Acta Crystallographica Section C

Crystal Structure Communications

Volume 63, Part 11 (November 2007)

organic compounds

gz3073 scheme

Acta Cryst. (2007). C63, o626-o630 [ doi:10.1107/S0108270107039558 ]

Two polymorphs of 2-(4-chlorophenyl)-4-methylchromenium perchlorate

A. D. Roshal, A. Sikorski, V. N. Baumer, A. I. Novikov and J. Blazejowski

Abstract: Crystallization (from ethyl acetate solution) of 2-(4-chlorophenyl)-4-methylchromenium perchlorate, C₁₆H₁₂ClO⁺·;ClO₄^-, (I), yields two monoclinic polymorphs with the space groups P2₁/n [polymorph (Ia)] and P2₁/c [polymorph (Ib)]; in both cases, Z = 4. Cations and anions, disordered in polymorph (Ib), form ion pairs in both polymorphs as a result of Cl-O [pi] interactions. Related by a centre of symmetry, neighbouring ion pairs in polymorph (Ia) are linked via [pi] - [pi] interactions between cationic fragments, and the resulting dimers are linked through a network of C-HO(perchlorate) interactions between adjacent cations and anions. The ion pairs in polymorph (Ib), arranged in pairs of columns along the a axis, are linked through a network of C-HO(perchlorate), C-Cl [pi] , [pi] - [pi] and C-ClO(perchlorate) interactions. The aromatic skeletons in polymorph (Ia) are parallel in the cationic fragments involved in dimers, but nonparallel in adjacent ion pairs not constituting dimers. In polymorph (Ib), these skeletons are parallel in pairs of columns, but nonparallel in adjacent pairs of columns; this is visible as a herring-bone pattern. Differences in the crystal structures of the polymorphs are most probably the cause of their different colours.

Formula: Two polymorphs of C₁₆H₁₂ClO⁺·ClO₄^-


	Structure factor file (CIF format) (135.7 kbytes) [ doi:10.1107/S0108270107039558/gz3073Iasup2.hkl ] Contains datablock Ia

	Structure factor file (CIF format) (134.9 kbytes) [ doi:10.1107/S0108270107039558/gz3073Ibsup3.hkl ] Contains datablock Ib

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