Linear trimers of diruthenium linked by polyyndiyl or phenylenediethynyl bridges: A family of unique electronic wires

A new family of wire-like molecules with butadiyndiyl (1a/b), hexadiyndiyl (2) and phenylenediethynyl (3) bridges linking three diruthenium units have been prepared. The single crystal X-ray diffraction study of la revealed structural details of the trimeric compounds, including a distance of 18 angstrom between two Ru-2 termini. Both the voltammetric and spectroscopic data point to an extensive electronic delocalization in trimers 1 and 2, and the lack of delocalization in 3, demonstrating the advantage of linear polyyndiyl in mediating intermetallic electronic couplings. Magnetic studies of compound la reveal that a spin transition may occur as the temperature increases from 1.8 to 300 K. (C) 2014 Elsevier Ltd. All rights reserved.