The complex phosphate K_0.92In_0.46Nb_0.54OPO₄: a new ­representative of the KTiOPO₄ family

The structure of the complex phosphate KIn_0.5Nb_0.5OPO₄ is merohedrally twinned about the [110] twofold axis. A cis-cis linkage of [MO₆] octa­hedra embodies a new subclass of 4/m symmetry structures.

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

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...π inter­actions. Related by a centre of symmetry, neighbouring ion pairs in polymorph (Ia) are linked via π–π inter­actions between cationic fragments, and the resulting dimers are linked through a network of C—H...O(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—H...O(perchlorate), C—Cl...π, π–π and C—Cl...O(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.