Ruthenium-acetylide barbituric derivatives: evidence for H-bonding donor effects

Ruthenium-σ-acetylide derivatives connected to barbituric acceptors through a π-conjugated bridge are subject to drastic color changes depending on the nature of the solvent, especially when the barbituric head bears NH groups. A comparative study of the solvatochromism of two homomorphic compounds is described, which underlines the H-bond donor character of such systems.