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

Abstract

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 S(0)→S(1) and S(0)→S(2) 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 (η(1)) 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.

Impact of 2,6-connectivity in azulene: optical properties and stimuli responsive behavior

“…26,[31][32][33][34][35][36][37][38] The only known 2,6-bissubstituted compounds either bear an alkyne or an alkyl chain at the 6 position, or they are connected to a metal center as a bridging ligand or, are part of a 6,6'-connected azulene dimer. [39][40][41][42] In this work, we report the systematic synthesis of 2,6diphenyl acetylene substituted azulene and investigation of its stimuli responsive behavior as a model compound for macromolecules. Di(phenylethynyl) substitution was particularly chosen in order to allow for easy correlation of the properties as model compounds.…”

Ancillary nitrile substituents as convenient IR spectroscopic reporters for self-assembly of mercapto- and isocyanoazulenes on Au(111)

“…1). [5][6][7][8] As an integral part of this quest, the initial examples of azulenic and biazulenic SAMs have been obtained by employing the isocyano anchoring groups. 6,9 Interestingly, a recent theoretical study has suggested that the hypothetical molecular wire derived from the currently unknown 2,6-dimercaptoazulene should exhibit higher conductivity in a wide bias range compared to that of its benzenoid isomer 2,6-dimercaptonaphthalene.…”

First π-linker featuring mercapto and isocyano anchoring groups within the same molecule: synthesis, heterobimetallic complexation and self-assembly on Au(111)

“…1b ). 31 , 44 The UV-vis spectra of 6 and 7 are nearly identical and feature very intense absorption bands at 454 ( ε = 3.1 × 10 4 M –1 cm –1 ) and 452 ( ε = 2.6 × 10 4 M –1 cm –1 ), respectively, that have a substantial contribution from the d π(Cr) → pπ*(CNAzulenyl) charge transfer ( Fig. 7 and S1 † ).…”