Silyl- and germyl-bridged neutral square-planar Ag4 clusters with short Ag–Ag distances exhibiting red emission†

Abstract

We report silyl- and germyl-bridged neutral square-planar Ag₄ clusters with very short Ag–Ag distances (2.695 and 2.704 Å), as revealed by single-crystal X-ray diffraction analysis. On the basis of the results of theoretical calculations, we attribute these short distances to attractive Ag–Ag interactions that reduce the optical energy gap, resulting in a red emission reaching wavelengths of up to 700 nm. These wavelengths are among the longest observed for emissions from Ag₄ clusters.