Inorganic Chemistry
Article
precipitate was formed. The desired white product (2.73 g, 62%) was
collected by filtration, washed with hexane (2 × 10 mL) and dried
under vacuum. Mp = 109 °C. δP{1H} (121 MHz, CDCl3): −10.5 (s).
δC{1H} (75 MHz, CDCl3): 150.6 (C1), 130.1 (C3) 125.9 (C4),
120.9 (C2). δH (300 MHz, CDCl3): 7.11−7.24 (20H, m, Ar). MS
(ES−) m/z: 480 [M − H]−. Elemental analysis calcd (%) for
C24H21NO6P2: C, 59.88; H, 4.40; N, 2.91. Found: C, 59.61; H, 4.20;
N 2.98. UV/vis (CH3CN): λ in nm (log ε) 263 (3.2). IR: νmax/cm−1
2961 (m, br, N−H), 2753 (m, br, C−H), 1800−2100 (w, br, CC),
1184 (s, PO), 933 (s, P−N−P).
Scheme 1. Structures of HtpOp and Htpip
Synthesis of KtpOp. Potassium hydride (0.49 g, 35% dispersion
in mineral oil, 3.69 mmol) was washed with pentane (3 × 5 mL)
under N2 and dried in vacuo for 20 min. THF (8 mL) was then
added, followed by HtpOp (1.54 g, 3.20 mmol) dissolved in 15 mL of
THF. The resulting suspension was stirred for 1 h at room
temperature under N2. The solvent was removed in vacuo to yield
a light brown viscous solution, which was dissolved in water (8 mL)
and extracted with pentane (3 × 5 mL). The volume of the aqueous
layer was reduced in vacuo, and the residue was transferred to the
freezer overnight. The resulting light brown solid was washed with
pentane (5 × 10 mL) and dried under vacuum to yield the desired
product (1.46 g, 88%). δP{1H} (121 MHz, CDCl3): −7.2 (s).
δC{1H} (75 MHz, CDCl3): 155.1(C1), 132.0 (C3) 126.6 (C4),
123.3 (C2). δH (300 MHz, CDCl3): 6.94−7.11 (20H, m, Ar).
MALDI-MS m/z: 519.6 [M]+, 557.6 [M + K]+. Elemental analysis
calcd (%) for C24H20NO6P2K(H2O): C, 53.63; H, 4.13; N, 2.61.
Found: C, 53.64; H, 3.67; N 2.70. Exact mass m/z (ESI-TOF)
C24H21NO6P2K calcd: 520.0481. Found: 520.0484.
formation of the lanthanide complexes has been mentioned
with only elemental analysis reported,15 apart from the
ytterbium crystal structure.16,17
We report herein the synthesis and full characterization of all
the lanthanide complexes Ln(tpOp)3 (Ln = Eu, Tb, Dy, Sm,
Gd, Er, Nd, and Yb) prepared from a key intermediate KtpOp,
as well as the formation of Y(tpOp)3 as a diamagnetic
analogue. A detailed analysis of their photophysical properties
based on their luminescence lifetimes and quantum yields is
reported to evaluate the complexes for their potential
applications in optical materials.
EXPERIMENTAL SECTION
■
General Methods. All the chemicals and solvents were
commercially available from Sigma-Aldrich, Alfa Aesar or Fisher
Scientific. NMR spectra were obtained on Bruker AC 300, AV 300,
AMX 400, AV 400, or DRX 500 spectrometers. Electrospray mass
spectra were recorded on a Micromass LC-TOF machine. Elemental
analyses were recorded on a Carlo Erba EA1110 simultaneous CHN
elemental analyzer. Single-crystal diffraction data were recorded on a
Bruker Smart 6000 diffractometer equipped with a CCD detector and
a copper tube source. The structures were solved by direct methods
and refined with the SHELXT.18 Generally, restraints were applied to
the geometry and atomic displacement parameters where disorder
occurred. Except for water molecules, hydrogen atom geometry was
idealized and they were refined using a riding model. The ligand
shielding was calculated using the program Solid-G.19
Synthesis of Ln(tpOp)3 (Ln = Eu, Tb, Dy, Sm, Gd, Nd, Er, and
Yb) and Y(tpOp)3. To a stirring solution of KtpOp (0.39 mmol) in
EtOH (10 mL) a solution of LnCl3·6H2O (0.13 mmol) in EtOH (5
mL) was added dropwise. The resulting white suspension was then
stored at −18 °C overnight, yielding a white, sticky precipitate. The
solvent was decanted off, and the remaining solid was stirred
vigorously with hexane (5 mL) to yield the product as a fine white
powder. The powder was collected by filtration, washed with hexane
(2 × 5 mL), and dried under vacuum.
Eu(tpOp)3. Yield: 0.13 g, 63%. δP{1H} (121 MHz, CDCl3): −80.0
(s). δC{1H} (75 MHz, CDCl3): 148.5 (C1), 128.0 (C3), 123.0 (C4),
3
119.2 (C2). δH (300 MHz, CDCl3): 7.29 (24H, t, J(H,H) = 7.3 Hz,
3
3
Hb), 7.19 (12H, t, J(H,H) = 7.1 Hz, Hc), 6.78 (24H, d, J(H,H) = 7.6
Hz, Ha). MS (ESI+): m/z 1616 [M + Na]+. Elemental analysis calcd
(%) for C72H60N3O18P6Eu: C, 54.28; H, 3.80; N, 2.64. Found: C,
54.14; H, 3.98; N 2.82. UV/vis (CH3CN): λ in nm (log ε) 263 (3.7).
Tb(tpOp)3. Yield: 0.12 g, 59%. δP{1H} (121 MHz, CDCl3): −33.8
(br,s). δC{1H} (75 MHz, CDCl3): 163.9 (C1), 126.2 (C3), 123.2
(C2), 121.2 (C4). δH (300 MHz, CDCl3): 6.35 (24H, br, Ha), 4.01
(12H, s, Hc), 3.21 (24H, s, Hb). MS (ESI+): m/z 1638 [M + K]+.
Elemental analysis calcd (%) for C72H60N3O18P6Tb: C, 54.05; H,
3.78; N, 2.63. Found: C, 53.83; H, 4.02; N 2.79. UV/vis (CH3CN): λ
in nm (log ε) 263 (3.7).
Photophysical Studies. UV−vis absorption spectra were
recorded on an Agilent Cary 60 UV−vis spectrophotometer.
Luminescence spectra were recorded on an Edinburgh Instruments
FLSP920 steady-state and time-resolved spectrometer with F900
software and on a Photon Technology International spectrometer.
The excitation and emission spectra are corrected for lamp/
photomultiplier tube/instrument response as required according to
spectral response correction files recommended by the manufacturer.
Time-resolved lifetime measurements were carried out by using a
Continuum Surelight Nd:YAG laser (10 Hz, 4−6 ns) as the excitation
source using a 355 nm harmonic. Data were recorded using a LeCroy
9350AM 500 MHz oscilloscope. Lifetimes were fitted with Kaleida-
Graph software using a nonlinear least-squares iterative technique.
The luminescence quantum yields for Tb(tpOp)3, Eu(tpOp)3,
Dy(tpOp)3, Nd(tpOp)3, and Yb(tpOp)3 were measured with an
integrating sphere apparatus from Edinburgh Instruments. In the
quantum yield measurements, we used standards to validate the
instrumental set up as recommended in the IUPAC technical
reports.20,21 Each sample was measured several times under
comparable conditions. The quantum yield for Sm(tpOp)3 was
determined using the optical dilute method with [Ru(bpy)3]Cl2 as the
reference.22
Dy(tpOp)3. Yield: 0.12 g, 58%. δP{1H} (121 MHz, CDCl3): −2.2
(br,s). δC{1H} (75 MHz, CDCl3): 163.0 (C1), 128.2 (C3), 123.5
(C2), 120.5 (C4). δH (300 MHz, CDCl3): 5.66 (24H, br, Ha), 4.25
(12H, s, Hc), 3.32 (24H, s, Hb). MS (ESI+): m/z 1643 [M + K]+.
Elemental analysis calcd (%) for C72H60N3O18P6Dy: C, 53.93; H,
3.77; N, 2.62. Found: C, 54.10; H, 3.63; N 2.67. UV/vis (CH3CN): λ
in nm (log ε) 263 (3.7). IR: νmax/cm−1 1900−2100 (w, CC), 1150
(s, PO), 921 (m, P−N−P).
Sm(tpOp)3. Yield: 0.11 g, 52%. δP{1H} (121 MHz, CDCl3): −4.0
(s). δC{1H} (75 MHz, CDCl3): 151.5 (C1), 129.2 (C3), 124.2 (C4),
3
120.8 (C2). δH (300 MHz, CDCl3): 7.13 (24H, d, J(H,H) = 7.9 Hz,
3
3
Ha), 7.02 (24H, t, J(H,H) = 7.5 Hz, Hb), 6.93 (12H, t, J(H,H) = 6.9
Hz, Hc). MALDI-MS: m/z 1591.5 [M]+. Elemental analysis calcd (%)
for C72H60N3O18P6Sm: C, 54.34; H, 3.80; N, 2.64. Found: C, 54.15;
H, 3.92; N 2.67. UV/vis (CH3CN): λ in nm (log ε) 263 (3.7).
Gd(tpOp)3. Yield: 0.13 g, 58%. MS (ESI+): m/z 1637 [M + K]+.
Elemental analysis calcd (%) for C72H60N3O18P6Gd: C, 54.10; H,
3.78; N, 2.63. Found: C, 54.10; H, 3.94; N 2.66. UV/vis (CH3CN): λ
in nm (log ε) 263 (3.6).
Synthesis of HtpOp. A suspension of triphenyl phosphate (6.01
g, 18.4 mmol) and sodium amide (1.51 g, 8.59 mmol) in 60 mL of dry
toluene was heated at reflux for 4 h under N2. The resulting mixture
was cooled to 40 °C, and 50 mL of water was added to dissolve the
sodium phenoxide. The toluene layer was extracted, acidified with
dilute HCl (9.2 mL, 1 M), and washed with water (2 × 20 mL). The
volume of the solution was concentrated to about 4 mL, and 40 mL of
hexane was added. The solution was then stirred until a white
B
Inorg. Chem. XXXX, XXX, XXX−XXX