Synthesis, Structures, and Photophysical Properties of Ruthenium(II)Quinolinolato ComplexesJing 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 Republicof 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 MeOHproduced 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 methylligands of these complexes are most likely derived from thedecarbonylation 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 withexcess 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 withexcess CyNC in the presence of NH4PF6 afforded [RuII(MeQ)(CyNC)2(CO)(PPh3)]

+ (12). All complexes have beencharacterized by IR, ESI/MS, 1H NMR and elemental analysis. The crystal structures of complexes 3, 4, 8, and 12 have beendetermined by X-ray crystallography. The UV and emission spectra of these complexes have also been investigated. All complexesexhibit short-lived quinolinolate-based LC fluorescence in solution at room temperature and dual emissions derived from LCfluorescence and phosphorescence at 77 K glassy medium. These emissions are relatively insensitive to the nature of the ancillaryligands but are readily tunable by varying the substituents on the quinolinolato ligand.

■ INTRODUCTION

The use of the aluminum 8-quinolinolato complex AlQ3 and itsderivatives in electroluminescent devices has attracted enor-mous attention due to their excellent electron-transporting andemissive properties.1 The structure−function relationship ofvarious AlQ3 complexes has been extensively studied,2 whichhas led to the development of AlQ3 derivatives with tunableHOMO−LUMO energy gaps and emission colors from blue tored.2 A number of metal complexes bearing variousquinolinolato ligands have also been investigated.3 In contrastto AlQ3 derivatives, which only exhibit singlet emission,luminescence derived from both the singlet and triplet emissiveexcited 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 inluminescent devices.3f A ruthenium(II) quinolinolato complexbearing a bipyridyl ligand has recently been shown to bepotentially useful in dye-sensitized solar cell devices.4 We reportherein the synthesis, characterization, and photophysicalproperties of a new class of ruthenium(II) quinolinolatocomplexes bearing various ancilliary ligands.

■ EXPERIMENTAL SECTIONPhysical Measurements and Instrumentation. IR spectra were

recorded as KBr pellets on a Nicolet Avatar 360 FT-IR spectrometer at4 cm−1 resolution. UV−vis absorption spectra were recorded on eithera Perkin-Elmer Lambda 19 or a Shimadzu UV3100 spectropho-tometer. 1H NMR spectra were recorded on a Varian (300 MHz)NMR spectrometer or a Bruker (400 MHz) NMR spectrometer. Thechemical shifts (δ, ppm) were reported with reference totetramethylsilane (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-Packard8452A diode array spectrophotometer. Steady-state emission andexcitation spectra at room temperature and at 77 K were recorded on aSPEX FluoroLog 3-TCSPC spectrofluorometer. Solutions wererigorously degassed on a high-vacuum line in a two-compartmentcell with no less than four successive freeze−pump−thaw cycles. Time-resolved emission measurements were carried out in the spectral modeof a Edinburgh Instruments LP920-KS using the third harmonicoutput (355 nm; 6−8 ns fwhm pulse width) of a Spectra-PhysicsQuanta-Ray Q-switched LAB-150 pulsed Nd:YAG laser (10 Hz) as theexcitation 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, 2012Published: October 10, 2012

Article

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© 2012 American Chemical Society 7101 dx.doi.org/10.1021/om300621x | Organometallics 2012, 31, 7101−7108

MeOH/CH2Cl2 sample solutions contained in a quartz tube inside aliquid nitrogen filled quartz optical Dewar flask. The emission lifetimeswere measured in the TCSPC mode with NanoLED-375LH (λex 375nm; pulse width <750 ps) as the excitation source. Luminescencequantum yields were determined using the optical dilution methoddescribed 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 diffractometerusing graphite-monochromatized Cu Kα radiation (λ = 1.54178 Å).Details of the crystal data and structure refinement are summarized inTable 1. The structures were resolved by heavy-atom Pattersonmethods or direct methods and refined by full-matrix least squaresusing SHELX-977 and expanded using Fourier techniques.8 All non-hydrogen atoms were refined anisotropically. H atoms were generatedby the program SHELXL-97.7 The positions of H atoms werecalculated on the basis of riding mode with thermal parameters equalto 1.2 times that of the associated C atoms and participated in thecalculation 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.[RuI I(PPh3)3Cl2] ,

9 [RuI I{P(C6H4Me)3}3Cl2] ,9 c [RuI I{P-

(C6H4OMe)3} 3C l 2 ] ,9 c [Ru I I (PPh3) 3 (CO)(H)2] ,

1 0 and[RuII(PPh3)3(CO)(H)(Cl)]

11 were synthesized according to literatureprocedures. Other chemicals were of reagent grade and were usedwithout further purification.[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 paleyellow precipitate was collected and air-dried. It was recrystallized byslow evaporation of a CH2Cl2/MeOH (1/3, v/v) solution of thecomplex. Yield: 300 mg, 73%. IR (KBr, cm−1): ν(CO) 1904, ν(Ru−H) 1950. ESI-MS: m/z 812 [M − H]+, 655 [M − MeQ]+. 1H 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, ArH), 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;

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 synthesizedaccording 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(CO) 1907, ν(Ru−H) 1944. ESI-MS: m/z896 [M − H]+, 739 [M − MeQ]+. 1H NMR (400 MHz, CDCl3): δ7.35−7.40 (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(CO) 1902, ν(Ru−H)1964. ESI-MS: m/z 992 [M − H]+, 835 [M − MeQ]+. 1H NMR (400MHz, 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)(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(CO) 1894. ESI-MS: m/z812 [M − CH3]

+, 669 [M −MeQ]+. 1H NMR (400 MHz, CD2Cl2): δ7.53 (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, ArH), 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 forC48H41NO2P2Ru: C, 69.72; H, 5.00; N, 1.69. Found: C, 69.66; H,

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 C55.25H45.50Cl0.50N3O3P2Ru C43H45N3O2PRuF6PMr 1162.81 826.83 980.18 912.83T/K 133 (2) 173 (2) 133 (2) 133 (2)cryst syst monoclinic triclinic triclinic monoclinicspace group P21/n P1 P1 P21/na/Å 12.4343(3) 9.2381(3) 12.5278(5) 12.4298(3)b/Å 28.1257(5) 12.5884(4) 13.1009(5) 24.7828(6)c/Å 15.6486(3) 17.4284(5) 16.4148(5) 13.3653(3)α/deg 90 82.761(2) 101.879(3) 90β/deg 101.690(2) 86.015(3) 92.797(3) 94.183(2)γ/deg 90 74.412(3) 111.000(3) 90V/Å3 5359.18(18) 1935.36(10) 2439.04(15) 4106.15(17)Z 4 2 2 4ρcalcd/g cm−3 1.441 1.419 1.335 1.477F(000) 2392 852 1009 1872no. of collected rflns 23 013 12 258 16 693 29 571no. of unique rflns 10 291 6737 8596 7306R(int) 0.025 0.027 0.018 0.026final R indices, I > 2σ(I) R1(obsd) = 0.048 R1(obsd) = 0.034 R1(obsd) = 0.036 R1(obsd) = 0.040

wR2(all) = 0.139 wR2(all) = 0.118 wR2(all) = 0.108 wR2(all) = 0.099GOF 1.11 1.23 1.08 1.03no. of params 733 489 589 578

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5.12; N, 1.72. UV/vis (CH2Cl2): λmax (nm) (ε (mol−1 dm3 cm−1)):249 sh (39 610), 356 (5810), 426 (3390).[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 refluxedfor 1 day under argon, and the resulting yellow microcrystalline solidwas collected and washed with ice-cold methanol (3 × 4 mL). Yield:120 mg, 71%. IR (KBr, cm−1): ν(CO) 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 = 19.9Hz, 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).[RuII(ClQ)(H)(CO)(PPh3)2] (6). Complex 6 was prepared by a

procedure similar to that for 5, except ClQH was used instead ofQH. Yield: 135 mg, 77%. IR (KBr, cm−1): ν(CO) 1918, ν(Ru−H)1945. ESI-MS: m/z 832 [M − H]+, 655 [M − ClQ]+. 1H NMR (300MHz, 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).[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(CO) 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, ArH), 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)[Ru

II(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 (100mL), and the mixture was refluxed for 1 day under argon to give a lightyellow solution. After filtration, the solvent was removed by rotaryevaporation. The residue was redissolved in H2O (50 mL), andPPh4Cl (100 mg) was added to give a light yellow precipitate, whichwas purified by column chromatography on silica gel using acetone/CH2Cl2 (1/4, v/v) as eluent. Recrystallization by slow diffusion ofdiethyl ether into a CH2Cl2 solution of 8 afforded light yellow singlecrystals suitable for X-ray diffraction analysis. Yield: 81 mg, 34%. IR(KBr, cm−1): ν(CN) 2096, ν(CO) 1937. ESI-MS (negative): m/z 602 [M]−. 1H NMR (400 MHz, CD2Cl2): δ 7.85−7.92 (m, 9H, ArH), 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)[Ru

II(Q)(CN)2(CO)(Ph3P)] (9). The complex was synthesizedaccording to a procedure similar to that for 8, except 5 (200 mg, 0.25mmol) was used instead of 1. Yield: 70 mg, 30%. ESI-MS (negative):m/z 588 [M]−. IR (KBr, cm−1): ν(CN) 2096, ν(CO) 1940. 1HNMR (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}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:

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).

(PPh4)[RuII(ClQ)(CN)2(CO)(Ph3P)] (10). This complex was prepared

according to a procedure similar to that for 8, except 6 was usedinstead of 1. Yield: 75 mg, 31%. IR (KBr, cm−1): ν(CN) 2097,ν(CO) 1940. ESI-MS (negative): m/z 602 [M]−. 1H NMR (400MHz, CD3OD): δ 8.91 (t, J = 3.4 Hz, 1H, Ar H), 8.47 (dd, J = 8.6, 1.3Hz, 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 forC54H40ClN3O2P2Ru·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 usedinstead of 1. ESI-MS (negative): m/z 664 [M]−. Yield: 89 mg, 35%. IR(KBr, cm−1): ν(CN) 2098, ν(CO) 1942. 1H NMR (400 MHz,CD3OD): 8.89 (t, J = 3.5 Hz, 1H, Ar H), 8.27 (d, J = 9.0 Hz, 1H, ArH), 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 = 8.2Hz, 1H, Ar H). 31P{1H} NMR (162 MHz, CDCl3): δ 51.0 (s, PPh3),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(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. Thevolume of the solution was then reduced to 2 mL, and diethyl ether (5mL) was added to give a brown precipitate, which was collected andrecrystallized from CH2Cl2/diethyl ether. Yield: 72 mg, 30%. IR (KBr,cm−1): ν(CN) 2201, ν(CO) 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 inMeOH 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 ligandsof these complexes are most likely derived from thedecarbonylation of methanol. Similar decarbonylation reactionshave 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 Ananalogous reaction occurs between [RuII(PPh3)3Cl2] andMeQH 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 inEtOH.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)].Attempts to synthesize carbonyl hydrido complexes contain-

ing other substituted quinolinolato ligands (XQ) such as Q,

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ClQ, and PhQ using the same strategy as for the MeQcomplexes were unsuccessful; instead, [RuII(XQ)2(PPh3)2](XQ = Q, ClQ, PhQ) was formed as the major product. Thisdifference in reactivity may be attributed to the steric effect of

the methyl substituent in MeQ, which hinders the formation ofthe bis(quinolinolato) complex. We then attempted to preparecarbonyl hydrido complexes containing these quinolinolatoligands (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)] wereproduced, which were difficult to separate, as they have verysimilar solubility and polarity. On the other hand, when thedihydrido complex [RuII(PPh3)3(CO)(H)2] was used as thestarting material, [RuII(XQ)(PPh3)2(CO)(H)] (XQ = Q (5),ClQ (6), PhQ (7)) (Scheme 1b) could be isolated in moderateyields. Similar to the case for 1−3, these complexes arediamagnetic and air-stable in the solid state but slowlydecompose in solution. The two substituted triphenylphos-phine ligands in 1−7 are trans to each other, which is consistentwith the observation of a single resonance in the 31P{1H} NMRand is confirmed by the X-ray crystal structures of 3 and 4 (seebelow). This ligand arrangement is thermodynamicallyfavorable, as the steric repulsions between the two bulkyligands can be minimized.14 Facile cis to trans isomerizations ofruthenium(II) complexes with two monodentate bulkyphosphine ligands have also been commonly reported.14b,c

Treatment of 1 and 5−7 with excess KCN in MeOHfollowed by metathesis with PPh4Cl afforded PPh4

+ salts of theanionic 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 thephosphine ligands can also be substituted by an isocyanideligand such as CyNC, resulting in the formation of[RuII(MeQ)(CyNC)2(CO)(PPh3)]

+ (12) (Scheme 1d), iso-lated as the PF6

− salt. Complexes 8−12 are stable in the solidstate and in solution and are very soluble in common organicsolvents.

Scheme 1. Synthetic Routes for Various Ruthenium(II)Complexes

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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All complexes have been characterized by 1H NMR, 31P{1H}NMR, IR, ESI-MS, and elemental analysis (see Figures S1−S9in the Supporting Information). The structures of 3, 4, 8, and12 have also been determined by X-ray crystallography. Allcomplexes show 1H NMR signals with chemical shifts andintegral ratios consistent with their chemical formulations. Forthe hydrido complexes (1−3 and 5−7), an upfield triplet signalat ca. −10.7 ppm, typical of metal hydride complexes, withcoupling constants in the range of 19.6−20.4 Hz and anintegral ratio of one proton were observed. The observation ofthe triplet splitting is the result of the coupling of the hydridewith the two chemically equivalent cis-triphenylphosphineligands. These coupling constants are also in the range foundin related ruthenium(II) phosphine hydride complexes.10

The IR spectra of all carbonyl hydrido complexes (1−3 and5−7) show one weak and one strong absorption in the regionof 1900−1960 cm−1, corresponding to ν(Ru−H) and ν(CO)stretches, respectively. These ν(CO) 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 relatedRu(II) carbonyl hydrido complexes.15 The cyano complexes(8−11) also show a strong ν(CN) stretch at ca. 2100 cm−1,while the isocyano complex (12) shows a strong ν(CN)stretch at 2200 cm−1.

X-ray Crystal Structures. The structures of 3, 4, 8, and 12have been determined by X-ray crystallography (Figure 1).Selected bond distances and angles of these complexes aresummarized in Table 2. The ruthenium centers in thesecompounds adopt a distorted-octahedral geometry. All carbonyl

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) 2.351(10) Ru(1)−N(1) 2.207(3)Ru(1)−P(2) 2.344(10) Ru(1)−C(1) 1.827(4)Ru(1)−O(2) 2.114(3) Ru(1)−H(1) 1.50(6)

N(1)−Ru(1)−P(1) 94.00(9) C(1)−Ru(1)−P(2) 88.34(13)N(1)−Ru(1)−P(2) 91.03(9) C(1)−Ru(1)−O(2) 176.77(15)N(1)−Ru(1)−H(1) 168(2) C(1)−Ru(1)−N(1) 105.26(16)C(1)−Ru(1)−P(1) 95.38(13) C(1)−Ru(1)−H(1) 86(2)

Complex 4

Ru(1)−C(2) 1.829(3) Ru(1)−N(1) 2.213(2)Ru(1)−O(1) 2.090(18) Ru(1)−P(1) 2.371(7)Ru(1)−C(1) 2.156(3) Ru(1)−P(2) 2.382(7)

C(2)−Ru(1)−O(1) 178.49(10) C(1)−Ru(1)−P(1) 89.22(7)C(2)−Ru(1)−C(1) 94.56(11) N(1)−Ru(1)−P(1) 91.56(5)O(1)−Ru(1)−C(1) 84.07(9) C(2)−Ru(1)−P(2) 89.45(8)C(2)−Ru(1)−N(1) 103.47(10) O(1)−Ru(1)−P(2) 91.18(5)O(1)−Ru(1)−N(1) 77.91(8) C(1)−Ru(1)−P(2) 89.65(7)C(1)−Ru(1)−N(1) 161.97(9) N(1)−Ru(1)−P(2) 90.23(5)C(2)−Ru(1)−P(1) 88.34(8) P(1)−Ru(1)−P(2) 177.43(2)O(1)−Ru(1)−P(1) 91.00(5)

Complex 8

Ru(1)−P(1) 2.313(7) Ru(1)−C(1) 1.833(3)Ru(1)−O(2) 2.108(2) Ru(1)−C(2) 2.054(3)Ru(1)−N(1) 2.176(2) Ru(1)−C(3) 2.063(3)

O(1)−C(1)−Ru(1) 177.2(3) C(1)−Ru(1)−C(3) 88.53(13)O(2)−Ru(1)−P(1) 91.18(6) C(2)−Ru(1)−P(1) 90.08(8)O(2)−Ru(1)−N(1) 78.14(8) C(2)−Ru(1)−O(2) 88.74(10)N(1)−Ru(1)−P(1) 169.24(7) C(2)−Ru(1)−N(1) 88.46(10)C(1)−Ru(1)−P(1) 87.19(9) C(3)−Ru(1)−P(1) 96.20(9)C(1)−Ru(1)−O(2) 178.36(10) C(3)−Ru(1)−O(2) 91.77(11)C(1)−Ru(1)−N(1) 103.49(11) C(3)−Ru(1)−N(1) 85.48(11)C(1)−Ru(1)−C(2) 91.15(13)

Complex 12

Ru(1)−P(1) 2.343(8) Ru(1)−C(1) 1.877(3)Ru(1)−O(2) 2.090(2) Ru(1)−C(2) 2.012(3)Ru(1)−N(1) 2.169(3) Ru(1)−C(3) 2.017(3)

O(1)−C(1)−Ru(1) 175.3(3) C(1)−Ru(1)−C(2) 96.36(13)O(2)−Ru(1)−P(1) 93.31(6) C(1)−Ru(1)−C(3) 90.85(14)O(2)−Ru(1)−N(1) 79.02(9) C(2)−Ru(1)−P(1) 90.60(9)N(1)−Ru(1)−P(1) 172.29(7) C(2)−Ru(1)−O(2) 87.22(11)N(2)−C(2)−Ru(1) 172.9(3) C(2)−Ru(1)−N(1) 88.29(11)N3−C(3)−Ru(1) 172.3(3) C(2)−Ru(1)−C(3) 170.75(12)C(1)−Ru(1)−P(1) 86.36(10) C(3)−Ru(1)−P(1) 95.64(9)C(1)−Ru(1)−O(2) 176.41(12) C(3)−Ru(1)−O(2) 85.62(11)

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ligands in these complexes are trans to the oxygen atom of thequinolinonato ligand with Ru−C(CO) bond distances in therange of 1.827−1.877 Å, which are typically observed in otherRu(II) carbonyl complexes.15 In 3 and 4, the twotriphenylphosphine ligands are trans to each other, while thehydrido ligand in 3 and the methyl ligand in 4 are trans to thenitrogen atom of the quinolinolato ligand with Ru−H and Ru−CH3 bond distances of 1.49 and 2.15 Å, respectively, which arecomparable with those of related ruthenium complexes.16 Thelonger Ru−N(quinolinolato ligand) bond lengths in 3 (2.205Å) 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 (2.05Å),18 8 (2.176 Å), and 12 (2.169 Å) are presumably due to thestrong trans influence of the hydrido and methyl ligands. TheX-ray crystal structures of 8 and 12 indicate that isomerizationof PPh3 from the cis to the trans position relative to thequinolinolato ligand has occurred during a ligand substitutionreaction by CN− or CNR. These ligand rearrangements mayarise from the release of steric strain of the bulky PPh3 ligand.The slight deviation of the CN−C bond angle (175.3°) ofisocyanide ligands from the linearity in 12 is attributed to the π-back-bonding with Ru(II), as commonly observed in metalisocyanide complexes.19

UV−Vis Absorption and Emission Spectroscopy. Theelectronic absorption spectra of 1−12 show intense ligand-centered π−π* transitions in the UV region (λ ≤ 300 nm), withmolar absorption coefficients on the order of 104 mol−1 dm3

cm−1 (Table 3). In addition to these intense absorptions, allcomplexes also display two moderately intense absorptionshoulders or bands at 330−358 and 410−440 nm, with molarabsorption coefficients on the order of 103 mol−1 dm3 cm−1

(Table 3, Figure 2). These absorptions show an energydependence on the electronic nature of the quinolinolato ligand

but are almost insensitive to the electronic nature of otherancillary ligands. Moreover, these absorptions are similar to theπ−π* transitions of quinolinlato ligands in related metalcomplexes such as [OsII(CO)3(RQ)(L)] (RQ = Q, MeQ; L =Cl, I, CF3CO2),

3e AlQ3,3a and IrQ3.

3a On the basis of previousspectroscopic studies and the absorption energy trends in thesecomplexes, these absorptions are tentatively assigned to themetal-perturbed π−π* transitions of the quinolinolato ligands.Homoleptic transition-metal quinolinolato complexes such as

RhQ3, PdQ2, IrQ3, and PtQ2 show red emission arising fromligand-centered (LC) phosphorescence,3a,b,d while the complex[Os(CO)3(RQ)(L)] shows dual emission bands derived from amixture of LC fluorescence and phosphorescence.3e In contrast,compounds 1−12 display only green photoluminescence withemission maxima in the range of 500−530 nm (Table 3). Theseemissions are relatively insensitive to the nature of thephosphine and other ancillary ligands, as reflected by thesimilar emission energies of compounds 1−3, 8, and 12. On theother hand, the emission energies of these compounds are

Table 3. Photophysical Data for Complexes 1−12

medium (T/K) emissiona λem/nm ϕemb absorptionc λabs/nm (ε/dm3 mol−1 cm−1)

1 CH2Cl2 (298) 500 0.0291 265 sh (24 350), 354 (6930), 421 (3710)glassd (77) 456, 580, 629

2 CH2Cl2 (298) 500 0.0270 271 sh (27 990), 352 (6440), 425 (3630)glassd (77) 455, 578, 628

3 CH2Cl2 (298) 501 0.0287 272 sh (30 750), 341 (6370), 424 (3010)glassd (77) 456, 582, 630

4 CH2Cl2 (298) 500 0.0036 249 sh (39 610), 356 (5810), 426 (3390)glassd (77) 463, 587, 633

5 CH2Cl2 (298) 504 0.0227 268 sh (23 790), 353 (7660), 424 (4440)glassd (77) 448, 578, 625

6 CH2Cl2 (298) 518 0.0278 263 sh (22 270), 351 (5900), 441 (4190)glassd (77) 472, 603, 653

7 CH2Cl2 (298) 519 0.0573 265 sh (22 280), 303 sh (12 790), 358 (7280), 440 (5820)glassd (77) 464, 602, 654

8 CH2Cl2 (298) 512 0.0322 269 (23 250), 276 (23 890), 330 (7010), 346 sh (2600), 410 (5560)glassd (77) 456, 524, 576

9 CH2Cl2 (298) 516 0.0274 262 (17 160), 269 (17 790), 275 sh (15 510), 331 sh (3370), 347 sh (2890), 428 (3500)glassd (77) 454, 582, 625

10 CH2Cl2 (298) 528 0.0247 262 (25 300), 268 (24 800), 275 sh (21 150), 341 (6400), 355 (6000), 438 (4370)glassd (77) 476, 564, 667

11 CH2Cl2 (298) 529 0.00324 262 (28 870), 269 (29 230), 276 (26 900), 298 sh (13 930), 352 (6020), 433 (4790)glassd (77) 474, 607

12 CH2Cl2 (298) 501 0.0006 272 (24 540), 412 (3010)glassd (77) 463, 580

aExcitation at 400 nm. Emission maxima are uncorrected values. bLuminescence quantum yield with excitation at 436 nm. cIn dichloromethane at298 K. dEtOH/MeOH/CH2Cl2 (4/1/1, v/v/v).

Figure 2. UV/vis absorption spectra of 1, 5, 6, and 7 in CH2Cl2 at 298K.

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more sensitive to the nature of the substituent on thequinolinolato ligand, as illustrated by the following emissiontrend of 1 (500 nm for MeQ) < 5 (504 nm for Q) < 6 (518 nmfor ClQ) ≤ 7 (519 nm for PhQ) (Figure 3). Such emission

energy dependence and the close resemblance of theseemissions to the fluorescence of other quinolinolato metalcomplexes3a−3e strongly suggest that they arise fromquinolinolato ligand-centered (LC) fluorescence. The short-lived emission lifetimes of < 3 ns are consistent with thefluorescence assignment. To eliminate the possible mixing ofthe 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 varioustimes (>1 ns) after the laser excitation. The absence of red LCphosphorescence in these complexes may be attributed toinefficient intersystem crossing from the singlet to the tripletstate or very efficient nonradiative decay from the triplet state.The dependence of the intersystem crossing efficiency on thesubstituent of the quinolinolato and other ancillary ligands hasalso been reported in a series of osmium quinolinolatocomplexes [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 emissionbands. These are similar to the dual emissions, correspondingto the LC fluorescence and phosphorescence, observed in PbQ2and BiQ3 in 77 K EtOH glassy medium. The high-energyemission bands of these complexes are structureless, similar tothose observed in AlQ3, PbQ2, and BiQ3, whereas the low-energy emissions show a structured emission band similar tothe LC phosphorescence of RhQ2, IrQ3, and PtQ2 in 77 KEtOH glassy medium. On the basis of previous spectroscopicstudies,3a−e the two emission bands of 1 and 5−7 are alsotentatively assigned to the LC fluorescence and phosphor-escence.

■ CONCLUSIONWe have prepared and characterized a new series ofruthenium(II) quinolinolato complexes bearing various ancil-lary ligands, which show diverse electronic properties. Allcomplexes exhibit short-lived quinolinolate-based LC fluores-cence in solution at room temperature and dual emissionsderived from LC fluorescence and phosphorescence in 77 Kglassy medium. These emissions are relatively insensitive to the

nature of the ancillary ligands but are readily tunable throughchanging the substituents on the quinolinolato ligand.

■ ASSOCIATED CONTENT

*S Supporting InformationCIF files giving crystallographic data for 3, 4, 8, and 12 andfigures giving 1H NMR and mass spectra of selected complexesand excitation and emission spectra of 5. This material isavailable 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.).

NotesThe authors declare no competing financial interest.

■ ACKNOWLEDGMENTS

The work described in this paper was supported by the HongKong University Grants Committee Area of Excellence Scheme(AoE/P-03/08) and a GRF grant (CityU 101408). The flashphotolysis system was supported by a Special Equipment Grantfrom the University Grants Committee of the Hong Kong(SEG_CityU02).

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Figure 3. Overlaid emission spectra of selected complexes (1, 5, 6, and7) in (a) CH2Cl2 at 298 K and (b) EtOH/MeOH/CH2Cl2 (4/1/1, v/v/v) glassy medium at 77 K.

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