Novel ruthenium(II) and zinc(II) complexes for two-photon absorption related applications

Article abstract of DOI:10.1039/b706715a

Two new fluorene derivatized 1,10-phenanthroline ligands and related tris-chelate Ru(ii) or Zn(ii) coordination complexes have been synthesised. The linear and nonlinear (two-photon induced fluorescence) photophysical measurements have contributed to highlight the possibility to tune the absorption spectral range and excited lifetime, depending on ligand substitution and nature of the metal. More significantly, the observation of two-photon absorption (TPA) associated with long-lived metal-to-ligand charge-transfer (MLCT) excited states in the Ru(ii)-based chromophores, opens a wide range of applications in the near infrared. The Royal Society of Chemistry 2007.

Full text of DOI:10.1039/b706715a

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PAPER
www.rsc.org/dalton | Dalton Transactions
Novel ruthenium(II) and zinc(II) complexes for two-photon absorption related
applications
a
a
a
b
c
a
C. Girardot, G. Lemercier,* J.-C. Mulatier, J. Chauvin, P. L. Baldeck and C. Andraud*
Received 4th May 2007, Accepted 18th May 2007
First published as an Advance Article on the web 20th June 2006
DOI: 10.1039/b706715a
Two new fluorene derivatized 1,10-phenanthroline ligands and related tris-chelate Ru(II) or Zn(II)
coordination complexes have been synthesised. The linear and nonlinear (two-photon induced
fluorescence) photophysical measurements have contributed to highlight the possibility to tune the
absorption spectral range and excited lifetime, depending on ligand substitution and nature of the
metal. More significantly, the observation of two-photon absorption (TPA) associated with long-lived
metal-to-ligand charge-transfer (MLCT) excited states in the Ru(II)-based chromophores, opens a wide
range of applications in the near infrared.
Introduction
with those of corresponding 5-oligofluorene-1,10-phenanthroline
type ligands and related Zn complexes. The choice of ligands
L1 and L2, bearing a fluorene or a bifluorene for C1 and C2
respectively, was based on TPA properties of oligofluorenes that
we have recently ascribed to excitonic coupling between neighbor
1
2
Owing to its wide-ranging applications (photodynamic therapy,
3
photochemical delivery of biological messenger, confocal
4
5
6
microscopy, three dimensional data storage, microfabrication
7
and optical power limiting ), the two-photon absorption (TPA)
process , is a very attractive third order nonlinear optics (NLO)
effect. In this field, coordination complexes have received less
18
monomers. In the spectral range 700–940 nm and in order
to identify unambiguously the MLCT transition through two-
8
ꢀ
ꢀ
photon process, the properties of Zn complexes (C 1 and C 2) have
been studied in comparison with those of Ru complexes. Due to
the high ionisation potential of this metal, they should not present
any MLCT type transition.
9
interest than organic chromophores, in spite of indisputable
10
advantages: synthetic tailorability and the possibility of long
luminescence lifetime of the MLCT (metal-to-ligand charge
transfer) triplet excited state (a few microseconds are generally
11,12
obtained for Ru(II) complexes for example ). The access via TPA
3
Results and discussion
to the MLCT state could therefore generate interesting properties
in fluorescence based effects (two-photon excited fluorescence,
Ligands L1 and L2 were prepared according to a Suzuki cross-
13
TPEF) such as biological imaging or O
2
sensing, and in pro-
19
coupling reaction starting from 5-bromo-1,10-phenanthroline
cesses involving excited state re-absorption such as optical power
20
and already described boronic acid 2 and 3, respectively (see
14
limiting. In this context, the high stability and inertia in solution
of Ru(II) complexes allow their utilization in practical applications.
To the best of our knowledge, only a few studies were carried out
on MLCT transitions by TPA at a single wavelength (750, 800 and
Scheme 1). Related ruthenium and zinc complexes (see Fig. 1)
were obtained by reaction under reflux of three equivalents of
ligand with one equivalent of either ruthenium trichloride (in
dimethylformamide) or zinc acetate (in ethanol), respectively and
1
5
16
8
80 nm) for ruthenium(II) and rhenium(I) complexes or Z-scan
precipited by NH
4
PF
6
. All systems were fully characterized by
17
experiments giving rise to two-photon transitions spectra.
3
Concerning the luminescence of the MLCT state and as in
the case of the linear absorption, the TPEF of Ru(II) complexes
involves the excitation of either singlet excited states of the ligand
1
or the MLCT state. Therefore, TPA properties of ruthenium
complexes will be closely related to those of ligands and the
optimisation of these latter is a relevant step. In this context,
this paper deals with the synthesis and TPA properties of new
ruthenium complexes C1 and C2 (see Fig. 1 later), in comparison
a
◦
Laboratoire de Chimie, UMR n 5182, CNRS/ENS-Lyon, 46 All e´ e
d’Italie, 69364, Lyon, cedex 07, France. E-mail: gilles.lemercier@ens-
lyon.fr; Fax: +33 4 72 72 88 60; Tel: +33 4 72 72 87 33
b
D e´ partement de Chimie Mol e´ culaire, UMR-5250, ICMG FR-2607, CNRS,
Universit e´ Joseph Fourier, BP 53 38041, Grenoble, cedex 9, France; Fax: +33
4
72 72 88 60; Tel: +33 4 72 72 87 33
c
◦
Laboratoire de Spectrom e´ trie Physique, UMR n 5588 CNRS/Universit e´
Joseph Fourier and CNRS, 140 rue de la physique, BP 87 38402 Saint
Martin d’H e` res cedex, France; Fax: +33 4 72 72 88 60; Tel: +33 4 72 72 87
◦
Scheme 1 Reagents and conditions: (i) oleum/Br
2
, 135 C, 48 h (70%).
◦
(ii) Pd(PPh
3
)
4
, Na
2
CO
3
(1 M), toluene, 80 C, 48 h (60% for L1 and 67%
3
3
for L2).
This journal is © The Royal Society of Chemistry 2007
Dalton Trans., 2007, 3421–3426 | 3421

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Fig. 3 Absorption and luminescence spectra at room temperature of
ligands L2 and related Ru (C2) and Zn (C 2) complexes in acetonitrile.
ꢀ
ꢀ
ꢀ
Fig. 1 Ru (Zn) complexes C1 (C 1) and C2 (C 2) involving ligands L1 and
L2, respectively (general atom numbering also given for NMR description).
NMR, elementary analysis and mass spectroscopy (see experi-
mental part).
two first bands were also observed in ligand L1 (L2) at 270 (265)
and 310 (340) nm. Theoretical calculations on excited states of
L1 and L2 allowed to determine the origin of these two bands.
Theoretical linear maximum absorption wavelengths of L1 and
L2 are reported in parentheses in Table 1; a satisfying agreement
between experimental and calculated data was obtained. L1 and
L2 present a theoretical absorption at 264 and 261 nm respectively,
close to that of the phenanthroline calculated at 261 nm. The
description of relevant orbitals involved in these transitions
allowed to relate these latter mainly to the phenanthroline itself, as
shown in Fig. 4 for L1, the transition calculated at 264 nm, which
corresponds mainly to the excitation from the occupied HOMO-2
to the unoccupied LUMO, is only centered on the phenanthroline
moiety. This confirms the attribution of these L1 and L2 bands.
Theoretical absorption bands of L1 and L2 at 287 and 294 nm,
related to experimental transitions at 310 and 340 nm respectively,
correspond to the excitation from the HOMO to the LUMO+1
for both bands, as shown in Fig. 5 in the case of L1, the
HOMO is mainly localised on the fluorene, while the LUMO+1
is concentrated on the bipyridyl moiety, indicating the charge
transfer (CT) character of this transition. The bathochromic
shift of this transition between L1 and L2 in experimental and
theoretical spectra is in good agreement with this CT origin.
ꢀ
ꢀ
Absorption spectra of complexes C1 (C2) and C 1 (C 2) are
displayed in Fig. 2 (Fig. 3), in comparison with those of related
ligands L1 (L2); maximum wavelengths are reported in Table 1.
Three types of bands were observed in these complexes : (i) a band
lying in the range 260–270 nm, (ii) a band pointing at 330 (305)
ꢀ
ꢀ
and 335 (330) nm for C1 (C 1) and C2 (C 2), respectively, (iii) a
group of bands between 410 and 460 nm for C1 and C2 only. The
ꢀ
ꢀ
All these bands still exist in Ru (C1, C2) and Zn (C 1, C 2)
complexes : the phenanthroline band was observed at 266 and
267 nm in Ru complexes, and 270 and 265 nm in Zn analogs,
Fig. 2 Absorption and normalised luminescence spectra at room tem-
ꢀ
perature of ligands L1 and related Ru (C1) and Zn (C 1) complexes in
acetonitrile.
ꢀ
ꢀ
Table 1 Photophysical characteristics in acetonitrile of ligands L1 and L2, related Ru complexes C1 and C2, and Zn complexes C 1 and C 2
a
b
−1
−1
c
φd
e
f
g
Compound
k
abs /nm
e /L mol cm
k
em /nm
s /ns
k
TPA /nm
r
TPA /GM
L1
L2
C1
C2
270 (264), 310 (287)
265 (261), 340 (294)
266, 330, 410–460
267, 335, 410–460
270, 305
265, 330
262 (261), 440–460
40300, 25100
28000, 61300
156200, 49500, 30900
116600, 177300, 32100
137800, 69600
81000, 134900
398
418
590
595
480
—
0.93
0.30
0.09
0.11
0.15
—
1.4
1.7
1700
2500
6.1
—
890
530
16
75
560 (488, 520sh)
740, 850, 930
750, 850, 930
595, 750
h
40, 15, 15
90, 15, 15
88, 10
—
h
ꢀ
C 1
ꢀ
C 2
—
h
12
[
Ru(Phen)
3
](PF
6
)
2
117400, 19300
590
0.03
750, 850, 930
20, 10, 10
a
b
c
k
abs : one-photon absorption maximum wavelength (theoretical value in parentheses). e: molecular absorption coefficient at kabs . kem: emission maximum
d
wavelength. φ: fluorescence quantum yield determined relative to the MSB for organic compounds and to the Ru(bipy)
3
(PF
TPA: two-photon absorption cross-section, GM stands for G o¨ ppert–
Molar extinction coefficient at 440 nm, sh: shoulder.
6 2
) for ruthenium complexes.
e
f
g
s: luminescence lifetime.
kTPA: maximum two-photon absorption wavelength. r
Mayer with 1 GM = 10− cm s photon
50
4
−1
.
h
3
422 | Dalton Trans., 2007, 3421–3426
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ꢀ
Fig. 6 Excitation spectra of L1, C1 and C 1 in acetonitrile, emission
spectra of C1 (acetonitrile).
value reported for [Ru(Phen)
addition of three fluorenes going from [Ru(Phen)
3
](PF
6
)
2
(Table 1). Interestingly, each
](PF to C2,
Fig. 4 Representation of HOMO-2 (a) and LUMO+1 (b) of L1 orbitals
mainly involved in the transition calculated at 264 nm.
3
)
6 2
increases the lifetime of the complex by approximately 0.8 ls. This
trend has already been observed in similar complexes involving
the pyrene unit and ascribed to a thermal equilibration between
the lowest-lying triplet states located at the two electronically-
21
ꢀ
distinct subunits. C 1 presents an emission band centered at
4
80 nm (Table 1 and Fig. 2) excited only in intraligand states, no
ꢀ
information could be obtained for C 2, probably due to the lability
of the complex at the low concentrations used for luminescence
measurements, since in this case, only the fluorescence of the ligand
L2 was observed. Complexation by zinc induces a large shift of
8
0 nm of the ILCT emission band with respect to that of L1.
Although the Zn complexation leads to a lengthening of the decay
time of the fluorescence, it keeps the same order of magnitude
(
6.1 ns) than that of L1 (1.4 ns), in good agreement with a singlet
state emission.
Two-photon excitation spectra of L1, L2, Zn complex Cꢀ1
and Ru complexes C1 and C2 are displayed in Fig. 7 and
Fig. 8, respectively. Ligands L1 and L2 present a wide TPA
band at 530 (16 GM) and 560 (75 GM) nm. Although these
TPA maxima are close to half wavelength linear absorptions (270
Fig. 5 Representation of HOMO (a) and LUMO+1 (b) of L1 orbitals
mainly involved in the transition calculated at 287 nm.
the usual intraligand charge transfer (ILCT) band is observed
ꢀ
ꢀ
in Ru (C1, C2) and Zn (C 1, C 2) complexes with no significant
wavelength shift with respect to parent ligand (the highest shift of
2
0 nm is observed in the case of C1). C1, C2, as [Ru(Phen)
3
6 2
](PF ) ,
present bands between 420 and 460 nm, which are ascribed to
MLCT transitions between the Ru(II) dp and the ligand p* orbitals.
ꢀ
ꢀ
As expected, this type of transition is not observed in C 1 and C 2.
The interest of these bands will be discussed below.
Luminescence spectra consist in broad bands centered at 590
and 595 nm for C1 and C2, respectively (see Table 1, Fig. 2 and
Fig. 3). Related excitation spectra of these emissions, involving
ꢀ
intraligand bands and MLCT (Fig. 6 for L1, C1 and C 1), are in
3
good agreement with the emission from the MLCT state. This is
also evidenced by the long luminescence lifetimes measured for C1
and C2 (1.7 and 2.5 ls, respectively) as compared to those of the
ligands (results gathered in Table 1). Let us stress that, although the
introduction of a fluorene unit on each branch of the ligand does
not induce a shift of the emission band for C1 and C2, it leads
to a lengthening of their decay time when comparing with the
ꢀ
Fig. 7 Two-photon excitation spectra of L1, L2, and C 1 measured in
acetonitrile (the experimental uncertainty for two-photon measurements
is ± 15%). For comparison, linear excitation spectrum of C 1 was also
ꢀ
reported.
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photophysical properties of related octupolar zinc and ruthe-
nium(II) complexes. The possibility to tune the excited-state
lifetime or the absorption spectral range has been demonstrated.
This paper contributes to show the great interest of Ru and
Zn complexes for TPA based effects, in both complexes, TPA
intraligand charge transfer bands were observed with an enhanced
efficiency. In that context, synthesis of longer fluorene chains
is in progress to complete the series. For the first time in
Ru coordination complexes, detection of the MLCT band led
to a TPA spectral enlargement (500–900 nm) with respect to
that of related ligands. The longer luminescence decay times
in these complexes (several ns and ls in Zn and Ru systems,
respectively) with respect to these ligands could be in favor of
excited state reabsorption, which could lead to optimize optical
limiting phenomenon induced by TPA. Furthermore and as far
as reactivity and luminescence properties are concerned, access to
2
+
Fig. 8 Two-photon excitation spectra of C1, C2, Ru(Phen)
3
measured
in acetonitrile (the experimental uncertainty is ± 15%). For comparison,
3
the long lived triplet MLCT excited state by TPA (in the 700–
linear excitation spectrum of C2 was also reported.
1
000 nm spectral range), opens up the way to applications such
23
24
and 265 nm, respectively), which was shown above to involve
only the phenanthroline moiety, the width of these bands allows
to assume the existence of several transitions. Theoretical TPA
properties of L2 confirms the existence of two transitions at 520
and 488 nm (Table 1); these transitions involve configurations
between molecular orbitals centered on the phenanthroline itself
and CT type configurations. The partial CT character of these
transitions is in good agreement with the experimental intensity
increase and bathochromic shift of these bands from L1 to L2. It
is worth noting that TPA spectra do not match linear absorption
in spite of the non-centrosymmetry of these systems in which
one-photon absorption transitions are also allowed in TPA, since
one-photon absorption transitions at 310 (for L1) and 340 nm
as photodecomposition of water, molecular switches, DNA
recognition and binding or time and spatial resolved O sensors,
including in living cells. These two last points are currently being
studied in the group and will be reported in a forthcoming article.
25
26
2
13
Experimental
Syntheses
Thin-layer chromatography was carried out on Merck Kieselgel
60F254 precoated on alumina silica gel plates. Preparative flash
1
chromatography was performed on Merck Gerduran 60.
H
1
3
and C NMR spectra were recorded on a Bruker DPX 200
spectrometer (at 200.13 MHz for H and 50.32 MHz for C) and
also on a Varian Unity Plus at 499.84 MHz for H. Elemental
1
13
(
for L2) were not detected in TPA spectra at 620 and 680 nm,
respectively. The weak efficiency of the 1,10-phenanthroline as an
acceptor group, may be responsible for this behavior.
A TPA band is observed at 595 nm for C 1, with a cross-
section rTPA of 90 GM, the matching between one- and two-
1
analysis were carried out by the Service Central d’Analyse,
CNRS. UV/Vis spectra were recorded in the 200–800 nm range on
a UV/Vis Jasco V-550; kmax are given in nm and molar extinction
ꢀ
−
1
−1
photon absorption spectra (see Fig. 7), is in agreement with the
octupolar structure of these complexes. As for C 1, below 560 nm
coefficients e in L mol cm . Melting temperatures (mp) were
ꢀ
measured on a Perkin-Elmer DSC7 micro-calorimeter.
and due to position of their emission band, spectra could not be
registered in the 470–650 nm wavelength range for Ru complexes.
In the 700–950 nm range, two TPA bands at 750 and 850–930 nm
were observed for C1 and C2 (Fig. 8). As previously mentioned
Preparation of ligands L1 and L2
Typical procedure for L1. In a 250 mL round bottom flask
under inert atmosphere, boronic acid 2 (4.5 g, 11.9 mmol) and 5-
bromo-1,10-phenanthroline 1 (3.08 g, 11.9 mmol) were dissolved
ꢀ
for C 1, most of these bands can be superimposed with those of
22
linear excitation spectra. The antenna effect induced transition
at 750 nm, presents an enhanced efficiency from C1 to C2 (40 to
in a mixture of 60 mL toluene and 60 mL of a 1 M Na
aqueous solution. After addition of catalyst Pd(PPh (412 mg,
0.36 mmol, 3%), the reaction mixture was refluxed under stirring
2
CO
3
9
0 GM, respectively, see Table 1), due to the ligand substitution
)
3 4
with an additional fluorene unit.
◦
1
The near-IR maxima rTPA value at 850 and 930 nm (∼15 GM
for 3 d. Yield: 60%; mp: 121 C. H NMR (499.84 Hz, 300 K,
3
5
for both complexes and [Ru(Phen)
3
](PF
6
)
2
) does not depend on
CD
1.5 Hz, H
7.82 (1H, m, H13), 7.72 (1H, m, H
17), 7.55 (1H, d, H11), 7.48–7.39 (3H, m, H14, H15, H16), 2.08 (4H,
m, Halkyl), 1.19–1.10 (12H, m, Halkyl), 0.83–0.75 (10H, m, Halkyl).
2
Cl
2
) 9.20 (2H, m, H
, H ), 7.94–7.92 (1H, m, H12), 7.89 (1H, s, H
), 7.62 (1H, m, H ), 7.57 (1H, s,
2
, H
9
), 8.40–8.34 (2H, m, J = 8 Hz, J =
the ligand. This transition corresponds to the MLCT band, and
its spectral distribution is observed here for the first time in Ru
complexes by two-photon excitation. The origin of this band is
confirmed from Zn complexes spectra, in which no absorption
was observed in the same wavelength range.
4
7
6
), 7.86–
3
8
H
1
3
C NMR (50.32 MHz, 300 K, CDCl ) 150.9, 150.8, 149.9, 149.8,
3
1
1
4
46.4, 145.6, 140.9, 140.3, 139.2, 137.2, 135.7, 134.4, 128.5, 128.0,
27.3, 126.8, 126.2, 124.3, 123.2, 122.8, 122.5, 119.8, 119.7, 55.1,
Conclusions
0.1, 31.3, 29.5, 23.7, 22.4, 13.8. Anal. Calcd for C37
H
40
N
2
·0.5H
2
O:
In conclusion, we have presented herein two new fluorene-
substituted 1,10-phenanthroline ligands and the preparation and
C, 85.17; H, 7.92. Found: C, 85.13; H, 8.01%. UV-vis (CHCl ) kmax
(e) = 312 (21400); 272 (35000); 240 (21200); 217 (18900).
3
3
424 | Dalton Trans., 2007, 3421–3426
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◦
1
L2. Yield: 67%; mp: 128 C. H NMR (499.84 Hz, 300 K,
267(101900); 243(92700); 215(75900). HRMS(MALDI): Calcd for
3
5
+
CDCl
.5 Hz, H
or H ), 7.98–7.48 (13H, m), 7,36–7.29 (3H, m, H18, H19, H20),
.08–2.00 (8H, m, Halkyl), 1.15–1.03 (24H, m, Halkyl), 0.82–0.69
3
) 9.21 (2H, m, H
2
, H
9
), 8.35–8.33 (1H, m, J = 8 Hz, J =
RuC186
H
216
N
6
: 2635.60194 M ; Exp. : 2635.61245.
3
5
1
H
2
(
1
1
1
1
2
3
or H
8
), 8.30–8.28 (1H, m, J = 8 Hz, J = 1.5 Hz,
ꢀ
◦
1
C 2. Yield: 76%; mp: not found (20–450 C). H NMR
8
3
(499.84 Hz, 300 K, CD
2
Cl
2
) 8.85–8.79 (2H, m, H
2
, H ), 8.6–8.4
9
(2H, m), 8.25–8.22 (1H, m), 8.06–7.62 (12H, m), 7.43–7.38 (3H, m,
1
3
20H, m, Halkyl). C NMR (50.32 MHz, 300 K, CDCl
51.49, 151.41, 150.97, 150.04, 141.00, 140.80, 140.71, 140.44,
40.30, 139.63, 139.41, 137.40, 135.90, 128.80, 128.16, 126.79,
26.37, 126.28, 126.05, 124.57, 123.36, 122.91, 122.72, 121.51,
21.40, 120.15, 119.89, 119.72, 55.39, 55.16, 40.35, 40.28, 31.45,
9.66, 29.61, 29.25, 23.90, 22.52, 14.00, 13.98. Anal. Calcd for
3
) 151.70,
H
18, H19, H20), 2.19–2.09 (8H, m, Halkyl), 1.16 (24H, m, Halkyl), 0.82–
0
.73 (20H, m, Halkyl). Anal. Calcd. for ZnC186
H
216
N
6
P
2
F
12·4H
2
O:
C, 75.39; H, 7.60; N, 2.80. Found: C, 75.35; H, 7.64; N, 3.11%.
UV-vis (CHCl
3
) kmax (e) = 335(145300); 301(92600); 275(91100);
2
43(86000); 214(63900).
C
62
H
72
N
2
·0.3H
UV-vis (CHCl
13 (23100).
2
O: C, 87.72; N, 3.29%. Found: C, 87.66; N, 3.29%.
) kmax (e) = 341 (61400); 268 (28900); 242 (36600);
Physical measurements
3
2
Luminescence. The steady-state emission spectra were
recorded on a Photon Technology International (PTI) SE-900M
spectrofluorimeter. All the samples were prepared in a glovebox in
ꢀ
ꢀ
Preparation of complexes C1, C2, C 1 and C 2
deoxygenated CH CN and contained in 1 cm quartz cell. The
3
Ruthenium and zinc complexes were obtained by reaction under
samples were maintained in aerobic conditions with a Teflon
ꢀ
reflux of three equivalents of ligand (L1 and L2 for C1, C 1 and,
◦
cap. Emission quantum yield φ
L
were determined at 25 C in
ꢀ
C2, C 2, respectively) with one equivalent of ruthenium trichloride
deoxygenated acetonitrile solutions with a CH
3
CN solution of
= 0.03) as a standard, according to
(
in dimethylformamide) and zinc acetate (in ethanol) for C1, C2
II
Ref
[
Ru (phen)
3
](PF
6
)
2
(φ
L
ꢀ
ꢀ
and C 1, C 2, respectively and precipited by NH
4
PF .
6
eqn (1),
Typical procedure for C1: a DMF solution of 600 mg of
compound L1 (1.17 mmol) was dropwise added, under argon,
ꢀ
ꢁ
−ODRef
S
L
I
1 − 10
S
L
Ref
L
φ =
ꢀ
ꢁ φ
(1)
to 100 mg of RuCl
refluxed for a night. Saturated aqueous solution of NH
3
·3H
2
O (0.38 mmol) dissolved in DMF and
PF was
Ref
−ODS
IL
1 − 10
4
6
where I
L
, the emission intensity, was calculated from the spectrum
then added to the resulting solution at room temperature. 556 mg
of a red precipitate was collected by filtration, washed three times
ꢂ
area I(k)dk and OD represents the optical density at the
excitation wavelength. The superscripts “S” and “Ref” refer to the
sample and the standard, respectively. The luminescence lifetime
measurements for the complexes C1 and C2 were performed after
with H
2
O and twice with pentane. Dissolved in dichloromethane,
SO4. After filtration and
the resulting solution was dried over Na
2
evaporation, the desired complex was recristallized in absolute
ethanol to yield 410 mg of a red solid (white solid for zinc
irradiation at k = 337 nm obtained with a 4 ns pulsed N
2
laser
◦
1
(optilas VSL-337ND-S) and recorded at the emission maximum
wavelength using a monochromator and a photomultiplicator
tube (Hamamatsu R928) coupled with an ultra-fast oscilloscope
complexes). Yield: 79%; mp: not found (20–450 C). H NMR
499.84 MHz, CD Cl ) d 8.62 (2H, m, H , H ), 8.35–8.17 (3H,
m, H , H , H ), 7.99 (1H, m, H12), 7.89–7.84 (2H, m, H13, H or
), 7.57 (1H, m, H or H ), 7.65 (2H, m, H11, H17), 7.44 (3H,
m, H14, H15, H16), 2.09 (4H, m, Halkyl), 1.13 (12H, m, Halkyl), 0.82–
(
2
2
4
7
2
6
9
3
(
Tektronix TDS 520A). Fluorescence decay measurements of the
ligands L1 and L2 were performed after irradiation at kexc
00 nm obtained by the second harmonic of a Titanium :
H
8
8
3
=
4
0
.75 (10H, m, Halkyl). Anal. Calcd. for RuC111
H
120
N
6
P
2
F
12·H
2
O:
Saphire laser (picosecond Tsunami laser spectra physics 3950-
MIBB) at a 8 MHz repetition rate. The Fluotime 200 from
AMS technologies is used for decay acquisition. It consists of
a GaAs microchannel plate photomultiplier tube (Hamamatsu
model R3809U-50) followed by a time-correlated single photon
counting system from picoquant (PicoHarp300).
C, 68.47; H, 4.32; N, 4.32. Found: C, 68.44; H, 4.38; N, 4.38%.
UV-vis (CHCl
3
): kmax (e) = 452(29900); 422(28100); 345(42600);
3
08(48900); 270(125500); 216(52600). ESI-HRMS Calcd for
+
RuC111
H
120
N
6
PF : 1783.82543 M , exp: 1783.83670.
6
ꢀ
◦
1
C 1. Yield: 61%; mp: 401 C; H NMR (499.84 MHz, CDCl
3
)
8
H
.77–8.46 (4H, m, H
2
, H
3
, H
8
, H
9
), 8.14–8.06 (2H, m, H
, H12), 7.84–7.82 (1H, m, H13),
6
, H or
4
Nonlinear optical measurements. The TPEF technique was
used to measure the two-photon absorption cross-section rTPA
using a femtosecond Ti-sapphire laser and a nanosecond OPO
pumped by tripled Nd:YAG laser as excitation sources in the
7
), 8.02–8.79 (2H, m, H
4
or H
7
7
2
.57–7.52 (2H, m, H11, H17), 7.42 (3H, m, H14, H15, H16), 2.07–
.05 (4H, m, Halkyl), 1.15–1.06 (12H, m, Halkyl), 0.82–0.75 (10H,
m, Halkyl). Anal. Calcd. for ZnC111
H
120
N
6
P
2
F
12·2H
2
O: C, 69.09; H,
7
7
00–950 and 450–650 nm ranges, respectively (spectral range 650–
00 nm is inaccessible with our experimental set-up). The TPA
6
3
.47; N, 4.35; Zn, 3.38. Found: C, 68.97; H, 6.42; N, 4.48; Zn,
.59%. UV-vis (CHCl
3
) kmax (e) = 340 (40000); 273 (137500); 241
27
experimental set-up has already been described. TPA excitation
spectra were recorded from fluorescence detected by a fiber
optic CCD spectrometer and collected at 90 of the incident.
The TPA cross-section was determined from 2 × 10 mol L
(
55300); 218 (52700).
◦
1
◦
C2. Yield: 60%; mp: not found (20–450 C). H NMR
−
3
−1
(
8
499.84 Hz, 300 K, CD Cl ) 8.64–8.62 (2H, m, H , H ), 8.47–
.25 (4H, m, H , H , H , H ), 8.04–8.25 (11H, m), 7.45–7.36 (3H,
2
2
4
7
2
3
8
9
solutions in acetonitrile of molecules, using the reference TPA
m, H18, H19, H20), 2.19–1.76 (8H, m, Halkyl), 1.16 (24H, m, Halkyl),
.82–0.75 (20H, m, Halkyl). Anal. Calcd. for RuC186
C, 76.33; H, 7.43; N, 2.87. Found: C, 76.30; H, 7.97; N,
.02%. UV-vis (CHCl
) : kmax (e) = 459(27100); 334(145200);
cross-section of 210 GM (GM for G o¨ ppert–Mayer unit, 1 GM =
−
50
4
−1 −1
0
H
216
N
6
P
2
F
12
:
10 cm photon s ) at 840 nm for Rhodamine B in methanol as
reported in Table 2 of ref. 28 in order to scale two-photon excited
fluorescence spectra and the pulse energy was kept low enough
3
3
This journal is © The Royal Society of Chemistry 2007
Dalton Trans., 2007, 3421–3426 | 3425

View Article Online
to ensure a quadratic dependence of the fluorescence signal on
input energy. For each of our compound, fluorescence efficiencies,
including the concentration dependent self-quenching, were taken
into account by comparison with the one-photon fluorescence
that was obtained at visible wavelengths in the same excitation
and collection geometry.
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653.
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11.
Semi-empirical quantum chemistry calculations were used, fol-
lowing the method described in ref. 14a, to analyse one- and
two-photon absorption spectra. The geometry of molecules was
14 (a) Y. Morel, A. Irimia, P. Najechalski, Y. Kervella, O. Stephan, P. L.
Baldeck and C. Andraud, J. Chem. Phys., 2001, 114, 5391; (b) M. G.
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29
optimized in the ground state by CACHE.
1
5 (a) F. N. Castellano, H. Malak, I. Gryczynski and J. R. Lakowicz,
Inorg. Chem., 1997, 36, 5548; (b) S. K. Hurst, M. P. Cifuentes,
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Acknowledgements
The authors thank J. Bernard for technical assistance and Direc-
tion G e´ n e´ rale de l’Armement for financial support.
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426 | Dalton Trans., 2007, 3421–3426
This journal is © The Royal Society of Chemistry 2007