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

Liliana Dobrzańska

doi:10.3390/ma15051852

Abstract

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.

Highlights

Controlling the formation of crystal structures is still far out of reach
Are not isostructural, either with one another, or with the corresponding compounds obtained with 1,3-bis(imidazol-1-ylmethyl)-5-methylbenzene, 1,3-bis(imidazol-1-ylmethyl)-2,4,6trimethylbenzene or with the silver complexes formed by 1,3-bis(imidazol-1-ylmethyl)benzene or 1,3-bis(imidazol-1-ylmethyl)-5-methylbenzene with CF3 SO3 − as the counterion
The formation of crystal structures with a much denser packing observed in the case of the complexes formed with bimb and counterions BF4 − and PF6 −

Summary

Introduction

Controlling the formation of crystal structures is still far out of reach. Even minor modifications of the molecular composition can lead to enormous differences in the crystalline products. This is not so surprising considering that crystal structure prediction methods can generate hundreds of forms which show little difference in total lattice energy, even for simple organic molecules of the same composition [1,2]. Molecular flexibility adds more complexity to this matter. Systematic studies on isostructurality (equivalence of crystal structures) [3,4], as well as the occurrence of polymorphism (multiple crystalline forms of particular composition) [5,6] allow us to gain some insight into this topic. We have shown that 1,3-bis(imidazol-1-ylmethyl)benzene (bib) and 1,3-bis(imidazol-1ylmethyl)-5-methylbenzene (bimb) form isostructural 1D Ag(I) complexes with CF3 SO3 −

Methods

Results

Conclusion