In the crystal, mol­ecules are stacked in columns along the a axis by π–π inter­actions [centroid–centroid distances = 3.815 (3) and 3.990 (3) Å].

1-[(E)-2-(2-Hy­droxy-5-methyl­phen­yl)diazen-2-ium-1-yl]naphthalen-2-olate

The title zwitterion, C₁₇H₁₄N₂O₂, crystallizes with two independent mol­ecules in the asymmetric unit, both of which are approximately planar, the dihedral angles between the benzene ring and the naphthalene ring system being 4.39 (12)° in one mol­ecule and 5.83 (12)° in the other, and show an E conformation with respect to the azo double bond. An intra­molecular N—H...O hydrogen bond in each molecule helps to establish their near planar conformation. In the crystal, mol­ecules are linked through O—H...O hydrogen bonds into infinite chains running along the a-axis direction. In addition, the chains are stacked along the b axis via π–π inter­actions between the benzene and the naphthalene rings of adjacent mol­ecules, the centroid–centroid distances being 3.722 (3) and 3.823 (4) Å.

2-Hy­droxy­methyl-1,3-dimethyl-1H-imidazol-3-ium triiodide

The crystal packing of the title salt, C₆H₁₁N₂O⁺·I₃⁻, can be described as consisting of alternating layers of cations and anions parallel to the (100) plane along the a-axis direction. The components are linked by O—H...I, C—H...I and C—H...O interactions, generating a three-dimensional network. The O atom deviates from the imidazol ring by 0.896 (2) Å.