Luminescent Carbonyl Hydrido Ruthenium(II) Diimine Coordination Compounds: Structural, Photophysical, and Electrochemical Properties

Article abstract of DOI:10.1002/ejic.201600438

A series of luminescent carbonyl hydrido ruthenium(II) complexes with various diimine ligands with diverse electronic properties, including Me₂bpy (bpy = bipyridine), Me₂phen (phen = phenanthroline), PhenCOOH, PhenCN, Me₂Ph₂phen, Ph₂phen, and π-conjugating dipyrido[3,2-d:2′,3′-f]quinoxaline (dpq), dipyrido[3,2-a:2′,3′-c](6,7,8,9-tetrahydro)phenazine (dpqc), and dipyridophenazine (dppz) have been synthesized and characterized. Four of these complexes have been structurally characterized by X-ray crystallography. The photophysical and electrochemical properties of these complexes have been studied. The effects of the electronic features and π-conjugation of the diimine ligand on the electronic and photophysical properties of these complexes have also been discussed. Our study revealed that the luminescence performance of these complexes could be significantly enhanced by increasing the rigidity and π-conjugation of the diimine ligand.

Full text of DOI:10.1002/ejic.201600438

DOI: 10.1002/ejic.201600438
Full Paper
Luminescent Ru Complexes
Luminescent Carbonyl Hydrido Ruthenium(II) Diimine
Coordination Compounds: Structural, Photophysical, and
Electrochemical Properties
Fei Yu,[a] Wing-Kin Chu,[b,c] Chang Shen,[a] Ya Luo,[a] Jing Xiang,*[a] Shu-Qi Chen,[a]
Chi-Chiu Ko,*[b] and Tai-Chu Lau*[b]
Abstract: A series of luminescent carbonyl hydrido ruthenium- been structurally characterized by X-ray crystallography. The
(II) complexes with various diimine ligands with diverse elec- photophysical and electrochemical properties of these com-
tronic properties, including Me2bpy (bpy
= bipyridine), plexes have been studied. The effects of the electronic features
Me2phen (phen phenanthroline), PhenCOOH, PhenCN, and π-conjugation of the diimine ligand on the electronic and
=
Me2Ph2phen, Ph2phen, and π-conjugating dipyrido[3,2-d:2′,3′-f]- photophysical properties of these complexes have also been
quinoxaline (dpq), dipyrido[3,2-a:2′,3′-c](6,7,8,9-tetrahydro)- discussed. Our study revealed that the luminescence perform-
phenazine (dpqc), and dipyridophenazine (dppz) have been ance of these complexes could be significantly enhanced by
synthesized and characterized. Four of these complexes have increasing the rigidity and π-conjugation of the diimine ligand.
Introduction
with other ancillary ligands could lead to high fundamental
anisotropies that have found useful applications in biophysical
studies.[19–21] We also have demonstrated the importance and
effectiveness of using ancillary ligands in enhancing and tuning
the excited state and phosphorescence properties of MLCT
emitters.[22]
On the basis of our recent work on luminescent carbonyl
hydridoquinolinolato RuII complexes,[23] we report here a new
series of luminescent carbonyl hydrido RuII diimine complexes
bearing different types of diimine ligands such as Me2bpy,
Tris(bipyridyl) RuII complex and its derivatives have been exten-
sively studied, owing to the rich photophysical properties in-
cluding their metal-to-ligand charge-transfer (MLCT) phospho-
rescent, as well as good thermal and photostability.[1–3] These
complexes have been used in a wide variety of applications
including photosensitizers, photochemical molecular devices,
dye-sensitized solar cells as well as biological applications such
as DNA probes, lipid probes, and fluorescence-polarization im-
munoassays.[4–11] The ease of the modification of the redox
properties as well as the ground-state and excited-state proper-
ties of this family of complexes through the functionalization
of the bipyridine ligands is also an attractive feature of this class
of complexes.[12–17] Previous studies have revealed that the re-
placement of one of the diimine ligands in [RuII(bpy)3]2+ (bpy =
bipyridine) with phosphine ligands can significantly increase
the quantum yields of the complexes.[18] The decrease in molec-
ular symmetry by replacing one or two of the diimine ligands
Me2phen (phen
= phenanthroline), PhenCOOH, PhenCN,
Me2Ph2phen, Ph2phen, and π-conjugating dipyrido[3,2-d:2′,3′-f]-
quinoxaline (dpq), dipyrido[3,2-a:2′,3′-c](6,7,8,9-tetrahydro)-
phenazine (dpqc), and dipyridophenazine (dppz). The photo-
physical and electrochemical properties of these complexes
have been investigated. The effects of the electronic and steric
properties of the diimine ligands on the luminescent properties
of the complexes will be discussed.
Results and Discussion
[a] College of Chemistry and Environmental Engineering, Yangtze University,
Jingzhou 434020, Hu Bei, P. R. China
E-mail: xiangjing@yangtzeu.edu.cn
http://www.yangtzeu.edu.cn/
Synthesis and Characterization
[b] Department of Biology and Chemistry, Institute of Molecular Functional
Materials, City University of Hong Kong,
The diimine ligands 1,10-phenanthroline-2-carboxylic acid
(PhenCOOH),[24] 2-cyano-1,10-phenanthroline (PhenCN),[24] di-
pyrido[3,2-d:2′,3′-f]quinoxaline (dpq),[25] dipyrido[3,2-a:2′,3′-
c](6,7,8,9-tetrahydro)phenazine (dpqc),[25] and dipyridophen-
azine (dppz)[26] were prepared according to literature proce-
dures. The luminescent carbonyl hydrido ruthenium(II) diimine
complexes [RuII(N N)(CO)(H)(PPh3)2]PF6 [N N = Me2bpy (1),
Me2phen (2), PhenCOOH (3), Me2Ph2phen (5), Ph2phen (6), dpq
(7), dpqc (8), dppz (9)] were prepared by ligand-substitution
Tat Chee Avenue, Kowloon Tong, Hong Kong, China
E-mail: BHTCLAU@cityu.edu.hk
vinccko@cityu.edu.hk
http://www.cityu.edu.hk/
[c] Faculty of Science and Technology, Technological and Higher Education
Institute of Hong Kong,
20A Tsing Yi Road, Tsing Yi, Hong Kong, P. R. China
Supporting information for this article is available on the WWW under
http://dx.doi.org/10.1002/ejic.201600438.
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reactions of the carbonyl bis(hydrido)tris(triphenylphosphine)- acterized by the strong ν(P–F) stretches at around 840 cm–1.
ruthenium(II) precursor [RuII(CO)(H)2(PPh3)3] with the corre- The carboxylic acid and cyano substituents in the diimine li-
sponding diimine ligands in ethanol under reflux conditions gands of 3 and 4 are characterized by ν(C=O) at 1618 cm–1 and
(Scheme 1). Attempts were also made to use [RuII(CO)(H)Cl- ν(C≡ N) at 2237 cm–1.
1
All complexes show H NMR and 31P{1H} NMR signals with
chemical shifts and integral ratios consistent with their pro-
posed structures. The hydrido ligands in these complexes are
characterized by the upfield triplet signals with chemical shift
(PPh3)3] as the synthetic precursor; however, a mixture of
[RuII(N N)(CO)(H)(PPh3)2]+ and [RuII(N N)(CO)(Cl)(PPh3)2]+ were
formed in this case, which are difficult to separate owing to
their similar solubility and polarity. Similar reaction between
[RuII(CO)(H)2(PPh3)3] and PhenCN leads to the formation of
[RuII(PhenCONH2)(CO)(PPh3)2]+ instead of the expected complex
[RuII(PhenCN)(CO)(H)(PPh3)2]+, owing to the hydrolysis of the co-
ordinated ligand PhenCN. Electrospray ionization mass spec-
trometry (ESI-MS) of the amide complex shows a predominant
peak at m/z = 876 in the positive range, corresponding to
the parent ion peak. There is also a strong C=O stretch at
1622 cm–1 and a sharp N–H stretch at 3163 cm–1 in the IR spec-
trum. Hydrolysis of the PhenCN ligand could be prevented by
carrying out the reaction in the presence of Et2NH·HCl. In this
1
(δ) in the range –9.61 to –12.09 ppm in the H NMR spectra.
The triplet splitting of the hydride signals with coupling con-
stants of 18.5 to 19.9 Hz is the result of the coupling between
the hydrido ligand and the phosphorus atoms of the two chem-
ically equivalent cis-phosphine ligands. The coupling constants
are also in the typical range found for related hydrido
ruthenium(II) phosphine complexes.[28] Although the two pyr-
idyl moieties are related by symmetry in the free diimine li-
gands of 1, 2, 5–7, and 9, the 1H signals of the two pyridyl
moieties in these complexes split into two sets (Figures S1–S5
in the Supporting Information). This suggest that these diimine
ligands are trans to two different ligands. In the 31P{1H} NMR
spectra, the two PPh3 in each of these complexes only show a
singlet signal with a chemical shift (δ) in the range 44.5–
47.4 ppm and the PF6– anion is characterized by a septet signal
at about δ = –144 ppm. The observation of the sharp singlet
signals in the 31P{1H} NMR spectra together with the unsymmet-
rical chemical environments for the two pyridyl moieties of the
diimine ligands confirms the geometric isomerism of these
complexes, in which the diimine ligands are trans to the carb-
onyl and the hydrido ligand, and the two triphenylphosphine
ligands are arranged in a trans configuration. The geometrical
arrangements of these ligands are further confirmed by the X-
ray crystal structures of 3, 7, 8, and 9.
–
way, trans-[RuII(PhenCN)(CO)(H)(PPh3)2]+ is obtained as the PF6
salt in excellent yield. All the complexes have been character-
1
ized by H NMR, 31P{1H} NMR, IR spectroscopy, ESI-MS, and ele-
mental analysis. The structures of 3 and 7–9 have been deter-
mined by X-ray crystallography.
X-ray Crystal Structure Determination
By slow diffusion of diethyl ether into concentrated dichloro-
methane solutions of the complexes, single crystals of 3 and 7–
9 with quality suitable for X-ray crystallography were obtained.
The perspective drawings of the complex cations of 3 and 7–9
are shown in Figure 1. The crystal data and selected bond
lengths and angles are given in Tables S1 and S2, respectively.
In these structures, the ruthenium centers adopt distorted octa-
Scheme 1. Synthetic routes to 1–9.
Complexes 1–9 all exhibit a predominant [M]+ peak in the hedral geometries with two PPh3 ligands trans to each other
ESI-MS (m/z = 839 for 1, m/z = 863 for 2, m/z = 879 for 3, m/z = and located in the axial positions relative to the diimine ligand,
860 for 4, m/z = 1015 for 5, m/z = 987 for 6, m/z = 887 for 7, which is trans to one carbonyl ligand and one hydrido ligand.
–
m/z = 941 for 8, and m/z = 937 for 9). In the IR spectra, except The presence of a PF6 counter anion in each of these com-
4 and 6, the complexes all show one weak and one strong plexes has also been identified. In all these structures, the Ru–
absorption in the region 1906–2030 cm–1, corresponding to C(CO) distances are in the range 1.84–1.87 Å, which are in good
ν(Ru–H) and ν(C≡ O) stretches, respectively. These ν(Ru–H) and agreement with those reported for related RuII complexes.[29]
ν(C≡ O) stretching frequencies are comparable to those in As found in the crystal structures of other RuII diimine com-
[RuII(CO)(H)2(PPh3)3] and are in the typical range reported for plexes,[30] the bite angles of the chelating diimine ligands at
related complexes.[27] The different π-accepting properties of the RuII metal centers are in range 75.9–76.9°. Except for the
these diimine ligands are reflected in the stretching frequencies structure of 3, the Ru–N bond lengths of all of these complexes
of the C≡ O stretches of these complexes. The ν(Ru–H) stretch is are in the range 2.120–2.199 Å, typical for RuII diimine com-
not observed for 4 and 6 probably owing to overlap of the plexes.[31] The significantly longer Ru–N bond adjacent to the
ν(Ru–H) band with the strong and relatively broad ν(C≡ O) ab- carboxylic acid substituent in 3 (2.236 Å) can be attributed to
–
sorption. The counter anions (PF6 ) of these complexes are char- steric hindrance of the bulky –COOH group on the cis-carbonyl
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ligand. The carboxylic acid group in the structure of 3 is close UV/Vis Absorption Properties
to the carbonyl and is non-coplanar with the phenanthroline
The UV/Vis absorption properties of all complexes in dichloro-
methane solution have been investigated. These complexes dis-
solved in dichloromethane give yellow or orange solutions. The
UV/Vis absorption data are collected in Table 1 and selected
overlaid absorption spectra are shown in Figure 3. The absorp-
tion spectra of complexes show intense absorptions with molar
extinction coefficients on the order of 104 dm3 mol–1 cm–1 in
the high energy UV region (235–330 nm). These are assigned
to the ligand-centered (LC) π→π* transitions of the PPh3 and
diimine ligands. Owing to the extended π-conjugation of the
diimine ligands in 4 and 9, their LC absorptions are much lower
in energy. In addition to the intense UV absorption, these com-
plexes show moderately intense absorption bands or shoulders
with λabs in the range 390–465 nm with molar extinction coeffi-
cients on the order of 103 dm3 mol–1 cm–1 and tailing to the
visible region down to approximately 470–540 nm. These ab-
sorption bands or shoulders are ascribed to the 1MLCT
[dπ(Ru)→π*(N N)] transitions. In accordance with this assign-
plane with a dihedral angle of 53.8° to minimize steric repul-
1
sion. Both H NMR and 31P NMR spectroscopy confirmed that
there is only one geometrical isomer present in solution in all
these complexes. In the structures of 7–9, the diimine ligands
showed a good coplanarity even for 8, with a cyclohexyl moi-
ety, which shows a high degree of disorder on the carbon atom
of the cyclohexyl ring.
Table 1. UV/Vis absorption data for 1–9 in CH2Cl2 solution at 298 K.
Absorption λabs [nm] (ε [dm3 mol–1 cm–1])
1
2
3
4
5
6
7
8
9
267 sh (20980), 271 sh (20270), 290 sh (15620), 308 sh (11870), 396 (1470)
226 sh (59060), 275 sh (25090), 318 sh (7230), 395 (870)
232 (38680), 270 sh (20220), 276 sh (19800), 325 sh (6160), 425 sh (1370)
276 (37350), 290 sh (26010), 324 sh (9080), 378 (3640), 465 (1180)
225 sh (61930), 248 sh (38270), 292 sh (33060), 330 sh (10270) 402 (2250)
225 sh (55410), 289 sh (28950), 322 sh (12290), 401 sh (3690)
256 sh (47680), 298 sh (23600), 322 sh (6550), 401 (2500)
Figure 1. ORTEP drawings of the cationic structures of (a) 3, (b) 7, (c) 8, and
(d) 9. Hydrogen atoms, except the hydrido ligand and that in the carboxylic
acid group, have been omitted for clarity. Thermal ellipsoids are drawn at the
30 % probability level.
224 sh (50380), 268 sh (33460), 308 sh (15860), 342 sh (5653), 404 (1780)
225 sh (54850), 277 sh (55990), 312 sh (16940), 364 (10170), 412 (2920)
The two PPh3 ligands are slightly bent towards the carbonyl
group as revealed from the angles of P–Ru–P being in the range
165.2–170.2°. This is probably due to the steric repulsion be-
tween the phenyl rings of the PPh3 and the chelating diimine
ligands. Close scrutiny of the phosphine and the diimine li-
gands in these crystal structures reveals that there are π···π
interactions between the diimine ligand and phenyl rings of
the PPh3 ligands. These π···π interactions are characterized by
centroid-to-centroid distances of 3.5–3.9 Å between the two
interacting rings as illustrated in the structures of complexes 3
and 9 (Figure 2). In addition to intramolecular π···π interactions
between the phosphine and diimine ligands, an intermolecular
hydrogen-bonding interaction between the carboxylic acids of
adjacent molecules in the structure of 3 also occurs and is char-
acterized by the short O···O distance of 2.78 Å, indicative of an
O–H···O interaction (Figure 2).
Figure 3. UV/Vis absorption spectra of 1–4 (a) and 5–9 (b) in CH2Cl2 solution
Figure 2. The supramolecular interactions in the structures of (a) 3 and (b) 9.
at 298 K.
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ment, these lowest absorptions of the complexes show a strong
dependence on the electronic nature of the diimine ligands.
Table 2. Emission data of 1–9.
φem ( × 103)
[b]
Medium
(T [K])
Emission
λem [nm] (τo [μs])
[a]
1
2
3
4
5
6
7
8
9
CH2Cl2 (298)
glass[c] (77)
CH2Cl2 (298)
glass[c] (77)
CH2Cl2 (298)
glass[c] (77)
CH2Cl2 (298)
glass[c] (77)
CH2Cl2 (298)
glass[c] (77)
CH2Cl2 (298)
glass[c] (77)
CH2Cl2 (298)
glass[c] (77)
CH2Cl2 (298)
glass[c] (77)
CH2Cl2 (298)
glass[c] (77)
573 (0.14)
1.1
–
Emission Properties
518 (136.5)
[d]
–
Complexes 2, 3, and 5 with bulky groups at the 2,9-positions
of phenanthroline and complex 9 with the dppz ligand are non-
emissive in solution at room temperature. The non-emissive na-
ture of 2, 3, and 5 can be attributed to the steric effects of the
substituents, which weaken the Ru–N bond and the corre-
sponding ligand field strength to render a lower-lying ligand
field non-radiative deactivating state.[32] Whereas for 9, the non-
emissive property is due to the presence of the non-lumines-
cent state associated with the phenazine moiety.[33]
Except for the complexes with the above non-radiative deac-
tivating factors, this complex system generally shows photo-
luminescence at room temperature as reflected by the yellow
to orange–red emissions observed for 1, 4, and 6–8 (Figure 4).
Upon photoexcitation, these complexes in dichloromethane so-
lution at room temperature show structureless emission bands
with maxima in the range 573–660 nm and lifetimes in the
range 0.14–2.25 μs (Table 2). With reference to previous spec-
troscopic studies of other RuII diimine complexes[34] and the
observed emission energy trend [1 (573 nm) > 8 (581 nm) > 6
(584 nm) > 7 (595 nm) > 4 (660 nm)], which is in line with
the decreasing π-accepting ability of the diimine ligands, these
emissions are assigned to MLCT [dπ(Ru)→π*(N N)] phosphores-
cence. It is noteworthy that the increase in rigidity of the di-
imine ligand framework from 2,2′-bipyridine to the π-conju-
gated diimine ligands in 7–8 led to improved luminescent
quantum yields.[35]
517 (237.2)
[d]
–
–
544 (359.3)
660 (2.22)
594 (168.2)
3.5
–
[d]
–
535 (421.5)
579 (2.25)
540 (563.1)
592 (2.16)
531 (188.3)
580 (1.82)
518 (161.4)
25.2
16.1
10.2
–
[d]
–
538, 583 (14.5)
[a] Excitation at 420 nm. Emission maxima are uncorrected values. [b] Lumi-
nescence quantum yield with excitation at 436 nm by using [Ru(bpy)3Cl2] as
a standard or with excitation at 350 nm by using quinine sulfate as a stan-
dard. [c] In EtOH/MeOH (4:1, v/v). [d] Non-emissive.
state. Complex 9 displays luminescence with a highly structured
emission band with vibrational progression spacing of approxi-
mately 1435 cm–1. The significantly different emission charac-
teristics of 9 is suggestive of a different emission origin. The
observation of the structured emission bands suggests the as-
3
signment of the LC excited state of the dppz ligand.
Figure 5. Overlaid emission spectra of 1, 3, 4, 5, and 8 in glass medium at
77 K.
Figure 4. Overlaid emission spectra of 1, 4, 6, and 8 in CH2Cl2 at room tem-
perature.
The emission of these complexes are found to be slightly
sensitive to the solvent environment, which is consistent with
In 77 K EtOH/MeOH (4:1, v/v) glassy medium, these com- their MLCT nature. The emission profiles of complexes 6–8 in
plexes also display strong luminescence (Figure 5, Table 2). Ex- different solvent media, such as acetone, MeCN, CH2Cl2, DMF,
cept for 9, all complexes show structureless emission bands and MeOH, were investigated and are shown in Figures S6–S8.
with a similar energy trend but are considerably blueshifted The emissions of 6 show a blueshift in emission energy with
and longer-lived than their solution emissions. These emissions decreasing solvent polarity from a DMF solution (588 nm) to a
are also tentatively assigned to be derived from the 3MLCT CH2Cl2 solution (582 nm). Such a solvent dependence may be
[dπ(Ru)→π*(N N)] excited state. The considerably blueshifted due to the increase in the dipole moment of the excited state,
emission in the low-temperature glassy medium is due to the which is more stabilized in a polar solvent medium, in compari-
rigidochromic effect commonly observed in MLCT emitters.[36] son to its ground state. However, complexes 7 and 8 have dpq
The sub-microsecond excited-state lifetimes in the glassy me- and dpqc ligands that readily form hydrogen-bonding interac-
dium at 77 K further support the assignment of a triplet excited tions with protic solvents. Thus, their solvotochromic effects are
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more complicated than that of 6 and result from the simultane- the diimine ligand. For 9, a second quasi-reversible reduction
ous contribution of solvent polarity and hydrogen-bonding ef- couple at –2.15 V (ΔEp = 94 mV and ipc/ipa = 1.14 vs. Cp2Fe+/0
)
fects.
is observed, which is assigned to the dppz ligand-based reduc-
tion as two successive dppz-based reductions are common for
complexes with the dppz ligand.[38]
Electrochemistry
The redox properties of all of the complexes in acetonitrile con-
Conclusions
taining 0.1
M nBu4NPF6 were studied by cyclic voltammetry and
We have developed and studied a series of new luminescent
RuII diimine complexes. Except those with non-radiative deacti-
vating diimine ligands, these complexes exhibit MLCT phospho-
rescence with emission energies, lifetimes, and quantum yields
that show strong dependence on the nature of the diimine
ligand. Although the quantum efficiencies of these complexes
are lower than those of the tris(bipyridyl) RuII complexes, we
demonstrate the possibility of developing new families of lumi-
nophores based on RuII complexes with one diimine ligand and
four different other ancillary ligands. We believe that by varying
the ancillary ligands we can modify and improve the phospho-
rescence characteristics. On the basis of these results, further
modification of the complexes with various types of ancillary
ligands for the development of new luminescent building
blocks, photosensitizers, and phosphorescent materials with en-
hanced luminescence properties is now in progress.
the electrochemical data are summarized in Table 3. Represent-
ative cyclic voltammograms of these complexes are shown in
Figure 6. These complexes show an irreversible oxidation wave
with Epa in the range +0.74 V to +1.27 V versus Cp2Fe+/0, which
is assigned to metal-centered Ru3+/2+ oxidation commonly ob-
served in RuII diimine complexes.[37] Such an assignment is sup-
ported by the higher oxidation potential observed for com-
plexes with electron-withdrawing substituents and π-conjugat-
ing diimine ligands. In the reduction scan, these complexes all
show a quasi-reversible reduction couple in the range –1.42 to
–2.01 V (ΔEp ≈ 61–72 mV and ipc/ipa ≈ 0.99–1.10 vs. Cp2Fe+/0).
The high sensitivity of the reduction potential to the electronic
nature of the diimine ligand is suggestive of the reduction of
Table 3. Electrochemical data for complexes 1–9 with 0.1
M [nBu4N]PF6 in
MeCN at 298 K.[a]
Oxidation Epa
Reduction E1/2 (vs. Fc+/0) [V][b]
(ΔEp [mV])[c]
(vs. Fc+/0) [V][b]
Experimental Section
1
2
3
4
5
6
7
8
9
+0.74
+0.91
+1.22
+1.27
+0.90
+0.85
+0.82
+0.81
+0.80
–2.01 (68)
–1.99 (69)
–1.72 (72)
–1.52 (85)
–1.94 (69)
–1.85 (70)
–1.78 (70)
–1.85 (69)
Materials and Reagents: The diimine ligands, 2,9-dimethyl-1,10-
phenanthroline (Me2Phen), 4,4′-dimethyl-2,2′-bipyridine (Me2bpy),
2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline (Me2Ph2phen), and
4,7-diphenyl-1,10-phenanthroline (Ph2Phen) were purchased from
Acros Organics. Triphenylphosphine and RuCl3 were purchased
from Strem Chemical Company. These commercially available rea-
gents were used without further purification. The diimine ligands
PhenCOOH,[24] PhenCN,[24] dpq,[25] dpqc,[25] and dppz,[26] and the
precursor complex [RuII(PPh3)(CO)(H)2][39] were synthesized accord-
ing to literature procedures. All other reagents and solvents were
of analytical grade and were used without further purification.
–1.42 (61), –2.15 (94)
[a] Working electrode: glassy carbon; scan rate: 100 mV s–1. [b] E1/2 = (Epa
+
Epc)/2, where Epa and Epc are the anodic and cathodic peak potentials, respec-
tively. [c] ΔEp = |Epa – Epc|.
Synthesis
General: All reactions were carried out under strictly anaerobic con-
ditions in an inert argon atmosphere by using standard Schlenk
techniques.
[RuII(Me2bpy)(CO)(H)(PPh3)2]PF6 (1): Me2bpy (46.5 mg,
0.25 mmol) was added to a suspension of [Ru(PPh3)3(CO)(H)2]
(200 mg, 0.21 mmol) in EtOH (150 mL). The mixture was heated at
reflux for 1 d under argon and then NH4PF6 (342 mg, 2.1 mmol)
was added. The mixture was further heated at reflux for 1 h. The
solvent was removed under reduced pressure and the pale-yellow
solid was collected and washed with ice-cold methanol (3 × 4 mL).
It was recrystallized by slow evaporation of diethyl ether into a
CH2Cl2 solution of the complex. Yield 82.5 mg, 46.7 %. Elemental
analysis calcd. (%) for C49H43F6N2OP3Ru (983.87): C 59.82, H 4.41, N
2.85; found C 59.76, H 4.53, N 2.71. IR (KBr): ν = ν(Ru–H) 2001;
˜
1
ν(C≡ O) 1936; ν(P–F) 834 cm–1. ESI-MS (positive): m/z = 839 [M+]. H
NMR (300 MHz, CDCl3): δ = 8.90 (d, J = 5.5 Hz, 1 H, bpy H), 8.01 (s,
2 H, bpy H), 7.56 (d, J = 5.6 Hz, 1 H, bpy H), 7.38–7.24 (m, 6 H,
phenyl H), 7.29–7.34 (m, 12 H, phenyl H), 7.17–7.25 (m, 12 H, phenyl
H), 6.44 (d, J = 5.7 Hz, 1 H, bpy H), 5.77 (s, 1 H, bpy H), 2.34 (s, 3 H,
-CH3), 2.28 (s, 3 H, -CH3), –11.45 (t, J = 19.4 Hz, 1 H, Ru–H) ppm.
Figure 6. Cyclic voltammograms of (a) 1 and (b) 9 in 0.1
M
[nBu4N]PF6 MeCN
solution with scan rate = 100 mV s–1
.
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–
31P{1H} NMR (162 MHz, CDCl3): δ = 45.7 (s, PPh3), –144.4 (sept, PF6
H), 7.50 (m, 2 H, phen H), 7.46 (s, 1 H, phen H), 7.39–7.29 (m, 9 H,
) ppm. UV/Vis (CH3CN): λmax/nm (ε/mol–1 dm3 cm–1): 267 sh (20980), phenyl H), 7.23–7.10 (m, 18 H, phenyl H), 6.81 (s, 1 H, phen H), 2.46
271 sh (20270), 290 sh (15620), 308 sh (11870), 396 (1470).
(s, 3 H, -CH3), 2.20 (s, 3 H, -CH3), –11.09 (t, J = 18.8 Hz, 1 H, Ru–H)
ppm. 31P{1H} NMR (162 MHz, CDCl3): δ = 43.5 (s, PPh3), –144.2 (sept,
PF6–) ppm. UV/Vis (CH3CN): λmax/nm (ε/mol–1 dm3 cm–1): 225 sh
(61930), 248 sh (38270), 292 sh (33060), 330 sh (10270), 402 (2250).
[RuII(Ph2Phen)(CO)(H)(PPh3)2]PF6 (6): The synthetic method used
was similar to that of 1 except that the ligand Ph2Phen (83.5 mg,
[RuII(Me2Phen)(CO)(H)(PPh3)2]PF6 (2): The synthetic method is
similar to that of 1 except that the ligand Me2Phen (52.1 mg,
0.25 mmol) was used instead of Me2bpy. Yield 82.5 mg, 46.7 %.
Yield 106.4 mg, 50.2 %. Elemental analysis calcd. (%) for
C51H43F6N2OP3Ru (1007.89): C 60.78, H 4.30, N 2.78; found C 60.86,
H 4.41, N 2.75. IR (KBr): ν = ν(Ru–H) 2026; ν(C≡ O) 1937; ν(P–F) 841 0.25 mmol) was used instead of Me2bpy. Yield 103.4 mg, 43.5 %.
˜
1
cm–1. ESI-MS (positive): m/z = 863 [M+]. H NMR (300 MHz, CDCl3):
Elemental analysis calcd. (%) for C61H47F6N2OP3Ru (1132.03): C
δ = 8.44 (d, J = 8.3 Hz, 1 H, phen H), 8.02 (t, J = 8.5 Hz, 2 H, phen
64.72, H 4.18, N 2.47; found C 64.80, H 4.26, N 2.35. IR (KBr): ν =
˜
1
H), 7.86 (d, J = 8.7 Hz, 1 H, phen H), 7.52 (d, J = 8.3 Hz, 1 H, phen ν(C≡ O) 1942; ν(P–F) 838 cm–1. ESI-MS (positive): m/z = 987 [M+]. H
H), 7.31–7.24 (m, 9 H, phenyl H), 7.20–6.95 (m, 21 H, phenyl H), 6.87
(d, J = 8.3 Hz, 1 H, phen H), 2.41 (s, 3 H, CH3), 2.09 (s, 3 H, CH3),
–11.25 (t, J = 18.8 Hz, 1 H, Ru–H) ppm. 31P{1H} NMR (162 MHz,
CDCl3): δ = 43.6 (s, PPh3), –144.2 (sept, PF6–) ppm. UV/Vis (CH3CN):
NMR (300 MHz, CDCl3): δ = 9.22 (d, J = 5.3 Hz, 1 H, phen H), 8.13
(d, J = 5.3 Hz, 1 H, phen H), 7.90 (dt, J = 9.4 Hz, 2 H, phen H), 7.67–
7.54 (m, 8 H, phenyl H), 7.48 (dd, J = 7.6, 1.7 Hz, 2 H, phen H), 7.43–
7.36 (m, 2 H, phen H), 7.37–7.29 (m, 8 H, phenyl H), 7.27–7.15 (m,
22 H, phenyl H), –11.00 (t, J = 19.1 Hz, 1 H, Ru–H) ppm. 31P{1H} NMR
(162 MHz, CDCl3): δ = 46.1 (s, PPh3), –144.2 (sept, PF6–) ppm. UV/
Vis (CH3CN): λmax/nm (ε/mol–1 dm3 cm–1): 225 sh (55410), 289 sh
(28950), 322 sh (12290), 401 sh (3690).
λ
max/nm (ε/mol–1 dm3 cm–1): 226 sh (59060), 275 sh (25090), 318 sh
(7230), 395 (870).
[RuII(PhenCOOH)(CO)(H)(PPh3)2]PF6 (3): Compound 3 was pre-
pared by a procedure similar to that for 1, except PhenCOOH
(56.1 mg, 0.25 mmol) was used instead of Me2bpy. Yield 84.6 mg, [RuII(dpq)(CO)(H)(PPh3)2]PF6 (7): The synthetic method used was
45.8 %. Elemental analysis calcd. (%) for
(1023.85): C 58.66, H 3.84, N 2.74; found C 58.59, H 3.92, N 2.81. IR
(KBr): ν = ν(Ru–H) 2007; ν(C≡ O) 1945; ν(P–F) 841; ν(C=O) 1618 cm–1
C
50H39F6N2O3P3Ru
similar to that of 1 except that the ligand dpq (58.06 mg,
0.25 mmol) was used instead of Me2bpy. Yield 111.8 mg, 51.6 %.
Elemental analysis calcd. (%) for C51H39F6N4OP3Ru (1031.87): C
.
˜
ESI-MS (positive): m/z = 879 [M+]. 1H NMR (300 MHz, CDCl3): δ = 59.36, H 3.81, N 5.43; found C 59.22, H 3.95, N 5.38. IR (KBr): ν =
˜
9.45 (s, 1 H, -COOH), 8.35 (d, J = 7.6 Hz, 1 H, phen H), 8.14 (d, J =
8.8 Hz, 2 H, phen H), 7.73 (d, J = 8.6 Hz, 2 H, phen H), 7.58 (d, J =
ν(Ru–H) 2006; ν(C≡ O) 1941; ν(P–F) 840 cm–1. ESI-MS (positive): m/z =
887 [M+]. 1H NMR (300 MHz, CDCl3): δ = 9.38 (d, J = 8.1 Hz, 1 H,
8.1 Hz, 1 H, phen H), 7.24–7.31 (m, 12 H, phenyl H), 7.17–7.22 (m, 6 dpq H), 9.29 (t, J = 6.7 Hz, 2 H, dpq H), 9.14 (dd, J = 4.1, 2.0 Hz, 2
H, phenyl H), 7.05–7.14 (m, 12 H, phenyl H), 5.77 (s, 1 H, phen H),
–12.09 (t, J = 19.9 Hz, 1 H, Ru–H) ppm. 31P{1H} NMR (162 MHz,
CDCl3): δ = 44.5 (s, PPh3), –144.2 (sept, PF6–) ppm. UV/Vis (CH3CN):
H, dpq H), 8.13 (d, J = 5.5 Hz, 1 H, dpq H), 7.84 (dd, J = 8.3, 5.1 Hz,
1 H, dpq H), 7.26–7.12 (m, 30 H, phenyl H), 7.09 (dd, J = 8.2, 5.3 Hz,
1 H, dpq H), –11.15 (t, J = 19.2 Hz, 1 H, Ru–H) ppm. 31P{1H} NMR
(162 MHz, CDCl3): δ = 46.1 (s, PPh3), –144.2 (sept, PF6–) ppm. UV/
Vis (CH3CN): λmax/nm (ε/mol–1 dm3 cm–1): 2256 sh (47680), 298 sh
(23600), 322 sh (6550), 401 (2500).
[RuII(dpqc)(CO)(H)(PPh3)2]PF6 (8): The synthetic method used was
similar to that of 1 except that the ligand dpqc (71.6 mg,
0.25 mmol) was used instead of Me2bpy. Yield 114.7 mg, 50.3 %.
λ
max/nm (ε/mol–1·dm3·cm–1): 232 (38680), 270 sh (20220), 276 sh
(19800), 325 sh (6160), 425 sh (1370).
[RuII(PhenCN)(CO)(H)(PPh3)2]PF6 (4): PhenCN (51.5 mg,
0.25 mmol) was added to a suspension of [Ru(PPh3)3(CO)(H)2]
(200 mg, 0.21 mmol) in the presence of excess Et2NH·HCl (169 mg,
2.1 mmol) in EtOH (150 mL). The mixture was heated at reflux for
1 d under argon and then NH4PF6 (342 mg, 2.1 mmol) was added. Elemental analysis calcd. (%) for C55H45F6N4OP3Ru (1085.97): C
The mixture was heated at reflux for a further 1 h. The solvent
was removed under reduced pressure and the pale-yellow solid was
collected and washed with by water (3 × 4 mL) and then by ice-
cold methanol (3 × 4 mL). It was recrystallized by slow evaporation
of a CH2Cl2/MeOH (1:3, v/v) solution of the complex. Yield 80.6 mg,
44.6 %. Elemental analysis calcd. (%) for C50H38F6N3OP3Ru (1004.85):
60.83, H 4.18, N 5.16; found C 60.66, H 4.30, N 5.08. IR (KBr): ν =
˜
ν(Ru–H) 1971; ν(C≡ O) 1951; ν(P–F) 841 cm–1. ESI-MS (positive): m/z =
941 [M+]. 1H NMR (300 MHz, CDCl3): δ = 9.35 (d, J = 8.2 Hz, 1 H,
dpqc H), 9.24 (d, J = 7.9 Hz, 1 H, dpqc H), 9.17 (d, J = 5.2 Hz, 1 H,
dpqc H), 8.02 (d, J = 5.7 Hz, 1 H, dpqc H), 7.74 (dd, J = 8.3, 5.1 Hz,
1 H, dpqc H), 7.24 (m, 6 H, phenyl H), 7.22–7.09 (m, 24 H, phenyl
H), 7.01 (dd, J = 8.2, 5.3 Hz, 1 H, dpqc H), 2.14 (m, 4 H, -CH2), 1.56
(m, 4 H, -CH2), –11.14 (t, J = 19.4 Hz, 1 H, Ru–H) ppm. 31P{1H} NMR
(162 MHz, CDCl3): δ = 46.2 (s, PPh3), –144.2 (sept, PF6–) ppm. UV/
Vis (CH3CN): λmax/nm (ε/mol–1·dm3·cm–1): 224 sh (50380), 268 sh
(33460), 308 sh (15860), 342 sh (5653), 404 (1780).
C 59.76, H 3.81, N 4.18; found C 59.81, H 3.92, N 4.15. IR (KBr): ν =
˜
ν(C≡ O) 1951; ν(P–F) 839 cm–1. ESI-MS (negative): m/z = 860 [M+]. 1H
NMR (300 MHz, CDCl3): δ = 9.13 (d, J = 6 Hz, 1 H, phen H), 8.49 (dd,
J = 15.8, 7.9 Hz, 2 H, phen H), 8.19 (d, J = 1.9 Hz, 2 H, phen H), 7.63
(dd, J = 7.8, 5.4 Hz, 1 H, phen H), 7.31–7.36 (m, 8 H, phenyl H),
7.10–7.22 (m, 22 H, phenyl H), 5.33 (s, 1 H, phen H), –10.43 (t, J =
18.5 Hz, 1 H, Ru–H) ppm. 31P{1H} NMR (162 MHz, CDCl3): δ = 45.0
(s, PPh3), –144.4 (sept, PF6–) ppm. UV/Vis (CH3CN): λmax/nm
(ε/mol–1 dm3 cm–1): 276 (37350), 290 sh (26010), 324 sh (9080), 378
(3640), 465 (1180).
[RuII(dppz)(CO)(H)(PPh3)2]PF6 (9): The synthetic method used was
similar to that of 1 except that the ligand dppz (70.6 mg,
0.25 mmol) was used instead of Me2bpy. Yield 112 mg, 49.3 %. Ele-
mental analysis calcd. (%) for C55H41F6N4OP3Ru (1081.93): C 61.06,
H 3.82, N 5.18; found C 61.17, H 3.95, N 5.02. IR (KBr): ν = ν(Ru–H)
˜
[RuII(Me2Ph2phen)(CO)(H)(PPh3)2]PF6 (5): The synthetic method
2019; ν(C≡ O) 1939; ν(P–F) 839 cm–1. ESI-MS (positive): m/z = 937
used was similar to that of 1 except that the ligand Me2Ph2phen [M+]. H NMR (300 MHz, CDCl3): δ = 9.53 (d, J = 7.2 Hz, 1 H, dppz
1
(90.1 mg, 0.25 mmol) was used instead of Me2bpy. Yield 107.6 mg, H), 9.43 (d, J = 8.2 Hz, 1 H, dppz H), 9.32 (d, J = 5.1 Hz, 1 H, dppz
44.2 %. Elemental analysis calcd. (%) for C63H51F6N2OP3Ru (1160.09):
H), 8.45 (dd, J = 6.6, 3.4 Hz, 2 H, dppz H), 8.15 (d, J = 4.3 Hz, 1 H,
dppz H), 8.08 (dd, J = 6.6, 3.4 Hz, 2 H, dppz H), 7.88 (dd, J = 8.2,
C 65.23, H 4.43, N 2.41; found C 65.20, H 4.60, N 2.49. IR (KBr): ν =
˜
ν(Ru–H) 2032; ν(C≡ O) 1938; ν(P–F) 838 cm–1. ESI-MS (positive): m/z = 5.2 Hz, 1 H, dppz H), 7.28–7.10 (m, 30 H, phenyl H), –11.19 (d, J =
1015 [M+]. 1H NMR (300 MHz, CDCl3): δ = 7.98 (d, J = 9.3 Hz, 1 H, 19.1 Hz, 1 H, Ru–H) ppm. 31P{1H} NMR (162 MHz, CDCl3): δ = 46.0
phen H), 7.82 (d, J = 9.2 Hz, 1 H, phen H), 7.75–7.53 (m, 11 H, phenyl
(s, PPh3), –144.2 (sept, PF6–) ppm. UV/Vis (CH3CN): λmax/nm
Eur. J. Inorg. Chem. 0000, 0–0
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(ε/mol–1·dm3·cm–1): 225 sh (54850), 277 sh (55990), 312 sh (16940),
364 (10170), 412 (2920).
per. These data can be obtained free of charge from The Cambridge
Crystallographic Data Centre.
Physical Measurements and Instrumentation: 1H NMR and
31P{1H} NMR spectra were recorded with a Bruker AV300 (300 MHz)
FT-NMR spectrometer. Chemical shifts (δ) are reported relative to
tetramethylsilane (Me4Si). All-positive-ion ESI mass spectra were re-
corded with a PE-SCIEX API 150 EX single-quadruple mass spec-
trometer. Elemental analysis was performed with an ElementarVario
MICRO Cube elemental analyzer. IR spectra of the solid samples as
KBr discs were obtained within the range 4000–400 cm–1 with an
AVATAR 360 FTIR spectrometer. All of the electronic absorption
spectra were recorded with a Hewlett–Packard 8453 or Hewlett–
Packard 8452A diode-array spectrophotometer. Steady-state emis-
sion and excitation spectra were measured at room temperature
and at 77 K with a Horiba JobinYvon Fluorolog-3-TCSPC spectro-
fluorometer. The solutions were rigorously degassed with a high-
vacuum line in a two-compartment cell with not less than four
successive freeze–pump–thaw cycles. The measurements at 77 K
were carried out with dilute solutions of the samples in EtOH/MeOH
(4:1, v/v) loaded in a quartz tube inside a quartz-walled Dewar flask
that contained liquid nitrogen. Luminescence quantum yields were
determined by using the optical dilution method described by De-
Acknowledgments
The authors gratefully acknowledge the financial support of the
National Natural Science Foundation of China (NNSFC) (grant
number 21201023). This work was also supported by the Hong
Kong University Grants Committee Area of Excellence Scheme
(grant number AoE/P-03-08).
Keywords: Luminescence · Photophysics · Electronic
structure · Conjugation · Ruthenium · N ligands
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Published Online: ■
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© 0000 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

Full Paper
Luminescent Ru Complexes
F. Yu, W.-K. Chu, C. Shen, Y. Luo,
J. Xiang,* S.-Q. Chen, C.-C. Ko,*
T.-C. Lau* .............................................. 1–9
Luminescent
Carbonyl Hydrido
Ruthenium(II) Diimine Coordination
Compounds: Structural, Photophysi-
cal, and Electrochemical Properties
Luminescent carbonyl hydrido ruthen- ties are discussed. The luminescence
ium(II) complexes with various diimine performance of these complexes could
ligands have been synthesized. The ef- be significantly enhanced by increas-
fects of the electronic features and di- ing the rigidity and π-conjugation of
imine ligand π-conjugation on the the diimine ligand.
electronic and photophysical proper-
DOI: 10.1002/ejic.201600438
Eur. J. Inorg. Chem. 0000, 0–0
www.eurjic.org
9
© 0000 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim