Spectroscopy of d6 Ru and Ir polypyridyl complexes for solar cells,

OLED and NLO applications: Insights from theory

Spectroscopy of d6 Ru and Ir polypyridyl complexes for solar cells,

OLED and NLO applications: Insights from theory

Simona Fantacci

Istituto CNR di Scienze e Tecnologie Molecolari (ISTM-CNR) &

UdR INSTM Perugia

Dipartimento di Chimica Via Elce di Sotto, 8, Perugia, 06123 - ITALY

Computational approach

• Geometry Optimizations (CP-ultrasoft pseudopotentials)

• Calculation of excited states energies and oscillator strengths by Time

Dependent-DFT (G03, ADF)

• Inclusion of solvation effects by a Polarizable Continuum Model

(PCM) (G03, CP, ADF)

Car-Parrinello (PBE//PWs)

G03(B3LYP/DVZP), ADF(TZP,BP86)

Methodology Overview

Spectroscopic properties of Ru- and Ir- complexes:a)S. Fantacci, F. De Angelis, A. Selloni J. Am. Chem. Soc. 2003,

125, 4381.b)F. De Angelis, S. Fantacci, A. Selloni Chem. Phys. Lett. 2004,

389, 204. c)S. Fantacci, F. De Angelis,..., A. Selloni J. Am. Chem. Soc. 2004,

126, 9715. d)F. De Angelis, A. Tilocca, A. Selloni J. Am. Chem. Soc. 2004,

126, 15024.e)S. Fantacci, F. De Angelis, A. Sgamellotti,... J . Am. Chem. Soc. 2005. 127,

14144.f)M. K. Nazeeruddin, F. De Angelis, S. Fantacci,... J. Am. Chem. Soc. 2005.

127, 16835.g)F. De Angelis, S. Fantacci, A. Selloni, M. K. Nazeeruddin Chem. Phys. Lett. 2005,

415, 115.h)F. Tessore, D. Roberto,..., R. Ugo, F. De Angelis Inorg. Chem. 2005, 44,

8967.i)F. De Angelis, S. Fantacci, A. Sgamellotti,.., R. Ugo Dalton Trans. 2005,

2006, 852. l) C. Barolo, M.K. Nazeeruddin, S. Fantacci,… M. Grätzel Inorg. Chem. 2006, 45,

4642.m) M.K. Nazeeruddin,… F. De Angelis, S. Fantacci, M. Grätzel Inorg. Chem. 2006, 45,

9245.n) F. De Angelis, S. Fantacci,... M. Grätzel, M.K. Nazeeruddin Inorg. Chem. 2007, 46,

in press.o) C. Dragonetti,… R. Ugo, F. De Angelis, S. Fantacci, A. Sgamellotti … Inorg. Chem. 2007, 46,

in press.

Ru(II)-polypyridyl sensitizers for TiO2 in dye sensitized solar cells (DSSCs)

M. Graetzel, Nature, 2001, 414, 338.; M. Graetzel Inorg. Chem. 2005, 44, 6841

1. The dye, adsorbed on the semiconductor oxide surface, absorbs light in the visible region.

2. An electron is then transferred from the dye excited state to the TiO2 conduction band.

3. The oxidized dye is regenerated by a support electrolyte.

[Ru(4,4’COOH2,2’bpy)2(NCS)2],[Ru(4,4’COOH2,2’bpy)2(NCS)2],defined as N3defined as N3

An efficient solar cell sensitizer should have broad range of visible light absorption, form long-living excited states with energies almost matching those of the TiO2 conduction band and show a high thermal stability.

N34-

Tuning the properties of Ru(II) TiO2 sensitizers

N3

N945

Effect of deprotonationand ligand substitution

Bypyridinefunctionalization

Ligand engineering

Cl

N621

N866

Energy (eV)

Inte

nsi

ty (

arb

. un

its)

Exp.Theor.MLCT (I)

MLCT (II)

*ethanolwater

(III)

Experimental and calculated absorption spectra of N3 in water solution LUMO

HOMO-3

HOMO

S. Fantacci, F. De Angelis, A. Selloni J. Am. Chem. Soc. 2003, 125, 4381. F. De Angelis, S. Fantacci, A. Selloni Chem. Phys. Lett. 2004, 389, 204.Md. K. Nazeeruddin, F. De Angelis,.. , M. Grätzel J. Am. Chem. Soc. 2005, 127, 16835.

Modeling of TiO2 surface

Stoichiometric anatase Ti38O76 cluster of nanometric dimensions

exposing (101) surfaces

B3LYP/3-21g* (NEQ-PCM)TD-DFT gap in solution: 3.20 eV KS gap in solution: 3.78 eVTD-DFT gap in vacuo: 2.82 eV KS gap in vacuo: 3.48 eV

Experimental gap in acqueous solutions: 3.20 – 3.30 eV F. De Angelis, A. Tilocca, A. Selloni J. Am. Chem. Soc. 2004, 126, 15024.

Car-Parrinello molecular dynamics simulation of N3 adsorption on TiO2 surface

Starting from the final configuration we performed local geometry optimizations placing the protons on different sites.

1H+ on dye / 1H+ on TiO2 1H+ on dye / 1H+ on TiO2

0H+ on dye / 2H+ on TiO2

0.0 kcal/mol +11.0 kcal/mol

+9.9 kcal/mol

1H+ on dye / 3H+ on TiO2

1 2

3 4

Simulation of the Absorption spectrum

Md. K. Nazeeruddin, R. Humphry-Baker, P. Liska, M. Grätzel, J. Phys. Chem. B, 2003, 107, 8981.Md. K. Nazeeruddin, F. De Angelis, S. Fantacci..,M. Grätzel J. Am. Chem. Soc., 2005, 127, 16845.

Ir(III)-polypyridyl complexes as phosphorescent dyes for OLED and NLO

6x106

4

2

0

Emission intensity [cps]

700600500400300Wavelength [nm]

2.0

1.5

1.0

0.5

0.0

Abs

orba

nce

[OD

]

Strong and tunable emission in the visible region (600-450 nm) Φmax=85%

High transparency in the visible region and high NLO response (βEFISH>2000 10-30esu)

[Ir(ppy)2(5-X-1,10-phen)]+

X=NMe2

X=NO2

Phosphorescent Ir(III) complexes for OLED

N N

NIr

2

X

X

PF6

-

+

N

N

NIr

2

X PF6

-

+

N

N

NIr

2

X PF6

-

+

N

N

NIr

2

PF6

-

+

N N

NIr

2

CH3

CH3

PF6

-

+

N

N

NIr

2

CH3

CH3

PF6

-

+

phenylpyridine-phenanthroline (ppy-phen) phenylquinoline-phenX = Me, NMe2, NO2 (ppq-phen)M.K. Nazeeruddin, R.T. Wegh, C. Klein, Q. Wang, F. De Angelis, S. Fantacci, M. Grätzel,

Inorg. Chem. 2006, 45, 9245.F. De Angelis, S. Fantacci, N. Evans, C. Klein,..., M. Grätzel, M.K. Nazeeruddin Inorg. Chem. 2007, 46, in press.C. Dragonetti, L. Falciola, P. Mussini, S. Righetto, D. Roberto, R. Ugo, F. De Angelis, S. Fantacci, A. Sgamellotti et al. Inorg. Chem. 2007, 46, in press.

Ir(III) cyclometallated complexes as multifunctional NLO Materials

-7.0

-6.0

-5.0

-4.0

-3.0

-2.0

-1.0

(phen)

(ppy)

3.24

0.310.27

2.07

0.48

0.91

t2g(Ir)-(ppy)

E(eV)

LUMO

HOMO

X=NMe2 X=NO2

X=NMe2 X=NO2

L+2

L+1

L

H

H-1

L+2

L+1

L

H

H-1

CompoundEFISH 1.907

b

(10-30 Dcm5esu-1)

X=H -1270

X=Me -1565

X=NMe2 -1330

X=NO2

-2230

X=NO2, NMe2

Absorption spectrum, SOS- X=NO2-NMe2

Only negative contributions to Positive and negative contributions to

C. Dragonetti, S. Righetto, D. Roberto, R. Ugo, A. Valore, F. De Angelis, S. Fantacci, A. Sgamellotti Chem. Comm. submitted

phen-(ILCT)Ir->phen (MLCT)

=transition dipole moment=excitation energy ground and excited state dipole moments

Conclusions

Acknowledgments:

Prof. Renato Ugo: Ir(III) complexes for OLED and NLO materials

Prof. Michael Grätzel: TiO2 Ru(II) photosensitizers and Ir(III) complexes for OLED

Dr. Filippo De Angelis: TiO2 calculations and CP simulations

•Theoretical and computational advances allow the study of systems of large and increasing complexity with unprecedented accuracy

•Quantitative agreement between theory and experimental optical properties of complex systems

•Interpretative and predictive power of modeling