Photoisomerization of trans ortho-, meta-, para- nitro diarylbutadienes:
A case of regioselectivity
Harsha Agnihotri1, Mahalingavelar Paramasivam1, Veerabhadraiah Palakollu1 and Sriram
Kanvah1, *
1
Department of Chemistry, Indian Institute of Technology Gandhinagar, Chandkheda,
Ahmedabad-382424, India.
Supporting Information
23rd June 2015
1
Table S1: Crystallographic data for diene 3
Compound
formula
M
Crystal
system
Space group
a/Å
b/Å
c/Å
α/°
β/°
γ/°
Volume/A3
Z
Dcalc/gcm-3
μ/mm-1
T/K
Reflns
collected
Unique
reflns
R1(I>2σ)
wR2(I>2 σ)
(I>2 σ)
3
C16H13NO2
251.27
Orthorhombic
Pca21
24.7041(7)
6.5046(2)
8.2383(2)
90.00
90.00
90.00
1323.81(6)
4
1.261
0.084
296(2)
2567
2347
0.0303
0.0832
2
Normalised Intensity
1.0
Heptane
Dioxane
THF
Acetonitrile
DMF
(1)
0.8
0.6
0.4
0.2
0.0
400
450
500
550
600
650
700
Wavelength (nm)
Normalised Intensity
(3)
0.8
0.6
0.4
0.2
Heptane
Dioxane
Tetrahydrofuran
Acetonitrile
DMF
(6)
1.0
Normalised Intensity
Acetonitrile
Heptane
Dioxane
Tetrahydrofuran
DMF
1.0
0.8
0.6
0.4
0.2
0.0
0.0
350
400
450
500
Wavelength (nm)
550
600
350
400
450
500
550
Wavelength (nm)
Fig S1. Normalized emission spectra of dienes (1) (3) and (6) in solvents of varying solvent
polarity. Dienes-(3) and (6) show weak emission profile and the sharp emission lines are due
to Raman Scattering peaks.
3
600
Acetonitrile
Dioxane
Heptane
Tetrahydrofuran
DMF
Normalised Intensity
1.0
0.8
0.6
0.4
CT Bands
0.2
0.0
350
400
450
500
550
600
650
Wavelength (nm)
Fig S2. Normalized emission spectra of diene (5) in solvents of varying solvent polarity. The
sharp emission lines are due to Raman peaks- despite taking adequate care (dry solvents)
these peaks could not be avoided.
4
b
a
c
Fig S3. (a) HPLC peak profile of diene (4) before and b) after irradiation obtained using 370
nm as detection wavelength. (c) 1H NMR spectra of diene (4) before irradiation.
5
0.35
0 min
30 sec
1 min
2 min
4 min
6 min
8 min
10 min
20 min
30 min
40 min
50 min
60 min
70 min
80 min
90 min
100 min
140 min
180 min
0.30
Absorbance
0.25
0.20
0.15
a
0.10
0.05
0.00
300
400
Wavelength (nm)
500
600
c
b
e
d
Fig S4. (a) UV-Vis absorption spectrum upon irradiation of diene (2) in acetonitrile at
different time intervals. HPLC peak profile of diene (2) (b) before and (c) after irradiation. 1H
NMR spectra of diene (2) (d) before irradiation and (e) after irradiation.
6
0.30
0 min
30 sec
1 min
2 min
4 min
6 min
8 min
10 min
15 min
20 min
30 min
40 min
50 min
60 min
80 min
100 min
120 min
140 min
180 min
a
Absorbance
0.25
0.20
0.15
0.10
0.05
0.00
200
300
400
500
600
Wavelength (nm)
b
d
c
e
Figure S5. (a) UV-Vis absorption spectrum upon irradiation of diene (5) in acetonitrile at
different time intervals. (b) HPLC peak profile before and after irradiation obtained using 330
nm as detection wavelength; (c) 1H NMR spectra before irradiation and (d) 1H NMR spectra
after irradiation of diene (5).
7
c
d
Figure S6. HPLC Peak profiles of (c) diene (3) and (d) diene (6) after irradiation
8
180 min
60 min
Hc
Hd Hc
’
Hd’
30 min
Hc
Hc
’
Hd
Hd’
0 min
J = 14-15 Hz
Ha
Ha’
Hb
Hb’
Figure S7. Time-dependent NMR study of (3) in CDCl3 at different time intervals.
9
J = 14-15 HZ
Ha
Ha’ Hb
Hb’
a
b
Hc’
Hd
Hd’
Hc
c
d
Figure S8. 1H NMR (3) (a) before irradiation and (b) after irradiation. COSY spectra (c) after
irradiation (mixture of tt and tc) and (d) of pure tc isomer.
10
120 min
60 min
0 min
Fig S9. Time-dependent irradiation of diene (6) in CDCl3 at different time intervals.
a
b
11
d
c
C
B
B +B’
A
A
Figure S10. 1H NMR spectra of diene (6) (a) before irradiation and (b) after irradiation.
COSY spectra (c) before irradiation and (d) after irradiation.
12
Figure S11. LCMS chromatogram and mass spectra of diene 6 after irradiation.
Procedure for Quantum yield measurement
Quantum yield (ϕPI) for the photoisomerization reaction was determined according to eq-1.
𝜙=
𝑛𝑟
𝑡 × 𝐼𝑎
(1)
where nr is the number of reacted molecules and Ia is the amount of light absorbed during
isomerization reaction in quanta/sec, t = time of irradiation.
The method of nr calculation: The 3 ml of 10-5 M solution of dienes (3) and (6) in organic solvents
was taken in quartz cell and measured the absorbance. The sample solution in the same cell was
irradiated using 10% copper sulphate pentahydrate solution as the cut-off solution filter for 1 minute
and noted the optical density. The number of reacted molecules (nr) in photochemical reaction was
calculated by formula (2)
𝑛𝑟 =
6.023 × 1020 𝑉1 𝑙𝑜𝑔10 𝐼𝑜 ⁄𝐼
𝜖2 𝑙
(2)
𝑉1 = volume of solution (3ml), 𝑙𝑜𝑔10 𝐼𝑜 ⁄𝐼 = optical density of the irradiated solution relative to
unirradiated solution, 𝜖2 = molar extinction coefficient of compound, 𝑙 = path length of
spectrophotometer cell (1 cm)
13
The method of Ia calculation: 3 ml of 6 × 10−3 M solution of potassium ferrioxalate was introduced
in a UV cell and the absorbance was measured at 510nm. The solution was irradiated under identical
conditions (as the sample solution) for 1 minute. After irradiation, 0.5 ml of buffered phenanthroline
was added in the cell and measured the absorbance at 510nm. The total number of Fe2+ produced after
irradiation was calculated by the formula (3)
𝑛𝐹𝑒 =
6.023 × 1020 𝑉1 𝑉3 𝑙𝑜𝑔10 𝐼𝑜 ⁄𝐼
𝑉2 𝜖𝑙
(3)
Where, V1 = volume of irradiated actinometer solution (3 ml), V2 = the volume of aliquot of irradiated
solution taken for the determination of the ferrous ions (3 ml), V3 = final volume after complexation
with phenanthroline (3.5 ml), 𝑙𝑜𝑔10 𝐼𝑜 ⁄𝐼 = optical density of the irradiated solution relative to
unirradiated solution at 510 nm, ϵ = (1.11 X 104 mole-1 l cm-1) the extinction coefficient of the
complex 𝐹𝑒(𝑝ℎ𝑒𝑛)32+ , 𝑙 = path length of spectrophotometer cell (1 cm). The amount of light
absorbed during isomerization reaction (Ia) in quanta/sec calculated from equation (4)
𝐼𝑎 =
𝑛𝐹𝑒
𝜙𝜆 ×𝑡×𝐹
(4)
where 𝜙𝜆 = the quantum yield of ferrous ion production at the irradiation wavelength (1.23), t is the
irradiation time, and F is the mean fraction of light absorbed by the ferrioxalate solution (taken as 1
should be 100%).
References
1. S.L. Murov, Chemical Actinometry Handbook of photochemistry, chapter 12 (2006) 601.
2. D. Phillips, A Quantitative Photochemical Experiment for Undergraduates, J. Chem. Edu 48 (1971) 198-199.
(Characterization data)
1H
NMR spectra of dienes before irradiation.
Diene (1): 1-((1E,3E)-4-(4-nitrophenyl)buta-1,3-dienyl)benzene
Yellow solid; UV (Acetonitrile) 1H NMR (CDCl3, 500 MHz, ppm) δ 8.19-8.18 (d, 2H, J =
9.5 Hz), δ 7.55-7.53 (d, 2H, J = 8.5 Hz), δ 7.47-7.46 (d, 2H, J = 7.5 Hz), δ 7.37-7.30 (m, 2H),
δ 7.28-7.258 (m, 1H), δ 7.13-7.08 (dd, 1H, J = 16 Hz), δ 7.00-6.95 (dd, 1H, J = 16 Hz), δ
6.81-6.78 (dd, 1H, J = 16 Hz), δ 6.71-6.68 (dd, 1H, J = 16 Hz).
C NMR (CDCl3, 500 MHz, ppm) δ 146.60, 143.93, 136.71, 136.10, 133.79, 130.11, 128.82,
13
128.39, 128.28, 126.76 , 126.65, 124.17.
14
Diene (2): 1-nitro-3-((1E,3E)-4-phenylbuta-1,3-dienyl)benzene
Yellow solid; UV (Acetonitrile) 1H NMR (CDCl3, 500 MHz, ppm) δ 8.28 (s, 1H), 8.07-8.05
(m, 1H), 7.72-7.71 (d, 1H, J = 7.5Hz), 7.51-7.46 (m, 3H), 7.37-7.34 (t, 2H), 7.28-7.27 (d,
1H), 7.10-7.05 (m, 1H)6.99-6.94 (m, 1H), 6.79-76 (d, 1H, J = 15.5Hz), 7.71-6.68 (d, 1H, J =
15.5Hz).
C NMR (CDCl3, 500 MHz, ppm) δ 148.7, 139.2, 136.8, 135.1, 132.1, 132.0, 129.8, 129.5,
13
128.7, 128.2, 128.1, 126.6, 121.8, 120.7.
15
Diene (3): 1-nitro-2-((1E,3E)-4-phenylbuta-1,3-dienyl)benzene
Yellow solid; UV (Acetonitrile) 1H NMR (CDCl3, 500 MHz, ppm) δ 7.92-7.91 (d, 1H, J =
8.0 Hz), 7.32-7.71 (d, 1H, J = 7.5 Hz), 7.58-7.55 (t, 1H), 7.47-7.45 (2H, d), 7.38-7.33 (m,
3H), 7.28-7.27 (d,1H, J = 7.5 Hz), 7.18-7.15 (d, 1H, J = 14.0 Hz), 7.03-6.94 (m, 2H), 6.776.74 (d, 1H, J = 15.0 Hz).
16
Diene (4): 4-((1E,3E)-4-(4-nitrophenyl)buta-1,3-dienyl)pyridine
Yellow solid; UV (Acetonitrile) 1H NMR (CDCl3, 500 MHz, ppm) δ 8.58-8.57 (d, 2H), 8.228.20 (d, 2H), 7.59-7.57 (d, 2H), 7.31-7.30 (d, 2H), 7.17-7.07 (m, 2H), 6.83-6.80 (d, 1H, J =
14.5Hz), 6.72-6.69 (d, 1H, J = 14.5Hz).
C NMR (CDCl3, 500 MHz, ppm) δ 151.7, 150.3, 147.1, 143.9, 143.1, 132.9, 132.8, 132.4,
13
127.0, 124.2, 120.83, HRMS [ESI] [M+1]+ 253.
17
Diene (5): 1-nitro-3-((1E,3E)-4-phenylbuta-1,3-dienyl)benzene
Yellow solid; UV (Acetonitrile) 1H NMR (CDCl3, 500 MHz, ppm) δ 8.57-8.56 (d, 2H), 8.31
(s, 1H), 8.12-8.10 (d, 1H), 7.74-7.73 (d, 1H), 7.54-7.50 (t, 1H), 7.31-7.30 (d, 2H), 7.16-7.04
(m, 2H), 6.82-6.79 (d, 1H, J = 15Hz), 6.70-6.67 (d, 1H, 15Hz).
18
C NMR (CDCl3, 500 MHz, ppm) δ 150.2, 144.0, 138.5, 132.7, 132.4, 132.3, 132.0, 131.0,
13
129.7, 122.5, 121.0, 120.8, HRMS [ESI] [M+1]+ 253.
19
Diene (6): 4-((1E,3E)-4-(2-nitrophenyl)buta-1,3-dienyl)pyridine
Yellow solid; UV (Acetonitrile) 1H NMR (CDCl3, 500 MHz, ppm) δ 8.57-8.56 (d, 2H), 7.967.94 (d, 1H), 7.72-7.70 (d, 1H), 7.61-7.58 (t, 1H), 7.43-7.42 (t, 1H), 7.31-7.26 (m, 3H), 7.207.15 (m, 1H, J = 15.5Hz), 6.96-6.91 (m, 1H, J = 15.5Hz), 6.68-6.65 (d, 1H, J = 15.5Hz).
C NMR (CDCl3, 500 MHz, ppm) δ 150.2, 147.9, 144.0, 133.0, 132.8, 132.2, 132.1, 129.8,
13
128.4, 127.9, 124.8, 120.8, HRMS [ESI] [M+1]+ 253.
20
1H
NMR Characterization of the dienes after photoisomerization
Photomixture of Diene (3): 1-nitro-2-((1E,3E)-4-phenylbuta-1,3-dienyl)benzene
21
1
H NMR (CDCl3, 500 MHz, ppm) δ 8.10-8.09 (d), 7.92-7.91(d), 7.73-7.71 (d), 7.63-7.55 (m),
7.47-7.45 (d), 7.36-7.34 (d), 7.30-7.26 (m), 7.18-7.15 (d, J = 14.5Hz, tt), 7.04-6.94 (m), 6.846.82 (d, J = 11.5Hz, tc), 6.77-6.74 (d, J = 15.5Hz, tt), 6.60-6.55 (t, J = 11.0Hz, tc).
Photomixture of Diene (6): 4-((1E,3E)-4-(2-nitrophenyl)buta-1,3-dienyl)pyridine
1
H NMR (CDCl3, 500 MHz, ppm) δ 8.58-8.57 (d), 8.51-8.50 (d), 8.15-8.13 (d), 7.97-7.95 (d),
7.72-7.71 (d), 7.68-7.65 (t), 7.61-7.58 (t), 7.53-7.52 (d), 7.50-7.46 (t), 7.44-7.40 (t), 7.31-7.30
(d), 7.20-7.15 (m), 7.10-7.04 (m), 6.99-6.97 (d, J = 11.5Hz, tc), 6.94-6.91 (m), 6.68-6.65 (d, J
= 15.5Hz, tt), 6.61-6.57 (t, J = 11.5Hz, tc).
22