Magnetic Circular Dichroism Evidence for an Unusual Electronic Structure of a Tetracarbene-Oxoiron(IV) Complex

Kód výsledku v IS VaVaI

<a href="https://www.isvavai.cz/riv?ss=detail&h=RIV%2F00216208%3A11310%2F16%3A10329519" target="_blank" >RIV/00216208:11310/16:10329519 - isvavai.cz</a>

Výsledek na webu

<a href="http://dx.doi.org/10.1021/jacs.6b07708" target="_blank" >http://dx.doi.org/10.1021/jacs.6b07708</a>

DOI - Digital Object Identifier

<a href="http://dx.doi.org/10.1021/jacs.6b07708" target="_blank" >10.1021/jacs.6b07708</a>

Jazyk výsledku

angličtina

Název v původním jazyce

Magnetic Circular Dichroism Evidence for an Unusual Electronic Structure of a Tetracarbene-Oxoiron(IV) Complex

Popis výsledku v původním jazyce

In biology, high valent oxo-iron(IV) species have been shown to be pivotal intermediates for functionalization of C-H bonds in the catalytic cycles of a range of O-2-activating iron enzymes. This work details an electronic-structure investigation of [Fe-IV(O)(L-NHC)(NCMe)](2+) (L-NHC = 3,9,14,20-tetraaza-1,6,12,17-tetraazoniapenta-cyclohexacosane-1(23),4,6(26),10,12(25),15,17(24),21-octaene, complex 1) using helium tagging infrared photodissociation (IRPD), absorption, and magnetic circular dichroism (MCD) spectroscopy, coupled with DFT and highly correlated wave function based-multireferenee calculations. The IRPD spectrum of complex 1 reveals the Fe-O- stretching vibration at 832 +/- 3 cm(-1). By analyzing the Franck-Condon progression, we can determine the same vibration occurring at 616 +/- 10 cm(-1) in the E(d(xy) -> d(xz,yz)) excited state. Both values are similar to those measured for [Fe-IV(O)(TMC)(NCMe)](2+) (TMC = 1,4,8,11-tetramethy1-1,4,8,11-tetraazacyclotetradecane). The low-temperature MCD spectra of complex 1 exhibit three pseudo A-term signals around 12 500, 17 000, and 24 300 cm(-1). We can unequivocally assign them to the ligand field transitions of d(xy) -> d(xz,yz), d(xz,yz) -> d(z2), and d(xz,yz) -> d(x2-y2), respectively, through direct calculations of MCD spectra and independent determination of the MCD C-term signs from the corresponding electron donating and accepting orbitals. In comparison with the corresponding transitions observed for [Fe-IV(0) (SR-TPA)(NCMe)](2+) (SR-TPA = tris(3,5-dirnethy14-methoxyp-yridy1-2-methy)amine), the excitations within the (FeO)(2+) core of complex 1 have similar transition energies, whereas the excitation energy for d(xz,yz) -> d(x2-y2) is significantly higher (similar to 12 000 cm-1 for [Fe-IV(O)(SR-TPA)(NCMe)](2+)). Our results thus substantiate that the tetracarbene ligand (L-NHC) of complex 1 does not significantly affect the bonding in the (FeO)(2+) unit but strongly destabilizes the d(x2-y2) orbital

Název v anglickém jazyce

Magnetic Circular Dichroism Evidence for an Unusual Electronic Structure of a Tetracarbene-Oxoiron(IV) Complex

Popis výsledku anglicky

In biology, high valent oxo-iron(IV) species have been shown to be pivotal intermediates for functionalization of C-H bonds in the catalytic cycles of a range of O-2-activating iron enzymes. This work details an electronic-structure investigation of [Fe-IV(O)(L-NHC)(NCMe)](2+) (L-NHC = 3,9,14,20-tetraaza-1,6,12,17-tetraazoniapenta-cyclohexacosane-1(23),4,6(26),10,12(25),15,17(24),21-octaene, complex 1) using helium tagging infrared photodissociation (IRPD), absorption, and magnetic circular dichroism (MCD) spectroscopy, coupled with DFT and highly correlated wave function based-multireferenee calculations. The IRPD spectrum of complex 1 reveals the Fe-O- stretching vibration at 832 +/- 3 cm(-1). By analyzing the Franck-Condon progression, we can determine the same vibration occurring at 616 +/- 10 cm(-1) in the E(d(xy) -> d(xz,yz)) excited state. Both values are similar to those measured for [Fe-IV(O)(TMC)(NCMe)](2+) (TMC = 1,4,8,11-tetramethy1-1,4,8,11-tetraazacyclotetradecane). The low-temperature MCD spectra of complex 1 exhibit three pseudo A-term signals around 12 500, 17 000, and 24 300 cm(-1). We can unequivocally assign them to the ligand field transitions of d(xy) -> d(xz,yz), d(xz,yz) -> d(z2), and d(xz,yz) -> d(x2-y2), respectively, through direct calculations of MCD spectra and independent determination of the MCD C-term signs from the corresponding electron donating and accepting orbitals. In comparison with the corresponding transitions observed for [Fe-IV(0) (SR-TPA)(NCMe)](2+) (SR-TPA = tris(3,5-dirnethy14-methoxyp-yridy1-2-methy)amine), the excitations within the (FeO)(2+) core of complex 1 have similar transition energies, whereas the excitation energy for d(xz,yz) -> d(x2-y2) is significantly higher (similar to 12 000 cm-1 for [Fe-IV(O)(SR-TPA)(NCMe)](2+)). Our results thus substantiate that the tetracarbene ligand (L-NHC) of complex 1 does not significantly affect the bonding in the (FeO)(2+) unit but strongly destabilizes the d(x2-y2) orbital

Druh

J_x - Nezařazeno - Článek v odborném periodiku (Jimp, Jsc a Jost)

CEP obor

CC - Organická chemie

OECD FORD obor

—

Projekt

<a href="/cs/project/GA14-20077S" target="_blank" >GA14-20077S: Nehemové železné katalyzátory: výzkum reakčních mechanismů</a><br>

Návaznosti

P - Projekt vyzkumu a vyvoje financovany z verejnych zdroju (s odkazem do CEP)

Rok uplatnění

2016

Kód důvěrnosti údajů

S - Úplné a pravdivé údaje o projektu nepodléhají ochraně podle zvláštních právních předpisů

Název periodika

Journal of the American Chemical Society

ISSN

0002-7863

e-ISSN

—

Svazek periodika

138

Číslo periodika v rámci svazku

43

Stát vydavatele periodika

US - Spojené státy americké

Počet stran výsledku

14

Strana od-do

14312-14325

Kód UT WoS článku

000387095000029

EID výsledku v databázi Scopus

2-s2.0-84994357229