Two interesting tetranuclear Ag(I) complexes based on dipyrido[3,2-f:2,3-h]-quinoxaline: Synthesis, structural, luminescence and theoretical studies

Two new isostructural tetranuclear Ag(I) complexes, formulated as [AgX(Dpq)]4 (X = I, 1; Br, 2; Dpq = dipyrido[3,2-f:2,3-h]-quinoxaline), were synthesized by slow diffusion method for the first time. The central portion of each structure consists of a (AgX)4 core and is surrounded by four Dpq ligands. The Dpq units in the tetrameric structures are found to stack in almost parallel and display π–π stacking interactions. Moreover, Ag–Ag interactions are observed in both complexes (3.1505(7) Å for 1 and 3.1136(7) Å for 2). Density functional theory and time-dependent density functional theory calculations at the B3LYP/LanL2DZ* + 6-31G* level were performed on 1 and 2 to rationalize their experimental absorption spectra. Both complexes exhibit intense luminescence in ethanol solution at room temperature.