Heteroleptic ruthenium(II) polypyridine complexes with a series of substituted 2,2′-bipyridine ligands

Article abstract of DOI:10.1080/00958972.2016.1156098

Five substituted-2,2′-bipyridine ligands L, (4-(p-methylphenyl)-6-phenyl-2,2′-bipyridine (L1), 4-(p-bromophenyl)-6-(p-bromophenyl)-2,2′-bipyridine (L2), 4-(p-bromophenyl)-6-phenyl-2,2′-bipyridine (L3), 4-phenyl-6-(p-bromophenyl)-2,2′-bipyridine (L4), and 4-(p-fluorophenyl)-6-(p-fluorophenyl)-2,2′-bipyridine (L5) were synthesized by stepwise formation. Reaction of cis-[RuCl₂(bpy)₂]2H₂O or cis-[RuCl₂(phen)₂]2H₂O and the substituted-2,2′-bipyridine ligands in the presence of KPF₆ afforded the corresponding cationic polypyridine-ruthenium complexes of the type [(bpy)₂Ru(L)](PF₆)₂ (bpy = 2,2′-bipyridine, 1-5) or [(phen)₂Ru(L)](PF₆)₂ (phen = 1,10-phenanthroline, 6-10), respectively. All complexes have been spectroscopically characterized by UV-vis, luminescence, and electrogenerated chemiluminescence. The structures of 1CH₃COCH₃, 3CH₃COCH₃, 52CH₃COCH₃, 6, 8, 9, and 10 have been determined by single-crystal X-ray diffraction.

Full text of DOI:10.1080/00958972.2016.1156098

Journal of Coordination Chemistry
ISSN: 0095-8972 (Print) 1029-0389 (Online) Journal homepage: http://www.tandfonline.com/loi/gcoo20
Heteroleptic ruthenium(II) polypyridine complexes
with a series of substituted 2,2′-bipyridine ligands
Zhi-Min Wang, Su-Mei Shen, Xiu-Yin Shen, Ya-Qin Xu, Ai-Quan Jia & Qian-
Feng Zhang
To cite this article: Zhi-Min Wang, Su-Mei Shen, Xiu-Yin Shen, Ya-Qin Xu, Ai-Quan Jia &
Qian-Feng Zhang (2016) Heteroleptic ruthenium(II) polypyridine complexes with a series of
substituted 2,2′-bipyridine ligands, Journal of Coordination Chemistry, 69:5, 851-861, DOI:
10.1080/00958972.2016.1156098
To link to this article: http://dx.doi.org/10.1080/00958972.2016.1156098
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Published online: 09 Mar 2016.
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Date: 08 April 2016, At: 13:02

Journal of Coordination Chemistry, 2016
Vol. 69, no. 5, 851–861
ꢀꢁꢁp://ꢂx.ꢂꢃꢄ.ꢃꢅg/10.1080/00958972.2016.1156098
Heteroleptic ruthenium(II) polypyridine complexes with a series
of substituted 2,2′-bipyridine ligands
a
b
c
d
d
Zhi-Min Wang , Su-Mei Shen , Xiu-Yin Shen , Ya-Qin Xu , Ai-Quan Jia and
d
Qian-Feng Zhang
ꢆ
b
Cꢃꢇꢇꢈgꢈ ꢃꢉ Bꢄꢃꢇꢃgꢊ & eꢋvꢄꢅꢃꢋꢌꢈꢋꢁ eꢋgꢄꢋꢈꢈꢅꢄꢋg, Zꢀꢈjꢄꢆꢋg sꢀꢍꢅꢈꢋ uꢋꢄvꢈꢅꢎꢄꢁꢊ, hꢆꢋgzꢀꢃꢍ, Pr Cꢀꢄꢋꢆ; dꢈpꢆꢅꢁꢌꢈꢋꢁ ꢃꢉ
c
appꢇꢄꢈꢂ Cꢀꢈꢌꢄꢎꢁꢅꢊ, Zꢀꢈjꢄꢆꢋg ecꢃꢋꢃꢌꢄc & tꢅꢆꢂꢈ Pꢃꢇꢊꢁꢈcꢀꢋꢄc, hꢆꢋgzꢀꢃꢍ, Pr Cꢀꢄꢋꢆ; scꢀꢃꢃꢇ ꢃꢉ Bꢄꢃꢇgꢄcꢆꢇ ꢆꢋꢂ Cꢀꢈꢌꢄcꢆꢇ
eꢋgꢄꢋꢈꢈꢅꢄꢋg, Zꢀꢈjꢄꢆꢋg uꢋꢄvꢈꢅꢎꢄꢁꢊ ꢃꢉ scꢄꢈꢋcꢈ & tꢈcꢀꢋꢃꢇꢃgꢊ, hꢆꢋgzꢀꢃꢍ, Pr Cꢀꢄꢋꢆ; iꢋꢎꢁꢄꢁꢍꢁꢈ ꢃꢉ mꢃꢇꢈcꢍꢇꢆꢅ eꢋgꢄꢋꢈꢈꢅꢄꢋg
ꢂ
ꢆꢋꢂ appꢇꢄꢈꢂ Cꢀꢈꢌꢄꢎꢁꢅꢊ, aꢋꢀꢍꢄ uꢋꢄvꢈꢅꢎꢄꢁꢊ ꢃꢉ tꢈcꢀꢋꢃꢇꢃgꢊ, mꢆ’ꢆꢋꢎꢀꢆꢋ, Pr Cꢀꢄꢋꢆ
ABSTRACT
ARTICLE HISTORY
rꢈcꢈꢄvꢈꢂ 25 ocꢁꢃbꢈꢅ 2015
accꢈpꢁꢈꢂ 9 fꢈbꢅꢍꢆꢅꢊ 2016
Five substituted-2,2′-bipyridine ligands L, (4-(p-methylphenyl)-6-phenyl-2,2′-
bipyridine (L1), 4-(p-bromophenyl)-6-(p-bromophenyl)-2,2′-bipyridine (L2), 4-(p-
bromophenyl)-6-phenyl-2,2′-bipyridine (L3), 4-phenyl-6-(p-bromophenyl)-2,2′-
bipyridine (L4), and 4-(p-fluorophenyl)-6-(p-fluorophenyl)-2,2′-bipyridine (L5)
were synthesized by stepwise formation. Reaction of cis-[RuCl (bpy) ]⋅2H O or cis-
KEYWORDS
rꢍꢁꢀꢈꢋꢄꢍꢌ cꢃꢌpꢇꢈx;
2,2′-Bꢄpꢊꢅꢄꢂꢄꢋꢈ; pꢃꢇꢊpꢊꢅꢄꢂꢄꢋꢈ;
1,10-pꢀꢈꢋꢆꢋꢁꢀꢅꢃꢇꢄꢋꢈ; cꢅꢊꢎꢁꢆꢇ
ꢎꢁꢅꢍcꢁꢍꢅꢈ
2
2
2
[
RuCl (phen) ]⋅2H O and the substituted-2,2′-bipyridine ligands in the presence
2 2 2
of KPF afforded the corresponding cationic polypyridine-ruthenium complexes
6
of the type [(bpy) Ru(L)](PF ) (bpy = 2,2′-bipyridine, 1–5) or [(phen) Ru(L)](PF )
2
6 2
2
6 2
(
phen = 1,10-phenanthroline, 6–10), respectively. All complexes have been
spectroscopically characterized by UV–vis, luminescence, and electrogenerated
chemiluminescence.The structures of 1⋅CH COCH , 3⋅CH COCH , 5⋅2CH COCH ,
3
3
3
3
3
3
6
, 8, 9, and 10 have been determined by single-crystal X-ray diffraction.
1. Introduction
Ruthenium(II) complexes containing polypyridyl chelating ligands have received attention because of
their applications in photochemistry, photophysics, and biochemistry [1]. The rich photophysical and
CONTACT Qꢄꢆꢋ-fꢈꢋg Zꢀꢆꢋg
zꢀꢆꢋgqꢉ@ꢆꢀꢍꢁ.ꢈꢂꢍ.cꢋ
sꢍppꢇꢈꢌꢈꢋꢁꢆꢇ ꢂꢆꢁꢆ ꢉꢃꢅ ꢁꢀꢄꢎ ꢆꢅꢁꢄcꢇꢈ cꢆꢋ bꢈ ꢆccꢈꢎꢎꢈꢂ ꢆꢁ ꢀꢁꢁp://ꢂx.ꢂꢃꢄ.ꢃꢅg/10.1080/00958972.2016.1156098.
©
2016 tꢆꢊꢇꢃꢅ & fꢅꢆꢋcꢄꢎ

852
Z.ꢀM. WAꢁꢂ ꢃT Aꢄ.
redox properties associated with these complexes make them potentially useful in areas as diverse
as light harvesting, electron transfer, non-linear optics, photovoltaics, self-assembly, and probes for
biologically relevant molecules such as DꢁA [2]. In particular, mononuclear ruthenium(II) complexes of
2
[
,2′-bipyridine (bpy), 1,10-phenanthroline (phen) and diimine analogs continue to be the focus of study
3, 4]. Ruthenium(II) complexes of the [Ru(bpy)3]2 family are especially interesting due to appropriate
+
2+
modifications in the bulky backbone [5], and the binding mode of the prototype complex [Ru(phen)3]
is still an issue of vigorous debate. The use of these complexes as photosensitizers for the conversion of
light (solar) energy to chemical or electrical energy has received attention [6, 7]. Ruthenium polypyridine
2
+
2+
intercalators like [Ru(bpy) (dppz)] and [Ru(phen) (dppz)] (dppz = dipyrido[3,2-a:2′,3′-c]phenazine)
2
2
2
+
have binding affinities of 106–107, which is obviously better than [Ru(bpy) ] having binding affinities
of 10 [8]. ꢃfficient synthetic routes to heteroleptic bis- and tris-(diimine)ruthenium(II) complexes are
3
3
important [9, 10]. Several routes for the synthesis of heteroleptic ruthenium(II) polypyridine complexes
have previously been reported. Although the synthesis of heteroleptic tris-(diimine)ruthenium(II) com-
plexes with different bidentate dimine ligands was first reported in the early 1980s [11], synthetic
2
+
methodology to a class of these related complexes has normally involved the use of [Ru(bpy) Cl ] ,
2
2
2
+
[
Ru(phen) Cl ] , or [Ru(ꢄ) Cl ] (ꢄ = diimine ligand) as the starting reagent [12]. An alternative method-
2 2 2 2
ology leading to the formation of heteroleptic bis- and tris-(diimine)ruthenium(II) complexes involves
halide bridge splitting combined with other chemical or photochemical reactions [13, 14]; the designed
−
complexes were finally isolated from crystallization with PF . It is our longstanding interest to study
6
ruthenium complexes with a variety of donor ligands, and we have reported a series of ruthenium
complexes with nitrogen- and sulfur-donor ligands [15–17]. As a part of the program to investigate the
synthetic route and photophysical properties with different substituted-2,2′-bipyridine ligands, a series
of the heteroleptic ruthenium(II) polypyridine complexes were synthesized and characterized, with
substituted-2,2′-bipyridine ligands shown in scheme 1. The UV–vis, luminescence, and electrogenerated
2
+
chemiluminescence (ꢃCꢄ) of these complexes relative to [Ru(bpy)3] are also reported in this article.
2. Experimental
2
.1. General considerations
Oxygen- or moisture-sensitive reactions were performed in oven-dried glassware attached to a vacuum
line using Schlenk techniques. Dry solvents were distilled from suitable desiccants under nitrogen.
Commercially available RuCl ⋅3H O (Shanghai HaiTops Chemistry Co ꢄtd) was used without purification.
3
2
2
,2′-Bipyridine (bpy) and 1,10-phenanthroline (phen) were purchased from Alfa Aesar ꢄtd and used
as supplied. cis-[RuCl (bpy) ]⋅2H O [18] and cis-[RuCl (phen) ]⋅2H O [19] were prepared according to
2
2
2
2
2
2
literature methods.
1
13
H and C ꢁMR spectra were recorded on a Bruker AV400-MHz Avance ꢁMR spectrometer at 400 MHz
1
13
for H ꢁMR and 100 MHz for C ꢁMR. ꢃlectronic absorption spectra were obtained on a Shimadzu
UV-3000 spectrophotometer. Photoluminescence (Pꢄ) spectra were measured with a Shimadzu
RF-5301PC fluorescence spectrophotometer. Positive-ion ꢃSI mass spectra were recorded on a Perkin
ꢃlmer Sciex API 365 mass spectrometer. ꢃlemental analyses were carried out using a Perkin-ꢃlmer 2400
CHꢁ analyzer. The electrochemiluminescence experiments were carried out by using a chemilumi-
nescence analyzer (Xi’an Remax ꢃlectronic Science Tech Co ꢄtd, China). Solutions used to obtain ꢃCꢄ
were 2.5 × 10− M ruthenium(II) complexes and 0.05 M tri-n-propylamine (TPA) with 0.2 M potassium
phosphate (aqueous and mixed 50:50 (v/v) CH Cꢁ/H O) as an electrolyte. The photomultiplier tube
4
3
2
was biased at 600 V. The ꢃCꢄ cell was placed directly on top of the PMT window and was enclosed in a
−
1
light-tight box. ꢃCꢄ was measured by cycles from 0 to 2 V versus Ag/AgCl at 0.1 V s using cyclic voltam-
metry and the light intensity recorded every 0.1 mV. A glass carbon electrode (3.0 mm diameter) was
used as the working electrode after pre-treating with conventional procedure. The counter electrode
2
was a platinum disk (50 mm ).

JOURꢁAꢄ OF COORDIꢁATIOꢁ CHꢃMISTRY
853
O
-
I
N
+N
pyridine, N2
reflux
N
+
I2
O
L'
R1
R1
R1
O
KOH, MeOH:H O (5:1)
2
NH4OAc, L', EtOH
+
reflux
reflux
R2
CHO
O
N
N
R2
R2
L1: R = Me, R = H
1
2
L2: R1 = Br, R2 = H
L3: R = H, = Br
R
1
2
2
L4: R = Br, R = Br
1
L5: R1 = F, R2 = F
Scheme 1. sꢊꢋꢁꢀꢈꢎꢄꢎ ꢃꢉ L1–L5 [20].
R1
2+
_
N
N
Ru
2O
2
[PF6]
.
H
2
]
l
2
R2
py
)
2C
(
b
2O
u
cis-
[
R
/
H
N
N
R1
H
tO
E
,
F
6
N
N
P
K
1
-5
R1
2+
N
N
cis-[Ru(
R2
p
h
e
K
n)
2
PF6 , E
Cl
] .2
2
tO
H2
H
O
/
H2
L1: R = Me, R2 = H
1
O
N
_
2[PF6]
L2: R1 = Br, R2 = H
N
R2
L3: R = H,
R = Br
1
1
1
2
Ru
L4: R = Br, R = Br
N
N
2
L5: R = F,
R = F
2
N
N
6
-10
Scheme 2. sꢊꢋꢁꢀꢈꢎꢄꢎ ꢃꢉ pꢃꢇꢊpꢊꢅꢄꢂꢄꢋꢈ ꢅꢍꢁꢀꢈꢋꢄꢍꢌ cꢃꢌpꢇꢈxꢈꢎ 1–10.
2
.2. X-ray diffraction measurements
Crystallographic data and experimental details for [(bpy) Ru(L1)](PF ) ⋅CH COCH (1⋅CH COCH ),
2
6 2
3
3
3
3
[
[
(
(bpy) Ru(L3)](PF ) ⋅CH COCH
(3⋅CH COCH ), [(bpy) Ru(L5)](PF ) ⋅2CH COCH
(5⋅2CH COCH ),
3 3
2
6 2
3
3
3
3
2
6 2
3
3
(phen) Ru(L1)](PF ) (6), [(phen) Ru(L3)](PF ) (8), [(phen) Ru(L4)](PF ) (9), and [(phen) Ru(L5)]
2
6 2
2
6 2
2
6 2
2
PF ) (10) are summarized in table (1). Intensity data were collected on a Bruker SMART APꢃX 2 CCD
6
2

854
Z.ꢀM. WAꢁꢂ ꢃT Aꢄ.

JOURꢁAꢄ OF COORDIꢁATIOꢁ CHꢃMISTRY
855
Figure 1. mꢃꢇꢈcꢍꢇꢆꢅ ꢎꢁꢅꢍcꢁꢍꢅꢈ ꢃꢉ ꢁꢀꢈ cꢆꢁꢄꢃꢋ ꢄꢋ [(bpꢊ) rꢍ(L1)](Pf ) ⋅Ch CoCh (1⋅Ch CoCh ). tꢀꢈꢅꢌꢆꢇ ꢈꢇꢇꢄpꢎꢃꢄꢂꢎ ꢆꢅꢈ ꢎꢀꢃwꢋ ꢆꢁ ꢁꢀꢈ 40%
2
6 2
3
3
3
3
−
pꢅꢃbꢆbꢄꢇꢄꢁꢊ ꢇꢈvꢈꢇ. tꢀꢈ [Pf ] ꢆꢅꢈ ꢃꢌꢄꢁꢁꢈꢂ ꢉꢃꢅ cꢇꢆꢅꢄꢁꢊ.
6
Figure 2. mꢃꢇꢈcꢍꢇꢆꢅ ꢎꢁꢅꢍcꢁꢍꢅꢈ ꢃꢉ ꢁꢀꢈ cꢆꢁꢄꢃꢋ ꢄꢋ [(bpꢊ) rꢍ(L3)](Pf ) ⋅Ch CoCh (3⋅Ch CoCh ). tꢀꢈꢅꢌꢆꢇ ꢈꢇꢇꢄpꢎꢃꢄꢂꢎ ꢆꢅꢈ ꢎꢀꢃwꢋ ꢆꢁ ꢁꢀꢈ 40%
2
6 2
3
3
3
3
−
pꢅꢃbꢆbꢄꢇꢄꢁꢊ ꢇꢈvꢈꢇ. tꢀꢈ [Pf ] ꢆꢅꢈ ꢃꢌꢄꢁꢁꢈꢂ ꢉꢃꢅ cꢇꢆꢅꢄꢁꢊ.
6
diffractometer using graphite-monochromated Mo-Kα radiation (λ = 0.71073 Å) at 293(2) K. The col-
lected frames were processed with SAIꢁT [21]. The data were corrected for absorption using SADABS
2
[
22]. Structures were solved by direct methods and refined by full-matrix least-squares on F using
the SHꢃꢄXTꢄ software package [23, 24]. All non-hydrogen atoms except for the lattice solvent mol-
ecules were refined anisotropically. The positions of all hydrogens were generated geometrically
(Csp3–H = 0.96 Å and Csp2–H = 0.93 Å), assigned isotropic thermal parameters, and allowed to ride on
their respective parent carbon or nitrogen before the final cycle of least-squares refinement. Solvent
molecules such as acetone in 5⋅2CH COCH were isotropically refined or without hydrogens due to
3
3
heavy disorder, which probably resulted in the relatively high R values in the final refinement.

856
Z.ꢀM. WAꢁꢂ ꢃT Aꢄ.
Figure 3. mꢃꢇꢈcꢍꢇꢆꢅ ꢎꢁꢅꢍcꢁꢍꢅꢈ ꢃꢉ ꢁꢀꢈ cꢆꢁꢄꢃꢋ ꢄꢋ [(bpꢊ) rꢍ(L5)](Pf ) ⋅2Ch CoCh (5⋅2Ch CoCh ). tꢀꢈꢅꢌꢆꢇ ꢈꢇꢇꢄpꢎꢃꢄꢂꢎ ꢆꢅꢈ ꢎꢀꢃwꢋ ꢆꢁ ꢁꢀꢈ
2
6 2
3
3
3
3
−
4
0% pꢅꢃbꢆbꢄꢇꢄꢁꢊ ꢇꢈvꢈꢇ. tꢀꢈ [Pf ] ꢆꢅꢈ ꢃꢌꢄꢁꢁꢈꢂ ꢉꢃꢅ cꢇꢆꢅꢄꢁꢊ.
6
Figure 4. mꢃꢇꢈcꢍꢇꢆꢅ ꢎꢁꢅꢍcꢁꢍꢅꢈ ꢃꢉ ꢁꢀꢈ cꢆꢁꢄꢃꢋ ꢄꢋ [(pꢀꢈꢋ) rꢍ(L1)](Pf ) (6). tꢀꢈꢅꢌꢆꢇ ꢈꢇꢇꢄpꢎꢃꢄꢂꢎ ꢆꢅꢈ ꢎꢀꢃwꢋ ꢆꢁ ꢁꢀꢈ 40% pꢅꢃbꢆbꢄꢇꢄꢁꢊ ꢇꢈvꢈꢇ.
2
6 2
−
tꢀꢈ [Pf ] ꢆꢅꢈ ꢃꢌꢄꢁꢁꢈꢂ ꢉꢃꢅ cꢇꢆꢅꢄꢁꢊ.
6
3. Results and discussion
The syntheses of L1–L5 and polypyridine ruthenium complexes 1–10 are illustrated in schemes 1 and 2,
respectively. The ligands investigated in this study have a bidentate 4′-phenyl-6′-phenyl-2,2′-bipyridine
framework substituted in the 4′-position with the phenyl rings bearing different para R substituents.
The synthesis of these five ligands was based on a literature method [25]. Interaction of cis-[RuCl (b-
2
py) ]⋅2H O or cis-[RuCl (phen) ]⋅2H O and the substituted-2,2′-bipyridine ligands in the presence of KPF
2
2
2
2
2
6
in ethanol/water afforded the corresponding cationic polypyridine-ruthenium complexes, [(bpy) Ru(L)]
2
(
PF ) (bpy = 2,2′-bipyridine, 1–5, SI) and [(phen) Ru(L)](PF ) (phen = 1,10-phenanthroline, 6–10, SI).
6
2
2
6
2
The two chlorides in cis-[RuCl (bpy) ]⋅2H O or cis-[RuCl (phen) ]⋅2H O were extracted by KPF and the
2
2
2
2
2
2
6
cationic ruthenium was then attacked by L to form six-nitrogen coordinated complexes in relatively
good yields.

JOURꢁAꢄ OF COORDIꢁATIOꢁ CHꢃMISTRY
857
Figure 5. mꢃꢇꢈcꢍꢇꢆꢅ ꢎꢁꢅꢍcꢁꢍꢅꢈ ꢃꢉ ꢁꢀꢈ cꢆꢁꢄꢃꢋ ꢄꢋ [(pꢀꢈꢋ) rꢍ(L3)](Pf ) (8). tꢀꢈꢅꢌꢆꢇ ꢈꢇꢇꢄpꢎꢃꢄꢂꢎ ꢆꢅꢈ ꢎꢀꢃwꢋ ꢆꢁ ꢁꢀꢈ 40% pꢅꢃbꢆbꢄꢇꢄꢁꢊ ꢇꢈvꢈꢇ.
2
6 2
−
tꢀꢈ [Pf ] ꢆꢅꢈ ꢃꢌꢄꢁꢁꢈꢂ ꢉꢃꢅ cꢇꢆꢅꢄꢁꢊ.
6
−
Figure 6. mꢃꢇꢈcꢍꢇꢆꢅ ꢎꢁꢅꢍcꢁꢍꢅꢈ ꢃꢉ ꢁꢀꢈ cꢆꢁꢄꢃꢋ ꢄꢋ [(pꢀꢈꢋ) rꢍ(L4)](Pf ) (9). tꢀꢈ [Pf ] ꢆꢅꢈ ꢃꢌꢄꢁꢁꢈꢂ ꢉꢃꢅ cꢇꢆꢅꢄꢁꢊ.tꢀꢈꢅꢌꢆꢇ ꢈꢇꢇꢄpꢎꢃꢄꢂꢎ ꢆꢅꢈ ꢎꢀꢃwꢋ
2
6 2
6
ꢆꢁ ꢁꢀꢈ 40% pꢅꢃbꢆbꢄꢇꢄꢁꢊ ꢇꢈvꢈꢇ.
Structures of 1⋅CH COCH , 3⋅CH COCH , 5⋅2CH COCH , 6, 8, 9, and 10 have been established
3
3
3
3
3
3
by X-ray crystallography. Structures of the cationic part of these Ru(II) polypyridine complexes are
shown in figures (1–7). The rutheniums are all in octahedral coordination environment containing
two 2,2′-bpy or phen units and one substituted-2,2′-bipyridine ligand. The characteristic bond lengths
and angles of these Ru(II) polypyridine complexes are summarized in table (2). The Ru–ꢁ(bpy) bond
lengths in 1⋅CH COCH , 3⋅CH COCH , and 5⋅2CH COCH are 2.032(7)–2.075(6) Å, which agree well with
3
3
3
3
3
3
2
+
those in [Ru(bpy) (pbnHH)] (pbn = 2-(2-pyridyl)benzo[b]-1,5-naphthyridine) (av. 2.060(2) Å) [26].
2
The Ru–ꢁ(phen) bond lengths in 6, 8, 9, and 10 are from 2.056(6) to 2.083(4) Å, slightly longer than
the Ru–ꢁ(bpy) bond distances in 1⋅CH COCH , 3⋅CH COCH , and 5⋅2CH COCH . The bond lengths of
3
3
3
3
3
3
Ru–ꢁ(5) in the seven new complexes are all shorter than that of Ru–ꢁ(6), i.e. Ru–ꢁ (the substituted
pyridine), probably due to steric hindrance. The ꢁ(bpy)–Ru–ꢁ(bpy) bond angles from 77.5(2)° to 79.6(3)°
in 1⋅CH COCH , 3⋅CH COCH , and 5⋅2CH COCH are near to those of ꢁ(phen)–Ru–ꢁ(phen) from 79.3(2)°
3
3
3
3
3
3
to 79.95(13)° in 6, 8, 9 and 10.

858
Z.ꢀM. WAꢁꢂ ꢃT Aꢄ.
Figure 7. mꢃꢇꢈcꢍꢇꢆꢅ ꢎꢁꢅꢍcꢁꢍꢅꢈ ꢃꢉ ꢁꢀꢈ cꢆꢁꢄꢃꢋ ꢄꢋ [(pꢀꢈꢋ) rꢍ(L5)](Pf ) (10). tꢀꢈꢅꢌꢆꢇ ꢈꢇꢇꢄpꢎꢃꢄꢂꢎ ꢆꢅꢈ ꢎꢀꢃwꢋ ꢆꢁ ꢁꢀꢈ 40% pꢅꢃbꢆbꢄꢇꢄꢁꢊ ꢇꢈvꢈꢇ.
2
6 2
−
tꢀꢈ [Pf ] ꢆꢅꢈ ꢃꢌꢄꢁꢁꢈꢂ ꢉꢃꢅ cꢇꢆꢅꢄꢁꢊ.
6
Table 2. sꢈꢇꢈcꢁꢈꢂ bꢃꢋꢂ ꢇꢈꢋgꢁꢀꢎ (Å) ꢆꢋꢂ ꢆꢋgꢇꢈꢎ (°) ꢉꢃꢅ 1⋅Ch CoCh , 3⋅Ch CoCh , 5⋅2Ch CoCh , 6, 8, 9, ꢆꢋꢂ 10.
3
3
3
3
3
3
Complex
(bpꢊ) rꢍ(L1)](Pf ) 1
Ru–ꢁ (bpy/phen)
Ru–ꢁ(L)
ꢁ(bpy/phen)–Ru–ꢁ(bpy/phen)
ꢁ(L)–Ru–ꢁ(L)
[
[
[
[
[
[
[
2.063(6)
2.039(6)
2.107(5)
77.5(2)
78.5(2)
79.0(2)
2
6 2
2.075(6)
2.061(6)
2.055(5)
(bpꢊ) rꢍ(L3)](Pf ) 3
2.065(5)
2.040(5)
2.118(5)
78.2(2)
78.4(2)
78.51(19)
78.3(3)
2
6 2
2
2
2
.061(5)
.057(5)
.053(5)
(bpꢊ) rꢍ(L5)](Pf ) 5
2.034(7)
2.026(8)
2.112(7)
79.6(3)
78.9(3)
2
6 2
2.041(7)
2.049(7)
2.032(7)
(pꢀꢈꢋ) rꢍ(L1)](Pf ) 6
2.063(3)
2.057(3)
2.119(3)
79.56(13)
79.95(13)
78.46(12)
78.45(18)
78.6(2)
2
6 2
2.077(3)
2.067(3)
2.081(3)
(pꢀꢈꢋ) rꢍ(L3)](Pf ) 8
2.068(5)
2.054(5)
2.123(4)
79.3(2)
79.9(2)
2
6 2
2
2
2
.072(5)
.062(5)
.072(5)
(pꢀꢈꢋ) rꢍ(L4)](Pf ) 9
2.056(6)
2.043(5)
2.114(5)
79.5(2)
79.5(2)
2
6 2
2.076(5)
2.062(5)
2.062(5)
(pꢀꢈꢋ) rꢍ(L5)](Pf ) 10
2.060(5)
2.053(4)
2.119(4)
79.58(17)
79.89(17)
78.91(15)
2
6 2
2.083(4)
2.072(4)
2.066(4)
The UV–Vis absorption spectra of new Ru(II)-bpy and Ru(II)-phen complexes, together with [Ru(bpy)3]
PF ) , in CH Cꢁ at room temperature are shown in figure 8(a) and (b), respectively. Complexes 1–5 have
(
6
2
3
similar spectra, while the spectra of 6–10 are also very close. The UV-vis absorption spectra of 1–5 are
dominated by two intense absorption bands at 198 and 290 nm, and a comparatively less intense band
1
at 450 nm. The former is assigned to a typical spin-allowed π–π* transition of the ligands and the latter
to metal-to-ligand charge transfer (MꢄCT). These spectra are similar to that of [Ru(bpy) ](PF ) . For 6–10,
3
6 2
1
the two absorption bands of π–π* transition are at 198 and 267 nm and the MꢄCT transition at 450 nm.

JOURꢁAꢄ OF COORDIꢁATIOꢁ CHꢃMISTRY
859
a) 0.35
(b) 0.30
(
Ru1
Ru6
Ru2
Ru7
0
0
0
0
0
0
0
.30
.25
.20
.15
.10
.05
.00
Ru3
0.25
Ru8
Ru9
Ru10
Ru(bpy) (PF )
3 6 2
Ru4
Ru5
Ru(bpy)
3
(PF
6
)
2
0
0
0
0
.20
.15
.10
.05
0.00
2
00
300
400
500
600
700
200
300
400
500
600
700
Wavelength (nm)
Wavelength (nm)
Figure 8. (ꢆ)tꢀꢈ uV–vꢄꢎ ꢆbꢎꢃꢅpꢁꢄꢃꢋ ꢎpꢈcꢁꢅꢆ ꢃꢉ 1–5 ꢆꢋꢂ [rꢍ(bpꢊ) ](Pf ) ꢄꢋ Ch Cn ꢎꢃꢇꢍꢁꢄꢃꢋ. (b)tꢀꢈ uV–vꢄꢎ ꢆbꢎꢃꢅpꢁꢄꢃꢋ ꢎpꢈcꢁꢅꢆ ꢃꢉ 6–10
3
6 2
3
ꢆꢋꢂ [rꢍ(bpꢊ) ](Pf ) ꢄꢋ Ch Cn ꢎꢃꢇꢍꢁꢄꢃꢋ.
3
6 2
3
b) 2.50
(
2
2
1
1
0
0
.5
.0
.5
.0
.5
.0
(a)
Ru6
Ru7
Ru8
Ru9
Ru10
Ru1
Ru2
Ru3
Ru4
Ru5
2
2
1
.25
.00
.75
1.50
.25
1.00
1
0
0
0
0
.75
.50
.25
.00
550
600
650
700
750
550
575
600
625
650
675
700
Wavelength (nm)
Wavelength (nm)
Figure 9. (ꢆ) lꢍꢌꢄꢋꢈꢎcꢈꢋcꢈ ꢈꢌꢄꢎꢎꢄꢃꢋ ꢎpꢈcꢁꢅꢆ ꢃꢉ 1–5 ꢄꢋ Ch Cn ꢎꢃꢇꢍꢁꢄꢃꢋ. (b) lꢍꢌꢄꢋꢈꢎcꢈꢋcꢈ ꢈꢌꢄꢎꢎꢄꢃꢋ ꢎpꢈcꢁꢅꢆ ꢃꢉ 6–10 ꢄꢋ Ch Cn ꢎꢃꢇꢍꢁꢄꢃꢋ
3
3
(
λ = 460 ꢋꢌ).
ꢈx
(b) 2500
2
2
2
1
1
1
1
500
250
000
750
500
250
000
(
a)
Ru1
Ru2
Ru3
Ru4
Ru5
Ru6
Ru7
Ru8
Ru9
Ru10
2000
1500
1000
7
5
2
50
00
50
0
5
00
0
1
.00
1.25
1.50
1.75
2.00
1.0
1.2
1.4
1.6
1.8
2.0
Potential (V)
Potential (V)
Figure 10. (ꢆ) eCl ꢄꢋꢁꢈꢋꢎꢄꢁꢄꢈꢎ ꢃꢉ 1–5. (b) eCl ꢄꢋꢁꢈꢋꢎꢄꢁꢄꢈꢎ ꢃꢉ 6–10.

860
Z.ꢀM. WAꢁꢂ ꢃT Aꢄ.
The room temperature Pꢄ spectra of 1–10 in CH Cꢁ solution are illustrated in figure (9). Complexes
3
all emit weak luminescence because of the rotation of diphenyl rotors of the substituted-2,2′-bipyridine
ligands in solution. Complexes 1–5 emit orange luminescence (see figure 9(a)) with emission wave-
lengths between 600 and 607 nm, red shifted compared to that of [Ru(bpy) ](PF ) (598 nm) because
3
6 2
the substituted-2,2′-bipyridine ligands have larger conjugation than 2,2′-bipyridine. There is no obvi-
ous change caused by different substituents on phenyl groups. When 2,2′-bipyridine was replaced by
more conjugated 1,10-phenanthroline, the emission wavelength of 6–10 (see figure 9(b)) red shifted
to 610 nm.
The potential-ꢃCꢄ intensity curves of 1–10 are shown in figure (10). The peak potentials between 1.27
and 1.40 V are assigned to electrooxidation of ruthenium(II) complexes. In general, the ꢃCꢄ comes from
3
the radiation transition of triplet state MꢄCT [27]. ꢄike the weak luminescence, the ꢃCꢄ intensities of
1
–10 are also weak (below 2500) compared to [Ru(bpy) ](PF ) (ca. 20,000 under the same conditions).
3 6 2
For 1–5, the brominated complexes 2–4 have stronger ꢃCꢄ intensity than other complexes. For 6–10,
the intensity difference is not obvious except that 9 has slightly stronger luminescence.
In summary, a series of new substituted-2,2′-bipyridine ligands have been synthesized and used to
prepare the corresponding bpy- and phen-Ru(II)-polypyridine cationic complexes with defined struc-
tures. The UV–vis, luminescence, and ꢃCꢄ properties of the ruthenium complexes were investigated. ꢁo
obvious change was observed in optical properties caused by different substituents on phenyl rings. The
Pꢄ spectra show that [(bpy) Ru(L)](PF ) and [(phen) Ru(L)](PF ) with more conjugated ligand system
2
6 2
2
6 2
led to red shift compared to [Ru(bpy) ](PF ) . As a matter of fact, the IR spectrum obtained for some
3
6 2
2
+
[
Ru(ꢄ)3] (where ꢄ = bpy, 2,2′-bipyrimidine (bmp), 2,2′-bipyrazine (bpz), and phen) displays character-
istic peaks from 1100 to 1800 cm . It is thus understood that the vibrational frequencies observed for
−
1
2+
[
[
Ru(ꢄ)3] arise exclusively in the ligand part of the complex [28]. Recent report of similar Ru(II) complexes,
Ru(bpy) (pipz)]2 and [Ru(phen) (pipz)] (pipz = 2-pyridine-1H-imidazo[4,5-b]phenazine), involved in
+
2+
2
2
DꢁA binding properties is quite interesting, as both complexes are efficient DꢁA photocleavers [29],
which should draw us to further explore the photo-chemistry and -biochemistry properties of the
present bpy- and phen-Ru(II)-polypyridine cationic complexes.
Supplementary material
Crystallographic data for [(bpy) Ru(L1)](PF ) ⋅CH COCH (1⋅CH COCH ), [(bpy) Ru(L3)](PF ) ⋅CH COCH (3⋅CH COCH ),
2
6 2
3
3
3
3
2
6 2
3
3
3
3
[
(
(bpy) Ru(L5)](PF ) ⋅2CH COCH (5⋅2CH COCH ), [(phen) Ru(L1)](PF ) (6), [(phen) Ru(L3)](PF ) (8), [(phen) Ru(L4)](PF )
2 6 2 3 3 3 3 2 6 2 2 6 2 2 6 2
9), and [(phen) Ru(L5)](PF ) (10) have been deposited with the Cambridge Crystallographic Data Center as supplementary
2
6 2
publication ꢁos. CCDC 1401755-1401761, respectively. Copies of the data can be obtained free of charge on application
to CCDC, 12 Union Road, Cambridge CB2 1ꢃZ, UK [Fax: (+44)1233-336-033; ꢃ-mail: deposit@ccdc.cam.ac.uk].
Disclosure statement
ꢁ
o potential conflict of interest was reported by the authors.
Funding
This work was supported by the ꢁatural Science Foundation of China [grant number 21372007]; Science & Technology
Department of Zhejiang Province [grant number 2013C31059], [grant number 2014C31149].
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