Absence of Ligand-Mediated Symmetry Reduction in a Solid Solution: Cu(NC₅H₅)₄[(NbOF₅) _1-x(WO₂F₄)_x] (0 ≤ x ≤ 1)

Organic chromophores crystallizing in nonpolar space groups (P1) have been converted to polar structures (P1) by solid solution symmetry reduction to produce materials with measurable SHG signals. Here, the inorganic compound Cu(NC₅H₅)₄NbOF₅ is used to demonstrate that solid solution symmetry reduction depends on molecular recognition of the guest species at crystal growth faces. In the solid solution Cu(NC₅Hs)₄[(NbOF₅)_1-x(WO ₂F₄)_x] (0 ≤ x ≤ 1) the [WO₂F₄]^2- guest molecular ions disrupt the local symmetry, but owing to the lack of recognition of guest anions at the crystal growth surfaces, the full three-dimensional structure retains the host's symmetry.