Counterion Effect and Isostructurality in a Series of Ag(I) Complexes Containing a Flexible, Imidazole Based Dipodal Ligand

From Isostructurality to Structural Diversity of Ag(I) Coordination Complexes Formed with Imidazole Based Bipodal Ligands, and Disclosure of a Unique Topology

Two Ag(I) complexes with 1,3-bis(imidazol-1-ylmethyl)benzene (bib) and counterions BF₄⁻ (1) and PF₆⁻ (2) were synthesized in order to check their behavior in forming molecular/crystal structures. This allows comparison with the final products of analogous syntheses performed with similar bidentate ligands containing methyl substituents on the benzene ring, namely 1,3-bis(imidazol-1-ylmethyl)-5-methylbenzene (bimb) and 1,3-bis(imidazol-1-ylmethyl)-2,4,6-trimethylbenzene (bitmb). The Ag(I) complexes obtained with the methylated ligands mentioned above form isostructural pairs of waved 1D chains or dinuclear boxes, of general formula {[Ag(bimb)]X}_n and [Ag₂(btmb)₂]X₂, respectively (X = BF₄⁻, PF₆⁻), under the same reaction conditions. SCXRD analyses of 1 and 2 revealed the formation of polymeric coordination compounds of formula {[Ag₂(bib)₃](BF₄)₂}_n and {[Ag(bib)]PF₆}_n, respectively, different from those observed for bimb. The 3D coordination polymer 1 forms a unique 5,5-c net of 5,5T188 topological type, observed for the very first time for a coordination compound, with silver cations adopting a trigonal geometry, whereas 2 shows the presence of 1D single-stranded cationic helices with linear coordination of the metal centers. Interestingly, these complexes differ not only from the mentioned isostructural pairs of related Ag(I) complexes, but also from the isostructural pair of compounds obtained as the final product when reacting bib and bimb with the larger counterion CF₃SO₃⁻. Hirshfeld surface analyses indicate a higher contribution of F⋯H intermolecular contacts in 2 than in 1, with H⋯H contacts being dominant in the latter.