Long-Lived MLCT Excited States-RuII Complexes with a Helical Bis-Phen Ligand

Article abstract of DOI:10.1002/ejic.200300161

The synthesis of a new Ru^II complex [Ru(L ₁)(4,7-dpphen)]²⁺, bearing a tetradentate bis-1,10-phenanthroline ligand L₁, is described. X-ray crystal structure analysis shows that the tetradentate ligand L₁ coils around the metal and occupies both axial and two of the equatorial positions of the complex. ¹H NMR studies clearly indicate that the complex has C₂ symmetry in solution. The room temperature luminescence properties of [Ru(L₁)(4,7-dpphen)]²⁺ have been studied, as have those of the related complex [Ru(L₂)(4,4′-dmbp)] ²⁺. For both complexes, the luminescence quantum yields and lifetimes are three to ten times higher than those of [Ru(bpy)₃] ²⁺. These unusual results are explained by the geometrical constraints imposed by the tetradentate ligands L₁ and L₂ in their respective complexes, resulting in an effective decoupling between the ³MLCT and ³MC excited states. Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003.

Full text of DOI:10.1002/ejic.200300161

FULL PAPER
Long-Lived MLCT Excited States-RuII Complexes with a Helical Bis-Phen
Ligand
[a]
[a]
Christine Goze,[a] Jean-Claude Chambron,[a][‡] Valerie Heitz,* Didier Pomeranc,
´
[a]
[a]
[b]
´
Xavier J. Salom-Roig, Jean-Pierre Sauvage,* Angeles Farran Morales, and
Francesco Barigelletti*[b]
Keywords: Luminescence / N ligands / Photochemistry / Ruthenium
The synthesis of a new RuII complex [Ru(L1)(4,7-dpphen)]2+
bearing a tetradentate bis-1,10-phenanthroline ligand L1, is
described. X-ray crystal structure analysis shows that the These unusual results are explained by the geometrical con-
,
both complexes, the luminescence quantum yields and life-
times are three to ten times higher than those of [Ru(bpy)3]2+
.
tetradentate ligand L1 coils around the metal and occupies
both axial and two of the equatorial positions of the complex.
1H NMR studies clearly indicate that the complex has C2
symmetry in solution. The room temperature luminescence
properties of [Ru(L1)(4,7-dpphen)]2+ have been studied, as
have those of the related complex [Ru(L2)(4,4Ј-dmbp)]2+. For
straints imposed by the tetradentate ligands L1 and L2 in their
respective complexes, resulting in an effective decoupling
3
3
between the MLCT and MC excited states.
( Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim,
Germany, 2003)
Introduction
gands rather than to electronic delocalisation in their
frame systems.
[Ru(bipy)3]2ϩ (bipy ϭ 2,2Ј-bipyridine) continues to be the
most popular transition metal complex in the field of
photochemistry and electron transfer.[1] A huge number of
derivatives have been prepared and studied by numerous
groups with the improvement of the photochemical proper-
ties of Ru-polypyridine complexes in mind, in view of their
utilisation in, for instance, molecular photovoltaics and the
chemical conversion of light energy.[2,3] In fact, the photo-
chemical stability, the thermal stability of the reduced and
oxidized states, the energy levels of the singlet and triplet
Results and Discussion
The synthesis of [RuL1(4,7-dpphen)](PF6)2 is described in
Figure 1 (4,7-dpphen represents 4,7-diphenyl-1,10-phen-
anthroline, as shown in Figure 2). This complex contains
the 1,4-phenylenebis(7-bromo-1,10-phenanthroline) ligand
L1, which was synthesized from 7-p-bromophenyl-4-methyl-
1,10-phenanthroline (1). At first, 1 was obtained through a
Skraup reaction between 4-methyl-8-aminoquinoline[5,6]
and p-bromophenyl β-chloroethyl ketone[7] in sulfuric acid
in the presence of arsenic pentoxide, in 71% yield.[8] Sub-
sequent treatment of 1 with LDA at Ϫ70 °C, followed by
addition of α,αЈ-dibromo-p-xylene at Ϫ40 °C, afforded L1
in 7% yield, which is quite low in comparison with a similar
reaction producing L2 in 88% yield.[5,6] This may be due to
lower stability of the carbanion of 1.
Coordination of ligand L1 on the ruthenium centre was
achieved under high-dilution conditions in refluxing dichlo-
roethane with use of [Ru(CH3CN)4Cl2] as precursor com-
plex, as described by von Zelewsky and co-workers.[9] The
intermediate complex, [RuL1Cl2], formed during the reac-
tion, was treated directly with 4,7-dpphen in a refluxing
mixture of water and ethanol. After anion exchange with
an aqueous solution of KPF6 and separation by column
chromatography, the complex [RuL1(4,7-dpphen)](PF6)2
3
MLCT states, the emission quantum yield, the MLCT ex-
cited state lifetime, and the redox properties of the ground
and excited states are important parameters that can, to a
large extent, be controlled by the structural features of the
chelates.[1,4] We now report that, through the use of tetra-
dentate bis-1,10-phenanthroline ligands, which impose a
helical geometry to the system in a strictly controlled fa-
shion, the obtained ruthenium() complexes display un-
usually long-lived excited states. This behaviour is probably
due to a cage-like effect for the employed tetradentate li-
[‡]
´
´
Present address: Universite de Bourgogne, Faculte des Sciences
Gabriel, LIMSAG, UMR5633 du CNRS; 6, Boulevard Gabriel;
21100 Dijon, France
[a]
[b]
´
Laboratoire de Chimie Organo-Minerale, UMR 7513 du
´
´
CNRS, Universite Louis Pasteur, Faculte de Chimie,
4, rue Blaise Pascal, 67070 Strasbourg Cedex, France
Istituto ISOF-CNR,
Via P. Gobetti 101, 40129 Bologna, Italy
3752
 2003 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
DOI: 10.1002/ejic.200300161
Eur. J. Inorg. Chem. 2003, 3752Ϫ3758

Long-Lived MLCT Excited States-RuII Complexes with a Helical Bis-Phen Ligand
FULL PAPER
Figure 1. Synthesis of ligand L1 and preparation of the correspond-
ing ruthenium() complex [RuL1(4,7-dpphen)](PF6)2
Figure 2. Chemical formulae of the ligands and the complexes
studied
was isolated in 44% yield. The C2 symmetry of the complex
in solution is clearly shown by analysis of its 1H NMR spec-
trum (Figure 3). Protons H2 and H9 and protons Hb1 and
Hb2 of ligand L1 are particularly sensitive to geometric and equatorial positions are occupied by the 4,7-dpphen ligand.
˚
electronic changes on going from the free ligand L1 to the The RuϪN distances range between 2.057(9) A and
˚
Ru-coordinated ligand L1 in [RuL1(4,7-dpphen)](PF6)2, as 2.076(9) A. This structure is close to that of the complex
shown in Figure 3. Protons Hb1 and Hb2, homotopic in L1 [RuL2(4,4Ј-dmbp)](PF6)2,[5] but with less distortion from
(singlet at δ ϭ 7.13 ppm), become diastereotopic in the C2 linearity. The angle Br(1)ϪRuϪBr(2) is 174.6(9)°, as com-
symmetric complex [RuL1(4,7-dpphen)](PF6)2, appearing as pared with 169.9(7)° for OϪRuϪO. The distance
a
pair of doublets [δ(Hb1)
ϭ
6.67 ppm, δ(Hb2)
ϭ
Br(1)···Br(2) is 21.86(8) A.
˚
6.32 ppm]). In the non-coordinated ligand L1, protons H2
The synthesis of the ruthenium complex [RuL2(4,4Ј-
and H9 have low-field chemical shifts typical of protons lo- dmbp)](PF6)2 has been described previously.[5,6] This com-
cated α to the nitrogen atom of a free 1,10-phenanthroline plex contains a bis-1,10-phenanthroline ligand L2, func-
[δ(H2) ϭ 9.04 ppm and δ(H9) ϭ 9.19 ppm]. These protons tionalized with a p-anisyl group on each position 7 of the
are shifted upfield in the complex [δ(H2) ϭ 7.39 ppm and phenanthroline unit (Figure 2), and differs from the former
δ(H9) ϭ 7.99 ppm], since coiling of the ligand around the mainly in the nature of the ancillary ligand [4,4Ј-dimethyl-
ruthenium centre places H2 in the shielding field of the 2,2Ј-bipyridine (4,4Ј-dmbp)].
other phenanthroline of L1 and H9 in that of the ancillary
Figure 5 shows the absorption spectra (1·10Ϫ5 , aceto-
ligand 4,7-dpphen.
nitrile) of the investigated complexes containing the tetra-
The X-ray crystal structure of the complex [RuL1(4,7- dentate ligands L1 and L2; for purposes of comparison, the
dpphen)](PF6)2 was solved (Figure 4).[10] The complex crys- spectrum of [Ru(bpy)3](PF6)2 is also shown.
tallises in the monoclinic P12/n1 space group, with two
For the [RuL2(4,4Ј-dmbp)](PF6)2 and [RuL1(4,7-
molecules in the unit cell. The structure clearly shows that dpphen)](PF6)2 complexes, the lowest-lying 1MLCT band
the axial and two equatorial positions are occupied by the maxima fall at slightly lower energies Ϫ 458 and 460 nm,
nitrogen atoms of the ligand L1 and that the remaining respectively Ϫ than that of the reference complex [Ru-
Eur. J. Inorg. Chem. 2003, 3752Ϫ3758
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V. Heitz, J.-P. Sauvage, F. Barigelletti et al.
FULL PAPER
1
Figure 3. 400 MHz H NMR spectra (low field region, CD2Cl2) of ligand L1 and complex [RuL1(4,7-dpphen)](PF6)2
An observation of interest relates to the presence of in-
tense absorption bands appearing at 310Ϫ320 nm for
[RuL2(4,4Ј-dmbp)](PF6)2 and [RuL1(4,7-dpphen)](PF6)2,
but not exhibited by [Ru(bpy)3](PF6)2 (see Figure 5). This
1
is a spectral region in which MC (d-d) transitions are ex-
pected for RuII-polypyridine complexes.[1] This type of tran-
sition is Laporte-forbidden, and its extinction coefficient is
estimated ε ഠ 102 Ϫ1·cmϪ1 for [Ru(bpy)3]2ϩ [14]
The fact
.
that for [RuL1(4,7-dpphen)](PF6)2 and Ϫ even more so Ϫ
for [RuL2(4,4Ј-dmbp)](PF6)2, the forbidden nature of the
transition appears to be substantially lifted may be associ-
ated with permanent or transient distortions of the octa-
hedral environment around the metal centre; the X-ray re-
sults (see above) are consistent with this interpretation. Fi-
nally, the absorption features in the 280Ϫ290 nm spectral
1
portion are LC in nature and are probably attributable to
the ligand subunits directly coordinated to the metal cen-
tre,[1] as shown by the fact that their intensities are similar;
see Figure 5.
Figure 4. X-ray crystal structure of [RuL1(4,7-dpphen)](PF6)2
Room temperature luminescence properties of
[RuL2(4,4Ј-dmbp)](PF6)2 and [RuL1(4,7-dpphen)](PF6)2,
obtained in degassed acetonitrile, are illustrated in Table 1;
for purposes of comparison, luminescence results for [Ru-
(bpy)3](PF6)2 are also listed.
(bpy)3](PF6)2 (452 nm). The absorption intensities at the
MLCT band maxima are ε ϭ 20300 and 20600 Ϫ1·cmϪ1
,
respectively, and hence about 40% higher than that of the
reference complex (ε ϭ 14300 Ϫ1·cmϪ1). This is an effect
due to the ‘‘transfer term’’ for the promoted electron,[11Ϫ13]
The room temperature luminescence profiles (shown in
the average displacement of which during the MLCT tran- the inset of Figure 5), the band peaks and the lifetime val-
sition is larger than that occurring in the case of ues are consistent with a 3MLCT nature for the lowest-lying
[Ru(bpy)3]2ϩ
.
The MLCT absorption features for level of the investigated Ru-polypyridine luminophores. The
[RuL2(4,4Ј-dmbp)](PF6)2 and [RuL1(4,7-dpphen)](PF6)2 band maxima of [RuL2(4,4Ј-dmbp)](PF6)2 and [RuL1(4,7-
thus suggest that the MLCT transitions in the visible region dpphen)](PF6)2 are slightly lower in energy than that of
probably involve the extended frames of the L2 and L1 li- [Ru(bpy)3](PF6)2, consistently with the absorption results.
gands, respectively {and also of the ligand 4,7-dpphen in The relevant observation here is that, for the two complexes
the case of [RuL1(4,7-dpphen)](PF6)2}.
containing the tetradentate ligands L1 and L2, the lumi-
3754
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Long-Lived MLCT Excited States-RuII Complexes with a Helical Bis-Phen Ligand
FULL PAPER
Figure 5. Ground state absorption spectra in acetonitrile for [RuL2(4,4Ј-dmbp)](PF6)2 (full line), [RuL1(4,7-dpphen)](PF6)2 (dash), and
[Ru(bpy)3](PF6)2 (dash-dot-dot); the inset shows luminescence spectra obtained from excitation of isoabsorbing solutions at 450 nm
Table 1. Luminescence properties (O2-free acetonitrile solvent, excitation at 450 or 337 nm)
298 K
kr ϫ 104, sϪ1[a]
77 K
λmax, nm
λmax, nm
ϕ
τ, µs
knr ϫ 105, sϪ1[b]
τ, µs
[RuL2(4,4Ј-dmbp)](PF6)2
[RuL1(4,7-dpphen)](PF6)2
[Ru(bpy)3](PF6)2
614
612
608
0.30
0.28
0.086
4.0
8.6
0.90
7.5
3.3
9.6
1.8
0.83
10.2
608
610
585
10.5
11.2
4.9
[a]
[b]
kr ϭ ϕ / τ. knr ϭ (1 Ϫ ϕ)/τ.
nescence quantum yields (Φ) and lifetimes (τ) are three to for the luminescent MLCT excited state with respect to the
ten times larger than those for [Ru(bpy)3](PF6)2. In these curve for the ground state (GS) (i.e., a high degree of de-
complexes, this happens because the non-radiative tran- localisation is accompanied by a small displacement).
sitions (as quantified by the appropriate rate constant knr; Analysis of the luminescence profiles affords the displace-
see Table 1), known to govern the luminescence properties ment parameter, the HuangϪRys electron-vibrational coup-
in the Ru-polypyridine complexes,[1,4] appear to be substan- ling constants pertinent to average frequencies (SM) of li-
tially depressed. Below we briefly discuss possible reasons gand origin, h ωM ϭ 1350 cmϪ1, corresponding to the vi-
-
for this behaviour.
brational progression exhibited by the low-temperature lu-
With regard to the nature of the non-radiative processes minescence spectra.[15,16] The results of the vibronic analysis
deactivating the 3MLCT luminescent level in Ru-polypyrid- on the corrected luminescence profiles (on an energy scale,
ine complexes, three main issues can be considered. These spectra obtained in frozen solvent at 77 K) are illustrated
are: (i) the effect of the electronic delocalisation in the li- in Figure 6 and summarized in Table 2.
gand system,[13,15,16] (ii) the effect of the energy gap law (re-
While for complexes containing highly delocalised ligand
garding the direct MLCT-to-GS transition),[17,18] and (iii)
systems, such as dipyrido-phenazine,[19] pyrimidine-substi-
3
the thermal accessibility from the luminescent 3MLCT level tuted terpyridine (tpy)[20] or back-to-back bis-tpy,[13] this
3
of a higher-lying MC state, an effective doorway both to type of vibronic analysis provides SM values of between 0.2
photochemistry (ligand release) and to fast, non-radiative and 0.5, for [RuL2(4,4Ј-dmbp)](PF6)2 and [RuL1(4,7-
3
deactivation (because of the strong MC-GS coupling).[1] dpphen)](PF6)2 we find SM ϭ 0.75 and 0.78 (Table 2). These
Given the extended ligand systems of L1 and L2, and also values are not greatly different from that for [Ru-
of 4,7-dpphen, we have addressed the role of electronic de- (bpy)3](PF6)2 (SM ϭ 0.92) taken as a prototype of a complex
localisation, point (i), in detail. The extent of delocalisation in which the ligand system is not greatly delocalised. The
is related to the displacement of the potential energy curve vibronic analysis does not therefore support delocalisation
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V. Heitz, J.-P. Sauvage, F. Barigelletti et al.
FULL PAPER
fect, due to coordination of the tetradentate L1 and L2 li-
gands.
In conclusion, we have been able to show that the use
of a bis-phen ligand, displaying geometrically constraining
properties with respect to the coordination sphere of the
complexed ruthenium() centre, produces effective decoup-
3
3
ling between the MLCT and the MC excited states. This
effect results in remarkably long-lived 3MLCT excited states
for the corresponding ruthenium()-tris(diimine) com-
plexes.
Experimental Section
Materials: Starting materials were from commercial sources and
were used as received. THF was distilled from sodium/benzo-
phenone prior to use. Reactions performed under an atmosphere
of argon used standard Schlenk techniques. [Ru(CH3CN)4Cl2] was
prepared according to the literature procedure.[9]
1
Physical Measurements: H NMR: Bruker WP200SY (2OOMHz)
and Bruker AM (400 MHz) instruments; the reported chemical
shifts are referenced to Me4Si as an internal standard. Mass spec-
troscopic data were obtained on a ZAB-HF (FAB) spectrometer
with a nitrobenzyl alcohol matrix.
Figure 6. Vibronic analysis of the luminescence profiles for
[RuL1(4,7-dpphen)](PF6)2 (a), [RuL2(4,4Ј-dmbp)](PF6)2 (b), and
[Ru(bpy)3](PF6)2 (c), obtained at 77 K, acetonitrile, excitation at
450 nm; see text for further details
7-(p-Bromophenyl)-4-methyl-1,10-phenanthroline (1): A mixture of
4-methylquinolin-8-ylamine (1.5 g, 9.5 mmol), arsenic acid (5.65 g,
13.3 mmol), and phosphoric acid (15 mL) was heated at 100 °C. p-
Bromophenyl-β-chloroethylketone[7] (3.28 g, 13.3 mmol) was added
over a period of 1 h at such a rate that the temperature did not
exceed 120 °C. After the addition the temperature was raised to
140 °C for 2 hours. After cooling, the mixture was poured onto ice
and the resulting solution was neutralised with aqueous sodium
hydroxide (30%), resulting in the precipitation of a brown solid.
The mixture was left at 0 °C overnight. The precipitate was ex-
tracted several times with boiling toluene, the combined solutions
were dried with MgSO4, and the solvent was evaporated. The crude
product was chromatographed on silica, eluted with hexane/ethyl
acetate (50:50), with a gradient to ethyl acetate/methanol (99:1),
yielding 1 as a pale brown solid (2.34 g, 71%). 1H NMR (200 MHz,
Table 2. Parameters from vibronic analysis (from fitting of the 77 K
luminescence profiles, Equation (2) of text)
[b]
E00, cmϪ1 [a]
SM
[RuL2(4,4Ј-dmbp)](PF6)2
[RuL1(4,7-dpphen)](PF6)2
[Ru(bpy)3](PF6)2
16680
16540
17250
0.78
0.75
0.92
[a] Energy of the luminescent level (0Ϫ0 transition). [b] HuangϪRys
-
factor for frequencies of ligand origin, h ωM ϭ 1350 cmϪ1
.
3
CDCl3): δ ϭ 2.78 (s, 3 H, CH3), 7.42 (d, J ϭ 8.12 Hz, 2 H, Hm),
in the ligands as a crucial factor for explaining the quite
different luminescence features of [RuL2(4,4Ј-dmbp)](PF6)2
and [RuL1(4,7-dpphen)](PF6)2, in comparison with the case
of [Ru(bpy)3](PF6)2. Effects related to point (ii) above (en-
ergy-gap law)[17,18] would also be expected to be of limited
importance, given that the luminescent levels are not too
apart from one another in energy (Table 2). In conclusion,
we point to the fact that the tetradentate L1 and L2 ligands
contain two bidentate subunits linked together. Literature
3
3
7.49 (d, J ϭ 4.42 Hz, 1 H, H3), 7.53 (d, J ϭ 4.42 Hz, 1 H, H8),
3
3
7.70 (d, J ϭ 8.12 Hz, 2 H, Ho), 7.86 (d, J ϭ 9.34 Hz, 1 H, H5),
3
3
7.97 (d, J ϭ 9.36 Hz, 1 H, H6), 9.07 (d, J ϭ 4.42 Hz, 1 H, H2),
9.22 (d, 3J ϭ 4.42 Hz, 1 H, H9) ppm. FAB-MS: m/z ϭ 349.4 [M
ϩ H]ϩ.
L1: Diisopropylamine (0.162 mL, 1.15 mmol) was dissolved in
THF (4 mL) under argon. n-Butyllithium (1.5 , 0.764 mL) was
added at 0 °C, and the mixture was stirred at 0 °C for 1 h. Com-
pound 1 (400 mg, 1.15 mmol) was dissolved in THF (10 mL) under
examples exist in which constraints against elongation of argon and transferred by cannula at Ϫ40 °C to the freshly prepared
LDA solution. The solution instantly turned dark red and was
stirred for 1 hour at Ϫ70 °C and for 1/2 h at Ϫ40 °C. α,αЈ-Di-
bromo-p-xylene (151.2 mg, 0.057 mmol) was dissolved in THF
(5 mL) under argon and transferred to the reaction mixture at Ϫ40
°C by cannula. The mixture was stirred at room temperature over-
night, during which the dark red solution turned pale brown. The
solution was poured into water and extracted with dichlorometh-
ane. The combined organic phases were washed with ethanol in
order to remove the oligomers and chromatographed on alumina,
eluted with dichloromethane with a gradient to dichloromethane/
the RuϪN bonds (inhibiting ligand release as a conse-
quence of extreme elongation) can result in a sort of cage-
like effect; this type of restrictions can originate from physi-
cal interactions, as found within zeolite frameworks, for in-
stance,[21] or can be imposed at the molecular level by link-
ing the coordinating bpy units together, thus yielding caged
or hemi-caged complexes.[22] For the luminescent levels of
both the [RuL2(4,4Ј-dmbp)](PF6)2 and the [RuL1(4,7-
dpphen)](PF6)2 complexes, the reduced role of the non-radi-
ative relaxation is probably related to such a cage-type ef- methanol (98:2), to yield L1 as a brown solid (32 mg, 7%). 1H
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Eur. J. Inorg. Chem. 2003, 3752Ϫ3758

Long-Lived MLCT Excited States-RuII Complexes with a Helical Bis-Phen Ligand
FULL PAPER
NMR (400 MHz, CD2Cl2): δ ϭ 3.09 (m, 4 H, CH2), 3.42 (m, 4 H, photon-counting apparatus (N2 lamp, excitation at 337 nm). The
CH2), 7.13 (s, 4 H, Hb1ϩHb2), 7.44 (d, 3J ϭ 4.20 Hz, 2 H, H3),
uncertainty in the evaluated lifetimes is 8%.
3
3
7.47 (d, J ϭ 8.25 Hz, 4 H, Ho), 7.58 (d, J ϭ 4.39 Hz, 2 H, H8),
3
3
7.73 (d, J ϭ 8.22 Hz, 4 H, Hm), 7.90 (d, J ϭ 9.37 Hz, 2 H, H5),
3
3
8.05 (d, J ϭ 9.43 Hz, 2 H, H6), 9.04 (d, J ϭ 4.32 Hz, 2 H, H2),
9.19 (d, 3J ϭ 4.35 Hz, 2 H, H9) ppm. FAB MS: m/z ϭ 801 [M
ϩ H]ϩ.
(1)
[RuL1(4,7-dpphen)](PF6)2: Compound L1 (50 mg, 0.062 mmol) was
dissolved in 1,2-dichloroethane (15 mL) under argon. Freshly pre-
pared [Ru(CH3CN)4Cl2] (21 mg, 0.062 mmol) was dissolved in 1,2-
dichloroethane (15 mL) under argon. The two solutions were sim-
ultaneously added dropwise to refluxing 1,2-dichloroethane
(800 mL) at a rate of 5 mL/h. After completion of the addition, the
dark violet mixture was heated at reflux for two more hours, and
allowed to cool overnight. The solvent was evaporated, and the
resulting dark violet solid was dissolved in a mixture of ethanol/
water (8 mL/1 mL) under argon. 4,7-Diphenylphenanthroline (4,7-
dpphen, 20.6 mg, 0.062 mmol) was then added, and the reaction
mixture was heated for 4 h, during which the solution turned or-
ange-red. After the mixture had cooled, the ethanol was evaporated
and the product was precipitated with a saturated aqueous solution
of potassium hexafluorophosphate. The resulting precipitate was
filtered under vacuum and chromatographed on silica, eluting with
a gradient of dichloromethane/methanol, from 100:0 to 90:10. The
complex [RuL1(4,7-dpphen)](PF6)2 was obtained as an orange solid
Vibronic band intensities of the luminescence spectra on an energy
scale (cmϪ1) were analysed according to a fitting procedure pro-
posed by Meyer and co-workers.[25,26] For the luminescence spectra
obtained at 77 K we used a two-mode analysis according to the
following expression [Equation (2)]:
(2)
where I(v¯ ) is the luminescence intensity profile, v¯ϰ is the energy of
the 0Ϫ0 transition (hereafter indicated as Eϰ), v are vibrational
quantum numbers, M and L are labels for average and low fre-
1
-
-
quency modes, taken as h ωM ϭ 1350 cmϪ1 and h ωM ϭ 400 cmϪ1
,
(41 mg, 44%). TLC: one spot, Rf ϭ 0.62 (CH2Cl2/MeOH, 8:2). H
NMR (400 MHz, CD2Cl2): δ ϭ 3.11 (m, 2 H, CH2), 3.28 (m, 2 H,
CH2), 3.42 (m, 2 H, CH2), 3.94 (m, 2 H, CH2), 6.32 (dd, 3J ϭ 7.95,
4J ϭ 1.6 Hz, 2 H, Hb2), 6.67 (dd, 3J ϭ 8.07, 4J ϭ 1.72 Hz, 2 H,
respectively, SM and SL are displacement parameters along the
indicated vibrational modes, and v¯1/2 is the bandwidth at half maxi-
mum (fwhm) of the vibronic line.
3
3
Hb1), 7.18 (d, J ϭ 5.36 Hz, 2 H, H3), 7.39 (d, J ϭ 5.4 Hz, 2 H,
H2), 7.55 (d, 3J ϭ 8.52 Hz, 4 H, Ho), 7.59 (d, 3J ϭ 5.5 Hz, 2 H,
H8), 7.61 (m, 10 H, Har), 7.68 (d, J ϭ 5.52 Hz, 2 H, H3Ј,8Ј), 7.79
3
(d, J ϭ 8.52 Hz, 4 H, Hm), 7.99 (d, J ϭ 5.4 Hz, 2 H, H9), 8.24
3
3
Acknowledgments
Thanks are due to the EU for financial support (A. F. M., TMR
contract CT98-0226), and to Prof. T. J. Meyer and D. J. P. Claude
for kindly providing the software for the vibronic analysis. X. J. S.
(d, J ϭ 9.32 Hz, 2 H, H5), 8.28 (d, J ϭ 9.2 Hz, 2 H, H6), 8.29 (s,
2 H, H5Ј,6Ј), 8.57 (d, 3J ϭ 5.52 Hz, 2 H, H2Ј,9Ј) ppm. FAB MS:
m/z ϭ 1379.1 [M Ϫ PF6Ϫ]ϩ, 1234.2 [M Ϫ 2PF6Ϫ ϩ eϪ]ϩ, 617.6 [M
3
3
Ϫ 2PF6 ]
Ϫ 2ϩ/2.
´
R. thanks the Rectorat de l’Universite Louis Pasteur for financial
Optical Spectroscopy: Absorption spectra were recorded with a
PerkinϪElmer Lambda 9 spectrophotometer in dilute (10Ϫ5 )
acetonitrile solutions. Luminescence experiments were performed
in pump-freeze-thaw degassed acetonitrile at room temperature and
at 77 K (liquid nitrogen temperature, samples were in capillary
tubes immersed in a quartz finger Dewar).
support. D. P. thanks the French Ministry of education for a fellow-
ship.
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Received March 27, 2003
3758
 2003 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjic.org
Eur. J. Inorg. Chem. 2003, 3752Ϫ3758