Synthesis, structures, and photophysical properties of ruthenium(II) quinolinolato complexes

Article abstract of DOI:10.1021/om300621x

Reaction of [Ru^II(PR₃)₃Cl₂] with 2-methyl-8-quinolinolate (MeQ) in the presence of Et₃N in MeOH produced the neutral carbonyl hydrido complexes [Ru^II(MeQ)(PR ₃)₂(CO)(H

Full text of DOI:10.1021/om300621x

Article
pubs.acs.org/Organometallics
Synthesis, Structures, and Photophysical Properties of Ruthenium(II)
Quinolinolato Complexes
Jing Xiang,†,‡ Larry Tso-Lun Lo,† Chi-Fai Leung,† Shek-Man Yiu,† Chi-Chiu Ko,*,† and Tai-Chu Lau*,†
†Department of Biology and Chemistry, City University of Hong Kong, Tat Chee Avenue, Kowloon, Hong Kong, People's Republic
of China
‡College of Chemistry and Environmental Engineering, Yangtze University, Jingzhou 434020, HuBei, People's Republic of China
S
* Supporting Information
ABSTRACT: Reaction of [RuII(PR3)3Cl2] with 2-methyl-8-
quinolinolate (MeQ) in the presence of Et3N in MeOH
produced the neutral carbonyl hydrido complexes
[RuII(MeQ)(PR3)2(CO)(H)] (R = Ph (1), MeC6H4 (2),
MeOC6H4 (3)). An analogous reaction occurs between
[RuII(PPh3)3Cl2] and MeQH in ethanol to give [RuII(MeQ)-
(PPh3)2(CO)(CH3)] (4). The carbonyl, hydride, and methyl
ligands of these complexes are most likely derived from the
decarbonylation of ROH. Reaction of [RuII(PPh3)3(CO)(H)2]
with 5-substituted quinolinolato ligands (XQ, X = H, Cl, Ph)
produced the neutral complexes [RuII(XQ)(PPh3)2(CO)(H)] (XQ = Q (5), ClQ (6), PhQ (7)). Treatment of 1 and 5−7 with
+
excess KCN in MeOH following by metathesis with PPh4Cl afforded PPh4 salts of the anionic carbonyl dicyano complexes
[RuII(XQ)(CO)(CN)2(PPh3)]− (XQ = MeQ (8), Q (9) ClQ (10), PhQ (11)). Under similar conditions, reaction of 1 with
excess CyNC in the presence of NH4PF6 afforded [RuII(MeQ)(CyNC)2(CO)(PPh3)]+ (12). All complexes have been
1
characterized by IR, ESI/MS, H NMR and elemental analysis. The crystal structures of complexes 3, 4, 8, and 12 have been
determined by X-ray crystallography. The UV and emission spectra of these complexes have also been investigated. All complexes
exhibit short-lived quinolinolate-based LC fluorescence in solution at room temperature and dual emissions derived from LC
fluorescence and phosphorescence at 77 K glassy medium. These emissions are relatively insensitive to the nature of the ancillary
ligands but are readily tunable by varying the substituents on the quinolinolato ligand.
INTRODUCTION
EXPERIMENTAL SECTION
■
■
Physical Measurements and Instrumentation. IR spectra were
recorded as KBr pellets on a Nicolet Avatar 360 FT-IR spectrometer at
4 cm−1 resolution. UV−vis absorption spectra were recorded on either
a Perkin-Elmer Lambda 19 or a Shimadzu UV3100 spectropho-
The use of the aluminum 8-quinolinolato complex AlQ3 and its
derivatives in electroluminescent devices has attracted enor-
mous attention due to their excellent electron-transporting and
emissive properties.1 The structure−function relationship of
various AlQ3 complexes has been extensively studied,2 which
has led to the development of AlQ3 derivatives with tunable
HOMO−LUMO energy gaps and emission colors from blue to
red.2 A number of metal complexes bearing various
quinolinolato ligands have also been investigated.3 In contrast
to AlQ3 derivatives, which only exhibit singlet emission,
luminescence derived from both the singlet and triplet emissive
excited states have also been reported in some heavy-transition-
metal quinolinolato complexes.3a−g
We have been interested in the development of ruthenium-
(II) quinolinolato complexes with potential applications in
luminescent devices.3f A ruthenium(II) quinolinolato complex
bearing a bipyridyl ligand has recently been shown to be
potentially useful in dye-sensitized solar cell devices.4 We report
herein the synthesis, characterization, and photophysical
properties of a new class of ruthenium(II) quinolinolato
complexes bearing various ancilliary ligands.
1
tometer. H NMR spectra were recorded on a Varian (300 MHz)
NMR spectrometer or a Bruker (400 MHz) NMR spectrometer. The
chemical shifts (δ, ppm) were reported with reference to
tetramethylsilane (TMS). Electrospray ionization mass spectra (ESI-
MS) were obtained on a PE SCIEX API 365 mass spectrometer.
Elemental analyses were done on an Elementar Vario EL III analyzer.
Electronic absorption spectra were recorded on a Hewlett-Packard
8452A diode array spectrophotometer. Steady-state emission and
excitation spectra at room temperature and at 77 K were recorded on a
SPEX FluoroLog 3-TCSPC spectrofluorometer. Solutions were
rigorously degassed on a high-vacuum line in a two-compartment
cell with no less than four successive freeze−pump−thaw cycles. Time-
resolved emission measurements were carried out in the spectral mode
of a Edinburgh Instruments LP920-KS using the third harmonic
output (355 nm; 6−8 ns fwhm pulse width) of a Spectra-Physics
Quanta-Ray Q-switched LAB-150 pulsed Nd:YAG laser (10 Hz) as the
excitation source. Measurements of the EtOH/MeOH/CH2Cl2 (4/1/
1, v/v/v) glass samples at 77 K were carried out with dilute EtOH/
Received: July 5, 2012
Published: October 10, 2012
© 2012 American Chemical Society
7101
dx.doi.org/10.1021/om300621x | Organometallics 2012, 31, 7101−7108

Organometallics
Article
Table 1. Crystal Data and Structure Refinement Details for Complexes 3, 4, 8, and 12
3·2CH2Cl2
4
8·0.25CH2Cl2·H2O
12
formula
C53H51NO8P2Ru·2CH2Cl2
C48H41NO2P2Ru
826.83
C55.25H45.50Cl0.50N3O3P2Ru
C43H45N3O2PRuF6P
912.83
Mr
1162.81
133 (2)
monoclinic
P21/n
980.18
133 (2)
triclinic
T/K
173 (2)
133 (2)
monoclinic
P21/n
cryst syst
triclinic
space group
P1
̅
P1
̅
a/Å
12.4343(3)
28.1257(5)
15.6486(3)
90
9.2381(3)
12.5884(4)
17.4284(5)
82.761(2)
86.015(3)
74.412(3)
1935.36(10)
2
12.5278(5)
13.1009(5)
16.4148(5)
101.879(3)
92.797(3)
111.000(3)
2439.04(15)
2
12.4298(3)
24.7828(6)
13.3653(3)
90
b/Å
c/Å
α/deg
β/deg
101.690(2)
90
94.183(2)
90
γ/deg
V/Å3
5359.18(18)
4
4106.15(17)
4
Z
ρcalcd/g cm−3
1.441
1.419
1.335
1.477
F(000)
2392
852
1009
1872
no. of collected rflns
no. of unique rflns
R(int)
23 013
12 258
16 693
29 571
10 291
6737
8596
7306
0.025
0.027
0.018
0.026
final R indices, I > 2σ(I)
R1(obsd) = 0.048
wR2(all) = 0.139
1.11
R1(obsd) = 0.034
wR2(all) = 0.118
1.23
R1(obsd) = 0.036
wR2(all) = 0.108
1.08
R1(obsd) = 0.040
wR2(all) = 0.099
1.03
GOF
no. of params
733
489
589
578
MeOH/CH2Cl2 sample solutions contained in a quartz tube inside a
liquid nitrogen filled quartz optical Dewar flask. The emission lifetimes
were measured in the TCSPC mode with NanoLED-375LH (λex 375
nm; pulse width <750 ps) as the excitation source. Luminescence
quantum yields were determined using the optical dilution method
described by Demas and Crosby5 with an aqueous solution of
[Ru(bpy)3]Cl2 (ϕem = 0.0426 with 436 nm excitation) as reference.
X-ray Crystallography. Crystal structures were determined on an
Oxford Diffraction Gemini S Ultra X-ray single-crystal diffractometer
using graphite-monochromatized Cu Kα radiation (λ = 1.54178 Å).
Details of the crystal data and structure refinement are summarized in
Table 1. The structures were resolved by heavy-atom Patterson
methods or direct methods and refined by full-matrix least squares
using SHELX-977 and expanded using Fourier techniques.8 All non-
hydrogen atoms were refined anisotropically. H atoms were generated
by the program SHELXL-97.7 The positions of H atoms were
calculated on the basis of riding mode with thermal parameters equal
to 1.2 times that of the associated C atoms and participated in the
calculation of final R indices.
Synthesis and Characterization. Materials and Reagents. 8-
Hydroxyquinoline (QH), 2-methyl-8-hydroxyquinoline (MeQH), 5-
chloro-8-hydroxyquinoline (ClQH), and 5-phenyl-8-hydroxyquinoline
(PhQH) were purchased from Aldrich Chemical Co.
[RuII(PPh3)3Cl2],9 [RuII{P(C6H4Me)3}3Cl2],9c [RuII{P-
(C6 H4 OMe)3 }3 Cl2 ],9 c [RuI I (PPh3 )3 (CO)(H)2 ],1 0 and
[RuII(PPh3)3(CO)(H)(Cl)]11 were synthesized according to literature
procedures. Other chemicals were of reagent grade and were used
without further purification.
H 4.84; N, 1.72. Found: C, 69.10; H, 4.72; N, 1.77. UV/vis (CH2Cl2):
λmax (nm) (ε (mol−1 dm3 cm−1)): 265 sh (24 350), 354 (6930), 421
(3710).
[RuII(MeQ)(H)(CO){P(C6H4Me)3}2] (2). The complex was synthesized
according to a procedure similar to that for 1, except [Ru{P-
(C6H4Me)3}3Cl2] was used instead of [Ru(PPh3)3Cl2]. Yield: 268 mg,
59%. IR (KBr, cm−1): ν(CO) 1907, ν(Ru−H) 1944. ESI-MS: m/z
1
896 [M − H]+, 739 [M − MeQ]+. H NMR (400 MHz, CDCl3): δ
7.35−7.40 (dt, J = 8.0, 4.9 Hz, 12H, Ar H), 6.90 (d, J = 6.8 Hz, 12H,
Ar H), 6.76 (t, J = 7.8 Hz, 1H, Ar H), 6.54 (d, J = 8.4 Hz, 1H, Ar H),
6.22 (d, J = 7.8 Hz, 1H, Ar H), 6.15 (d, J = 8.2 Hz, 1H, Ar H), 5.30 (s,
1H, Ar H), 2.23 (s, 18H, PC6H4−CH3), 2.04 (s, 3H, Ar−CH3),
−10.69 (t, J = 20.2 Hz, 1H, Ru−H). 31P{1H} NMR (162 MHz,
CDCl3): δ 41.9 (s, P(C6H4Me)3). Anal. Calcd for C53H51NO2P2Ru: C,
70.97; H, 5.73; N, 1.56. Found: C, 70.78; H, 5.82; N, 1.60. UV/vis
(CH2Cl2): λmax (nm) (ε (mol−1 dm3 cm−1)): 271 sh (27 990), 352
(6440), 425 (3630).
[RuII(MeQ)(H)(CO){P(C6H4OMe)3}2] (3). The complex was synthe-
sized according to a procedure similar to that for 1, except
[Ru{P(C6H4OMe)3}3Cl2] was used instead of [RuII(PPh3)3Cl2].
Yield: 275 mg, 55%. IR (KBr, cm−1): ν(CO) 1902, ν(Ru−H)
1964. ESI-MS: m/z 992 [M − H]+, 835 [M − MeQ]+. 1H NMR (400
MHz, CD2Cl2): δ 7.51 (d, J = 8.4 Hz, 1H, Ar H), 7.36−7.42 (m, 12H,
Ar H), 6.80 (t, J = 7.8 Hz, 1H, Ar H), 6.65−6.71 (m, 13H, Ar H), 6.25
(d, J = 7.7 Hz, 1H, Ar H), 6.18 (d, J = 7.1 Hz, 1H, Ar H), 3.74 (s, 18H,
CH3O−), 2.07 (s, 3H, −CH3), −10.75 (t, J = 20.4 Hz, 1H, Ru−H).
31P{1H} NMR (162 MHz, CDCl3): δ 39.3 (s, P(C6H4OMe)3). Anal.
Calcd for C53H51NO8P2Ru: C, 64.11; H, 5.18; N, 1.41. Found: C,
64.20; H, 5.22; N, 1.37. UV/vis (CH2Cl2): λmax (nm) (ε (mol−1 dm3
cm−1)): 272 sh (30 750), 341 (6370), 424 (3010).
[RuII(MeQ)(H)(CO)(PPh3)2] (1). MeQH (79 mg, 0.5 mmol) in
MeOH (20 mL) was slowly added to a suspension of [Ru(PPh3)3Cl2]
(500 mg, 0.5 mmol) in MeOH (150 mL) containing Et3N (0.5 mL).
The resulting mixture was refluxed for 5 h under argon, and the pale
yellow precipitate was collected and air-dried. It was recrystallized by
slow evaporation of a CH2Cl2/MeOH (1/3, v/v) solution of the
complex. Yield: 300 mg, 73%. IR (KBr, cm−1): ν(CO) 1904, ν(Ru−
[RuII(MeQ)(Me)(CO)(PPh3)2] (4). The synthesis is similar to that for
1, except EtOH (150 mL) was used as solvent instead of MeOH.
Yield: 279 mg, 67%. IR (KBr, cm−1): ν(CO) 1894. ESI-MS: m/z
812 [M − CH3]+, 669 [M − MeQ]+. 1H NMR (400 MHz, CD2Cl2): δ
7.53 (d, J = 8.6 Hz, 1H, Ar H), 7.28−7.30 (m, 19H, Ar H), 7.15−7.20
(m, 12H, Ar H), 6.92 (t, J = 7.8 Hz, 1H, Ar H), 6.68 (d, J = 8.4 Hz,
1H, Ar H), 6.48 (d, J = 7.1 Hz, 1H, Ar H), 6.35 (d, J = 8.4 Hz, 1H, Ar
H), 1.80 (s, 3H, Ar−CH3), 0.52 (t, J = 6.5 Hz, 3H, Ru-CH3). 31P{1H}
NMR (162 MHz, CDCl3): δ 34.0 (s, PPh3). Anal. Calcd for
C48H41NO2P2Ru: C, 69.72; H, 5.00; N, 1.69. Found: C, 69.66; H,
1
H) 1950. ESI-MS: m/z 812 [M − H]+, 655 [M − MeQ]+. H NMR
(400 MHz, CDCl3): δ 7.46−7.51 (m, 14H, Ar H), 7.12−7.23 (m,
18H, Ar H), 6.79 (t, J = 7.8 Hz, 1H, Ar H), 6.58 (d, J = 7.8 Hz, 1H, Ar
H), 6.31 (s, 1H, Ar H), 6.19 (s, 1H, Ar H), 1.97 (s, 3H; −CH3),
−10.62 (t, J = 20.0 Hz, 1H, Ru−H). 31P{1H} NMR (162 MHz,
CDCl3): δ 44.1 (s, PPh3). Anal. Calcd for C47H39NO2P2Ru: C, 69.45;
7102
dx.doi.org/10.1021/om300621x | Organometallics 2012, 31, 7101−7108

Organometallics
Article
5.12; N, 1.72. UV/vis (CH2Cl2): λmax (nm) (ε (mol−1 dm3 cm−1)):
249 sh (39 610), 356 (5810), 426 (3390).
C, 68.71; H, 4.67; N, 4.31. UV/vis (CH2Cl2): λmax (nm) (ε (mol−1
dm3 cm−1)): 262 (17 160), 269 (17 790), 275 sh (15 510), 331 sh
(3370), 347 sh (2891), 428 (3500).
[RuII(Q)(H)(CO)(PPh3)2] (5). 8-Hydroxyquinoline (HQ) (61 mg,
0.42 mmol) was added to a suspension of [Ru(PPh3)3(CO)(H)2]
(200 mg, 0.21 mmol) in MeOH (150 mL). The mixture was refluxed
for 1 day under argon, and the resulting yellow microcrystalline solid
was collected and washed with ice-cold methanol (3 × 4 mL). Yield:
120 mg, 71%. IR (KBr, cm−1): ν(CO) 1904, ν(Ru−H) 1955. ESI-
MS: m/z 798 [M − H]+, 655 [M − Q]+. 1H NMR (300 MHz,
CDCl3): δ 7.73 (d, J = 4.9 Hz, 1H, Ar H), 7.43−7.51 (m, 13H, Ar H),
7.10−7.21 (m, 18H, Ar H), 6.91 (t, J = 7.9 Hz, 1H, Ar H), 6.50 (dd, J
= 8.3, 4.7 Hz, 1H, Ar H), 6.27−6.31 (m, 2H, Ar H), −9.88 (t, J = 19.9
Hz, 1H, Ru−H). 31P{1H} NMR (162 MHz, CDCl3): δ 44.5 (s, PPh3).
Anal. Calcd for C46H37NO2P2Ru: C, 69.16; H, 4.67; N, 1.75. Found:
C, 69.20; H, 4.80; N, 1.77. UV/vis (CH2Cl2): λmax (nm) (ε (mol−1
dm3 cm−1)): 268 sh (23 790), 353 (7660), 424 (4440).
(PPh4)[RuII(ClQ)(CN)2(CO)(Ph3P)] (10). This complex was prepared
according to a procedure similar to that for 8, except 6 was used
instead of 1. Yield: 75 mg, 31%. IR (KBr, cm−1): ν(CN) 2097,
1
ν(CO) 1940. ESI-MS (negative): m/z 602 [M]−. H NMR (400
MHz, CD3OD): δ 8.91 (t, J = 3.4 Hz, 1H, Ar H), 8.47 (dd, J = 8.6, 1.3
Hz, 1H, Ar H), 7.94 (ddd, J = 7.4, 5.6, 1.9 Hz, 4H, Ar H), 7.71−7.84
(m, 23 H, Ar H), 7.54 (dd, J = 8.3, 4.6 Hz, 1H, Ar H), 7.38−7.43 (m,
9H, Ar H), 6.82 (d, J = 8.6 Hz, 1H, Ar H). 31P{1H} NMR (162 MHz,
+
CDCl3): δ 50.9 (s, PPh3), 22.8 (s, PPh4 ). Anal. Calcd for
C54H40ClN3O2P2Ru·H2O: C, 66.22; H, 4.32; N, 4.29. Found: C,
66.45; H, 4.47; N, 4.17. UV/vis (CH2Cl2): λmax (nm) (ε (mol−1 dm3
cm−1)): 262 (25 300), 268 (24 800), 275 sh (21 150), 341 (6400), 355
(6000), 438 (4370).
(PPh4)[RuII(PhQ)(CN)2(CO)(Ph3P)] (11). This complex was prepared
according to a procedure similar to that for 8, except 7 was used
instead of 1. ESI-MS (negative): m/z 664 [M]−. Yield: 89 mg, 35%. IR
[RuII(ClQ)(H)(CO)(PPh3)2] (6). Complex 6 was prepared by a
procedure similar to that for 5, except ClQH was used instead of
QH. Yield: 135 mg, 77%. IR (KBr, cm−1): ν(CO) 1918, ν(Ru−H)
1
(KBr, cm−1): ν(CN) 2098, ν(CO) 1942. H NMR (400 MHz,
1
1945. ESI-MS: m/z 832 [M − H]+, 655 [M − ClQ]+. H NMR (300
CD3OD): 8.89 (t, J = 3.5 Hz, 1H, Ar H), 8.27 (d, J = 9.0 Hz, 1H, Ar
H), 7.95 (t, J = 7.3 Hz, 4H, Ar H), 7.72−7.88 (m, 23H, Ar H), 7.40−
7.47 (m, 13H, Ar H), 7.35 (d, J = 8.4 Hz, 2H, Ar H), 6.98 (d, J = 8.2
Hz, 1H, Ar H). 31P{1H} NMR (162 MHz, CDCl3): δ 51.0 (s, PPh3),
MHz, CDCl3): δ 7.77 (d, J = 7.7 Hz, 2H, Ar H), 7.47−7.54 (m, 10H,
Ar H), 7.11−7.28 (m, 20H, Ar H), 6.93 (d, J = 8.6 Hz, 1H, Ar H), 6.65
(m, 1H, Ar H), 6.19 (d, J = 8.6 Hz, 1H, Ar H), −10.75 (t, J = 20.3 Hz,
1H, Ru−H). 31P{1H} NMR (162 MHz, CDCl3): δ 44.3 (s, PPh3).
Anal. Calcd for C46H36ClNO2P2Ru: C, 66.31; H, 4.35; N, 1.68. Found:
C, 66.23; H, 4.10; N, 1.56. UV/vis (CH2Cl2): λmax (nm) (ε (mol−1
dm3 cm−1)): 263 sh (22 270), 351 (5900), 441 (4190).
+
22.8 (s, PPh4 ). Anal. Calcd for C60H45N3O2P2Ru·H2O: C, 70.58; H,
4.64; N, 4.12. Found: C, 70.37; H, 4.72; N, 4.08. UV/vis (CH2Cl2):
λmax (nm) (ε (mol−1 dm3 cm−1)): 262 (28 870), 269 (29 230), 276
(26 900), 298 sh (13930), 352 (6021), 433 (4790).
[RuII(PhQ)(H)(CO)(PPh3)2] (7). Complex 7 was prepared by a
procedure similar to that for 5, except PhQH was used instead of QH.
Yield: 110 mg, 59%. IR (KBr, cm−1): ν(CO) 1914, ν(Ru−H) 1942.
ESI-MS: m/z 874 [M − H]+, 655 [M − PhQ]+. 1H NMR (300 MHz,
CDCl3): δ 7.85 (d, J = 4.6 Hz, 1H, Ar H), 7.65 (d, J = 8.2 Hz, 1H, Ar
H), 7.52−7.58 (m, 12H, Ar H), 7.40 (t, J = 7.3 Hz, 3H, Ar H), 7.29 (d,
J = 7.5 Hz, 1H, Ar H), 7.25 (d, J = 1.5 Hz, 1H, Ar H), 7.14−7.21 (m,
18H, Ar H), 6.90 (d, J = 8.2 Hz, 1H, Ar H), 6.51 (dd, J = 8.6, 4.6 Hz,
1H, Ar H), 6.35 (d, J = 8.2 Hz, 1H, Ar H), −9.80 (t, J = 19.6 Hz, 1H,
Ru−H). 31P{1H} NMR (162 MHz, CDCl3): δ 44.3 (s, PPh3). Anal.
Calcd for C52H41NO2P2Ru: C, 71.39; H, 4.72; N, 1.60. Found: C,
71.22; H, 4.69; N, 1.61. UV/vis (CH2Cl2): λmax (nm) (ε (mol−1 dm3
cm−1)): 265 sh (22 280), 303 sh (12 790), 358 (7280), 440 (5820).
(PPh4)[RuII(MeQ)(CN)2(CO)(PPh3)] (8). KCN (163 mg, 2.5 mmol)
was added to a suspension of 1 (200 mg, 0.25 mmol) in MeOH (100
mL), and the mixture was refluxed for 1 day under argon to give a light
yellow solution. After filtration, the solvent was removed by rotary
evaporation. The residue was redissolved in H2O (50 mL), and
PPh4Cl (100 mg) was added to give a light yellow precipitate, which
was purified by column chromatography on silica gel using acetone/
CH2Cl2 (1/4, v/v) as eluent. Recrystallization by slow diffusion of
diethyl ether into a CH2Cl2 solution of 8 afforded light yellow single
crystals suitable for X-ray diffraction analysis. Yield: 81 mg, 34%. IR
(KBr, cm−1): ν(CN) 2096, ν(CO) 1937. ESI-MS (negative): m/
[RuII(MeQ)(CyNC)2(CO)(PPh3)]PF6 (12). A mixture of 1 (200 mg,
0.25 mmol), CyNC (272 mg, 2.5 mmol, 10 mol equiv), and NH4PF6
(407 mg, 2.5 mmol) in MeOH (40 mL) was refluxed for 1 day. The
volume of the solution was then reduced to 2 mL, and diethyl ether (5
mL) was added to give a brown precipitate, which was collected and
recrystallized from CH2Cl2/diethyl ether. Yield: 72 mg, 30%. IR (KBr,
cm−1): ν(CN) 2201, ν(CO) 1988, ν(P−F) 840. ESI-MS
(positive): m/z 768 (M+). 1H NMR (400 MHz, CD2Cl2): δ 8.19
(d, J = 8.4 Hz, 1H, Ar H), 7.76−7.82 (m, 6H, Ar H), 7.52−7.61 (m,
9H, Ar H), 7.38−7.43 (m, 2H, Ar H), 7.04 (d, J = 7.8 Hz, 1H, Ar H),
7.00 (d, J = 7.6 Hz, 1H, Ar H), 2.98 (s, 3H, Ar CH3), 1.38−1.44 (m,
4H, C−H), 1.04−1.20 (m, 16H, C−H), 0.81−0.93 (m, 2H, C−H).
31P{1H} NMR (162 MHz, CDCl3): δ 39.8 (s, PPh3), −144.4 (septet,
−
PF6 ). Anal. Calcd for C43H45F6N3O2P2Ru: C, 56.58; H, 4.97; N, 4.60.
Found: C, 56.61; H, 5.04; N, 4.55. UV/vis (CH2Cl2): λmax (nm) (ε
(mol−1 dm3 cm−1)): 272 (24 540), 412 (3010).
RESULTS AND DISCUSSION
■
Synthesis and Characterization. The reaction of
[RuII(PR3)3Cl2] with MeQ in the presence of Et3N in
MeOH produced the neutral carbonyl hydrido complex
[RuII(MeQ)(PR3)2(CO)(H)] (R = Ph (1), MeC6H4 (2),
MeOC6H4 (3); Scheme 1a). The carbonyl and hydrido ligands
of these complexes are most likely derived from the
decarbonylation of methanol. Similar decarbonylation reactions
have been reported: for example, the formation of
[RuII(PPh3)3(CO)(Cl)(H)] from the reaction between
[RuII(PPh3)3(Cl)2] and MeOH in the presence of base.12 An
analogous reaction occurs between [RuII(PPh3)3Cl2] and
MeQH in ethanol to give [RuII(MeQ)(PPh3)2(CO)(CH3)]
(4). This reaction is similar to the formation of [TpRuII(CH3)-
(CO)(PPh3)] from the reaction of [(Tp)RuIICl(PPh3)-
(CH3CN)] (Tp = hydrotris(pyrazolyl)borate) with NaBH4 in
EtOH.13 On the other hand, when the reaction of
[RuII(PR3)3Cl2] with MeQ was carried out in PhCH2OH,
[RuII(MeQ)(PPh3)2(CO)(H)] (1) was formed exclusively,
rather than [RuII(MeQ)(PPh3)2(CO)(Ph)].
1
z 602 [M]−. H NMR (400 MHz, CD2Cl2): δ 7.85−7.92 (m, 9H, Ar
H), 7.72−7.77 (m, 9H, Ar H), 7.57−7.63 (m, 9H, Ar H), 7.40−7.43
(m, 9H, Ar H), 7.21 (t, J = 7.9 Hz, 2H, Ar H), 6.74 (d, J = 6.8 Hz, 1H,
Ar H), 6.69 (d, J = 8.0 Hz, 1H; Ar H), 3.04 (s, 3H; Ar−CH3). 31P{1H}
+
NMR (162 MHz, CDCl3): δ 50.7 (s, PPh3), 22.8 (s, PPh4 ). Anal.
Calcd for C55H43N3O2P2Ru·H2O: C, 68.88; H, 4.73; N, 4.38. Found:
C, 68.67; H, 4.82; N, 4.17. UV/vis (CH2Cl2): λmax (nm) (ε (mol−1
dm3 cm−1)): 269 (23 250), 276 (23 890), 330 (7010), 346 sh (2600),
410 (5564).
(PPh4)[RuII(Q)(CN)2(CO)(Ph3P)] (9). The complex was synthesized
according to a procedure similar to that for 8, except 5 (200 mg, 0.25
mmol) was used instead of 1. Yield: 70 mg, 30%. ESI-MS (negative):
1
m/z 588 [M]−. IR (KBr, cm−1): ν(CN) 2096, ν(CO) 1940. H
NMR (400 MHz, CD3OD): 8.84 (t, J = 3.5 Hz, 1H, Ar H), 8.19 (d, J =
8.5 Hz, 1 Hz, Ar H), 7.94 (t, J = 7.3 Hz, 4H, Ar H), 7.21−7.84 (m,
23H, Ar H), 7.39−7.42 (m, 8 H, Ar H), 7.38 (d, J = 4.5 Hz, 1H, Ar H),
7.34 (d, J = 7.9 Hz, 1H, Ar H), 6.89−6.95 (m, 2H, Ar H). 31P{1H}
+
Attempts to synthesize carbonyl hydrido complexes contain-
ing other substituted quinolinolato ligands (XQ) such as Q,
NMR (162 MHz, CDCl3): δ 51.0 (s, PPh3), 22.9 (s, PPh4 ). Anal.
Calcd for C54H41N3O2P2Ru·H2O: C, 68.64; H, 4.59; N, 4.45. Found:
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the methyl substituent in MeQ, which hinders the formation of
the bis(quinolinolato) complex. We then attempted to prepare
carbonyl hydrido complexes containing these quinolinolato
ligands (Q, ClQ, and PhQ) by using [RuII(PPh3)3(CO)(H)-
(Cl)] as the starting material. However, mixtures of [RuII(XQ)-
(PPh3)2(CO)(H)] and [RuII(XQ)(PPh3)2(CO)(Cl)] were
produced, which were difficult to separate, as they have very
similar solubility and polarity. On the other hand, when the
dihydrido complex [RuII(PPh3)3(CO)(H)2] was used as the
starting material, [RuII(XQ)(PPh3)2(CO)(H)] (XQ = Q (5),
ClQ (6), PhQ (7)) (Scheme 1b) could be isolated in moderate
yields. Similar to the case for 1−3, these complexes are
diamagnetic and air-stable in the solid state but slowly
decompose in solution. The two substituted triphenylphos-
phine ligands in 1−7 are trans to each other, which is consistent
with the observation of a single resonance in the 31P{1H} NMR
and is confirmed by the X-ray crystal structures of 3 and 4 (see
below). This ligand arrangement is thermodynamically
favorable, as the steric repulsions between the two bulky
ligands can be minimized.14 Facile cis to trans isomerizations of
ruthenium(II) complexes with two monodentate bulky
phosphine ligands have also been commonly reported.14b,c
Treatment of 1 and 5−7 with excess KCN in MeOH
followed by metathesis with PPh4Cl afforded PPh4+ salts of the
anionic carbonyl dicyano complexes [RuII(XQ)(CO)-
(CN)2(PPh3)]− (XQ = MeQ (8), Q (9), ClQ (10), PhQ
(11)) (Scheme 1c). Similarly, the hydrido ligand and one of the
phosphine ligands can also be substituted by an isocyanide
ligand such as CyNC, resulting in the formation of
[RuII(MeQ)(CyNC)2(CO)(PPh3)]+ (12) (Scheme 1d), iso-
Scheme 1. Synthetic Routes for Various Ruthenium(II)
Complexes
ClQ, and PhQ using the same strategy as for the MeQ
complexes were unsuccessful; instead, [RuII(XQ)2(PPh3)2]
(XQ = Q, ClQ, PhQ) was formed as the major product. This
difference in reactivity may be attributed to the steric effect of
−
lated as the PF6 salt. Complexes 8−12 are stable in the solid
state and in solution and are very soluble in common organic
solvents.
Figure 1. Perspective drawings of (a) 3, (b) 4, (c) the anion of 8, and (d) the cation of 12. Thermal ellipsoids are drawn at 50% probability.
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Table 2. Selected Bond Distances (Å) and Angles (deg) with Estimated Standard Deviations (Esd's) in Parentheses for 3, 4, 8,
and 12
Complex 3
Ru(1)−P(1)
Ru(1)−P(2)
Ru(1)−O(2)
N(1)−Ru(1)−P(1)
N(1)−Ru(1)−P(2)
N(1)−Ru(1)−H(1)
C(1)−Ru(1)−P(1)
2.351(10)
2.344(10)
2.114(3)
94.00(9)
91.03(9)
168(2)
Ru(1)−N(1)
Ru(1)−C(1)
Ru(1)−H(1)
C(1)−Ru(1)−P(2)
C(1)−Ru(1)−O(2)
C(1)−Ru(1)−N(1)
C(1)−Ru(1)−H(1)
2.207(3)
1.827(4)
1.50(6)
88.34(13)
176.77(15)
105.26(16)
95.38(13)
86(2)
Complex 4
Complex 8
Complex 12
Ru(1)−C(2)
Ru(1)−O(1)
Ru(1)−C(1)
1.829(3)
2.090(18)
2.156(3)
178.49(10)
94.56(11)
84.07(9)
103.47(10)
77.91(8)
161.97(9)
88.34(8)
91.00(5)
Ru(1)−N(1)
Ru(1)−P(1)
Ru(1)−P(2)
C(1)−Ru(1)−P(1)
N(1)−Ru(1)−P(1)
C(2)−Ru(1)−P(2)
O(1)−Ru(1)−P(2)
C(1)−Ru(1)−P(2)
N(1)−Ru(1)−P(2)
P(1)−Ru(1)−P(2)
2.213(2)
2.371(7)
2.382(7)
89.22(7)
91.56(5)
89.45(8)
91.18(5)
89.65(7)
90.23(5)
177.43(2)
C(2)−Ru(1)−O(1)
C(2)−Ru(1)−C(1)
O(1)−Ru(1)−C(1)
C(2)−Ru(1)−N(1)
O(1)−Ru(1)−N(1)
C(1)−Ru(1)−N(1)
C(2)−Ru(1)−P(1)
O(1)−Ru(1)−P(1)
Ru(1)−P(1)
Ru(1)−O(2)
Ru(1)−N(1)
2.313(7)
2.108(2)
2.176(2)
177.2(3)
91.18(6)
78.14(8)
169.24(7)
87.19(9)
178.36(10)
103.49(11)
91.15(13)
Ru(1)−C(1)
Ru(1)−C(2)
Ru(1)−C(3)
C(1)−Ru(1)−C(3)
C(2)−Ru(1)−P(1)
C(2)−Ru(1)−O(2)
C(2)−Ru(1)−N(1)
C(3)−Ru(1)−P(1)
C(3)−Ru(1)−O(2)
C(3)−Ru(1)−N(1)
1.833(3)
2.054(3)
2.063(3)
88.53(13)
90.08(8)
88.74(10)
88.46(10)
96.20(9)
91.77(11)
85.48(11)
O(1)−C(1)−Ru(1)
O(2)−Ru(1)−P(1)
O(2)−Ru(1)−N(1)
N(1)−Ru(1)−P(1)
C(1)−Ru(1)−P(1)
C(1)−Ru(1)−O(2)
C(1)−Ru(1)−N(1)
C(1)−Ru(1)−C(2)
Ru(1)−P(1)
Ru(1)−O(2)
Ru(1)−N(1)
2.343(8)
2.090(2)
2.169(3)
175.3(3)
93.31(6)
79.02(9)
172.29(7)
172.9(3)
172.3(3)
86.36(10)
176.41(12)
Ru(1)−C(1)
Ru(1)−C(2)
Ru(1)−C(3)
1.877(3)
2.012(3)
2.017(3)
96.36(13)
90.85(14)
90.60(9)
87.22(11)
88.29(11)
170.75(12)
95.64(9)
85.62(11)
O(1)−C(1)−Ru(1)
O(2)−Ru(1)−P(1)
O(2)−Ru(1)−N(1)
N(1)−Ru(1)−P(1)
N(2)−C(2)−Ru(1)
N3−C(3)−Ru(1)
C(1)−Ru(1)−P(1)
C(1)−Ru(1)−O(2)
C(1)−Ru(1)−C(2)
C(1)−Ru(1)−C(3)
C(2)−Ru(1)−P(1)
C(2)−Ru(1)−O(2)
C(2)−Ru(1)−N(1)
C(2)−Ru(1)−C(3)
C(3)−Ru(1)−P(1)
C(3)−Ru(1)−O(2)
All complexes have been characterized by 1H NMR, 31P{1H}
NMR, IR, ESI-MS, and elemental analysis (see Figures S1−S9
in the Supporting Information). The structures of 3, 4, 8, and
12 have also been determined by X-ray crystallography. All
The IR spectra of all carbonyl hydrido complexes (1−3 and
5−7) show one weak and one strong absorption in the region
of 1900−1960 cm−1, corresponding to ν(Ru−H) and ν(CO)
stretches, respectively. These ν(CO) and ν(Ru−H)
stretching frequencies are comparable with those in [RuII(CO)-
(H)2(PPh3)3]10 and are in the range reported for other related
Ru(II) carbonyl hydrido complexes.15 The cyano complexes
(8−11) also show a strong ν(CN) stretch at ca. 2100 cm−1,
while the isocyano complex (12) shows a strong ν(CN)
stretch at 2200 cm−1.
X-ray Crystal Structures. The structures of 3, 4, 8, and 12
have been determined by X-ray crystallography (Figure 1).
Selected bond distances and angles of these complexes are
summarized in Table 2. The ruthenium centers in these
compounds adopt a distorted-octahedral geometry. All carbonyl
1
complexes show H NMR signals with chemical shifts and
integral ratios consistent with their chemical formulations. For
the hydrido complexes (1−3 and 5−7), an upfield triplet signal
at ca. −10.7 ppm, typical of metal hydride complexes, with
coupling constants in the range of 19.6−20.4 Hz and an
integral ratio of one proton were observed. The observation of
the triplet splitting is the result of the coupling of the hydride
with the two chemically equivalent cis-triphenylphosphine
ligands. These coupling constants are also in the range found
in related ruthenium(II) phosphine hydride complexes.10
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Table 3. Photophysical Data for Complexes 1−12
a
b
c
medium (T/K)
emission λem/nm
ϕem
absorption λabs/nm (ε/dm3 mol−1 cm−1
)
1
CH2Cl2 (298)
500
0.0291
0.0270
0.0287
0.0036
0.0227
0.0278
0.0573
0.0322
0.0274
0.0247
0.00324
0.0006
265 sh (24 350), 354 (6930), 421 (3710)
d
glass (77)
456, 580, 629
500
2
CH2Cl2 (298)
271 sh (27 990), 352 (6440), 425 (3630)
272 sh (30 750), 341 (6370), 424 (3010)
249 sh (39 610), 356 (5810), 426 (3390)
268 sh (23 790), 353 (7660), 424 (4440)
263 sh (22 270), 351 (5900), 441 (4190)
265 sh (22 280), 303 sh (12 790), 358 (7280), 440 (5820)
d
glass (77)
455, 578, 628
501
3
CH2Cl2 (298)
d
glass (77)
456, 582, 630
500
4
CH2Cl2 (298)
d
glass (77)
463, 587, 633
504
5
CH2Cl2 (298)
d
glass (77)
448, 578, 625
518
6
CH2Cl2 (298)
d
glass (77)
472, 603, 653
519
7
CH2Cl2 (298)
d
glass (77)
464, 602, 654
512
8
CH2Cl2 (298)
269 (23 250), 276 (23 890), 330 (7010), 346 sh (2600), 410 (5560)
d
glass (77)
456, 524, 576
516
9
CH2Cl2 (298)
262 (17 160), 269 (17 790), 275 sh (15 510), 331 sh (3370), 347 sh (2890), 428 (3500)
262 (25 300), 268 (24 800), 275 sh (21 150), 341 (6400), 355 (6000), 438 (4370)
262 (28 870), 269 (29 230), 276 (26 900), 298 sh (13 930), 352 (6020), 433 (4790)
272 (24 540), 412 (3010)
d
glass (77)
454, 582, 625
528
10
11
12
CH2Cl2 (298)
d
glass (77)
476, 564, 667
529
CH2Cl2 (298)
d
glass (77)
474, 607
501
CH2Cl2 (298)
d
glass (77)
463, 580
a
b
c
Excitation at 400 nm. Emission maxima are uncorrected values. Luminescence quantum yield with excitation at 436 nm. In dichloromethane at
d
298 K. EtOH/MeOH/CH2Cl2 (4/1/1, v/v/v).
ligands in these complexes are trans to the oxygen atom of the
quinolinonato ligand with Ru−C(CO) bond distances in the
range of 1.827−1.877 Å, which are typically observed in other
Ru(II) carbonyl complexes.15 In 3 and 4, the two
triphenylphosphine ligands are trans to each other, while the
hydrido ligand in 3 and the methyl ligand in 4 are trans to the
nitrogen atom of the quinolinolato ligand with Ru−H and Ru−
CH3 bond distances of 1.49 and 2.15 Å, respectively, which are
comparable with those of related ruthenium complexes.16 The
longer Ru−N(quinolinolato ligand) bond lengths in 3 (2.205
Å) and 4 (2.213 Å) in comparison to those in cis,trans,cis-
[RuII(Q)2(PPh3)2] (2.10 Å),17 rac-[RuII(bpy)2(Q)]PF6 (2.05
Å),18 8 (2.176 Å), and 12 (2.169 Å) are presumably due to the
strong trans influence of the hydrido and methyl ligands. The
X-ray crystal structures of 8 and 12 indicate that isomerization
of PPh3 from the cis to the trans position relative to the
quinolinolato ligand has occurred during a ligand substitution
reaction by CN− or CNR. These ligand rearrangements may
arise from the release of steric strain of the bulky PPh3 ligand.
The slight deviation of the CN−C bond angle (175.3°) of
isocyanide ligands from the linearity in 12 is attributed to the π-
back-bonding with Ru(II), as commonly observed in metal
isocyanide complexes.19
UV−Vis Absorption and Emission Spectroscopy. The
electronic absorption spectra of 1−12 show intense ligand-
centered π−π* transitions in the UV region (λ ≤ 300 nm), with
molar absorption coefficients on the order of 104 mol−1 dm3
cm−1 (Table 3). In addition to these intense absorptions, all
complexes also display two moderately intense absorption
shoulders or bands at 330−358 and 410−440 nm, with molar
absorption coefficients on the order of 103 mol−1 dm3 cm−1
(Table 3, Figure 2). These absorptions show an energy
dependence on the electronic nature of the quinolinolato ligand
Figure 2. UV/vis absorption spectra of 1, 5, 6, and 7 in CH2Cl2 at 298
K.
but are almost insensitive to the electronic nature of other
ancillary ligands. Moreover, these absorptions are similar to the
π−π* transitions of quinolinlato ligands in related metal
complexes such as [OsII(CO)3(RQ)(L)] (RQ = Q, MeQ; L =
Cl, I, CF3CO2),3e AlQ3,3a and IrQ3.3a On the basis of previous
spectroscopic studies and the absorption energy trends in these
complexes, these absorptions are tentatively assigned to the
metal-perturbed π−π* transitions of the quinolinolato ligands.
Homoleptic transition-metal quinolinolato complexes such as
RhQ3, PdQ2, IrQ3, and PtQ2 show red emission arising from
ligand-centered (LC) phosphorescence,3a,b,d while the complex
[Os(CO)3(RQ)(L)] shows dual emission bands derived from a
mixture of LC fluorescence and phosphorescence.3e In contrast,
compounds 1−12 display only green photoluminescence with
emission maxima in the range of 500−530 nm (Table 3). These
emissions are relatively insensitive to the nature of the
phosphine and other ancillary ligands, as reflected by the
similar emission energies of compounds 1−3, 8, and 12. On the
other hand, the emission energies of these compounds are
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more sensitive to the nature of the substituent on the
quinolinolato ligand, as illustrated by the following emission
trend of 1 (500 nm for MeQ) < 5 (504 nm for Q) < 6 (518 nm
for ClQ) ≤ 7 (519 nm for PhQ) (Figure 3). Such emission
nature of the ancillary ligands but are readily tunable through
changing the substituents on the quinolinolato ligand.
ASSOCIATED CONTENT
■
S
* Supporting Information
CIF files giving crystallographic data for 3, 4, 8, and 12 and
figures giving 1H NMR and mass spectra of selected complexes
and excitation and emission spectra of 5. This material is
available free of charge via the Internet at http://pubs.acs.org.
AUTHOR INFORMATION
■
Corresponding Author
*E-mail: bhtclau@cityu.edu.hk (T.-C.L.); vinccko@cityu.edu.
hk (C.-C.K.).
Notes
The authors declare no competing financial interest.
ACKNOWLEDGMENTS
Figure 3. Overlaid emission spectra of selected complexes (1, 5, 6, and
7) in (a) CH2Cl2 at 298 K and (b) EtOH/MeOH/CH2Cl2 (4/1/1, v/
v/v) glassy medium at 77 K.
■
The work described in this paper was supported by the Hong
Kong University Grants Committee Area of Excellence Scheme
(AoE/P-03/08) and a GRF grant (CityU 101408). The flash
photolysis system was supported by a Special Equipment Grant
from the University Grants Committee of the Hong Kong
(SEG_CityU02).
energy dependence and the close resemblance of these
emissions to the fluorescence of other quinolinolato metal
complexes3a−3e strongly suggest that they arise from
quinolinolato ligand-centered (LC) fluorescence. The short-
lived emission lifetimes of < 3 ns are consistent with the
fluorescence assignment. To eliminate the possible mixing of
the LC phosphorescence in the tail of the green emission, time-
resolved emission spectroscopy has also been performed.
However, no additional emission band was identified at various
times (>1 ns) after the laser excitation. The absence of red LC
phosphorescence in these complexes may be attributed to
inefficient intersystem crossing from the singlet to the triplet
state or very efficient nonradiative decay from the triplet state.
The dependence of the intersystem crossing efficiency on the
substituent of the quinolinolato and other ancillary ligands has
also been reported in a series of osmium quinolinolato
complexes [OsII(CO)3(RQ)(L)].3e
The emission spectra of selected compounds (1 and 5−7)
have also been measured in 77 K EtOH/MeOH/CH2Cl2 (4/1/
1, v/v/v) glassy medium (Figure 3b), which show two emission
bands. These are similar to the dual emissions, corresponding
to the LC fluorescence and phosphorescence, observed in PbQ2
and BiQ3 in 77 K EtOH glassy medium. The high-energy
emission bands of these complexes are structureless, similar to
those observed in AlQ3, PbQ2, and BiQ3, whereas the low-
energy emissions show a structured emission band similar to
the LC phosphorescence of RhQ2, IrQ3, and PtQ2 in 77 K
EtOH glassy medium. On the basis of previous spectroscopic
studies,3a−e the two emission bands of 1 and 5−7 are also
tentatively assigned to the LC fluorescence and phosphor-
escence.
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We have prepared and characterized a new series of
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dx.doi.org/10.1021/om300621x | Organometallics 2012, 31, 7101−7108