Probing Solid-State Breathing and Structural Transformations in a Series of Silver(I) Porous Coordination Polymers

Key observations of the role anions and solvents play in the solid-state flexibility of a series of isostructural silver(I) porous coordination polymers (PCPs) are reported. Building upon earlier results for the perchlorate salt, the structural transformations of two new analogues of a 3D PCP [Ag(dpzm)]X (1) (dpzm = 2,2′-dipyrazinylmethane; X = PF₆, ClO₄, BF₄), which contain either PF₆ (1a) or BF₄ (1c) counterions, are investigated. These materials undergo a remarkable guest-induced single-crystal to single-crystal (SC-SC) solid-state contraction and expansion, which is accurately elucidated by X-ray crystallography. The extent of breathing for PCPs 1a-1c is shown to relate to the type of anion contained within their 3D structures and the nature of the solvent guest. Using X-ray diffraction, further light is shed on structural transformations that take place upon desolvation for this group of materials. These investigations reveal that, while the as-synthesised forms (containing DMSO) undergo a transformation (porous 3D to close-packed 3D; porous 3D to 2D) upon desolvation, the solvent-exchanged forms are more stable.