Substituent Effects on Nitrosyl Iron Corrole Complexes Fe(Ar₃C)(NO)

Abstract

A series of nitrosyl tris(5,10,15-aryl)corrolate complexes of iron(III) Fe(Ar3C)(NO) with different substituents on the aryl groups have been prepared, and certain spectroscopic and reaction properties were compared. The cyclic voltammetric analysis of the various Fe(Ar3C)(NO) complexes demonstrated that both the one-electron oxidation and one-electron reduction potentials respond in systematic and nearly identical trends relative to the electron-donor properties of the substituents. A similar pattern was seen in the nitrosyl stretching frequency, nu(NO), which modestly decreased with the stronger donor substituents. Flash photolysis of Fe(Ar3C)(NO) solutions in toluene leads to NO dissociation followed by rapid [NO]-dependent decay of the transients formed (presumably Fe(Ar3C)) to regenerate the original spectra. As was seen in an earlier flash photolysis study of Fe(TNPC)(NO) (TNPC3- = 5,10,15-tris(4-nitro-phenyl)corrolate; Joseph, C.; Ford, P. C. J. Am. Chem. Soc. 2005, 127, 6737-6743), the second-order rate constants, k(NO), are all much faster ((1-9) x 10(8) M(-1) s(-1) at 298 K) than those for analogous iron(III) complexes of porphyrins. However, on a more microscopic level there is no obvious pattern in these rates with respect to the donor properties of the aryl ring substituents. The high reactivity of the ferric triarylcorrolates with NO data is interpreted in terms of the strongly electron-donating character of the Ar3C3- ligand and the quartet electronic configuration of the Fe(Ar3C) intermediate.

Photometric Detection of Nitric Oxide Using a Dissolved Iron(III) Corrole as a Sensitizer

“…In addition to some minor changes, the most significant NO‐induced difference is the hypsochromic shift of the Soret band from approximately 407 to 380 nm that accompanies a moderate increase of the band intensity (Figure ). This spectral change suggests a ligand exchange that leads to the formation of the nitrosyl complex 2 (Figure ), as similar Fe–nitrosyl complexes possess Soret bands at virtually identical wavelengths, as shown in Table . Similar spectral responses upon NO binding are reported for structurally similar iron(III) porphyrins …”

“…In such photonic sensing approaches, self‐assembling chromophores that reversibly bind NO appear favored for a continuous mode of operation. Promising molecules for these sensing layers are iron(III) corroles, which change their UV/Vis spectra upon NO binding . Furthermore, corroles are excellent candidates due to their ability to be modified at their periphery, which allows the introduction of solubilizing/adhesive groups or amphiphilicity, tuning of their electronic properties (addition of electron donating or withdrawing groups) or introduction of sterically demanding groups that might further enhance selectivity through steric constraints at the transition metal binding site.…”

“…Promising moleculesf or these sensing layers are iron(III) corroles, whichc hange their UV/Vis spectra upon NO binding. [42][43][44] Furthermore, corroles are excellent candidates due to their ability to be modified at their periph-The potential of an iron(III) corrole complex for use in the detection of nitric oxide (NO) was investigated. The reversible conversion of an dissolved iron(III) corrole to its corresponding nitrosyl complex using gaseous nitric oxide was monitored by UV/Vis spectroscopy.T he spectrald ifferences between both coordination compoundsw ere used to determine photometrically small amountso fn itric oxide in the sub-parts-per-million range.…”

β-Nitro Derivatives of Iron Corrolates

“…(TArPC)FeNO: 7 , 8 , 9 , 10 and 11 were characterized by comparison with an authentic sample prepared according to literature methods, 18 while 12 was isolated in trace amounts and identified by comparison with literature UV-vis data. 19 Spectroscopic data for 13 , 14 , 17 and 18 were in agreement with data reported earlier in the literature.…”

Nitration of iron corrolates: further evidence for non-innocence of the corrole ligand

“…14 Characterization of the second band (25% yield) indicated the formation of a nitrosyl complex, due to the presence of a characteristic NO stretching band at 1790 cm −1 in the IR spectrum. However the 1 H NMR spectrum showed a non-symmetric substitution pattern of resonances for the β-pyrrolic protons, with a singlet at 8.57 ppm indicating a mono-substituted pyrrole subunit.…”