Inorganic Chemistry
Article
mmol), and KI (0.435 g, 2.62 mmol) in DMF (7 mL) was stirred at 80
°C for 3 h. Then the reaction mixture was cooled to room
temperature, poured dropwise into water, and extracted with ethyl
acetate (4 × 15 mL). The extract was washed with water (3 × 20 mL),
dried over Na2SO4, and evaporated under vacuum. The resulting
crystalline substance was purified by using chromatography on silica
(elution with 1:1 hexane/CHCl3), yielding 0.233 g of 5 (52%). NMR
spectra are in accordance with the previously reported data.40 1H
NMR (600 MHz, acetone-d6): δ 4.29 (t, J = 6.4 Hz, 2H, CH2), 1.91−
1.83 (m, 2H, CH2), 1.62−1.54 (m, 2H, CH2), 0.99 (t, J = 7.4 Hz, 3H,
CH3). 13C NMR (151 MHz, acetone-d6): δ 156.27, 135.78, 113.34,
110.41, 77.04, 32.74, 19.59, 13.99.
proposed that this process occurs because of the protonation of
molecules.23−28 In particular, in chlorinated solvents, it can be
caused by traces of HCl that inevitably form upon storage of
CHCl3 or C2H2Cl4, especially upon exposure to light. The
addition of pyridine removes the proton from the Pc molecule,
restoring the spectral appearance. Notably, β-AlkO-substituted
Pc complexes do not reveal such a high sensitivity to acidic
impurities in solvents, so rather high concentrations of strong
acids are required for their protonation.
Because both the aggregation of Pc complexes and its
participation in an acid−base equilibrium strongly alter their
properties, it became an attractive goal to combine both of
these features in one multifunctional molecule. The target
molecule could be designed on the basis of crown ether Pc
derivatives whose aggregation can be precisely controlled by
interaction with alkali metals. Indeed, crown ether derivatives
are very promising building blocks for the assembly of
molecules into cofacial and brick-wall supramolecular struc-
tures,29−33 which also lead to a change in the optical and
nonlinear-optical properties of molecules.34−36 Recently, we
reported that the introduction of donor oxanthrene fragments
into a crown ether Pc molecule leads to moderate extension of
the absorbance range and also enables control of the
aggregation.37 We suppose that the combination of a crown
ether group with a peripherally substituted oxanthrene moiety
in the Pc complex will allow us to create a molecule with
tunable absorption in the visible/NIR spectral range. Herein,
we report the synthesis, X-ray structures, and optical properties
of the nonperipherally substituted 15-crown-5-oxanthrenocya-
nine 2H2, as well as their MgII and ZnII complexes 2Mg and
2Zn, showing cation- and acid−base-induced switching of the
absorption between 686 and 1028 nm.
Phthalonitrile 1. A mixture of benzo-15-crown-5-quinone
obtained as described earlier37 (0.66 g, 2.21 mmol) and 10% Pd/C
(34 mg) in DMF (37 mL) was degassed and then stirred for 1.5 h in a
stream of H2 until it became colorless, which corresponded to the
formation of catechol 6. Then, the mixture was taken into a syringe
through a nylon syringe filter, and the resulting colorless filtrate was
transferred into a flask with a degassed mixture of 5 (0.76 g, 2.23
mmol) and K2CO3 (0.92 g, 6.67 mmol). The resulting suspension was
stirred for 24 h at 70 °C. Then, it was poured into water and extracted
with chloroform (4 × 50 mL); the extract was washed with water and
dried over Na2SO4, and the solvent was evaporated under vacuum.
The resulting oil was purified by chromatography on silica (elution
with 1:1 hexane/CHCl3), yielding 0.58 g of 1 (48%). Mp: 128 °C. 1H
NMR (600 MHz, CDCl3): δ 6.51 (s, 1H, HAr), 4.19 (t, J = 6.5 Hz, 2H,
OCH2), 4.11−4.07 (m, 2H, α-CH2crown), 3.92−3.87 (m, 2H, β-CH2),
3.80−3.71 (m, 4H, γ,δ-CH2), 1.84−1.78 (m, 2H, CH2), 1.57−1.53 (m,
2H, CH2), 1.00 (t, J = 7.4 Hz, 3H, CH3). 13C NMR (151 MHz,
CDCl3): δ 146.79, 146.58, 140.97, 133.44, 112.83, 104.49, 103.91,
75.76, 71.08, 70.53, 69.99, 69.47, 32.09, 19.05, 13.91. ESI HRMS for
+
C30H36N2NaO9 : (experimental) m/z 591.233 ([M + Na]+);
(theoretical) m/z 591.232.
Magnesium Oxanthrenocyaninate (2Mg). A mixture of nitrile
1 (102 mg, 0.18 mmol), Mg(OAc)2 (13 mg, 0.09 mmol),
hydroquinone (10 mg, 0.09 mmol), and DBU (30 μL, 0.2 mmol) in
5 mL of i-AmOH was refluxed for 48 h under a slow stream of argon.
After cooling, the reaction mixture was added dropwise to hexane (50
mL). The resulting precipitate was filtered and washed off the filter
with CHCl3. Chromatography on alumina in a CHCl3/MeOH mixture
afforded green complex 2Mg, which was additionally purified by a Bio-
Beads SX-1 column packed in CHCl3 + 5 vol % MeOH. Yield: 39 mg
EXPERIMENTAL SECTION
■
2,3-Dichloro-5,6-dicyano-1,4-benzoquinone (DDQ), Na2SO4, hydro-
quinone, triphenylphosphineoxide (Ph3PO), 1,8-diazabicyclo[5.4.0]-
undec-7-ene (DBU), 1-bromobutane, KI, K2CO3, NaHSO3, [2.2.2]-
cryptand, Zn(OAc)2, Mg(OAc)2, KBPh4, and the solventsisoamyl
alcohol (i-AmOH), N,N-dimethylformamide (DMF), CF3COOH,
methanol (MeOH), acetonitrile (CH3CN), and toluenewere
available from commercial suppliers (Acros, Merck, Aldrich, and
Sigma). i-AmOH was distilled over sodium under argon. DBU was
dried, distilled over CaH2 under reduced pressure, and stored under
argon. Neutral alumina (Merck) and silica (Macherey Nagel, Kieselgel
60) were used for column chromatography. Chloroform (CHIMMED,
stabilized with 0.6−1% ethanol) was dried over CaCl2 and distilled
over CaH2. Toluene was distilled over CaH2. 4,5-Dichloro-3,6-
dihydroxyphthalonitrile (4) was synthesized by a previously reported
method.38 NMR spectra were recorded on Bruker Avance 600 and
Bruker Avance 300 spectrometers. NMR spectra were referenced to
1
(38%). H NMR (300 MHz, CHCl3 + MeOD): δ 6.70 (s, 1H), 5.02
(t, J = 6.6 Hz, 2H, 1CH2), 4.19−4.05 (m, 2H, α-CH2crown), 4.03−3.80
(m, β-CH2crown + HDO), 3.76−3.59 (m, 4H, γ,δ-CH2), 2.12−1.78 (m,
2H, 2CH2), 1.58 (m, 2H, 3CH2), 0.88 (t, J = 7.3 Hz, 3H). UV−vis
[CHCl3; λ, nm (log ε, M−1 cm−1)]: 736 (5.35), 660 (4.63), 378
(4.81), 319 (4.75). ESI HRMS for C120H144N8Na2O36Mg2+:
(experimental) m/z 1171.470 ([M + 2Na]2+); (theoretical) m/z
1171.466.
Zinc Oxanthrenocyaninate (2Zn). A mixture of nitrile 1 (100
mg, 0.18 mmol), Zn(OAc)2 (17 mg, 0.09 mmol), hydroquinone (10
mg, 0.09 mmol), and DBU (30 μL, 0.2 mmol) in 4 mL of i-AmOH
was refluxed for 48 h under a slow stream of argon. After cooling, the
reaction mixture was added dropwise to hexane (50 mL). The
resulting precipitate was filtered and washed off the filter with CHCl3.
Chromatography on alumina in a CHCl3/MeOH mixture afforded
green complex 2Zn, which was additionally purified by a Bio-Beads
SX-1 column packed in CHCl3 + 5 vol % MeOH. Yield: 25 mg (24%).
1H NMR (300 MHz, CDCl3): δ 6.79 (s, 1H, HAr), 5.11 (t, J = 6.6 Hz,
2H, OCH2), 4.25−4.16 (m, 2H, α-CH2crown), 4.02−3.91 (m, 2H, β-
CH2), 3.79 (s, 4H, γ,δ-CH2), 2.08−1.90 (m, 2H, CH2), 1.77−1.57 (m,
2H, CH2), 0.97 (t, J = 7.4 Hz, 3H, CH3). UV−vis [CHCl3; λ, nm (log
ε, M−1 cm−1)]: 732 (5.13), 656 (4.35), 399 (4.61), 303 (4.49). ESI
HRMS for C120H144N8Na2O36Zn2+: (experimental) m/z 1191.443 ([M
+ 2Na]2+); (theoretical) m/z 1191.438.
the residual solvent signal.39 The 2D H NOESY NMR spectra were
1
acquired by using pulse sequences supplied by the Bruker standard
pulse program library. UV−vis spectra were measured with a Thermo
Evolution 210 spectrometer in quartz cells with a 1 cm optical path.
Spectrophotometric titrations were performed in 1 cm quartz cells
with a Teflon stopper. Dosage of the titrant was performed with an
LA-100 syringe pump (Landgraf HLL). Matrix-assisted laser
desorption ionization time-of-flight mass spectra were measured on
a Bruker Daltonics Ultraflex spectrometer with 2,5-dihydroxybenzoic
acid as the matrix. High-resolution mass spectrometry (HRMS)
spectra were recorded on an Orbitrap electrospray ionization time-of-
flight (ESI-TOF) mass spectrometer. The photoluminescence spectra
(λex = 400 nm) at 20 °C were recorded on a Horiba Scientific
Flourolog spectrofluorimeter.
Oxanthrenocyanine 2H2. CF3COOH (0.5 mL) was added to a
solution of 2Mg (29.5 mg, 12 μmol) in CHCl3 (10 mL). Then the
mixture was stirred under reflux for 7 min. After cooling to room
temperature, K2CO3 (1 g) was added to the mixture. The solvent was
3,6-Dibutoxy-4,5-dichlorophthalonitrile (5). A mixture of 4
(0.3 g, 1.31 mmol), BuBr (0.42 mL, 3.93 mmol), K2CO3 (1.08 g, 7.86
B
Inorg. Chem. XXXX, XXX, XXX−XXX