Positional Isomers of Isocyanoazulenes as Axial Ligands Coordinated to Ruthenium(II) Tetraphenylporphyrin: Fine-Tuning Redox and Optical Profiles

Abstract

Two isomeric ruthenium(II) 5,10,15,20-tetraphenylporphyrins axially coordinated to the redoxactive, low-optical gap-containing 2-or 6-isocyanoazulene ligands have been prepared and characterized by NMR, UV-vis, and MCD spectroscopy methods, high-resolution mass spectrometry, and X-ray crystallography. The UV-vis and MCD spectra are suggestive of the presence of the low-energy, azulene-centered transitions in the Q-band region of the porphyrin chromophore. The first coordination sphere in new L2RuTPP complexes is reflective of compressed tetragonal geometry. The redox properties of the new compounds were studied by electrochemical and spectroelectrochemical methods and correlated with the electronic structures predicted by the Density Functional Theory calculations. The experimental and theoretical data are suggestive of the low-potential reduction processes centred at the axial azulene ligands and oxidation processes centred at the ruthenium ion or porphyrin core.

The 2-isocyanoazulene-gold(I) fragment as a versatile element for organometallic dyes and liquid crystals

“…Surprisingly, the great potential of isocyanide derivatives has barely been exploited to modulate the properties of azulene systems [43]. Only recently, a few mononuclear isocyanoazulene metal complexes of Cr(0), W(0), Cr(I) and Ru(II) have been reported [44][45][46][47][48], as well as a series of heterobimetallic Cr(0)/Au(I) complexes derived from 2-isocyano-6-mercaptoazulene [49].…”