The redox properties of ferrocenyl-substituted aryl azines

Abstract

A series of ferrocenyl substituted azines (1-Fc/Ar, where Ar = 4-NO2C6H4, 4-CNC6H4, 4-OCH3C6H4, C5H4N, ferrocene, anthracene, and pyrene) were investigated by electrochemical and photochemical techniques. All the 1-Fc/Ar exhibited oxidation waves within 60 mV of each other, consistent with the expected oxidation of the ferrocene moiety. The reduction properties of 1-Fc/Ar is governed by the nature of the Ar substituent. The standard reduction potentials suggest that ferrocene has comparable electron donating abilities as a 4-methoxyphenyl and 4-dimethyl aminophenyl group. The anthracenyl azines exhibit one-electron reversible reduction followed by dimerization of the radical anion resulting in dimerization rate constants (kd) between 5.1 × 104 and 1.5 × 105 M–1 s–1. 1-Fc/Anth and related azines undergo photochemical E/Z isomerization of the C=N bonds to produce E/Z and Z/Z isomers from the thermodynamically most stable E/E form. Fluorescence at 77 K, was observed for these compounds only after long- wavelength irradiation to produce a mixture of E/E, E/Z, and Z/Z isomers. Fluorescence quantum yields of 0.042, 0.090, and 0.176 were determined for 2-Anth/H, 2-Anth/Anth, and 1-Fc/Anth, respectively. The electrochemical, photochemical, and X-ray data suggest that the azine unit is a conjugation "limiter" and may be a general characteristic of azine molecules.Key words: azines, electrochemistry, cyclic voltammetry, reduction, electron transfer.

(Planar‐Chiral) Ferrocenylmethanols: From Anionic Homo Phospho‐Fries Rearrangements to α‐Ferrocenyl Carbenium Ions

“…[43] In contrast, 19 is the first example, which has not been formed by a condensation reaction with hydrazines. [44] Scheme 7. Synthesis of imino phosphates 18a-d, azine 19, amine 20 and anthrylferrocene 22.…”

Rare Earth Arene-Bridged Complexes Obtained by Reduction of Organometallic Precursors

“…Group 3 metal monoalkyl complexes with the general formula (NN TBS )M(CH2Ar)(THF) (M = Sc and Lu ), Ar = 3,5-C6H3Me2; M = Y and La , Ar = C6H5) and the uranium dialkyl complex (NN TBS )UBn2 were successfully synthesized (Chart 18 and Figure 5). The electron donating 1,1′-ferrocenediyl group (Sauro and Workentin, 2002) makes the amide donor bind strongly to the highly electropositive group 3 metals and uranium(IV) ion. By using NN TBS as the ancillary ligand for d 0 f n metal alkyl complexes, the C-H bond activation of aromatic heterocycles , successive C-C bond coupling Carver et al, 2010;Monreal and Diaconescu, 2010;Williams et al, 2010), dearomatization of aromatic heterocycles , and the unprecedented ring-opening of 1-methylimidazole Monreal et al, 2009), 1-methylbenzimidazole , or other aromatic heterocycles (Duhović et al, 2010) were observed and studied (Diaconescu, 2010a;Diaconescu, 2010b).…”

Electrochemistry and photoelectrochemistry of two donor–acceptor polythiophene polymers with acceptor moieties in the main chain

“…An opposite situation is observed for poly(BT-phen), probably, due to the presence of a rigid aromatic phenanthroline moiety and aromatic thiophene rings. This structure should possess a very pronounced tendency to be planar due to a strong interaction between the aromatic p-systems, and thus the energy required for any rearrangement should be much higher as compared to poly(BT-azine), with its non-aromatic and flexible [17][18][19][20][21] azine bridging moiety. The lower aromaticity of poly(BT-azine) could also lessen the extent of p-dimerization between neighboring chains (less sites available for p-stacking).…”

“…1, 4-Dimethylazine was of interest since it is not aromatic and therefore more flexible, unlike 1,10-phenanthroline. Furthermore, the azine as a single unit appears to be conjugated; however, in systems such as various aryl azines it does not act as a conjugated molecule [17][18][19][20][21] because of significant twisting of the aryl groups out of the best plane of the azine. Therefore, it was of interest to see if this moiety could be conjugated with the polythiophene backbone when incorporated into a conjugated macromolecule.…”