Synthesis and (Spectro)electrochemical Behavior of 2,5-Diferrocenyl-1-phenyl-1H-phosphole

Abstract

2,5-Diferrocenyl-1-phenyl-1H-phosphole (3) has successfully been prepared by a cyclization reaction of phenylphosphine with 1,4-diferrocenylbutadiyne. Subsequent reaction with elemental sulfur and selenium, respectively, leads to the formation of the appropriate phosphole sulfide (4) or selenide (5). Molecules 4 and 5 have structurally been characterized by single crystal X-ray diffraction. Despite the tetrahedral environment at the phosphorus atom, the c C 4 P ring itself is planar and coplanar to the cyclopentadienyl rings of the ferrocenyl termini. Electrochemical measurements revealed that the two ferrocenyl groups could be oxidized at discrete potentials, with separation of the individual redox waves of 280 mV (3), 240 mV (4) and 235 mV (5), respectively. These values agree with other examples of heterocyclic-bridged diferrocenyl compounds such as diferrocenyl thiophene (260 mV) and diferrocenyl furan (290 mV). Compounds [3] + , [4] + and [5] + exhibit IVCT absorptions of weak to moderate strength which conforms well to the predictions of the Hush two-state model for weakly coupled mixedvalence systems. These conclusions are supported by DFT and TD-DFT results, which satisfactorily model the observed structural and spectroscopic parameters. The computational work assists in assigning the various low energy (LF, IVCT) electronic transitions and also highlights the key role of the unsaturated cis-diene-like C 4 H 2 building block of the heterocycle in promoting the Fc à Fc + electron-transfer transition.

Transition-Metal Carbonyl Complexes of 2,5-Diferrocenyl-1-phenyl-1H-phosphole

“…For electrochemical and spectroelectrochemical measurements (vide infra), 2,5-diferrocenyl-1-phenyl-1H-phosphole sulfide (8) 33 was reacted with Fe 2 (CO) 9 in toluene to give tricarbonyl[(2,3,4,5,-η)-(2,5-diferrocenyl-1-phenyl-1H-phosphole 1-sulfide)]iron (9), in which the dienic system is η 4 coordinated to a Fe(CO) 3 building block (Scheme 2).…”

“…After complexation of the phosphorus atom to a M(CO) 5 unit, an increase of the 3 J PH coupling constant was observed in comparison with 1. 33 Additional complexation of the dienic system to Fe(CO) 3 (7,9) leads to a shift of the c C 4 H 2 P protons to higher field and to a decrease of the 3 J PH coupling constants, which is attributed to a decrease of the π-electron density and hence a decreased ring current.…”

“…33 When the dienic unit in 9 is η 4 coordinated to a Fe(CO) 3 unit, the intensity of the IVCT band (ε max ≈ 400 L mol −1 cm −1 ) decreases significantly and the full width at half-height (Δν 1/2 ≈ 4700 cm −1 ) increases ( Figure 7). Both electronic and steric reasons may be held accountable for this decreased coupling: (i) the lower electron density in 9 should cause a decreased electronic interaction and (ii) the deflection of the phosphole ring (the phosphorus atom is out of the C 4 plane by ca.…”

“…It could be shown that the oxidation of P III to P V resulted in a small decrease of the strength of the electronic interaction via the phosphole unit. 33 Earlier theoretical studies on 2,5-diferrocenyl-1-phenyl-1H-phosphole revealed that the electronic interaction of the ferrocenyl termini is mostly supported by the dienic system. 33 Therefore, we herein report about the coordination of the phosphorus atom and/or the dienic system to transition-metal carbonyl units to study the influence on the electronic interaction of the redox-active end groups.…”

Fabrication of a porphyrin-based electrochemical biosensor for detection of nitric oxide released by cancer cells

“…The redox behavior of the synthesized 5,10,15,20-tetrakis(4-methoxyphenyl)porphyrin (1) [40][41][42][43][44][45][46][47]. The cyclic voltammetry measurements were performed at 25°C at varied scan rates.…”