Electronic absorption, resonance Raman and excited-state resonance Raman spectroscopy of rhenium(I) and copper(I) complexes, with substituted dipyrido[3,2-a : 2′,3′-c]phenazine ligands, and their electron reduced products

Abstract

The electronic absorption and resonance Raman spectra of a series of rhenium(I) and copper(I) complexes with substituted dipyrido[3,2-a : 2 ,3 -c]phenazine (dppz) ligands were investigated. The ligands were benzo[i ]dipyrido[3,2-a : 2 ,3 -c]phenazine, 11,12-dimethyldipyrido[3,2-a : 2 ,3 -c]phenazine, 10-methyldipyrido[3,2-a : 2 ,3 -c]phenazine and 11-methyoxydipyrido[3,2-a : 2 ,3 -c]phenazine. The spectroelectrochemistry of the reduced complexes and the emission and resonance Raman spectra of the excited states are reported. Vibrational wavenumber calculations of the unsubstituted ligand suggest the presence of normal modes that are localized to various sections of the ligand structure; the resonance Raman spectra of the complexes are interpreted with reference to these calculations. The analysis of the spectra revealed that the Franck-Condon state initially formed by visible photoexcitation (450 nm) is metal-to-ligand charge-transfer in nature. Spectroelectrochemical resonance Raman and electronic absorption measurements revealed the spectral signatures for the radical anions of each of the ligands used in this study. These spectral features were used to assign the excited states formed by the complexes. Most of the complexes studied show spectral features in their excited-states that suggest that the predominant state formed within 5 ns of excitation is ligand-centred.a See Fig. 1 for numbering scheme. b The values in parentheses show the difference between the corresponding free ligand resonance, i.e. υ(complex) υ(ligand). c Insufficiently soluble in CDCl 3 to obtain a spectrum.

Synthesis, spectroscopic and electrochemical studies of a series of transition metal complexes with amino- or bis(bromomethyl)-substituted dppz-ligands: Building blocks for fullerene-based donor–bridge–acceptor dyads

“…Therefore the reductions are assigned as ligand based. All rhenium complexes show an irreversible oneelectron oxidation at +1.25 V which can be ascribed to the Re + /Re 2+ couple [24,33]. The potentials are not affected by substitution of the dppz ligands.…”

“…The potentials are not affected by substitution of the dppz ligands. The results of the complexes studied in this work are in good agreement with those obtained by Gordon et al [24,33].…”

“…Like the rhenium complexes, irreversible one-electron oxidations corresponding to oxidation of the Cu(I) metal center to Cu(II) are observed at $0.95 V. Again, the oxidation potentials showed no significant effect arising from the different substitution of the dppz ligands. The values for the oxidation Table 7 Electrochemical data a for [Ru(bpy) 2 (dppz)] 2+ complexes 1a-d in acetonitrile [Ru(bpy) 2 (L)] 2+ Ligand potentials for the Cu + /Cu 2+ redox pair differ from that reported by Gordon et al [33]. The oxidation potentials reported herein are shifted to more positive redox potential by ca.…”

Using Metal Complex Reduced States to Monitor the Oxidation of DNA

“…36–39,45–51 The complex displays absorption maxima at 364 nm and 382 nm in acetonitrile (ε ≈ 11,000 M −1 cm −1 ), 37,39 with a weak tail extending into the visible region. The emission spectrum (λ ex = 355 nm) in acetonitrile is bifurcated, exhibiting maxima at 555 nm and 595 nm.…”

Understanding excited-state structure in metal polypyridyl complexes using resonance Raman excitation profiles, time-resolved resonance Raman spectroscopy and density functional theory

“…The advent of computational chemistry has dramatically altered the way in which vibrational spectra are analysed for metal complexes. For example detailed studies of selective and perdeuerated dipyridophenazine (dppz) and rhenium complexes thereof [41,42], with the aid of DFT calculations, allowed a detailed assignment of the vibrational normal modes of dppz. Distinct normal modes were found for localised phenazine (phz) and phenanthroline (phen) ring-sections of the framework, corresponding to activity in the respective part of the ligand (see Fig.…”