Synthesis of polypyridyl ruthenium complexes with 2-(1-aryl)-1H-imidazo[4,5-f]-1,10-phenanthroline ligand
195
synthesized as reported previously [18]. 1H NMR (400 MHz,
CDCl3) δ (ppm) = 8.87 – 8.81 (m, 6H), 8.45 – 8.44 (d, 2H, J =
3 Results and discussion
3.1 UV-Vis absorptions
4.8 Hz), 8.41 (s, 2H), 8.28 – 8.24 (t, 2H, J = 8.0 Hz),
8.19 – 8.13 (m, 4H), 7.95 – 7.89 (m, 4H), 7.66 – 7.62 (t, 2H,
J = 6.0 Hz), 7.41 – 7.37 (t, 2H, J = 6.4 Hz). ESI-HRMS [(M-
PF6)+], calcd, m/z = 739.0753; found m/z = 739.0469; [(M-
2PF6)2+/2], calcd, m/z = 297.0553; found m/z = 297.0457.
[(bpy)2Ru(2-(1-phenyl)-1H-imidazo[4,5-f]-1,10-phe-
nanthroline)]2+(PF6)2 (2) was synthesized with similar
method to that of 3. 1H NMR (400 MHz, acetone-d6) δ
(ppm) = 13.38 (s, 1H), 9.18 (d, 1H, J = 8.0 Hz), 9.07 (d, 1H, J
= 8.0 Hz), 8.86 – 8.81 (m, 4H), 8.37 – 8.12 (m, 10H), 7.96 (m,
4H), 7.65 – 7.56 (m, 5H), 7.40 (s, 2H). 13C NMR (100 MHz,
acetone-d6): δ 158.3, 158.1, 153.8, 152.8, 152.6, 151.3, 151.1,
138.9, 138.8, 131.6, 131.3, 131.2, 130.3, 130.0, 128.7, 128.5,
127.4, 127.2, 127.0, 125.3, 125.2. ESI-HRMS: [(M-2PF6)2+/2]
calcd, m/z = 355.0740; found, m/z = 355.0754.
[(bpy)2Ru(2-(1-Pyrenyl)-1H-imidazo[4,5-f]-1,10-phenan-
throline)]2+(PF6)2 (3) A solution of [RuCl2(cymene)]2 (40 mg,
0.065 mmol) and 3-c (54.0 mg, 0.13 mmol) in ethanol (5 mL)
was stirred for 4 h. The reaction was monitored by TLC. Then
10 mL water and 2,2'-bipyridine (40.0 mg, 0.26 mmol) were
added to the solution, the mixture was then refluxed for an
additional 24 h. After cooling, the reaction mixture was
concentrated under reduced pressure and treated with a
saturated aqueous solution of NH4PF6, which gave a red
precipitate. The crude product was then subjected to column
chromatography (Silica gel, eluted with acetonitrile : water :
saturated aqueous NaNO3 = 100:9:1, v/v). The eluent was
treated with a saturated aqueous solution of NH4PF6, which
yielded a red precipitate. The solid was washed with water and
dried under vacuum. Red solid was obtained in 31.0% yield.
1H NMR (400 MHz, acetone-d6) δ (ppm) = 13.63 (s, 1H), 9.56
(d, 1H, J = 9.6 Hz), 9.27 (d, 1H, J = 8.0 Hz), 9.16 (d, 1H, J =
8.0 Hz), 8.85 (m, 4H), 8.65 (d, 1H, J = 8.0 Hz), 8.46 – 8.11 (m,
15H), 7.98 (d, 4H, J = 5.2 Hz), 7.63 (d, 2H, J = 6.0 Hz), 7.40 (s,
2H). 13C NMR (100 MHz, acetone-d6): δ 158.3, 158.1, 154.4,
152.9, 151.3, 138.9, 138.8, 133.6, 132.3, 131.9, 131.7, 131.5,
130.3, 129.9, 129.8, 128.7, 128.6, 128.2, 128.1, 127.6, 127.1,
126.7, 126.2, 125.8, 125.3, 125.2, 125.1, 124.5. ESI-HRMS:
[(M-2PF6)2+/2] calcd, m/z = 417.0896; found, m/z = 417.0901.
The UV-Vis absorptions of the Ru(II) polypyridine complexes
1, 2 and 3 were studied. The curves were shown in Figure 1
and the absorption maxima were compiled in Table 1. Similar
to the parent compound [Ru(bpy)2(1,10-phenanthroline)],
three main bands were observed for the UV-Vis absorption of
complexes 2 and 3, i.e., two ligand-centered π-π* transition
bands at 225 nm for bpy ligand and at 262 nm for phen ligand.
A broad absorption band centered at 445 nm was also
observed with a higher energy shoulder at 414 nm.
The main peak and the shoulder of this absorption band are
indicative of the presence of strongly overlapped MLCT
1
states, with similar energy levels, such as dπ(Ru)®π*(bpy)
and dπ(Ru)®π*(Phen) [13,19,20]. Ru(II) complexes 2 and
3 show absorption at 285 nm, which is due to the 1H-
imidazo[4,5-f]-1,10-phenanthroline ligand with extended π-
conjugation framework. For complex 3, new absorption bands
appeared at 370 nm, which is due to the absorption of pyrene
[21]. We propose that the pyrene unit and 1H-imidazo[4,5-f]-
Figure 1 UV-Vis absorption spectra of Ru(II) polypyridine
complexes 1, 2, and 3. Measurements were carried out using 1.0
´10–5 mol$L–1 solution in acetonitrile at 25°C.
Table 1 Photophysics parameters of the phosphorescent polyimine ruthenium complexes 1, 2 and 3
c)
c)
ε
kr
/
knr /
IAr/I
I /I
N2 O2
a)
b)
O2
lab /nm
lem /nm
F
t/ns
–1
–1
4
–1
6 –1
(solution)
(film)
/(L$mol $cm
)
( ´10
s
)
( ´10
s )
d)
1
2
3
445
457
458
594
608
609
17900
16728
20459
0.06
0.22
0.02
450
1125
2503
13.3
19.2
2.08
18.5
1.7
e)
1.13
0.48
35.9
1.8
e)
0.83
279.0
3.0
a) Result of deaerated solution, with complex 1 as the standard. b) The determination coefficients (r2) for complexes 1, 2 and 3 are 0.99, 0.99 and 0.95,
respectively. c) Radiative deactivation rate constant (kr) and non-radiative deactivation rate constant (knr). kr = Φem/τem; knr = 1/τem(1 – Φem). It is
assumed that the emitting excited state is produced by ISC with unit efficiency. d) The polymer film is IMPES-C [19]. e) The polymer film is IMPEK-C.
Frontiers of Chemistry in China Vol. 5, No. 2, 2010