Towards polymorphism control in coordination networks and metallo-organic saltsElectronic supplementary information (ESI) available: Powder XRD diffraction patterns, the TGA of 3and SEM and EDAX images of 30.5and 40.5; details of the crystal structures of 3xwith x= 0.95, 0.93 and 0.86 are available as cif files and are summarised in the ESI document. CCDC reference numbers 779347–779349. For ESI and crystallographic data in CIF or other electronic format see DOI: 10.1039/c0ce00230e

[{(4,4′-bipy)ZnCl2}n] (4) is known in three different polymorphs, in the space groups C2/c(4a), Pnma(4b) and Pban(4c). Solution synthesis produces a mixture of 4aand 4b, but solid-state synthesis, either by grinding together 4,4′-bipy and ZnCl2or by heating [4,4′-H2bipy][ZnCl4] 3to thermally eliminate HCl, generates only the 4bform, demonstrating that solid-state synthesis can exert control over polymorph formation; other solid-state preparations of 4such as reaction of basic zinc carbonate with [4,4′-H2bipy]Cl2or reaction of [4,4′-H2bipy][ZnCl4] 3with KOH also increase the amount of 4bgenerated relative to the solution synthesis. It is also possible to form the mixed-metal phases [{(4,4′-bipy)Co1−xZnxCl2}n] 4xas effectively homogeneous solid-solutions by the same techniques, and when x< 0.5 (i.e.there is more cobalt present than zinc) then only the Pbanpolymorph of the solid-solution is observed. When x> 0.5, the amount of this polymorph is still greater than would be expected for a predominantly zinc-containing phase. [ABSTRACT FROM AUTHOR]