the 3-D cardo structure{ of substituted fluorene would
improve rigidity and hinder unwanted aromatic p-stacking
interactions among all phenyl substituents, resulting in
materials with an enhanced morphological stability.
precipitation. The precipitate was collected by filtration and
washed with diethyl ether (10 mL). Yellow crystals of
[(dfppy)2Ir(fpy)] (FIrfpy) were obtained by cooling the
mixed solution of CH2Cl2 and methanol at room temperature
(125 mg, 146 mmol, 89%). 1H NMR (400 MHz, CD2Cl2): d
8.28 (d, J = 8.4 Hz, 1H), 8.23 (d, J = 8.8 Hz, 1H), 8.10 (d, J =
8.4 Hz, 1H), 7.78–7.73 (m, 4H), 7.66 (d, J = 5.6 Hz, 1H), 7.50
(d, J = 4.8 Hz, 1H), 7.03 (td, J = 7.0, 1.6 Hz, 1H), 6.96–6.92
(m, 2H), 6.88 (s, 1H), 6.51 (ddd, J = 12.4, 9.4, 2.4 Hz, 1H), 6.41
(ddd, J = 12.4, 9.4, 2.0 Hz, 1H), 5.68 (dd, J = 8.4, 1.2 Hz, 1H),
5.62 (dd, J = 8.4, 1.2 Hz, 1H). 19F{1H} NMR (470 MHz,
CD2Cl2): d 2112.1 (s, 1F), 2110.1 (s, 1F), 2109.8 (s, 1F),
2107.4 (s, 1F), 259.2 (s, 3F), 255.1 (s, 3F). MS (FAB, 192Ir):
observed m/z [assignment]: 851 [M+], 572 [M+ 2 fpy]. Anal.
Calcd. for C33H17F10IrN4: N, 6.58; C, 46.54; H, 2.01. Found:
N, 6.62; C, 46.72; H, 1.95%.
Experimental
Materials
The CF3 substituted pyridyl pyrrole ligand (fpyH) was
prepared from the reaction of hexafluoroacetylacetone and
2-(aminomethyl)pyridine in the presence of a catalytic amount
of sulfuric acid.27 The iridium complex [(dfppy)2Ir(m-Cl)]2 was
synthesized using IrCl3?nH2O and 4,6-difluorophenyl pyridine
in 2-ethoxyethanol according to the literature method. The
solvents were dried using standard procedures. All other
reagents were used as received from commercial sources, unless
otherwise stated.
Selected X-ray crystal data of FIrfpy: the asymmetric unit
contains half of a CH2Cl2 molecule which is disordered about
an inversion centre, formula: C33.5H18ClF10IrN4, M = 894.17,
Characterization
¯
triclinic, space group P1, a = 10.0361(1), b = 11.1106(1), c =
1H and 13C NMR spectra were recorded on Varian UNITY
INOVA 500 MHz, Varian Unity 300 MHz and Bruker-DRX
300 MHz spectrometers. Mass spectra were obtained by using
a JEOL JMS-HX 110 mass spectrometer. Differential scanning
˚
14.0054(1) A, a = 96.0383(7), b = 90.7590(6), c = 107.0188(5)u,
V = 1483.43(2) A , Z = 2, rcalcd = 2.002 g cm21, F(000) = 862,
3
˚
˚
crystal size 0.18 6 0.18 6 0.10 mm, l(Mo-Ka) = 0.7107 A,
T = 150 K, m = 4.687 mm21, 28743 reflections collected,
6797 with R(int) = 0.0438, final wR2(all data) = 0.0696.
R1[I . 2s(I)] = 0.0275. CCDC reference number 626385. For
crystallographic data in CIF or other electronic format see
DOI: 10.1039/b616043c
calorimetry (DSC) was performed by using
a SEIKO
EXSTAR 6000DSC unit at a heating rate of 20 uC min21
and a cooling rate of 50 uC min21. Samples were scanned from
30 to 280 uC, cooled to 0 uC, and then scanned again from
30 to 280 uC. The glass transition temperatures (Tg) were
determined from the second heating scan. UV-vis spectra were
measured using an HP 8453 diode-array spectrophotometer.
PL spectra were obtained using a Hitachi F-4500 luminescence
spectrometer. Cyclic voltammetry (CV) spectra were measured
using a BAS 100 B/W electrochemical analyzer operated at a
scan rate of 50 mV s21 in anhydrous CH2Cl2 solution with
0.1 M of supporting electrolyte tetrabutylammonium hexa-
fluorophosphate (TBAPF6). The potentials were measured
against an Ag/Ag+ (0.01 M AgNO3) reference electrode using
ferrocene as an internal standard. The HOMO energies of
organic thin films were measured using the Riken-Keili AC-2
atmospheric low-energy photoelectron spectrometer. The
LUMO energies of materials were estimated by subtracting
the optical energy gap from the measured HOMO. The low-
temperature phosphorescence spectrum of TPSi-F was
obtained using a composite spectrometer containing a mono-
chromator (Jobin Yvon, Triax 190) coupled with a liquid
nitrogen-cooled charge-coupled device (CCD) detector (Jobin
Yvon, CCD-10246256-open-1LS).
Preparation of 9-(4-bromophenyl)-9-phenyl-9H-fluorene
A mixture of 9-(4-bromophenyl)-9H-fluoren-9-ol (2.00 g,
5.95 mmol),28 benzene (8.49 g, 109 mmol), and CF3SO3H
(0.89 g, 5.93 mmol) was stirred and heated at reflux for 4 h
under N2. After cooling, the mixture was treated with a
saturated NaHCO3 solution and extracted with ethyl acetate.
The organic extract was dried over MgSO4 and the solvent was
evaporated in vacuo. The crude product was purified by
column chromatography (hexane–CH2Cl2) to give 9-(4-bro-
mophenyl)-9-phenyl-9H-fluorene (0.67 g, 28%). 1H NMR
(300 MHz, CDCl3): d 7.78–7.75 (m, 2 H), 7.39–7.35 (m, 4 H),
7.33 (dt, J = 8.7, 2.1 Hz, 2 H), 7.30–7.27 (m, 2H), 7.25–7.16 (m,
5 H), 7.06 (dt, J = 8.7, 2.1 Hz, 2 H). 13C NMR (75 MHz,
CDCl3): d 150.6, 145.3, 145.2, 140.1, 131.3, 129.9, 128.3, 128.0,
127.8, 127.7, 126.8, 126.0, 120.7, 120.3, 65.0. Anal. Calcd. for
C25H17Br: C, 75.58; H, 4.31. Found: C, 75.52; H, 4.64%.
Preparation of TPSi-F
n-Butyllithium in hexane (2.5 M, 0.60 mL) was added slowly
under N2 to a stirred solution of 9-(4-bromophenyl)-9-phenyl-
9H-fluorene (600 mg, 1.51 mmol) in anhydrous ether (50 mL)
at 278 uC. The mixture was warmed to 0 uC. A solution of
chlorotriphenylsilane (445 mg, 1.56 mmol) in ether (50 mL)
was added, and the resulting mixture was heated at reflux for
4 hours. After stopping the reaction, the precipitate was
collected by filtration, washed with water followed by ether
and dried under vacuum. Finally, the product was purified by
Preparation of FIrfpy
A mixture of [(dfpz)2IrCl]2 (101 mg, 82 mmol), fpyH (50 mg,
0.17 mmol) and Na2CO3 (87 mg, 0.82 mmol) in 2-ethoxy-
ethanol (20 mL) was heated to reflux for 4 hours. After cooling
to room temperature, excess water was added to induce
{ The term ‘cardio structure’ is defined as a structure containing at
least one element of the constitutive unit, which carries a lateral ring
connected to the main framework of a molecule by a quaternary
carbon atom.
1
high vacuum sublimation to yield TPSi-F (970 mg, 74%). H
NMR (300 MHz, CDCl3): d 7.77 (dd, J = 6.9, 0.6 Hz, 2 H),
J. Mater. Chem., 2007, 17, 1692–1698 | 1693
This journal is ß The Royal Society of Chemistry 2007