(E)-4-Bromo-2-[(2-hydroxy­phen­yl)iminiometh­yl]phenolate

The title compound, C₁₃H₁₀BrNO₂, crystallizes in a zwitterionic form. The zwitterion exists in a trans configuration about the C=N bond and is almost planar, the dihedral angle between the two benzene rings being 2.29 (9)°. An intra­molecular N—H...O hydrogen bond formed between the iminium NH⁺ and the phenolate O⁻ atoms generates an S(6) ring motif. In the crystal, the zwitterions are linked through O—H...O hydrogen bonds into chains along [101] and these chains are further connected through C—H...Br inter­actions into a two-dimensional network perpendicular to (101). C...C [3.572 (3)–3.592 (3) Å] and C...Br [3.5633 (19)–3.7339 (18) Å] short contacts are observed. The crystal studied was a twin with twin law 00, 00, 001 with a domain ratio of 0.09919 (2):0.90081 (2).

Bis[(E)-1-methyl-4-styrylpyridinium] 4-bromo­benzene­sulfonate iodide

In the title compound, 2C₁₄H₁₄N⁺·C₆H₄BrO₃S⁻·I⁻, two crystallographically independent cations exist in an E configuration with respect to the C=C ethenyl bond. One cation is approximately planar, whereas the other is twisted slightly, the dihedral angles between the pyridinium and phenyl rings of each cation being 0.96 (15) and 7.05 (16)°. In the crystal structure, the cations are stacked in an anti­parallel manner along the a axis through weak C—H...π inter­actions and π–π inter­actions, with centroid–centroid distances of 3.5544 (19) and 3.699 (2) Å. The 4-bromobenzene­sulfonate anions and the cations are linked together by weak C—H...O inter­actions. A short Br...I contact [3.6373 (4) Å] and C—H...I interactions are also observed.

3-Phenyl-1H-pyrrolo[2,1-c][1,4]oxazin-1-one

The mol­ecule of the title compound, C₁₃H₉NO₂, is slightly twisted with a dihedral angle of 4.85 (9)° between the nine-membered ring system and the phenyl ring. The nine non-H atoms of the 1H-pyrrolo[2,1-c][1,4]oxazin-1-one system are coplanar [r.m.s. deviation = 0.0122 (2) Å]. In the crystal, weak inter­molecular C—H...O inter­actions link mol­ecules into chains along [10]. The crystal studied was an inversion twin with a 0.48624 (9):0.51376 (9) domain ratio.