Dalton Transactions
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emissive excited state that has significant ligand-centred char-
acter, as supported by the TD DFT calculations (Fig. 5).†
The acetylide adduct 3a displays similar luminescence pro-
perties to the parent chloro complex (Fig. 8); there is no aug-
mentation in efficiency of the type often observed in
complexes of metals such as Pt(II) when there are low-lying d–d
Notes and references
‡Synthesis and characterisation of 2a. A suspension of 1,3-bis(1-isoquinolyl)-
benzene (0.050 g, 0.150 mmol) and rhodium trichloride trihydrate (0.053 g,
0.150 mmol) in 2-ethoxyethanol (7 mL) and water (3 mL) was heated to 80 °C for
24 h. After cooling to room temperature, the precipitate was collected via cen-
trifugation and washed with water (3 × 5 mL), ethanol (3 × 5 mL) and diethyl
states present, which are displaced to higher energy on the ether (3 × 5 mL). Upon drying in vacuo, the crude product (1a) was obtained as a
introduction of a strong-field acetylide co-ligand.18
The Ir(III) complexes 2b and 3b both display very intense
red luminescence in solution (Fig. 7 and 8). Again, some
yellow solid; further product was obtained by repeating the procedure with the
remaining solutions (0.059 g, 66%). The crude product, silver triflate (0.056 g,
0.22 mmol) and 2-phenylpyridine (200 μL, 1.78 mmol) were placed in a Schlenk
tube, which was degassed three times via evacuating and backfilling with nitro-
vibrational structure is apparent at room temperature, well-
gen. The mixture was heated at 110 °C under nitrogen for 20 h then cooled to
resolved at 77 K, suggestive of more ligand-centred character room temperature and CH2Cl2 (35 mL) was added. Solid residue was removed by
filtration and the filtrate washed with HCl (1 M, 3 × 35 mL), dried over MgSO4
than Ir(ppy)3 for example. The emission maxima and spectral
profiles satisfy well the requirements for good red emitters for
displays; e.g. C.I.E. colour coordinates for 2b are (0.65, 0.34).
Moreover, the luminescence quantum yields of around 0.5
and the solvent removed under reduced pressure. Purification was carried out by
column chromatography (silica, CH2Cl2–methanol, gradient elution from 100 : 0
to 99 : 1) to give the product as a yellow solid (0.065 g, 35%). 1H NMR (CDCl3,
700 MHz) δ = 10.27 (1H, d, 3J = 5.0, H6-ppy), 9.12 (2H, d, 3J = 7.7, H3-NCN), 8.62
(Table 2) are particularly high for red-emitting complexes, (2H, d, 3J = 7.7, H4′-NCN), 8.14 (1H, d, 3J = 11.2, H3-ppy), 8.10 (1H, td, 3J = 8.4,
3J = 1.4, H4-ppy), 7.63–7.70 (8H, m, H4-NCN and H5-ppy and H3′-ppy and H5-NCN
where the combined effects of increased non-radiative decay
and H8-NCN, and H6-NCN or H7-NCN), 7.53–7.56 (3H, m, H5′-ppy, and H6-NCN
through vibrational deactivation and decreased radiative decay
or H7-NCN), 7.22 (2H, d, 3J = 4.5, H5-NCN or H8-NCN), 6.74 (1H, td, 3J = 6.0, 4J =
constants (which vary as ν3) tend to limit efficiencies compared
1.0, H4′-ppy), 6.51 (1H, td, 3J = 5.5, 4J = 1.0, H5′-ppy), 5.91 (1H, d, 3J = 8.4, H6′-
ppy). 13C NMR (CDCl3, 176 MHz) δ = 188.5, 167.9, 165.7, 157.9, 150.7, 143.8,
143.8, 142.7, 138.0, 136.8, 130.7, 129.8, 128.2, 127.7, 127.6, 125.9, 123.0, 122.6,
122.3, 121.9, 120.9, 119.0, 113.6, 110.2, 92.3, 92.1. MS (ASAP+) m/z 623.0 [M]+.
HRMS (ASAP+) Calcd for C35H2335ClN3108Rh: m/z 623.0636. Found: m/z 623.0643.
Mp > 250 °C.
to structurally similar green emitters. The values are compar-
able to the most efficient red phosphors reported.12
In summary, bis(isoquinolyl)benzene is shown to bind as a
tridentate N^C2^N ligand to Rh(III) or Ir(III). Complexes incor-
porating this ligand in combination with a second, bidentate,
cyclometallating ligand are highly luminescent in the orange
or red region respectively. 2a has higher phosphorescence
quantum yield than any rhodium complex hitherto reported,
whilst the Ir(III) complexes 2b and 3b are excellent red emitters.
Given the recent successful demonstration of complexes of
related dipyridylbenzene ligands as OLED emitters,11b,13b and
the ability to further fine-tune the emission wavelength
through the bidentate ligand, these new compounds may be
attractive in such applications, as well as in the area of time-
resolved bioimaging, where intense, long-lived emission in the
red region – to which biological tissue is most transparent – is
particularly desirable.3d
§CCDC 937441 (biqbH), 937442 (2a), 937443 (2b).
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We thank EPSRC for support of this work in form of a doc-
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Fig. 8 Normalised luminescence spectra of 3a (blue) and 3b (red) in CH2Cl2 at
298 K (solid lines) and in diethyl ether–isopentane–ethanol (2 : 2 : 1 v/v) at 77 K
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Dalton Trans.