Single step site-selective reaction to construct a Ag2Au2 ← Ag4 supramolecular assembly from hybrid N-heterocyclic carbene (NHC): synthesis, structures and optoelectronic properties†

Abstract

Two supramolecular complex assemblies, [Ag₄(1)₂][PF₆]₄·4MeCN 2 and Ag(I)–Au(I) mixed metal complex [Ag₂Au₂(1)₂][PF₆]₄·4MeCN 3, have been prepared from 3-(pyridylmethyl)imidazo[1,5-a]pyridin-4-ylium hexafluorophosphate (1 HPF₆), which is the precursor of N-heterocyclic carbene (NHC). These complexes were subsequently analyzed using various spectroscopic techniques to confirm their structural and chemical properties. Transmetallation of Au(I) onto the Ag₄ macrocycle results in the formation of an Ag₂Au₂ macrocyclic assembly. Au(I) selectively binds with the soft donor C_carbene, whereas Ag(I) binds with comparatively hard donor N_py (py = pyridine). The geometries of 2 and 3 were established by single-crystal X-ray diffraction studies. Both molecules form a 2D network through M–M and several non-covalent interactions. Electrical conductivity measurements revealed that Ag(I) complex 2 is better conductor than Au(I) complex 3. Optoelectronic studies revealed the utility of complexes 2 and 3 as photovoltaic devices. Furthermore, MS-junction potential measurements show that they are suitable for semiconductor devices, with complex 2 being more efficient than complex 3. Finally, in this study, we aimed to explore the scope of (i) the development of heterobimetallic supramolecular organometallic complexes (SOC), (ii) the charge transport behaviour of SOCs, and (iii) the modification of intrinsically conductive SOCs-based electronics.