The National Centre for Sensor Research

Figure 2

ResultsThe emission spectrum and absorption spectra (both steady-state and

transient) of [Ru(bpy)2(dcb)2-] are shown in Figure 3 while the emission

lifetimes obtained for the partially deuteriated complexes are shown in the

Table A. Deuteriation reduces the rate of non-radiative deactivation of the

excited state. This leads to increased emission lifetimes provided the

excited state is based on the deuteriated ligand.

Figure 3

Excited-state resonance Raman measurements (Figure 4) clearly show

that the excited state is localised on the dcb2-. Resonances due to the

dcb3–• anion radical are observed at 1312 and 1212 cm-1.

Figure 4

IntroductionRuthenium polypyridyl complexes have been widely used as covalently

bound dyes in solar energy devices based on nanocrystalline TiO2. In

addition it has been shown that nanocrystalline TiO2 surfaces modified

with dinuclear RuOs polypyridyl complexes respond in a uniform

manner to irradiation as shown below in Figure 1.

Figure 1

In most cases the molecular components have been covalently attached

via 4,4’-dicarboxy-2,2’-bipyridine (H2dcb) type ligands. It is generally

assumed that in these assemblies injection into the TiO2 surface is

enhanced by the fact that the excited state is based on the dcb2- ligand.

This assumption is tested here for the model compound

[Ru(bpy)2(dcb)2-] (see Figure 2) by the use of deuteriation in

combination with emission lifetime measurements and resonance

Raman spectroscopy.

Deuteriation

Scheme 1

Table A

Towards Practical Molecular Devices:

the Incorporation of a Solid Substrate as an

Active Component in Molecular Assemblies

Noel M. O’Boyle,a Wesley R. Browne,a Steve Welter,b Ron T.F. Jukes,b Luisa De Cola,b Colin G. Coates,c

John J. McGarvey,c Johannes G. Vosa

a National Centre for Sensor Research, School of Chemical Sciences, Dublin City University, Dublin 9, Irelandb Molecular Photonics Group, IMC, University of Amsterdam, Nieuwe Achtergracht 166, NL-1018 WV Amsterdam, the Netherlands

c Queens University Belfast, School of Chemistry, Belfast BT9 5AG, Northern Ireland

ConclusionsBoth the variation in emission lifetime as well as the rR spectra observed confirm that the excited state in bpy/dcb2- complexes is dcb2- based. The

results clearly indicate that deuteriation is a powerful method for the study of the nature of the excited state in complexes of ruthenium.

AcknowledgementsThis work was supported by Enterprise Ireland and COST D19.

Ru

N

NN

N

N N

COOHHOOC

N N N N

CD3

D

D

D D

D

D

D3C

D2O

N N

D

D

D D

D

D

HOOC COOH

[O]

NaOD

(ns)

Ru(bpy)2(dcb2-) 562

Ru(bpy)2(d6-dcb2-) 633

Ru(d8-bpy)2(dcb2-) 573

Ru(d8-bpy)2(d6-dcb2-) 679

e-

e-

e-

Ru Os Ru Os

400 500 600 700 800

0.0

0.2

0.4

Ru(bpy)3

2+

Ru(bpy)2(dcb)

Ab

so

rba

nce

Wavelength (nm)

0

20000

40000

60000

80000

100000

120000

140000

160000

180000

Co

un

ts p

er s

eco

nd

1600 1500 1400 1300 1200

dcb*3-

dcb*3-

dcb*3-bpy

16

04

cm

-1

14

50

cm

-1

14

91

cm

-1

12

12

cm

-1

bpy

13

12

cm

-1

Wavenumber in cm-1

[Ru([H8]-bpy)

2([H

6]-dcb

2-)]

[Ru([H8]-bpy)

2([D

6]-dcb

2-)]

[Ru([D8]-bpy)

2([H

6]-dcb

2-)]

[Ru([D8]-bpy)

2([D

6]-dcb

2-)]

Ru(bpy)2(H2dcb)

d6-H2dcb