Substitution effects on the absorption spectra of nitrophenolate isomers

Marius Wanko; Jørgen Houmøller; Kristian Støchkel; Maj-Britt Suhr Kirketerp; Michael Åxman Petersen; Mogens Brøndsted Nielsen; Steen Brøndsted Nielsen; Angel Rubio

doi:10.1039/c2cp41636k

Substitution effects on the absorption spectra of nitrophenolate isomers

Marius Wanko, Jørgen Houmøller, Kristian Støchkel, Maj-Britt Suhr Kirketerp, Michael Åxman Petersen, Mogens Brøndsted Nielsen, Steen Brøndsted Nielsen, Angel Rubio

Department of Chemistry

19 Citations (Scopus)

Abstract

Charge-transfer excitations highly depend on the electronic coupling between the donor and acceptor groups. Nitrophenolates are simple examples of charge-transfer systems where the degree of coupling differs between ortho, meta and para isomers. Here we report the absorption spectra of the isolated anions in vacuo to avoid the complications of solvent effects. Gas-phase action spectroscopy was done with two different setups, an electrostatic ion storage ring and an accelerator mass spectrometer. The results are interpreted on the basis of CC2 quantum chemical calculations. We identified absorption maxima at 393, 532, and 399 nm for the para, meta, and ortho isomer, respectively, with the charge-transfer transition into the lowest excited singlet state. In the meta isomer, this π-π* transition is strongly redshifted and its oscillator strength reduced, which is related to the pronounced charge-transfer character, as a consequence of the topology of the conjugated π-system. Each isomer's different charge distribution in the ground state leads to a very different solvent shift, which in acetonitrile is bathochromic for the para and ortho, but hypsochromic for the meta isomer.

Original language	English
Journal	Physical Chemistry Chemical Physics
Volume	14
Issue number	37
Pages (from-to)	12905-12911
Number of pages	7
ISSN	1463-9076
DOIs	https://doi.org/10.1039/c2cp41636k
Publication status	Published - 5 Oct 2012

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title = "Substitution effects on the absorption spectra of nitrophenolate isomers",

abstract = "Charge-transfer excitations highly depend on the electronic coupling between the donor and acceptor groups. Nitrophenolates are simple examples of charge-transfer systems where the degree of coupling differs between ortho, meta and para isomers. Here we report the absorption spectra of the isolated anions in vacuo to avoid the complications of solvent effects. Gas-phase action spectroscopy was done with two different setups, an electrostatic ion storage ring and an accelerator mass spectrometer. The results are interpreted on the basis of CC2 quantum chemical calculations. We identified absorption maxima at 393, 532, and 399 nm for the para, meta, and ortho isomer, respectively, with the charge-transfer transition into the lowest excited singlet state. In the meta isomer, this π-π* transition is strongly redshifted and its oscillator strength reduced, which is related to the pronounced charge-transfer character, as a consequence of the topology of the conjugated π-system. Each isomer's different charge distribution in the ground state leads to a very different solvent shift, which in acetonitrile is bathochromic for the para and ortho, but hypsochromic for the meta isomer.",

author = "Marius Wanko and J{\o}rgen Houm{\o}ller and Kristian St{\o}chkel and Kirketerp, {Maj-Britt Suhr} and Petersen, {Michael {\AA}xman} and Nielsen, {Mogens Br{\o}ndsted} and Nielsen, {Steen Br{\o}ndsted} and Angel Rubio",

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doi = "10.1039/c2cp41636k",

language = "English",

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TY - JOUR

T1 - Substitution effects on the absorption spectra of nitrophenolate isomers

AU - Wanko, Marius

AU - Houmøller, Jørgen

AU - Støchkel, Kristian

AU - Kirketerp, Maj-Britt Suhr

AU - Petersen, Michael Åxman

AU - Nielsen, Mogens Brøndsted

AU - Nielsen, Steen Brøndsted

AU - Rubio, Angel

PY - 2012/10/5

Y1 - 2012/10/5

N2 - Charge-transfer excitations highly depend on the electronic coupling between the donor and acceptor groups. Nitrophenolates are simple examples of charge-transfer systems where the degree of coupling differs between ortho, meta and para isomers. Here we report the absorption spectra of the isolated anions in vacuo to avoid the complications of solvent effects. Gas-phase action spectroscopy was done with two different setups, an electrostatic ion storage ring and an accelerator mass spectrometer. The results are interpreted on the basis of CC2 quantum chemical calculations. We identified absorption maxima at 393, 532, and 399 nm for the para, meta, and ortho isomer, respectively, with the charge-transfer transition into the lowest excited singlet state. In the meta isomer, this π-π* transition is strongly redshifted and its oscillator strength reduced, which is related to the pronounced charge-transfer character, as a consequence of the topology of the conjugated π-system. Each isomer's different charge distribution in the ground state leads to a very different solvent shift, which in acetonitrile is bathochromic for the para and ortho, but hypsochromic for the meta isomer.

AB - Charge-transfer excitations highly depend on the electronic coupling between the donor and acceptor groups. Nitrophenolates are simple examples of charge-transfer systems where the degree of coupling differs between ortho, meta and para isomers. Here we report the absorption spectra of the isolated anions in vacuo to avoid the complications of solvent effects. Gas-phase action spectroscopy was done with two different setups, an electrostatic ion storage ring and an accelerator mass spectrometer. The results are interpreted on the basis of CC2 quantum chemical calculations. We identified absorption maxima at 393, 532, and 399 nm for the para, meta, and ortho isomer, respectively, with the charge-transfer transition into the lowest excited singlet state. In the meta isomer, this π-π* transition is strongly redshifted and its oscillator strength reduced, which is related to the pronounced charge-transfer character, as a consequence of the topology of the conjugated π-system. Each isomer's different charge distribution in the ground state leads to a very different solvent shift, which in acetonitrile is bathochromic for the para and ortho, but hypsochromic for the meta isomer.

U2 - 10.1039/c2cp41636k

DO - 10.1039/c2cp41636k

M3 - Journal article

C2 - 22898867

SN - 1463-9076

VL - 14

SP - 12905

EP - 12911

JO - Physical Chemistry Chemical Physics

JF - Physical Chemistry Chemical Physics

IS - 37

ER -

Substitution effects on the absorption spectra of nitrophenolate isomers

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