Spectroscopic and Reactivity Comparisons of a Pair of bTAML Complexes with FeV=O and FeIV=O Units

Santanu Pattanayak, Andrew J. Jasniewski, Atanu Rana, Apparao Draksharapu, Kundan K. Singh, Andrew Weitz, Michael Hendrich, Lawrence Que, Abhishek Dey, Sayam Sen Gupta

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Abstract

In this report we compare the geometric and electronic structures and reactivities of [FeV(O)] and [FeIV(O)]2- species supported by the same ancillary nonheme biuret tetraamido macrocyclic ligand (bTAML). Resonance Raman studies show that the FeO vibration of the [FeIV(O)]2- complex 2 is at 798 cm-1, compared to 862 cm-1 for the corresponding [FeV(O)] species 3, a 64 cm-1 frequency difference reasonably reproduced by density functional theory calculations. These values are, respectively, the lowest and the highest frequencies observed thus far for nonheme high-valent Fe=O complexes. Extended X-ray absorption fine structure analysis of 3 reveals an Fe=O bond length of 1.59 Å, which is 0.05 Å shorter than that found in complex 2. The redox potentials of 2 and 3 are 0.44 V (measured at pH 12) and 1.19 V (measured at pH 7) versus normal hydrogen electrode, respectively, corresponding to the [FeIV(O)]2-/[FeIII(OH)]2- and [FeV(O)]/[FeIV(O)]2- couples. Consistent with its higher potential (even after correcting for the pH difference), 3 oxidizes benzyl alcohol at pH 7 with a second-order rate constant that is 2500-fold bigger than that for 2 at pH 12. Furthermore, 2 exhibits a classical kinteic isotope effect (KIE) of 3 in the oxidation of benzyl alcohol to benzaldehyde versus a nonclassical KIE of 12 for 3, emphasizing the reactivity differences between 2 and 3.

Original languageEnglish (US)
Pages (from-to)6352-6361
Number of pages10
JournalInorganic Chemistry
Volume56
Issue number11
DOIs
StatePublished - Jun 5 2017

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Biuret
Benzyl Alcohol
Isotopes
reactivity
Ligands
ligands
X ray absorption
Bond length
Vibrations (mechanical)
Electronic structure
Density functional theory
Hydrogen
Rate constants
isotope effect
alcohols
Oxidation
Electrodes
fine structure
density functional theory
electronic structure

Cite this

Pattanayak, S., Jasniewski, A. J., Rana, A., Draksharapu, A., Singh, K. K., Weitz, A., ... Sen Gupta, S. (2017). Spectroscopic and Reactivity Comparisons of a Pair of bTAML Complexes with FeV=O and FeIV=O Units. Inorganic Chemistry, 56(11), 6352-6361. https://doi.org/10.1021/acs.inorgchem.7b00448

Spectroscopic and Reactivity Comparisons of a Pair of bTAML Complexes with FeV=O and FeIV=O Units. / Pattanayak, Santanu; Jasniewski, Andrew J.; Rana, Atanu; Draksharapu, Apparao; Singh, Kundan K.; Weitz, Andrew; Hendrich, Michael; Que, Lawrence; Dey, Abhishek; Sen Gupta, Sayam.

In: Inorganic Chemistry, Vol. 56, No. 11, 05.06.2017, p. 6352-6361.

Research output: Contribution to journalArticle

Pattanayak, S, Jasniewski, AJ, Rana, A, Draksharapu, A, Singh, KK, Weitz, A, Hendrich, M, Que, L, Dey, A & Sen Gupta, S 2017, 'Spectroscopic and Reactivity Comparisons of a Pair of bTAML Complexes with FeV=O and FeIV=O Units', Inorganic Chemistry, vol. 56, no. 11, pp. 6352-6361. https://doi.org/10.1021/acs.inorgchem.7b00448
Pattanayak S, Jasniewski AJ, Rana A, Draksharapu A, Singh KK, Weitz A et al. Spectroscopic and Reactivity Comparisons of a Pair of bTAML Complexes with FeV=O and FeIV=O Units. Inorganic Chemistry. 2017 Jun 5;56(11):6352-6361. https://doi.org/10.1021/acs.inorgchem.7b00448
Pattanayak, Santanu ; Jasniewski, Andrew J. ; Rana, Atanu ; Draksharapu, Apparao ; Singh, Kundan K. ; Weitz, Andrew ; Hendrich, Michael ; Que, Lawrence ; Dey, Abhishek ; Sen Gupta, Sayam. / Spectroscopic and Reactivity Comparisons of a Pair of bTAML Complexes with FeV=O and FeIV=O Units. In: Inorganic Chemistry. 2017 ; Vol. 56, No. 11. pp. 6352-6361.
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abstract = "In this report we compare the geometric and electronic structures and reactivities of [FeV(O)]− and [FeIV(O)]2- species supported by the same ancillary nonheme biuret tetraamido macrocyclic ligand (bTAML). Resonance Raman studies show that the FeO vibration of the [FeIV(O)]2- complex 2 is at 798 cm-1, compared to 862 cm-1 for the corresponding [FeV(O)]− species 3, a 64 cm-1 frequency difference reasonably reproduced by density functional theory calculations. These values are, respectively, the lowest and the highest frequencies observed thus far for nonheme high-valent Fe=O complexes. Extended X-ray absorption fine structure analysis of 3 reveals an Fe=O bond length of 1.59 {\AA}, which is 0.05 {\AA} shorter than that found in complex 2. The redox potentials of 2 and 3 are 0.44 V (measured at pH 12) and 1.19 V (measured at pH 7) versus normal hydrogen electrode, respectively, corresponding to the [FeIV(O)]2-/[FeIII(OH)]2- and [FeV(O)]−/[FeIV(O)]2- couples. Consistent with its higher potential (even after correcting for the pH difference), 3 oxidizes benzyl alcohol at pH 7 with a second-order rate constant that is 2500-fold bigger than that for 2 at pH 12. Furthermore, 2 exhibits a classical kinteic isotope effect (KIE) of 3 in the oxidation of benzyl alcohol to benzaldehyde versus a nonclassical KIE of 12 for 3, emphasizing the reactivity differences between 2 and 3.",
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AU - Jasniewski, Andrew J.

AU - Rana, Atanu

AU - Draksharapu, Apparao

AU - Singh, Kundan K.

AU - Weitz, Andrew

AU - Hendrich, Michael

AU - Que, Lawrence

AU - Dey, Abhishek

AU - Sen Gupta, Sayam

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N2 - In this report we compare the geometric and electronic structures and reactivities of [FeV(O)]− and [FeIV(O)]2- species supported by the same ancillary nonheme biuret tetraamido macrocyclic ligand (bTAML). Resonance Raman studies show that the FeO vibration of the [FeIV(O)]2- complex 2 is at 798 cm-1, compared to 862 cm-1 for the corresponding [FeV(O)]− species 3, a 64 cm-1 frequency difference reasonably reproduced by density functional theory calculations. These values are, respectively, the lowest and the highest frequencies observed thus far for nonheme high-valent Fe=O complexes. Extended X-ray absorption fine structure analysis of 3 reveals an Fe=O bond length of 1.59 Å, which is 0.05 Å shorter than that found in complex 2. The redox potentials of 2 and 3 are 0.44 V (measured at pH 12) and 1.19 V (measured at pH 7) versus normal hydrogen electrode, respectively, corresponding to the [FeIV(O)]2-/[FeIII(OH)]2- and [FeV(O)]−/[FeIV(O)]2- couples. Consistent with its higher potential (even after correcting for the pH difference), 3 oxidizes benzyl alcohol at pH 7 with a second-order rate constant that is 2500-fold bigger than that for 2 at pH 12. Furthermore, 2 exhibits a classical kinteic isotope effect (KIE) of 3 in the oxidation of benzyl alcohol to benzaldehyde versus a nonclassical KIE of 12 for 3, emphasizing the reactivity differences between 2 and 3.

AB - In this report we compare the geometric and electronic structures and reactivities of [FeV(O)]− and [FeIV(O)]2- species supported by the same ancillary nonheme biuret tetraamido macrocyclic ligand (bTAML). Resonance Raman studies show that the FeO vibration of the [FeIV(O)]2- complex 2 is at 798 cm-1, compared to 862 cm-1 for the corresponding [FeV(O)]− species 3, a 64 cm-1 frequency difference reasonably reproduced by density functional theory calculations. These values are, respectively, the lowest and the highest frequencies observed thus far for nonheme high-valent Fe=O complexes. Extended X-ray absorption fine structure analysis of 3 reveals an Fe=O bond length of 1.59 Å, which is 0.05 Å shorter than that found in complex 2. The redox potentials of 2 and 3 are 0.44 V (measured at pH 12) and 1.19 V (measured at pH 7) versus normal hydrogen electrode, respectively, corresponding to the [FeIV(O)]2-/[FeIII(OH)]2- and [FeV(O)]−/[FeIV(O)]2- couples. Consistent with its higher potential (even after correcting for the pH difference), 3 oxidizes benzyl alcohol at pH 7 with a second-order rate constant that is 2500-fold bigger than that for 2 at pH 12. Furthermore, 2 exhibits a classical kinteic isotope effect (KIE) of 3 in the oxidation of benzyl alcohol to benzaldehyde versus a nonclassical KIE of 12 for 3, emphasizing the reactivity differences between 2 and 3.

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