graduate research @ usc

Design and Syntheses of Polymeric Materials for Visible and Near-Infrared Emitting Applications

Sean Owen Clancy, Ph.D.

POLYMER LIGAND Eu+3

ET - Dexter

ET - Förster

S1

T1

S0

S1

T1

S0 7F2

5D0

5D2

All material contained within is copyright © 2006 Sean Owen Clancy and / or the respective institutions.

Polymeric Energy Transfer Complexes

O

O

ArylLn

L

L

C10H21O

OC10H21

n

N

N NLn

LL

L

C10H21O

OC10H21

n

O

O

Aryl

N

Er

N

N

N

C10H21O

OC10H21

n

• PM_aryl:Ln(L)2

• PM_trp:Ln(L)3

• PM_aryl:ErTPP

Loker Hydrocarbon Research Institute and Department of Chemistry University of Southern California

Graduate Research Overview• Background

• Harper Group Research • Research Goals and Motivation• Recent Applications• Lanthanides• Ligands• Color Tuning• Polymers Photophysics• Energy Transfer

• Visible Emission Resulting from Energy Transfer from Polymers to Ligands to Europium• Polymers with Pendant Terpyridines• Polymers with Pendant β-Diketonates

• Infrared Emission Resulting from Energy Transfer from Polymers to Ligands to Erbium

• Summary

• Future Work


Harper Group Research

• Energy Transfer Studies• Light Harvesting Dendrimers• Light Harvesting Polymers• Polymer Photophysics

• Lanthanide Complexes• β-Diketonate Ligands• Dative Bonding Heterocyclic Ligands

• Photonic Materials• Lanthanide Containing Materials• Organometallic Systems• PPV Syntheses• Polymer Sensors• Photonic Crystals• Quantum Dots• Two-Photon Dyes

N N

O

O

S

EuN

N

3

N N

OC10H21

C10H21On

N

N

N

n

• Loker Hydrocarbon Research Institute and Department of Chemistry University of Southern California

Research Goals and MotivationFacilitate Tunability and Processing• Polymers are easier to process than inorganic systems.• Polymeric device properties can be altered by changing the chemical structure of the

polymer.

Increase Efficiencies• Electrical excitation produces 25% singlets and 75% triplets.1• Polymeric devices typically have higher external quantum efficiencies than small

molecule devices.2,3

• Electrophosphorescent devices have higher efficiencies than electroluminescent devices.4

• Lanthanides exert the “heavy atom effect,” creating more triplet states,5 which the lanthanides can harvest and emit as pure colors.

• Improve efficiencies by bringing the donors and acceptors closer to each other.• Increase dopant/acceptor concentration and prevent aggregation as well.

1. Brown, A. R.; Pichler, K.; Greenham, N. C.; Bradley, D. D.; Friend, R. H.; Holmes, A. B. Chem. Phys. Lett., 1993, 210, 61.2. Baldo, M. A.; O'Brien, D. F.; Thompson, M. E.; Forrest, S. R. Phys. Rev. B, 1999, 60, 14422.3. Wilson, J. S.; Dhoot, A. S.; Seeley, A. J. A. B.; Khan, M. S.; Kohler, A.; Friend, R. H. Nature, 2001, 413, 828.4. Baldo, M.A.; Lamansky, S.; Burrows, P.E.; Thompson, M.E.; Forrest, S.R. Appl. Phys. Lett., 1999, 75, 4.5. Mukherjee, K. K. R. Fundamentals of Photochemistry, Wiley Eastern Ltd. India, 1992.


Background – Recent Applications• Conjugated polymers have many applications:

• Photovoltaics

• OLEDs

Flexible photovoltaic diode http://www.oc.chalmers.se/science/konjug_polymerer.htm

20” OLED full color display by IBM 2002.http://www.zurich.ibm.com/st/display/demo.html


Kodak EasyShare Digital CameraActive-matrix OLEDhttp://www.kodak.com/go/display/

Background – Lanthanides• Pure color emission (shielded f orbital transitions)• Robust metals (will not photobleach)• Induce heavy atom effect (improves rate of intersystem crossing)• Triplet harvesters• Reduce polymer degradation

• Eu+3, Sm+3, and Tb+3 can be used in visible devices• Er+3 can be used in EDFA (1.55 mm)• Nd+3 and Yb+3 can be used in IR-emitting devices

• Direct excitation is inefficient, to overcome• Laser source• Ligands

• Energy transfer is important• Conjugated organic ligands allow for ET• Ligands shield lanthanide ion from external environment, such as solvent (mode of energy loss) and other lanthanide ions (self quenching).


Background – Ligands

• Lanthanides have a high number of coordination sites (from six to twelve).• Their f orbitals are unable to form hybrid orbitals with ligand.• Need ligands to bind with more than one coordination site (multidentate).• Dative bonding ligands, such as terpyridine:

• Bidentate ligands, such as beta-diketonates, form both covalent and dative bonds:

NN

N

R1

O OH

R3R2

R1

O O

R3R2


Background – Color Tuning• PPV and PPP type polymers are widely used

R

R

R

R R RPFPPP PPV

N N

PPy PPyV

n n n nn

• Mechanical properties- Light weight, easy to process

• Infinite π-system• Give rise to a band structure• Band gap varies according to

structure

http://www.tn.utwente.nl/cms/polymers/conj_pol.htm


Background – Polymer Photophysics

a b c

d

e

f

g

h

S0

S1

T1

Energy level diagram showing modes of deactivation:

• a – absorbance

• b – fluorescence

• c – nonradiative decay

• d – intersystem crossing

• e – singlet energy transfer

• f – triplet energy transfer

• g – phosphorescence

• h – internal crossing


Background – Energy Transfer


Forster Energy Transfer

• Singlet to singlet• Coupled dipole-dipole interaction; through space

Dexter Energy Transfer

• Triplet to triplet• Exchange mechanism; through bond

D* A D A*

D* A D A*

Background – Energy Transfer Polymer to Ligand to Lanthanide

PO LY M ER LIG A N D Eu+3

ET - D exter

ET - Förster

S 1

T1

S 0

S 1

T1

S 0 7F2

5D 0

5D 2


Sensitization of Europium Chelates

Design and Synthesis of β-Diketone Ligands

S

OO

Ar

S

BTM DTM 3-PTM 9-PTM

Ar =


Sensitization of Europium ChelatesLigand Structures

BTM DTM 3-PTM 9-PTMHFA

S

O

O

S

CF3

O

O

CF3

S

O

O

S

O

O

S

O

O

Asymmetric –Extent of Conjugation LengthAsymmetric Vs. Symmetric


• Asymmetric ligands perturb the ligand field around a lanthanide.• The more asymmetric the field, the greater the lanthanide’s emission intensity.

• Shorter effective conjugation length increases the energies of a ligand.• Larger energy gap will reduce the possibility for back energy transfer.

• Minimizes a pathway for energy loss.


Sensitization of Europium ChelatesLigand Syntheses

S

O

S

O

S

O

O

S

O

O

S

O O

S

S

O O

S

O O

S

O O

O

O

O

O

S

O

O

NaH

THF

NaH

THF

NaH

THF

NaH

THF

BTM

DTM

3-PTM

9-PTM

Sensitization of Europium ChelatesPolymer Structures

O

O

ArylLn

L

L

C10H21O

OC10H21

N

N NLn

LL

L

C10H21O

OC10H21S

O

N

N

N

n n

Polymer Aryl Group

PM_th

PM_fu

PM_py

PM_pz

PM_trp


Sensitization of Europium ChelatesEnergy Level Tuning of Polyphenylenes – Primary Donors

The synthetic route to PM_es and P1 (i.) ethanol/ PTSA refluxed 24hrs; (ii.) Pd(PPh3)4, 2M Na2CO3, toluene, refluxed 72hrs).

(HO)2B B(OH)2

C10H21O

OC10H21

Br Br

COOH

Br Br

O O C10H21O

OC10H21

O O

n

i ii

(HO)2B B(OH)2

C10H21O

OC10H21

Br BrC10H21O

OC10H21

n

ii

PM_es

P1

+

+

Photophysical properties of P1 and PM_es in THF.EmissionPolymers Abs. Max

(nm) Max(nm)

FWHM(nm)

φFL τ(ns)

P1 350 411 61.5 0.386 0.690 3.24 2.31

PM_es 330 392 61.5 0.662 1.665 3.41 2.47

Singlet energy(eV)

Triplet energy(eV)



Synthesis of Polymers with Pendant TerpyridinesBound to Europium(III) β-Diketonates

N

N NLn

LL

L

C10H21O

OC10H21

n

PM_trp


Polymer with Terpyridines Synthesis

OH

OH

OC10H21

OC10H21

OC10H21

OC10H21

Br

Br

C10H21O

OC10H21

(HO)2B B(OH)2

Br-C10H21

K2CO3CH3CN

Br2

CH3Cl

n-Butyllithium

THFB(OMe)3

N

O

N

O

N+

I-

I2

N


Polymer with Terpyridines Synthesis

Br Br

CHO

NO

N NO

Br

Br

N

O

I-Br Br

NN

N

+

KOH

MeOHNH4OAc

MeOH

OC10H21

C10H21O

NN N

n

OC10H21

C10H21O

Br

NN N

(HO)2B B(OH)2

Br

PM_trp

Pd(PPh3)4

K2CO3, THF+


Polymer-Lanthanide Chelate Synthesis

OC10H21

C10H21O

NN N

n

O O

R2R1

3 eq NaOEt, 1 eq LnCl3

THF

3 eq

OC10H21

C10H21O

NN N

n

O O

R2R1

Ln

3



Materials Characterization and Photophysical Performance Data

PM_trp

N

N NLn

LL

L

C10H21O

OC10H21

n


Polymer with Terpyridines CharacterizationPolymer molecular weights were determined by gel permeation chromatography (GPC) and multiple angle laser light scattering (MALLS).

Polymer dn/dc (mL/g) Mn (g/mol) Mw (g/mol) PDI

PM_trp 0.1608 8.669 x 106 1.117 x 107 1.29

Photophysical properties of polymers PM_trp in THF.

PM_trp

Absorption maximum 320 nm

Fluorescence maximum 416 nm

FWHM 85 nm

Stokes’ shift 7,212 cm-1

ΦFL 0.062

Lifetime (weighting coefficient) 0.27 ns (0.60)1.49 ns (0.40)

Singlet energy level (ES) 3.32 eV

Triplet energy level (ET) 2.47 eV

Singlet-triplet gap (∆EST) 0.85 eV


Polymer with Terpyridines Characterization

300 350 400 450 500 550 600

0.0

0.2

0.4

0.6

0.8

1.0

1.2

PM_trp abs PM_trp ems

N

orm

aliz

ed in

tens

ity

Wavelength (nm)

The absorbance and emission spectra of polymer PM_trp in THF (ex = 320 nm).


PM_trp:Eu(L)3 Emission Spectra

325 350 375 400 425 450 475 500 525 550 575 600 625

0.0

2.0x105

4.0x105

Excited @ Poly Abs Max

PM_trp:Eu(BTM)3 PM_trp:Eu(DTM)3 PM_trp:Eu(3-PTM)3 PM_trp:Eu(9-PTM)3

Inte

nsity

(Cou

nts)

Wavelength (nm)


PM_trp:Eu(L)3 Emission Maxima

1 2 3 45.0x104

1.0x105

1.5x105

2.0x105

2.5x105

3.0x105

3.5x105

4.0x105

PM_trp:Eu(L)3 Emissions, where Ligands:1 = BTM, 2 = DTM, 3 = 3-PTM, 4 = 9-PTM

Residual Emission Europium Emission

Inte

nsity

Ligands


PM_th:Eu(L)2 Ligands Versus Energy Parameters

0

0.2

0.4

0.6

0.8

1

1.2

1 2 3 4

Ligands

Nor

mal

ized

Uni

ts

Emission Intensity DScm-1 DTcm-1


PM_trp:Ln(L)3 Systems, where Ligands: 1 = BTM, 2 = DTM, 3 = 3-PTM, 4 = 9-PTM.

∆S

• Smaller distances in singlet energies (∆S) from polymer to polymer-ligand complexes inversely relate to greater emission intensities from complexes.• Suggests Forster ET of greater significance than Dexter ET for polymer to ligand ET.

∆T


PM_trp:Ln(L)3 Systems, where Ligands: 1 = BTM, 2 = DTM, 3 = 3-PTM, 4 = 9-PTM.

0.70.750.8

0.850.9

0.951

1.05

1 2 3 4

Ligands

Norm

aliz

ed U

nits

DEST∆EST


• Greater distances in singlet to triplet energies for polymer-ligand complexes almost directly relate to greater emission intensities from complexes.• Suggests back energy transfer led to lower emission intensities for DTM and 3-PTM.

• Forward ISC favored by BTM and 9-PTM.

PM_trp:Ln(L)3 Systems CharacterizationPhotophysical properties of PM_trp gadolinium complexes.

PM_trp:Gd(HFA)3

PM_trp:Gd(BTM)3

PM_trp:Gd(DTM)3

PM_trp:Gd(3-PTM)3

PM_trp:Gd(9-PTM)3

Abs. Max (nm)(cm-1)

31731,546

35827,933

37426,738

37626,596

35827,933

Em. Max (nm)(cm-1)

40025,000

41024,390

42323,641

42923,310

41024,390

∆ (cm-1) 6,546 3,543 3,097 3,286 3,543

ES (eV)(cm-1)

3.4027,397

3.2125,907

3.0924,938

3.0724,722

3.2025,773

ET (eV)(cm-1)

2.7622,297

2.4619,841

2.4319,608

2.4820,000

2.4519,763

∆EST (eV) 0.64 0.75 0.66 0.59 0.75

Energy transfer efficiencies from PM_trp to L in PM_trp:Eu(L)3 systems, where L = BTM, DTM, 3-PTM, and 9-PTM.

BTM DTM 3-PTM 9-PTM

PM_trp:Eu(L)3 0.993 0.994 0.991 0.993


PM_trp:Ln(L)3 Systems CharacterizationThe energy transfer mechanism for the PM_trp:Eu(BTM)3 system.

3.21

2.46 2.46

3.40

2.76

Eu+3 BTM Polymer PM_trp BTM Eu+3

2.14

2.36

2.64

2.14

2.36

2.64

FÖRSTERMECHANISM

DEXTERMECHANISM

a

b

cd

e

f

h

i

g

Energy (eV)

h



Synthesis of Polymers with Pendant β-DiketonatesBound to Europium(III) β-Diketonates

O

O

ArylLn

L

L

C10H21O

OC10H21S

O

N

N

N

n

Polymer Aryl Group

PM_th

PM_fu

PM_py

PM_pz


Polymers with β-Diketonates Synthesis


Br Br

O OH

Br Br

O O

PTSA

EtOH

OC10H21

C10H21O

(HO)2B B(OH)2

Br Br

O O

Pd(PPh3)4, THF

KCO3 (aq.)

O O

OC10H21

C10H21On

O O

OC10H21

C10H21On

SONaH

THF

O

O

OC10H21

C10H21O

n

S

PM_es

PM_th

Polymer-Lanthanide Chelate Synthesis

O

O

OC10H21

C10H21O

n

Ar

O

O

OC10H21

C10H21O

n

Ar

O O

R2R1

O

O

R2

R1 Ln

2

3 eq NaOEt, 1 eq LnCl3

THF

2 eq



Materials Characterization and Photophysical Performance Data

O

O

ArylLn

L

L

C10H21O

OC10H21S

O

N

N

N

n

Polymer Aryl Group

PM_th

PM_fu

PM_py

PM_pz


Polymers with β-Diketonates CharacterizationPolymer molecular weights determined by GPC and MALLS in CHCl3.

Polymer dn/dcmL/g

Mng/mol

Mwg/mol

DP PDI

PM_es 0.0975 1.27x104 1.64x104 24 1.28

Photophysical properties polymers with β-diketonate pendant groups.

PM_th PM_fu PM_py PM_pz

Abs. Max (nm)(cm-1)

33030,300

33230,120

33030,300

33030,300

Em. Max (nm) (cm-1)

396.525,220

39125,575

39125,575

39625,250

FWHM (nm) 59 54 54.5 58.4

∆ (cm-1) 5,082 4,545 4,728 5,051

QE 0.2121 0.2154 0.1915 0.2134

Life Times (ns) 1.65 1.66 1.52 1.68

kf (s-1) 1.32 x 108 1.32 x 108 1.26 x 108 1.27 x 108

kST (s-1) 4.74 x 108 4.72 x 108 5.31 x 108 4.68 x 108

ES (eV)(cm-1)

3.4027,425

3.4027,425

3.4227,585

3.4027,425

ET (eV)(cm-1)

2.5020,165

2.5020,165

2.5020,165

2.4719,920

∆EST (eV) 0.90 0.90 0.92 0.93


350 375 400 425 450 475 500 525 550 575 600 625 650

0

1x105

2x105

3x105

4x105

5x105

6x105

Excited @ Poly Abs Max

PM_th:Eu(BTM)2 PM_th:Eu(DTM)2 PM_th:Eu(3-PTM)2 PM_th:Eu(9-PTM)2

Inte

nsity

(cou

nts)

Wavelength (nm)


PM_th:Eu(L)2 Emission Spectra

1 2 3 40

1x105

2x105

3x105

4x105

5x105

6x105 PM_th:Eu(L)2 Emissions, where Ligands:1 = BTM, 2 = DTM, 3 = 3-PTM, 4 = 9-PTM

Residual Emission Europium Emission

Inte

nsity

(cou

nts)

Ligand


PM_th:Eu(L)2 Emission Maxima


0

0.2

0.4

0.6

0.8

1

1.2

1 2 3 4

Ligands

Nor

mal

ized

Uni

ts

Emission Intensity DScm-1 DTcm-1

PM_th:Ln(L)2 Systems, where Ligands: 1 = BTM, 2 = DTM, 3 = 3-PTM, 4 = 9-PTM.


∆S

• Smaller distances in singlet energies (∆S) from polymer to polymer-ligand complexes inversely relate to greater emission intensities from complexes.• Suggests Forster ET of greater significance than Dexter ET for polymer to ligand ET.

∆T


0.75

0.8

0.85

0.9

0.95

1

1.05

1 2 3 4

Ligands

Nor

mal

ized

Uni

ts

DEST

PM_th:Ln(L)2 Systems, where Ligands: 1 = BTM, 2 = DTM, 3 = 3-PTM, 4 = 9-PTM.


∆EST

• Greater distances in singlet to triplet energies for polymer-ligand complexes almost directly relate to greater emission intensities from complexes.• Suggests back energy transfer led to lower emission intensities for DTM and 3-PTM.

• Forward ISC favored for BTM and 9-PTM.

PM_th:Ln(L)2 Systems CharacterizationPhotophysical properties of PM_th gadolinium complexes.

PM_th:Gd(HFA)2

PM_th:Gd(BTM)2

PM_th:Gd(DTM)2

PM_th:Gd(3-PTM)2

PM_th:Gd(9-PTM)2

Abs. Max (nm)(cm-1)

33130,211

35827,933

37426,738

37826,455

35827,933

Em. Max (nm)(cm-1)

39125,575

41624,038

42123,753

42723,419

40524,691

∆ (cm-1) 4,636 3,895 2,985 3,036 3,242

ES (eV)(cm-1)

3.4227,548

3.2326,042

3.0924,876

3.0624,691

3.2125,907

ET (eV)(cm-1)

2.7522,148

2.4219,531

2.3819,231

2.4019,380

2.3919,305

∆EST (eV) 0.67 0.81 0.71 0.66 0.82

Energy Transfer Efficiencies from Polymer to Ligand to PM_aryl:Eu(L)2 Systems, where L = HFA, BTM, DTM, 3-PTM, or 9-PTM.

BTM DTM 3-PTM 9-PTM

PM_fu:Eu(L)2 0.998 0.998 0.998 0.998

PM_py:Eu(L)2 0.999 0.998 0.998 0.998

PM_pz:Eu(L)2 0.998 0.998 0.997 0.998

PM_th:Eu(L)2 0.998 0.998 0.998 0.998


PM_th:Ln(L)2 Systems CharacterizationThe energy transfer mechanism for the PM_th:Eu(BTM)2 system.

3.23

2.42 2.42

3.42

2.75

Eu+3 BTM Polymer PM_th BTM Eu+3

2.14

2.36

2.64

2.14

2.36

2.64

FÖRSTERMECHANISM

DEXTERMECHANISM

a

b

cd

e

f

h

i

g

Energy (eV)

h


Conclusions – Europium Sensitization Project• Energy transfer has been shown to occur from polyphenylenes as the energy donors to ligand systems as intermediate acceptors and then to lanthanides as the terminal acceptors.

• Higher intensities of emission from lanthanide were due to:• Ligands that were asymmetric and had shorter effective conjugation lengths.• Binding acceptor complex directly to donor polymer.

• Pendant β-diketonates bind complex better than terpyridines.• Better matching of energy levels between ligand systems with lanthanides, as illustrated by BTM and 9-PTM being brighter than DTM and 3-PTM.

• Smaller relative singlet energy distances between polymer and polymer-ligandsystem (favoring Forster ET).• Larger relative singlet to triplet energy gaps on polymer-ligand systems (favoring forward ISC).

Applications• Organic / Polymer Light Emitting Diodes• Methods of Optimizing O/PLEDs• Sensors



Sensitization of Erbium Chelates

Synthesis of Polymers with Pendant β-DiketonatesBound to Erbium(III) meso-Tetraphenylporphyrinate

S

O

N

N

N

O

O

Aryl

N

Er

N

N

N

C10H21O

OC10H21

n

Polymer Aryl Group

PM_th

PM_fu

PM_py

PM_pz

Erbium Porphyrinate Synthesis

N

N

HNNHN

N NN

Li

Li

OO

OO

NN N

N

Er

Cl

O

O

LiN

SiSi

CH3

CH3

CH3

H3C

H3CCH3

DME

ErCl3

Toluene


Verified with x-ray crystal.

Polymer Erbium Chelate Synthesis

NN N

N

Er

Cl

O

O

O

O

OC10H21

C10H21O

n

S

O

O

N

N

N

N

ErS

n

NaOEt / EtOH

THF

C10H21O

OC10H21


Sensitization of Erbium Chelates

Photophysical Performance Data


S

O

N

N

N

O

O

Aryl

N

Er

N

N

N

C10H21O

OC10H21

n

Polymer Aryl Group

PM_th

PM_fu

PM_py

PM_pz

300 400 500 600 700-0.2

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

1.6

1.8 Cl(DME)ErTPP PM_th:ErTPP PM_fu:ErTPP PM_py:ErTPP PM_pz:ErTPP

Abs

orba

nce

Wavelength (nm)

Poly:ErTPP Absorbance Spectra


325 350 375 400 425 450 475 500 525 550

0.0

5.0x106

1.0x107

1.5x107

2.0x107

2.5x107

3.0x107

PM_th - Exc(323) Cl(DME)ErTPP - Exc(323) PM_th:ErTPP - Exc(323)

Inte

nsity

(cou

nts)

Wavelength (nm)

PM_th:ErTPP Visible EmissionExciting @ Poly Max, Relative to PM_th and Cl(DME)ErTPP


1400 1450 1500 1550 1600 1650 1700

3.0x104

3.1x104

3.2x104

3.3x104

3.4x104

3.5x104

3.6x104

3.7x104

3.8x104

3.9x104

4.0x104

4.1x104

4.2x104

4.3x104 Cl(DME)ErTPP - Exc(422) PM_th:ErTPP - Exc(424) PM_fu:ErTPP - Exc(424) PM_py:ErTPP - Exc(422) PM_pz:ErTPP - Exc(424)

Inte

nsity

(cou

nts)

Wavelength (nm)

Poly:ErTPP Infrared EmissionExciting at Porphyrin Absorbance Maxima

Room temperature IR emission at 10-5 M in degassed, anhydrous THF.


Poly:ErTPP Infrared EmissionExciting at Polymer Absorbance Maxima

1400 1450 1500 1550 1600 1650 1700

4.6x104

4.8x104

5.0x104

5.2x104

5.4x104

5.6x104 PM_th:ErTPP - Exc(323) PM_fu:ErTPP - Exc(323) PM_py:ErTPP - Exc(323) PM_pz:ErTPP - Exc(323)

Inte

nsity

(cou

nts)

Wavelength (nm)

Room temperature IR emission at 10-5 M in degassed, anhydrous THF.


Conclusions – Erbium Sensitization Project

• Energy transfer has been shown to occur from polyphenylenes as the energy donors to a porphyrin system as an intermediate acceptor and then to erbium as the terminal acceptors.

• Infrared emission from a room temperature solution was shown.

• Intensity of erbium emission indifferent to aryl group identity on beta-diketonate.

• Erbium emission ~33% more intense when excited at porphyrin absorbance max.

• Suggests less than ideal matching of energy levels between polymer and porphyrin ligand.

• Either need to modify polymer to match ligand or modify ligand to match polymer.

• Opportunity to provide higher doping densities when coordinating to polymer.


Summary


• Design and synthesis of polymers with higher singlet and triplet energies.• Kink introduced with para-meta alternation increased both singlet and triplet energy levels of polyphenylene polymers.

• Design and synthesis of europium complexes with lower triplet energies.• Changing the structure of one of the aryl groups on a β-diketonate results in predictable photophysical changes.

• Shorter conjugation length and higher asymmetry results in higher intensity of lanthanide emission.

• Higher intensity of lanthanide emission produced though the smaller relative singlet energy distances between polymer and polymer-ligand system (favoring Forster ET) and larger relative singlet to triplet energy gaps on polymer-ligand systems (favoring forward ISC).

• Design and synthesis of polymers with the ability to coordinate to lanthanides.• Polyphenylene-based polymers with pendant ligand functional groups in the repeat unit are able to donate energy to lanthanide complexes.

• Europium systems produced visible emission.• Erbium systems produced infrared emission.

Future Work

Extending this Research• Isolating the final complexes and characterizing by crystal structures or other means.

• Most likely to include model compounds of dimers or trimers of the monomer unit.

• Incorporating these materials into devices and analyzing their performance.

• See if Dexter ET becomes favored via electrophosphosphorescence, since more triplets should be formed.

• IR-emitting displays for reading while wearing night-vision goggles.

• IR-emitting materials for waveguides and other telecommunication devices.

• Polymer-bound iridium systems for LEDs and related devices.

• Sensors for a variety of analytes: biologicals, inorganics, and organics.


Knowledge, Skills, and AbilitiesEnhanced or Obtained via this Research

• Design and synthesis of: small molecule organics, organometallic complexes / coordination complexes, and polymers.

• Characterization of materials through a variety of techniques: NMR, mass spectrometry, elemental analysis, x-ray crystallography, absorption spectroscopy, fluorescence and phosphorescence spectroscopy, etc..

• Purification of materials via: column chromatography, preparative thin layer chromatography, medium pressure chromatography, ambient pressure and vacuum distillation, reprecipitation, recrystallization, and sublimation.

• Structure-property / structure-function relationship studies.

• Data analysis using a variety of software: Excel, Igor Pro, Origin, PhotoChemCAD, etc..


Acknowledgements

University of Southern CaliforniaResearch Adviser Harper Research GroupAaron W. Harper, Ph.D. Patrick J. Case, Ph.D.

Jeremy C. Collette, Ph.D.Committee Members Michael D. Julian, Ph.D.William P. Weber, Ph.D. Cory G. Miller, Ph.D.William H. Steier, Ph.D. Asanga B. Padmaperuma, Ph.D.

Funding was provided by:• A MURI grant administered by the Air Force Office of Scientific Research (contract number 413009) and • A PECASE grant administered by the Army Research Office (contract number DAAD 19-01-1-0788). • Harold G. Moulton Fellowship, Benson Endowed Fellowship, USC, and LHI.


graduate research @ usc

Documents

n n n pm

background ligands lanthanides

nn n bidentate ligands

dative bonding ligands

europium polymers

processing polymers

polymeric devices

visible devices