Intramolecular, Exciplex-Mediated, Proton-Coupled, Charge-Transfer Processes in N,N-dimethyl-3-(1pyrenyl)propan-1-ammonium Cations. Influence of Anion, Solvent Polarity, and Temperature.
Trevor M. Safkoa, Marcelo M. Faleirosb, Teresa D. Z. Atvarsb, and Richard G. Weissa,c*
a
Department of Chemistry and cInstitute for Soft Matter Synthesis and Metrology, Georgetown University,
37th and O Streets NW, Washington, DC 20057-1227, USA
b
Instituto de Química, Universidade Estadual de Campinas, Caixa Postal 6154, Campinas, SP, Brasil
*Email: [email protected]
Supporting Information
1.1 Materials
Methanol (anhydrous Sigma Aldrich, 99.8%), diethyl ether (anhydrous Sigma Aldrich, > 99%),
trifluoroacetic acid (Alfa Aesar, 99%), hydrobromic acid (Fluka, 99.8%), silver nitrate (Fisher, 99.7%),
chloroform-d (Cambridge Isotope Laboratories, Inc., 99.9%), 12M hydrochloric acid (Macron, 99%), 18M
sulfuric acid (Baker, 98%), p-toluenesulfonic acid monohydrate (Sigma Aldrich, 98.5%), and ethyl acetate
(Sigma Aldrich, > 99.7%) were used as received. Tetrahydrofuran (anhydrous, Sigma Aldrich, 99.9%) and
1,4-dioxane anhydrous (Sigma Aldrich, 99.8%) were dried and purified through distillation over sodium
and benzophenone. Dichloromethane (Fisher, 99.9%) was dried and purified by distillation over calcium
hydride.
1.2 Syntheses
The synthesis of N,N-dimethyl-3-(1-pyrenyl)propan-1-amine (PyA) was accomplished using a previously
established synthetic route.12 PyS were synthesized by dissolving PyA in diethyl ether and treating it with
3 equivalents of the corresponding acid as described below:
S1
N,N-dimethyl-3-(1-pyrenyl)propan-1-ammonium chloride (PyCl) was synthesized by dissolving 500 mg
(1.6 mmol) N,N-dimethyl-3-(1-pyrenyl)propan-1-amine in 30 mL diethyl ether, under flowing N2, in a oneneck round bottom flask. Gaseous HCl was formed by adding 12M hydrochloric acid to a stirred solution
of 18M sulfuric acid. The gaseous HCl was passed through a calcium chloride drying tube and bubbled
through the solution of N,N-dimethyl-3-(1-pyrenyl)propan-1-amine. The precipitate that formed upon
addition of the concentrated acid was recrystallized five times in dichloromethane and diethyl ether to
give N,N-dimethyl-3-(1-pyrenyl)propan-1-ammonium chloride (PyCl), mp 227 – 230 °C and > 99.4% purity
by HPLC. 1H NMR (CDCl3, 400 MHz): 2.46 (2H, m, CH2CH2CH2NH(CH3)2), 2.89 (6H, s, CH2CH2CH2NH(CH3)2),
3.00 (2H, m, CH2CH2CH2NH(CH3)2), 3.50 (2H, m, CH2CH2CH2NH(CH3)2), 7.81 (1H, m, ArH), 8.01 (3H, m,
ArH), 8.06 (5H, m, ArH), 12.73 (1H, s, NH). Elemental analysis calculated for C21H22N1Cl: C, 74.0; H, 7.1; N.
4.1. Found: C, 74.3; H, 6.9; N, 4.3.
N,N-dimethyl-3-(1-pyrenyl)propan-1-ammonium bromide (PyBr) was synthesized by dissolving 125
mg (0.4 mmol) N,N-dimethyl-3-(1-pyrenyl)propan-1-amine in 20 mL diethyl ether, under flowing N2, in a
one-neck round bottom flask. 3 equivalents of concentrated acid (195 μL 48% hydrobromic acid) were
added drop-wise at 0 °C. The precipitate that formed upon addition of the concentrated acid was
recrystallized three times in dichloromethane and diethyl ether to give N,N-dimethyl-3-(1pyrenyl)propan-1-ammonium bromide (PyBr) (mp: 224 – 226 °C). δH (CDCl3, 400 MHz), 2.50 (2H, m,
CH2CH2CH2NH(CH3)2), 2.71 (6H, s, CH2CH2CH2NH(CH3)2), 3.05 (2H, m, CH2CH2CH2NH(CH3)2), 3.51 (2H, m,
CH2CH2CH2NH(CH3)2), 7.85 (1H, m, ArH), 8.01 (3H, m, ArH), 8.18 (5H, m, ArH), 11.72 (1H, s, NH). HPLC
analysis indicated > 99.3% purity. Elemental analysis calculated for C21H22N1Br: C, 66.9; H, 6.1; N. 3.7.
Found: C, 67.2; H, 5.8; N, 3.8.
N,N-dimethyl-3-(1-pyrenyl)propan-1-ammonium trifluoroacetate (PyTFA) was synthesized by
dissolving 125 mg (0.4 mmol) N,N-dimethyl-3-(1-pyrenyl)propan-1-amine in 20 mL diethyl ether, under
flowing N2, in a one-neck round bottom flask. 3 equivalents of concentrated acid (408 μL trifluoroacetic
S2
acid) were added drop-wise at 0 °C. The precipitate that formed upon addition of the concentrated acid
was recrystallized three times in dichloromethane and diethyl ether to give N,N-dimethyl-3-(1pyrenyl)propan-1-ammonium trifluoroacetate (PyTFA) (mp: 161 – 162 °C). δH (CDCl3, 400 MHz), 2.33 (2H,
m, CH2CH2CH2NH(CH3)2), 2.70 (6H, s, CH2CH2CH2NH(CH3)2), 3.05 (2H, m, CH2CH2CH2NH(CH3)2), 3.45 (2H,
m, CH2CH2CH2NH(CH3)2), 7.81 (1H, m, ArH), 8.04 (3H, m, ArH), 8.17 (5H, m, ArH), 13.51 (1H, s, NH). HPLC
analysis indicated > 99.7% purity. Elemental analysis calculated for C23H22N1O2F3: C, 68.7; H, 5.5; N. 3.5.
Found: C, 68.4; H, 5.5; N, 3.7.
N,N-dimethyl-3-(1-pyrenyl)propan-1-ammonium nitrate (PyNO3) was synthesized through anion
substitution of PyBr with AgNO3. A concentrated solution of AgNO3 in methanol (64 mg in 5 mL) was
prepared and added drop-wise to a solution of 43 mg PyBr in 10 mL of methanol. Upon addition of the
AgNO3 solution, the clear solution turned cloudy and a precipitate formed. The PyNO3 salt was extracted
with chloroform and washed with water to remove excess AgNO3. 30 mg of crystalline N,N-dimethyl-3-(1pyrenyl)propan-1-ammonium nitrate (PyNO3) (mp: 158 – 160 °C) was isolated. δH (CDCl3, 400 MHz), 2.37
(2H, m, CH2CH2CH2NH(CH3)2), 2.79 (6H, s, CH2CH2CH2NH(CH3)2), 3.10 (2H, m, CH2CH2CH2NH(CH3)2), 3.48
(2H, m, CH2CH2CH2NH(CH3)2), 7.84 (1H, m, ArH), 8.04 (3H, m, ArH), 8.17 (5H, m, ArH), 12.01 (1H, s, NH).
HPLC analysis indicated > 99.4% purity. Elemental analysis calculated for C21H22N2O3: ½ H2O: C, 70.2; H,
6.5; N, 7.8. Found: C, 70.6; H, 6.4; N, 7.8.
N,N-dimethyl-3-(1-pyrenyl)propan-1-ammonium p-toluenesulfonate (PyTSA) was synthesized by
dissolving 123 mg (0.4 mmol) N,N-dimethyl-3-(1-pyrenyl)propan-1-amine in 20 mL diethyl ether, under
flowing N2, in a one-neck round-bottom flask. 3 equivalents of concentrated acid (200 mg ptoluenesulfonic acid in 20mL ether) were added drop-wise at 0 °C. As the acid was slowly added, the
yellow solution turned cloudy as a beige precipitate formed. The precipitate was filtered and
recrystallized three times with dichloromethane and diethyl ether to give N,N-dimethyl-3-(1pyrenyl)propan-1-ammonium p-toluenesulfonate (PyTSA) (mp: 129 – 131 °C). δH (CDCl3, 400 MHz), 2.32
S3
(3H, s, CH3(C6H4)SO3) 2.37 (2H, m, CH2CH2CH2NH(CH3)2), 2.70 (6H, s, CH2CH2CH2NH(CH3)2), 3.05 (2H, m,
CH2CH2CH2NH(CH3)2), 3.45 (2H, m, CH2CH2CH2NH(CH3)2), 7.13 (2H, d, CH3(C6H4)SO3), 7.80 (3H, m, ArH),
8.05 (6H, m, ArH), 8.19 (2H, d, CH3(C6H4)SO3), 11.22 (1H, s, NH). HPLC analysis indicated > 99.8% purity.
Elemental analysis calculated for C28H29NSO3: ½ H2O: C, 72.5; H, 6.3; N, 2.9. Found: C, 72.5; H, 6.3; N, 3.1.
N,N-dimethyl-3-(1-pyrenyl)propan-1-amine (PyA) was prepared by suspending 30 mg (0.09 mmol)
PyCl in 10 mL diethyl ether and stirring with 20 mL 30% NaOH under flowing N2 for 30 min. PyA was
extracted with diethyl ether and washed with water to remove excess base. The solution of PyA was dried
over Na2SO4 and concentrated on a rotary evaporator to give 23 mg PyA. HPLC analysis indicated greater
than 99.9% purity.
S4
1.3 Additional Experimental Results
Figure S1: Fluorescence spectra of 10-5 M PyS in THF from 193 – 313 K: a) PyCl, b) PyBr, c) PyTFA, d)
PyNO3, and e) PyTSA. Spectra were collected using λex 325 nm and normalized with respect to emission
intensity at 377 nm.
S5
Normalized Intensity (a.u.)
1.50
Ocean Optics
Cary Eclypse
1.25
1.00
0.75
0.50
0.25
0.00
350
400
450
500
550
600
650
700
Wavelength (nm)
Figure S2: Fluorescence spectrum of 10-5 M PyCl in THF at 298 K collected on an Ocean Optics 1K series
spectrometer and a Cary Eclipse fluorescence spectrometer. The differences observed in the emission
spectra are due to an overall lower sensitivity, particularly at shorter wavelengths, of the Ocean Optics
spectrometer, as are the hints of fine structure in the exciplex portions of the spectra; the spectra have
not been corrected for instrumental effects. This systematic variation does not affect conclusions derived
from the emission spectra from one PyS compared at different temperatures or from spectra of different
PyS compared at one temperature.
S6
Figure S3: 377 nm fluorescence decay histograms (λex = 325 nm) and residuals plots for 10-5 M PyCl, PyBr,
PyTFA, PyNO3, and PyTSA in THF. Fluorescence decays collected over 2066 channels with a 500 ns time
window.
S7
Table S1: Fits of SPC decay for 10-5 M PyS and PyA in THF at 515 nm (λex of 325 nm) at 223 – 330 K.
Compound
PyCl
PyBr
PyTFA
PyNO3
PyTSA
PyA
Temperature (K)
243
263
283
298
313
223
243
263
283
298
313
263
283
298
313
263
283
298
313
263
283
298
313
291
300
306
310
317
321
324
330
BEx1
-0.501
-0.513
-0.401
-0.478
-0.386
-0.483
-0.490
-0.288
-0.441
-0.425
-0.385
-0.421
-0.528
-0.686
-0.531
-0.488
-0.430
-0.477
-0.485
-0.497
-0.471
-0.562
-0.807
-0.515
-0.501
-0.540
-0.532
-0.515
-0.517
-0.562
-0.581
τEx1 (ns)
4.4
2.8
1.9
1.6
1.2
5.5
4.2
2.4
2.0
1.6
1.1
2.1
1.6
1.1
0.9
2.4
2.0
1.6
1.3
2.43
1.90
1.27
0.77
1.5
1.4
1.0
0.7
0.7
0.6
0.4
0.3
BEx2
0.499
0.487
0.599
0.522
0.614
0.517
0.510
0.712
0.559
0.575
0.615
0.579
0.472
0.314
0.469
0.512
0.570
0.523
0.515
0.503
0.529
0.438
0.193
0.485
0.499
0.460
0.468
0.485
0.483
0.438
0.419
τEx2 (ns)
8.8
10.5
12.7
14.4
17.5
9.6
9.3
11.5
12.8
14.5
17.5
11.5
12.8
14.7
17.2
11.7
12.9
14.8
17.0
11.8
13.3
15.0
17.8
14.6
15.9
16.8
17.8
19.2
20.0
20.4
21.1
χ2
1.0
1.1
1.0
1.1
1.1
1.1
1.2
1.0
1.2
1.2
1.1
1.0
1.2
1.0
1.0
1.1
1.1
1.1
1.1
1.0
1.1
1.1
1.1
1.2
1.2
1.2
1.3
1.1
1.3
1.3
1.0
S8
Table S2: Fits of SPC decays for 10-5 M PyS in THF at 377 nm (λex of 325 nm) at 298 K.
Compound
PyCl
PyBr
PyTFA
PyNO3
PyTSA
BLE1
0.872
0.901
0.940
0.914
0.918
τLE1 (ns)
1.77
2.41
2.06
1.86
0.87
BLE2
0.112
0.084
0.054
0.068
0.026
τLE2 (ns)
12.8
13.0
9.9
12.0
12.0
BLE3
0.016
0.015
0.005
0.018
0.056
τLE3 (ns)
156.6
126.5
122.3
171.7
186.7
χ2
1.1
1.3
1.2
1.3
1.1
Figure S4: Arrhenius plots for 10-5 M PyS and PyA in THF using time-correlated single photon counting
decay components a) τEx1 and b) τEx2 at 515 nm as a function of inverse temperature.
Table S3: Parameters associated with the data from Arrhenius plots in Figure S2 for 10 -5 M PyS and PyA
in THF to linear fits.
Compound
PyCl
PyBr
PyTFA
PyNO3
PyTSA
PyA
Arrhenius slope (τEx1) (K-1)
-1397.6 + 50.1
-1365.5 + 131.9
-1480.9 + 200.0
-1052.0 + 148.8
-1856.9 + 367.8
-2768.5 + 325.3
Arrhenius slope (τEx2) (K-1)
731.4 + 58.0
637.2 + 62.6
657.7 + 99.2
611.9 + 92.6
662.2 + 98.3
1034.4 + 92.4
S9
Figure S5: Eyring plots for 10-5 M PyS and PyA in THF using time-correlated single photon counting decay
components a) τEx1 and b) τEx2 at 515 nm as a function of inverse temperature.
Table S4: Parameters associated with the data from Eyring plots in Figure S3 for 10-5 M PyS and PyA in
THF to linear fits.
Compound
PyCl
PyBr
PyTFA
PyNO3
PyTSA
PyA
Eyring Slope (τEx1) (K-1)
-1123.1 + 50.3
-1091.0 + 130.8
-1194.9 + 195.4
-766.1 + 143.9
-1571.0 + 362.5
-4528.7 + 400.8
Eyring Intercept (τEx1)
-23.1 + 0.2
-23.1 + 0.5
-22.5 + 0.7
-24.3 + 0.5
-21.3 + 1.3
-11.7 + 1.3
Eyring Slope (τEx2) (K-1)
1005.9 + 63.4
911.7 + 66.4
943.7 + 104.5
897.9 + 97.8
948.1 + 103.5
1490.5 + 105.1
Eyring Intercept (τEx2) (K-1)
-32.5 + 0.2
-32.2 + 0.2
-32.3 + 0.4
-32.1 + 0.3
-32.3 + 0.4
-34.1 + 0.3
S10