Temperature dependence of spin-selective charge transfer pathways in donor-bridge-acceptor molecules with oligomeric fluorenone and p -phenylethynylene bridges

Amy M. Scott, Michael R Wasielewski

Research output: Contribution to journalArticle

19 Citations (Scopus)

Abstract

The temperature dependence of spin-selective intramolecular charge recombination (CR) in a series of 2,7-fluorenone (FN1-2) and p-phenylethynylene (PE1-2P) linked donor-bridge-acceptor molecules with a 3,5-dimethyl-4-(9-anthracenyl) julolidine (DMJ-An) electron donor and a naphthalene-1,8:4,5-bis(dicarboximide) (NI) acceptor was studied using nanosecond transient absorption spectroscopy in the presence of a static magnetic field. Photoexcitation of DMJ-An into its charge transfer band and subsequent electron transfer to NI results in a nearly quantitative yield of 1(DMJ+•-An-FNn-NI-•) and 1(DMJ+•-An-PEnP-NI-•), which undergo rapid radical pair intersystem crossing (RP-ISC) to produce the triplet RPs, 3(DMJ+•-An-FNn-NI -•) and 3(DMJ+•-An-PE nP-NI-•), respectively. The CR rate constants, k CR, in toluene were measured over a temperature range from 270 to 350 K, and a kinetic analysis of kCR in the presence of an applied static magnetic field was used to extract the singlet and triplet charge recombination rate constants, kCRS and kCRT, respectively, as well as the intersystem crossing rate constant, kST. Plots of ln (kT1/2) versus 1/T for PE1P show a distinct crossover at 300 K from a temperature-independent singlet CR pathway to a triplet CR pathway that is positively activated with a barrier of 1047 ± 170 cm -1. The singlet CR pathway via the FN1 bridge displays a negative activation energy that results from donor-bridge and bridge-acceptor torsional motions about the single bonds joining them. In contrast, the triplet CR pathway via the FN1-2 and PE1-2P bridges exhibits positive activation energies. The activation barriers to these torsional motions range from 1100 to 4500 cm-1 and can be modeled by semiclassical electron transfer theory.

Original languageEnglish
Pages (from-to)3005-3013
Number of pages9
JournalJournal of the American Chemical Society
Volume133
Issue number9
DOIs
Publication statusPublished - Mar 9 2011

Fingerprint

Genetic Recombination
Charge transfer
Molecules
Temperature
Rate constants
Electrons
Activation energy
Magnetic fields
Magnetic Fields
Photoexcitation
Naphthalene
Absorption spectroscopy
Joining
Toluene
Chemical activation
3,5-dimethyl-4-(9-anthracenyl)julolidine
Articular Range of Motion
Kinetics
Spectrum Analysis

ASJC Scopus subject areas

  • Chemistry(all)
  • Catalysis
  • Biochemistry
  • Colloid and Surface Chemistry

Cite this

@article{4a144160f2a84c83a5b8a8e473253f10,
title = "Temperature dependence of spin-selective charge transfer pathways in donor-bridge-acceptor molecules with oligomeric fluorenone and p -phenylethynylene bridges",
abstract = "The temperature dependence of spin-selective intramolecular charge recombination (CR) in a series of 2,7-fluorenone (FN1-2) and p-phenylethynylene (PE1-2P) linked donor-bridge-acceptor molecules with a 3,5-dimethyl-4-(9-anthracenyl) julolidine (DMJ-An) electron donor and a naphthalene-1,8:4,5-bis(dicarboximide) (NI) acceptor was studied using nanosecond transient absorption spectroscopy in the presence of a static magnetic field. Photoexcitation of DMJ-An into its charge transfer band and subsequent electron transfer to NI results in a nearly quantitative yield of 1(DMJ+•-An-FNn-NI-•) and 1(DMJ+•-An-PEnP-NI-•), which undergo rapid radical pair intersystem crossing (RP-ISC) to produce the triplet RPs, 3(DMJ+•-An-FNn-NI -•) and 3(DMJ+•-An-PE nP-NI-•), respectively. The CR rate constants, k CR, in toluene were measured over a temperature range from 270 to 350 K, and a kinetic analysis of kCR in the presence of an applied static magnetic field was used to extract the singlet and triplet charge recombination rate constants, kCRS and kCRT, respectively, as well as the intersystem crossing rate constant, kST. Plots of ln (kT1/2) versus 1/T for PE1P show a distinct crossover at 300 K from a temperature-independent singlet CR pathway to a triplet CR pathway that is positively activated with a barrier of 1047 ± 170 cm -1. The singlet CR pathway via the FN1 bridge displays a negative activation energy that results from donor-bridge and bridge-acceptor torsional motions about the single bonds joining them. In contrast, the triplet CR pathway via the FN1-2 and PE1-2P bridges exhibits positive activation energies. The activation barriers to these torsional motions range from 1100 to 4500 cm-1 and can be modeled by semiclassical electron transfer theory.",
author = "Scott, {Amy M.} and Wasielewski, {Michael R}",
year = "2011",
month = "3",
day = "9",
doi = "10.1021/ja1095649",
language = "English",
volume = "133",
pages = "3005--3013",
journal = "Journal of the American Chemical Society",
issn = "0002-7863",
publisher = "American Chemical Society",
number = "9",

}

TY - JOUR

T1 - Temperature dependence of spin-selective charge transfer pathways in donor-bridge-acceptor molecules with oligomeric fluorenone and p -phenylethynylene bridges

AU - Scott, Amy M.

AU - Wasielewski, Michael R

PY - 2011/3/9

Y1 - 2011/3/9

N2 - The temperature dependence of spin-selective intramolecular charge recombination (CR) in a series of 2,7-fluorenone (FN1-2) and p-phenylethynylene (PE1-2P) linked donor-bridge-acceptor molecules with a 3,5-dimethyl-4-(9-anthracenyl) julolidine (DMJ-An) electron donor and a naphthalene-1,8:4,5-bis(dicarboximide) (NI) acceptor was studied using nanosecond transient absorption spectroscopy in the presence of a static magnetic field. Photoexcitation of DMJ-An into its charge transfer band and subsequent electron transfer to NI results in a nearly quantitative yield of 1(DMJ+•-An-FNn-NI-•) and 1(DMJ+•-An-PEnP-NI-•), which undergo rapid radical pair intersystem crossing (RP-ISC) to produce the triplet RPs, 3(DMJ+•-An-FNn-NI -•) and 3(DMJ+•-An-PE nP-NI-•), respectively. The CR rate constants, k CR, in toluene were measured over a temperature range from 270 to 350 K, and a kinetic analysis of kCR in the presence of an applied static magnetic field was used to extract the singlet and triplet charge recombination rate constants, kCRS and kCRT, respectively, as well as the intersystem crossing rate constant, kST. Plots of ln (kT1/2) versus 1/T for PE1P show a distinct crossover at 300 K from a temperature-independent singlet CR pathway to a triplet CR pathway that is positively activated with a barrier of 1047 ± 170 cm -1. The singlet CR pathway via the FN1 bridge displays a negative activation energy that results from donor-bridge and bridge-acceptor torsional motions about the single bonds joining them. In contrast, the triplet CR pathway via the FN1-2 and PE1-2P bridges exhibits positive activation energies. The activation barriers to these torsional motions range from 1100 to 4500 cm-1 and can be modeled by semiclassical electron transfer theory.

AB - The temperature dependence of spin-selective intramolecular charge recombination (CR) in a series of 2,7-fluorenone (FN1-2) and p-phenylethynylene (PE1-2P) linked donor-bridge-acceptor molecules with a 3,5-dimethyl-4-(9-anthracenyl) julolidine (DMJ-An) electron donor and a naphthalene-1,8:4,5-bis(dicarboximide) (NI) acceptor was studied using nanosecond transient absorption spectroscopy in the presence of a static magnetic field. Photoexcitation of DMJ-An into its charge transfer band and subsequent electron transfer to NI results in a nearly quantitative yield of 1(DMJ+•-An-FNn-NI-•) and 1(DMJ+•-An-PEnP-NI-•), which undergo rapid radical pair intersystem crossing (RP-ISC) to produce the triplet RPs, 3(DMJ+•-An-FNn-NI -•) and 3(DMJ+•-An-PE nP-NI-•), respectively. The CR rate constants, k CR, in toluene were measured over a temperature range from 270 to 350 K, and a kinetic analysis of kCR in the presence of an applied static magnetic field was used to extract the singlet and triplet charge recombination rate constants, kCRS and kCRT, respectively, as well as the intersystem crossing rate constant, kST. Plots of ln (kT1/2) versus 1/T for PE1P show a distinct crossover at 300 K from a temperature-independent singlet CR pathway to a triplet CR pathway that is positively activated with a barrier of 1047 ± 170 cm -1. The singlet CR pathway via the FN1 bridge displays a negative activation energy that results from donor-bridge and bridge-acceptor torsional motions about the single bonds joining them. In contrast, the triplet CR pathway via the FN1-2 and PE1-2P bridges exhibits positive activation energies. The activation barriers to these torsional motions range from 1100 to 4500 cm-1 and can be modeled by semiclassical electron transfer theory.

UR - http://www.scopus.com/inward/record.url?scp=79952253877&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=79952253877&partnerID=8YFLogxK

U2 - 10.1021/ja1095649

DO - 10.1021/ja1095649

M3 - Article

VL - 133

SP - 3005

EP - 3013

JO - Journal of the American Chemical Society

JF - Journal of the American Chemical Society

SN - 0002-7863

IS - 9

ER -