2-[(3,3-Di­methyl­indolin-2-yl­idene)meth­yl]-4-[(3,3-dimethyl-3H-indol-1-ium-2-yl)methyl­idene]-3-oxo­cyclo­but-1-en-1-olate chloro­form disolvate

In the title squaraine dye solvate, C₂₆H₂₄N₂O₂·2CHCl₃, the dye mol­ecule is essentially planar, except for the methyl groups, having a maximum deviation over the 26-membered delocalized bond system of 0.060 (2) Å. It possesses crystallographic twofold rotational symmetry with the indole ring systems adopting a syn conformation. The mol­ecular structure features intra­molecular N—H...O hydrogen bonds enclosing conjoint S7 ring motifs about one of the dioxo­cyclo­butene O atoms, while the two chloro­form solvent mol­ecules are linked to the second O atom through C—H...O hydrogen bonds.

4-Hy­droxy-1,2,6-tri­methyl­pyridinium chloride monohydrate

In the crystal of the title hydrated mol­ecular salt, C₈H₁₂NO⁺·Cl⁻·H₂O, the water mol­ecule makes two O—H...Cl hydrogen bonds, generating [010] zigzag chains of alternating water mol­ecules and chloride ions. The cation is bonded to the chain by an O—H...O hydrogen bond and two weak C—H...Cl inter­actions. Weak aromatic π–π stacking [centroid–centroid separation = 3.5175 (15) Å] occurs between the chains.

1-Allyl-2-amino­pyridin-1-ium bromide

In the cation of the title salt, C₈H₁₁N₂⁺·Br⁻, the dihedral angle between the planes of the pyridinium ring and the allyl group is 79.4 (3)°. In the crystal, N—H...Br and weak C—H...Br hydrogen bonds link the cations and anions, forming chains of alternating R₂¹(7) and R₄²(8) rings, which run parallel to the c-axis direction. The crystal studied was an inversion twin with components in a 0.753 (12):0.247 (12) ratio.

4-Hy­droxy-1,2,6-tri­methyl­pyridinium bromide monohydrate

The title salt, C₈H₁₂NO⁺·Br⁻·H₂O, is isomorphous with the chloride analogue [Seethalakshmi et al. (2013). Acta Cryst. E69, o835–o836]. In the solid state, the cations, anions and water mol­ecules are inter­linked by a network of O—H...O, O—H...Br and C—H...Br inter­actions. The water mol­ecule makes two O—H...Br hydrogen bonds, generating [010] zigzag chains of alternating water mol­ecules and bromide anions. The cation is involved in two inter­molecular C—H...Cl inter­actions in the chloride salt, whereas three inter­molecular C—H...Br inter­actions are observed in the title bromide salt. This additional inter­molecular C—H...Br inter­action links the adjacent water and bromide zigzag chains via cationic mol­ecules. In addition, weak π–π stacking inter­actions are observed between pyridinium rings [centroid–centroid distance = 3.5664 (13) Å].