Zigzag vs Helicoidal Gold-Silver 1D Chains: Influence of Subtle Interactions in the Spatial Arrangement of Supramolecular Systems.

Abstract

The reaction of 4'-(2-thienyl)-2,2':6',2,2''-terpyridine (S-terpy) with the heterometallic complexes [Au2Ag2R4(OEt2)2]n (R = C6F5, C6Cl5) leads to the compounds [{Au(C6X5)2}Ag(S-terpy)]n (X = F (1), Cl (2)). The X-ray diffraction analysis of the complexes shows an alternating disposition of the metals -Au-Ag-Au-Ag- in 1D infinite polymeric chains. Despite the fact of having the same metallic sequence, the spatial arrangement observed for both complexes is very different, since for [{Au(C6F5)2}Ag(S-terpy)]n (1) the metals adopt a zigzag disposition, whereas an helicoidal distribution of the interacting metals is observed for the complex [{Au(C6Cl5)2}Ag(S-terpy)]n (2). These different arrangements are related to the perhalophenyl ligands present in the complexes, which appear with different spatial dispositions, being staggered in the case of C6F5 (1) and almost eclipsed in the case of C6Cl5 (2). In order to explain the reasons for these different structural arrangements, we performed a DFT-D3 computational analysis and a subsequent study of the qualitative characterization of the noncovalent interactions (NCIs) in real space.