Linear 6,6′-Biazulenyl Framework Featuring Isocyanide Termini: Synthesis, Structure, Redox Behavior, Complexation, and Self-Assembly on Au(111)

The key step in accessing the title species (5), the first nonbenzenoid diisocyanobiaryl, involved an unexpected homocoupling of a 6-bromoazulene derivative. The reversible 2e− reduction of 5 was addressed electrochemically and computationally. The shifts in energies of the S0→S1 and S0→S2 transitions for a series of related 6,6′-biazulenyl derivatives correlate with the e−-donating/-withdrawing strength of their 2,2′-substituents but follow opposite trends. Species 5 adsorbs end-on (η1) to the Au(111) surface via one of its −NC groups to form a 2-nm-thick film. In addition, bimetallic coordination of 5’s −NC termini can be readily achieved.