Probing the Electronic Properties of a Trinuclear Molecular Wire Involving Isocyanoferrocene and Iron(II) Phthalocyanine Motifs

Abstract

A new trinuclear iron(II) complex involving two isocyanoferrocene ligands axially coordinated to iron(II) phthalocyanine, (FcNC)2FePc [Fc = ferrocenyl; Pc = phthalocyaninato(2-) anion], was isolated and characterized using a variety of spectroscopic methods as well as single-crystal X-ray diffraction. The redox behavior of the above molecular wire was investigated through electrochemical, spectroelectrochemical, and chemical oxidation approaches and compared to that of the bis(tert-butylisocyano)iron(II) phthalocyanine reference compound, (t-BuNC)2FePc. For both complexes, the first oxidation involves the phthalocyanine ligand and results in the formation of a red phthalocyanine cation-radical-centered [(RNC)2FePc](+) species, as evidenced by their UV-vis and electron paramagnetic resonance spectra. Despite the ~11.5 Å distance between the isocyanoferrocene iron centers, the second and third oxidation potentials for (FcNC)2FePc are separated by ∼80 mV, which is indicative of a weak long-range metal-metal coupling in this system. Spectroscopic signatures of the mixed-valence [(FcNC)2FePc](2+) dication were obtained using spectroelectrochemical and chemical oxidation approaches. These experimentally assessed characteristics were also correlated with the electronic structure, redox properties, and spectroscopic signatures predicted by density functional theory (DFT) and time-dependent DFT analyses.

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

“…The UV-vis and MCD spectra of the complexes (2-CNAz)2RuTPP and (6-CNAz)2RuTPP are shown in Figure 1. As in the case of our previously reported (RNC)2RuTPP complexes, 18 the UV-vis and MCD spectra of (2-CNAz)2RuTPP and (6-CNAz)2RuTPP presented in this article are superposition of the spectra of RuTPP and axial ligands. In particular, since the intensities and energies of the * transitions of both azulenes and TPP fragments in the Q-band region are similar, UV-vis spectra of 1 and 2 are much less defined compared to the reference (t-BuNC)2RuTPP in which clear Q0-0 and Q0-1 bands were observed at 582 and 529 nm (Supporting Information).…”

Iron phthalocyanine with coordination induced electronic localization to boost oxygen reduction reaction

“…From the molecular structure, FePc with a tetracoordinate planar FeN 4 center offers extra coordination sites in the axial direction 19 , 20 , suggesting the symmetric electronic density can be modulated by suitable axial coordination 20 – 23 . Generally, the organic ligands with rich electron-donating functional groups, including oxygenic, nitrogenous, and sulfurous species, can be easily employed to coordinate with FePc 24 – 26 . However, organic ligands are not favored for electrocatalysis due to their poor conductivity.…”

Redox induced colour changes between red-violet and blue in hetero-metal complexes of the type [CoII(4′-ferrocenyl-2,2′;6′2′′-terpyridine)2]X2 (X = counter anion)

“…[13][14][15][16] The synthesis of hetero-metal complexes has been a well exemplified strategy for inducing colour variation in metal complexes, with interactions between the metal ions via bridging organic ligands commonly playing a role in the development of the various colours. [17][18][19][20][21][22][23][24] Here, we have focused on the use of the 4′-ferrocenyl-2,2′;6′2″-terpyridine ligand (Fctpy) 25,26 to synthesize hetero-metal cobalt terpyridine complexes. The ferrocene moiety in the Fctpy metalloligand was anticipated to interact electronically via the terpy group with a cobalt ion bound to the N 3 -donor domain of the latter (and vice versa) and be accompanied by a distinct colour change.…”