were combined via the covalent linkage to provide a white-light
emitter. Interestingly, when comparing two analogous com-
pounds in the ‘‘white-emitter’’ series bearing 2-phenylpyridine
or 2-(1H-pyrazol-1-yl)pyridine as cyclometalating ligands,
white-light emission was only observed in the latter case. More
detailed investigation of the photophysical properties of this
new class of compounds and their applications in light-emitting
materials, including energy transfer kinetics and electrolumi-
nescence studies in thin films, will be the subject of our future
research.
Acknowledgements
Marie Curie Research Training Network CHEXTAN (MRTN-
CT-2004-512161) is acknowledged for its financial support.
A.M.B. and P.C.-C. thank The Netherlands Organisation for the
Advancement of Research (NWO) and A.E.R. thanks Vidi and
Vici for their financial support. Authors thank Michiel Hilbers
for help with photophysical measurements and Theo Peters and
Roy Lensen for help with electrochemical measurements. M.J.
and M.F. thank Dr Daniel Blanco Ania for useful discussions
(NMR) and Victor Claessen for help with snapshots in Fig. 5.
Notes and references
Experimental
1 (a) Y. You and S. Y. Park, Dalton Trans., 2009, 1267–1282; (b)
L. Flamigni, A. Barbieri, C. Sabatini, B. Ventura and
F. Barigelletti, Top. Curr. Chem., 2007, 281, 143–203.
Setups
The photophysical measurements were carried out at Universiteit
van Amsterdam. Electronic absorption spectra were recorded in
a quartz cuvette (1 cm, Hellma) on a Hewlett-Packard 8543 diode
array spectrometer (range 190–1100 nm). Steady state fluores-
cence spectra were recorded using a Fluorolog 3 (Spex 1681)
fluorimeter equipped with a Xe arc light source, a Hamamatsu
R928 photomultiplier tube detector and a double excitation and
emission monochromator. Emission spectra were corrected for
source intensity and detector response by standard correction
curves, unless stated otherwise. Emission quantum yield were
measured in optically dilute solutions, using the indicated refer-
ence solution, according to the following:
ꢀ
2 (a) D. A. Poulsen, B. J. Kim, B. Ma, C. S. Zonte and J. M. J. Frechet,
Adv. Mater., 2010, 22, 77–82; (b) C. Ulbricht, B. Beyer, C. Friebe,
A. Winter and U. S. Schubert, Adv. Mater., 2009, 21, 4418–4441;
(c) B.-L. Li, Z.-T. Liu, Y.-M. He, J. Pan and Q.-H. Fan, Polymer,
2008, 49, 1527–1537; (d) V. Marin, E. Holder, R. Hoogenboom and
U. S. Schubert, Chem. Soc. Rev., 2007, 36, 618–635; (e) X.-
Y. Wang, A. Kimyonok and M. Weck, Chem. Commun., 2006,
3933–3935.
3 E. Holder, B. M. W. Langeveld and U. S. Schubert, Adv. Mater.,
2005, 17, 1109–1121.
4 (a) Z. Xie, L. Ma, K. E. deKrafft, A. Jin and W. Lin, J. Am. Chem.
Soc., 2010, 132, 922–923; (b) G. Di Marco, M. Lanza, A. Mamo,
I. Stefio, C. Di Pietro, G. Romeo and S. Campagna, Anal. Chem.,
1998, 70, 5019–5023.
5 (a) R. Gao, D. G. Ho, B. Hernandez, M. Selke, D. Murphy,
P. I. Djurovich and M. E. Thompson, J. Am. Chem. Soc., 2002,
124, 14828–14829; (b) B. Elias, F. Shao and J. K. Barton, J. Am.
Chem. Soc., 2008, 130, 1152–1153.
2
Fu ¼ [(ArIunu )/(AuIrnr2)]Fr
6 (a) M. Felici, P. Contreras-Carballada, J. M. M. Smits,
R. J. M. Nolte, R. M. Williams, L. De Cola and M. C. Feiters,
Molecules, 2010, 15, 2039–2059; (b) M. Felici, P. Contreras-
Carballada, Y. Vida, J. M. M. Smits, R. J. M. Nolte, L. De Cola,
R. M. Williams and M. C. Feiters, Chem.–Eur. J., 2009, 15, 13124–
13134.
7 (a) C. W. Tornøe, C. Christensen and M. Meldal, J. Org. Chem., 2002,
67, 3057–3064; (b) V. V. Rostovtsev, L. G. Green, V. V. Fokin and
K. B. Sharpless, Angew. Chem., 2002, 114, 2708–2711; Angew.
Chem., Int. Ed., 2002, 41, 2596–2599.
where u and r are the unknown and the reference, respectively, F
is the luminescence quantum yield, A is the absorption factor at
the excitation wavelength (<0.1), I is the integrated emission
intensity and n is the refractive index of the solvents. Lifetimes of
excited states were determined using a Nd:YAG laser (7 ns pulses
fwhm, excitation wavelength 355 nm) and a Hamamatsu C5680-
21 streak camera equipped with Hamamatsu M5677 low speed
single sweep unit. Streak cameras are high-speed light detectors,
which enable detection of the fluorescence as a function of the
spectral and the time evolution simultaneously.
8 H. C. Kolb, M. G. Finn and K. B. Sharpless, Angew. Chem., Int. Ed.,
2001, 40, 2004–2021.
9 For example see: (a) S. Albert-Seifried, C. E. Finlayson, F. Laquai,
ꢀꢁ
R. H. Friend, T. M. Swager, P. H. J. Kouwer, M. Jurıcek,
H. J. Kitto, S. Valster, R. J. M. Nolte and A. E. Rowan, Chem.–
Eur. J., 2010, 16, 10021–10029; (b) J. D. Megiatto, D. I. Schuster,
S. Abwandner, G. de Miguel and D. M. Guldi, J. Am. Chem. Soc.,
2010, 132, 3847–3861.
Samples
10 For example see; H. J. Kitto, E. Schwartz, M. Nijemeisland,
M. Koepf, J. J. L. M. Cornelissen, A. E. Rowan and
R. J. M. Nolte, J. Mater. Chem., 2008, 18, 5615–5624.
11 Recently, several examples using the triazole moiety as a potential
ligand were shown: (a) J. Hu, M. Zhang, L. B. Yu and Y. Ju,
Bioorg. Med. Chem. Lett., 2010, 20, 4342–4345 and references (39–
51) cited therein; (b) A. Kumar and P. S. Pandey, Tetrahedron Lett.,
2009, 50, 5842–5845; (c) J. Camponovo, J. Ruiz, E. Cloutet and
The stock solutions were prepared by dissolving the sample in
a minimum amount of CH2Cl2 and then the CH2Cl2 solution was
diluted with THF (solvents Uvasol grade). All complexes showed
a good solubility in CH2Cl2 except for 4c. As a reference,
Ru(bpy)3Cl2 in water was used (Fair ¼ 0.028 and Fargon
¼
0.042).21 All compounds showed a good stability as proven by no
changes in their UV-Vis spectra before and after the measure-
ments, except for compound 3c that showed the disappearance of
a band centred at 315 nm probably due to photodecomposition.
In several of the time resolved experiments at low temperature
(77 K) in rigid matrix, a complete precipitation of the complexes
was observed during the freezing procedure. These molecules
showed limited solubility in the solvents that give good glassy
matrices (butyronitrile, ethanol, etc.) making the time resolved
measurement under these conditions rather difficult.
ꢀꢁ
D. Astruc, Chem.–Eur. J., 2009, 15, 2990–3002; (d) M. Jurıcek,
ꢀ
P. H. J. Kouwer, J. Rehak, J. Sly and A. E. Rowan, J. Org. Chem.,
2009, 74, 21–25; (e) R. M. Meudtner and S. Hecht, Macromol.
Rapid Commun., 2008, 29, 347–351.
12 R. M. Meudtner, M. Ostermeier, R. Goddard, C. Limberg and
S. Hecht, Chem.–Eur. J., 2007, 13, 9834–9840.
13 D. J. V. C. van Steenis, O. R. P. David, G. P. F. van Strijdonck,
J. H. van Maarseveen and J. N. H. Reek, Chem. Commun., 2005,
4333–4335.
14 C. S. Andersen and K. V. Gothelf, Org. Biomol. Chem., 2009, 7,
58–60.
2110 | J. Mater. Chem., 2011, 21, 2104–2111
This journal is ª The Royal Society of Chemistry 2011