Some applications related to Chapter 11 material:

We will see how the kind of basic science we discussed in Chapter 11 will probably lead to good advances in applied areas such as:

1- Design of efficient solar cell dyes based on charge transfer absorption.

2- Strongly luminescent materials based on the Jahn-Teller effect.

1- Design of efficient solar cell dyes based on charge

transfer absorption

Pt

N

S

N

S

COO- COO-

Pt

N

S

N

S

PO3-PO3-

These complexes should have charge transfer from metal or ligand orbitals to the * orbitals.

diimine

dithiolate

CT-band for Pt(dbbpy)tdt

N

N

Pt

S

S

Data from: Cummings, S. D.; Eisenberg, R. J. Am. Chem. Soc. 1996, 118 1949-1960

X- Chloride

Connick W. B.; Fleeman, W. L. Comments on Inorganic Chemistry, 2002, 23, 205-230

X-thiolate

*bpy

dx2-y2

dxz-yz

dxy

dxz+-yz

dz2

bpy

{ (thiolate) +

d (Pt)

CT to diiminehv

0

10,000

20,000

30,000

40,000

50,000

60,000

70,000

200 300 400 500 600 700 800 900 1000 1100 1200 1300 1400 1500 1600

Wavelength, nm

, M

-1cm

-1 (

UV

/VIS

)

0

50

100

150

200

250

300

350

400

450

500

, M

-1cm

-1 (

NIR

)

Electronic absorption spectra for dichloromethane solutions of (dbbpy)Pt(dmid), 1, (thin line) and [(dbbpy)Pt(dmid)]2[TCNQ], 3, (thick line) in the UV/VIS region (left) and NIR region (right).

Smucker, B; Hudson, J. M.; Omary, M. A.; Dunbar, K.; Inorg. Chem. 2003, 42, 4717-4723

S

SS

Pt

S

O

N

N S

SS

Pt

S

O

N

N

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

250 350 450 550 650 750 850 950 1050

Wavelength (nm)

Ab

s.

70mg/10mL stock

1ml-2ml

0.5ml-2ml

1:10ml

1:100ml

1mlof 1/100 -2

0.5ml of 1/100-2

1:1000ml

Pt(dbbpy)tdt in Dichloroethane

hv

HOMO

LUMOClearly a dx2-y2 orbital, not a diimine *

By Brian Prascher,

Chem 4610 student, 2003

MO diagram for the M(diimine)(dithiolates) class!!!

So the lowest-energy NIR bands are d-d transitions and the LUMO is indeed dx2-y2, not diimine *

*bpy

dx2-y2

dxz-yz

dxy

dxz+-yz

dz2

bpy

{ (thiolate) +

d (Pt)

*bpy

dx2-y2

{ (thiolate) +

d (Pt)

WHO CARES!!

The above was science, let’s now see a potential application

• Silicon cells

– 10-20 % efficiency

– Corrosion

– Expensive (superior crystallinity required)

• Wide band gap semiconductors (e.g. TiO2;

SnO2; CdS; ZnO; GaP):

– Band gap >> 1 eV (peak of solar radiation)

– Solution: tether a dye (absorbs strongly across

the vis into the IR) on the semiconductor

– Cheaper!!… used as colloidal particles

Literature studies to date focused almost solely on dyes of Ru(bpy)32+

derivatives ==> Strong absorption across the vis region

(Grätzel; Kamat; T. Meyer; G. Meyer; others)

Na+

-S

Sodium thiophenoxide

3,4-methylbenzenethiol

SH

O O

2,5-dimethoxythiophenol

dmeobt

SH

dmbt

Na+

-S

4-methylbenzenethiol sodium salt

mbtPhS

X

N NPt

t-Bu

t-Bu

t-Bu

N

Y

+

-

ArS- groupY= Cl-, BF4

-, TCNQ-

TCNQ

N

N N

N

7,7,8,8-Tetracyanoquinodimethane

[M(N3)(X)]+Y- where M = Pt(II), Pd(II) or Ni(II); N3=triimine; X = anionic ligand

(SCN-, halide, RS-, etc.).

379 399 551.5 851

750

350 400 450 500 550 600 650 700 750 800 850 900 950 1000

Wavelength, nm

No

rmal

ized

ab

sorb

ance

Cl,Cl SCN,BF4 PhS,BF4 SCN,TCNQ

Absorption Spectra of [Pt(tbtrpy)X]+ Y- Complexes

• Using ArS- ligands as X shifts the CT absorption to the VIS region.

•Using TCNQ- as Y adds NIR absorptions.

2- Strongly luminescent materials based on the

Jahn-Teller effect

Forward, J.; Assefa, Z.; Fackler, J. P. J. Am. Chem. Soc. 1995, 117, 9103. McCleskey, T. M.; Gray, H. B. Inorg. Chem. 1992, 31, 1734.

Ground-state MO diagram of [Au(PR3)3]+ species, according to the literature:

a1'(dz2)

e''(dxz,dyz)

e'(dxy,dx2-y2)

a2''(pz)

e'

a1'

5d

6s

6p

[Au] +

(5d10) [Au(PR3)3]+ PR3

10

0

0

Molecular orbital diagrams (top) and optimized structures (bottom) for the 1A1’ ground state (left)

of the [Au(PH3)3]+ and its corresponding exciton (right).

Barakat, K. A.; Cundari, T. R.; Omary, M. A. J. Am. Chem. Soc. 2003, 125, 14228-14229

By Khaldoon Barakat,

Chem 5560 student, 2002

[Au(TPA)3]+

QM/MM optimized structures of triplet [Au(PR3)3]+ models.

em= 478 nm

em= 772 nm em= 640 nm

em= 496 nm

Barakat, K. A.; Cundari, T. R.; Omary, M. A. J. Am. Chem. Soc. 2003, 125, 14228-14229

WHO CARES!!

The above was science, let’s now see a potential application

RGB bright emissions in the solid state and at RT are required for a multi-color device….

AuL3 as LED materials?

• Glow strongly in the solid state at RT.• But [Au(PR3)3]+ X- don’t sublime into

thin films (ionic).

• How about neutral Au(PR3)2X?:– Do they also luminesce in the solid state at

RT?– Do they also exhibit distortion to a T-shape?

T-shape and BEYOND!

“Photocrystallography” and time-resolved EXAFS should tell us if these distortions toward and

beyond a T-shape will really take place experimentally…stay tuned!

Au(PPh3)2Cl. Bond angles shown are: B3LYP; HF (exptl.).

154.1º;138.4º

(132.1º)

103.5º;115.5º

(118.7º)

102.4º;106.2º

(109.2º)

hv191.8º;188.7º

84.7º;85.1º

83.6º;85.1º

154.1º;138.4º

(132.1º)

103.5º;115.5º

(118.7º)

102.4º;106.2º

(109.2º)

hv191.8º;188.7º

84.7º;85.1º

83.6º;85.1º

* The lifetime (7.9 s) suggests that the emission is phosphorescence from a formally triplet excited state.

300 350 400 450 500 550 600 650 700

Wavelength, nm

Photoluminescence spectra of Au(PPh3)2X

Excitation Emission

X=ClX=I X=Br