4-Pyridylisocyanide gold(i) and gold(i)-plus-silver(i) luminescent and mechanochromic materials: the silver role

Abstract

Crystallographic and DFT examination of the metalloligands [AuAr(CNPy-4)] (Ar = C₆F₅ (1), C₆F₃Cl₂-3,5 (2)) and their silver complexes [Ag[AuAr(CNPy-4)]₂](BF₄) (3 and 4) support that the marked luminescence red-shifts observed on moving from 1 to 2, from 1,2 to 3,4, or upon grinding, are not caused by electronic differences (either by changing the aryls C₆F₅/C₆F₃Cl₂, or by N coordination to silver), nor by non-existent Au⋯Ag interactions. They are always due to structural changes disturbing stronger π–π stackings in order to allow for shorter Au⋯Au interactions.