Probing Electronic Communications in Heterotrinuclear Fe–Ru–Fe Molecular Wires Formed by Ruthenium(II) Tetraphenylporphyrin and Isocyanoferrocene or 1,1′-Diisocyanoferrocene Ligands

Abstract

Two new heterotrinuclear Fe-Ru-Fe complexes of ruthenium(II) tetraphenylporphyrin axially coordinated with a pair of isocyanoferrocene ((FcNC)2RuTPP, 1) or 1,1'-diisocyanoferrocene (([C5H4NC]2Fe)2RuTPP, 2) ligands [Fc = ferrocenyl, TPP = 5,10,15,20-tetraphenylporphyrinato(2-) anion] were synthesized and characterized by UV-vis, magnetic circular dichroism, NMR, and FTIR spectroscopies as well as by electrospray ionization mass spectrometry and single-crystal X-ray diffraction. Isolation of insoluble polymeric {([C5H4NC]2Fe)RuTPP}n molecular wires (3) was also achieved for the first time. The redox properties of the new trinuclear complexes 1 and 2 were probed using electrochemical (cyclic voltammetry and differential pulse voltammetry), spectroelectrochemical, and chemical oxidation methods and correlated to those of the bis(tert-butylisocyano)ruthenium(II) tetraphenylporphyrin reference compound, (t-BuNC)2RuTPP (4). In all cases, the first oxidation process was attributed to the reversible oxidation of the Ru(II) center. The second and third reversible oxidation processes in 1 are separated by ∼100 mV and were assigned to two single-electron Fe(II)/Fe(III) couples, suggesting a weak long-range iron-iron coupling in this complex. Electrochemical data acquired for 2 are complicated by the interaction between the axial η(1)-1,1'-diisocyanoferrocene ligand and the electrode surface as well as by axial ligand dissociation in solution. Spectroelectrochemical and chemical oxidation methods were used to elucidate the spectroscopic signatures of the [1](n+), [2](n+), and [4](n+) species in solution. DFT and time-dependent DFT calculations aided in correlating the spectroscopic and redox properties of complexes 1, 2, and 4 with their electronic structures.

Photophysics, Redox Processes, and Electronic Structures of Ferrocenyl-Containing BODIPYs, aza-BODIPYs, BOPHYs, Transition-Metal Dipyrromethenes and aza-Dipyrromethenes

“…[16,44] Electrochemical data on ferrocene-merocyanine compounds 24 -25 and their non-ferrocene precursors are indicate that the first irreversible oxidation is localized on the BODIPY's π-system and DFT calculations correlate well with experimental data (Figure 3). [35] In the case of tetraferrocene-containing aza-BODIPY 8 and the corresponding aza-dipyrromethene 4, the DFT-predicted Comparison between experimental and TDDFTpredicted UV-Vis-NIR spectra of BODIPY 17.…”

Rational Control of Conformational Distributions and Mixed‐Valence Characteristics in Diruthenium Complexes

“…Notethe differences in symmetry of the peaks. To test this hypothesis, ac omputational procedure initially used to investigate the electronic and spectral properties of [1] + has been extended to [2] + and [3] + .T hus, ar elaxeds can in which partial structure optimisations were carried out with af ixed PÀRuÀRuÀPd ihedrala ngle in 108 steps (0 W 1808) was performed. In contrast to our previouss tudies on similar systems, [7,8] this investigation took into account dispersion interaction effects using Grimme'sD FT-D3 protocol.…”

“…In contrast to our previouss tudies on similar systems, [7,8] this investigation took into account dispersion interaction effects using Grimme'sD FT-D3 protocol. [43] This resulted in the identification of at otal of six local minima for each of [2] (Figure 4). Similar interactions are recognisable in the herringbone packing pattern of crystalline benzene (centre of mass separation 4.95-5.00 ), [44,45] and this is known as the most stable conformation of the benzene dimer (due to dispersion and quadrupole/quadrupolei nteractions).…”

“…However, it is becoming increasingly apparent that a very large number, and probably the majority, of genuine or purported mixed‐valence compounds display more convoluted near infrared (NIR) spectra, with band envelopes comprising multiple, overlapping bands which can have a distinct electronic origin. The identification of the ‘genuine’ IVCT transition within these band envelopes, and thus application of band‐shape analysis methods and interpretation from a Marcus–Hush model, is decidedly non‐trivial . For example, vibronic progressions can clearly be seen in the spectra of some purely organic systems, whereas spectra of metal‐based mixed‐valence complexes can also feature overlapping IVCT and localised d‐d transitions, an effect which becomes increasingly important for heavy‐metal complexes with large spin‐orbit coupling constants .…”

“…The identification of the 'genuine'I VCT transition within these band envelopes,a nd thus application of bandshape analysism ethods and interpretationf rom aM arcus-Hush model, is decidedly non-trivial. [2] For example, vibronic progressions can clearly be seen in the spectra of some purely organic systems, [3] whereas spectra of metal-based mixed-valence complexesc an also feature overlapping IVCT and localised d-d transitions, [4] an effect which becomes increasingly important for heavy-metal complexesw ith large spin-orbit coupling constants. [5] Coupling of IVCT with MLCT and LMCT transitions also leads to profound changes in the appearance of the spectroscopic envelopes, especially for systems near the localised-delocalised boundary.…”