Behavior of 1,8-Diaminonaphthalene
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Transcript Behavior of 1,8-Diaminonaphthalene
Photophysical Behavior of 1,8Diaminonaphthalene in Acidic Solutions
and in Zeolite Sieves
Master Thesis By
Abdul-Rahman Al-Betar
Appointed Committee
Prof. Uwe K. A. Klein Thesis Advisor
Prof. Shaikh A. Ali Member
Dr. Than Htun
Member
May 2004
1
Outline
Introduction
Aim of this study
General kinetics scheme of 1,8-DAN
Proposed kinetics scheme of 1,8-DAN
2
General Overview of Proton-Transfer
1950s
Kinetics of Proton-transfer reactions became the
subject of many studies
Eigen
Was the first to measure the fast recombination of
H+ and OH- using relaxation method
Forster and Weller
Were the first to explain the difference between
the ground and the excited states of the
dissociation constants
3
Short Pulse
It becomes possible to directly measure protontransfer of excited molecules
4-H-1-NS and 1-AN
Have been studied by means of laser-induced
picosecond spectroscopy
1,8-DAN
Is the subject of this research
4
OH
NH 2
SO34-hydroxy-1-naphalenesulphonate
1-Aminonaphthalene
NH 2 NH 2
1,8-diaminonaphthalene
5
Aim
of this Study
Paul et al. have studied 1,8-DAN in sulphuric acid
solutions. However, there is no complete analysis of the
overall reaction scheme.
To set up the complete behavior scheme of 1,8-DAN in
the ground and excited state with varying acidity.
Photochemical characterizations of zeolite, based on
fluorescence properties.
Which is a new insight for industry using
spectroscopic measurements
6
General Scheme of 1,8-DAN Proton Transfer
1,8-DAN has two amino groups that could be protonated
NH2
NH3
NH2
+
NH2
pK1
+
+H
Abs
NH2
+H
Flu
Abs
NH2
NH3
+
+H
NH3
pK1
pK2
Flu
Abs
NH2
NH3
+ H+
NH3
Flu
NH3
pK2
7
Absorption Spectra of 1,8-DAN by Paul et al.
neutral
mono-cation
di-cation
Abs.
1
0.8
0.6
0.4
0.2
0
220
270
320
370
nm
8
Absorption Spectra Of The Three Forms 1,8-DAN At
8.0*10-5 M
Neutral
pH 2
pH -1
8000
Extinction Coefficient ( e)
7000
6000
5000
4000
3000
2000
1000
0
250
270
290
310
330
350
370
390
Wavelength/nm
9
Only One Transition, Earlier Suggested by
Paul et al. for DANH+
Absorption spectra
disprove this
structure
H
H
H
H
+
N
N
H
10
Two Different Transitions For DANH+
NH2
330nm
H
H
NH2
NH2
280nm
280nm
NH2
330nm
11
Dissociation Constants
NH2
NH3
NH2
+
NH2
pK1
+
+H
Abs
NH2
+H
Flu
Abs
NH2
NH3
+
+H
NH3
pK1
pK2
Flu
Abs
NH2
NH3
+ H+
NH3
Flu
NH3
pK2
12
Dissociation Constants in the Ground State
pH = pKa + log [A- ] / [HA]
When [A-] equals [HA]
pH = pKa
pKa1 = 4.0
0.5
D Abs
0.4
0.3
0.2
0.1
0
0
1
2
3
4
5
6
7
8
9
10
pH
13
Dissociation Constants in the Ground
State
pKa2 = -0.1
0.25
D Abs.
0.2
0.15
0.1
0.05
0
-1.5
-1
-0.5
0
0.5
1
1.5
pH
14
Dissociation Constants in the Excited State
pK* was determined by Forster-Cycle
pKa* = pKa - h C NA (l -1 HA - l-1A- ) / 2.303 R T
Where
l is the wavelength taken at the 0-0 transition
between absorption and emission spectra
15
Absorption and fluorescence spectra of the
neutral of 1,8-DAN
Fluo. Neutral
Irel
Abs. Neutral
250
300
350
400
450
500
550
600
wavelength/nm
16
Acidity constants in the ground and first excited
states
Equilibrium
pKa
Paul et al.
DANH+ ↔ DAN + H+
4.2
DANH22+ ↔ DANH+ + H+ -0.1
pKa*
Our work
Paul et al.
4.0 ---0.1 -6.5
Our work
-9.7
-10.7
Where pKa* is theoretical values obtained from
Forster-Cycle
17
Fluorescence Spectra
NH2
NH3
NH2
+
NH2
pK1
+
+H
Abs
NH2
+H
Flu
Abs
NH2
NH3
+
+H
NH3
pK1
pK2
Flu
Abs
NH2
NH3
+ H+
NH3
Flu
NH3
pK2
18
Fluorescence Spectra of 1,8-DAN by Paul et
al.
neutral
mono-cation
di-cation
10
Irel
8
6
4
2
0
300
400
nm
500
600
19
Fluorescence Spectra Of The Three Forms 1,8DAN
Neutral
pH-1
pH2
10
8
6
Irel
Emission of
the neutral and
pH 2, show the
same emission
peak
at lEX= 340 nm
4
2
0
300
350
400
450
500
550
600
wavelength/nm
20
Fluorescence Spectra Of The Three Forms 1,8DAN
Emission of
the neutral and
pH 2,
at lEX = 300 nm
Neutral
pH -1
10
8
Irel
Red shift
due to
solvent
relaxation
pH 2
6
4
2
0
300
350
400
450
500
550
600
Wavelength/nm
21
Solvent Relaxation Process
Due to changes of
dipole moment on
excitation, shifting
of energy levels
occur with lower
energy gap
Which cause a red
shift in the
fluorescence
spectrum
S1
S0
22
Quenching Constant, kq
proton-induced fluorescence quenching has been
observed for mono-cation form prior to the
formation of di-cation
The quencher for the neutral form emission is
[H+]
Whereas, the quencher for the protonated form
emission is [H2O]free i.e. the proton acceptor
23
Neutral Form Quencher
0.01 M
0.5 M
0.05 M
0.7 M
0.1 M
0.9 M
0.2 M
1.0 M
8
Irel
6
4
2
0
300
350
400
450
500
550
600
w av elength/nm
24
Intermediate Emission
4M
3M
2M
1M
5M
6M
3
Irel
2
1
0
300
350
400
450
500
550
600
w av elength/nm
25
Protonated Form Quencher
11.8 M
10 M
9M
8M
8
Irel
6
4
2
0
300
350
400
450
500
550
600
wavelength/nm
26
Quenching Constant, kq
1
h
1
h0
k qt 0
h0
[H ]
Plotting 1/h Vs. [H+], gives slope = kq t0 /h0
kq = 1.26 x 109 M-1s-1
With good agreement to the finding by SternVolmer plot using lifetime ( kq = 1.29 x 109 M-1s-1)
Which is within 2% error
27
Stern-Volmer plot
t0
1 k qt 0 [ H ]
t
Plotting t0/t Vs. [H+], gives slope = kq t0
kq = 1.29 x 109 M-1S-1
t 0 /t
y = 9.9249x + 0.6813
12
10
8
6
4
2
0
0
0.2
0.4
0.6
0.8
1
[H+]
28
Proposed Scheme for Proton transfer
reactions of 1,8-DAN
NH 2 NH 2
Diabatic
process in
the excited
state
NH3 NH3
NH3 NH2
+ H+
kd
k'q [H2O]
+
kq[H ]
kf '
kf
Iabs
Iabs
Iabs
NH3 NH3
NH3 NH2
NH2 NH2
pk1
+ H+
4.0
+
+H
pk2
-0.1
29
Quenching Constant, kq’
h0
1 55.5k 'q t acidg [ H 2O ] free
h
Plotting h0/h Vs. g[H2O]free
k’q = 3.12 * 108 M-1s-1
y = 9612.5x 5 - 6889.7x 4 + 1688.9x 3 - 132.93x 2 - 6.2152x + 0.9989
0.8
g [H2O]free
g[H2O] Vs. g[HClO4], was
taken from earlier work by
El-Rayyes et al. and then
was applied to our
concentration in this work.
1
0.6
0.4
0.2
0
0
0.05
0.1
0.15
0.2
0.25
g[HClO4]
30
Fluorescence Decay Measurements
The decay of the neutral and the mono-cation
form have very similar decays,
Both are single-exponential and nicely fit the
equation:
I(t) = I0 e-t/t
Whereas the decay for the di-cation form shows
bi-exponential decay and nicely fit the equation:
I(t) = A1 e-t/t1 + A2 e-t/t2
31
Fluorescence Decay Profile Of The
Three Forms Of 1,8-DAN
Neutral
ph 2
ph -1.1
12000
10000
No. Count
Decay
emission of
the neutral
and pH 2
are similar
8000
6000
4000
2000
0
0
5
10
time/ns
15
20
25
32
Lifetime Measurements t
t1 /ns
1,8-DAN
Paul et al.
Neutral
t2 /ns
Our work
Paul et al.
Our work
1.6
7.7
---
Mono-cation 7.4
8.3
---
Di-cation
---
1.6
---
22.2
33
Energy Surface for
the Mono-cation
Form
S1
+
H2 O
E
427
KJ/mol
412
KJ/mol
363
KJ/mol
S0
0.25KJ/
mol
9.9KJ/mol
H
NH2
NH2
H
NH2
NH2
NH 2 NH 2
+ H+
280nm
330nm
330nm
280nm
330nm 330nm
34
Energy Surface for the
Di-cation Form
No [H2O]free
+ [H2O]free
+
NH 3
H
NH 3
NH2
NH2
+ H+
280nm
280nm
280nm
330nm
35
Zeolite Y Sieves
Zeolite Y has a
major channel of 12
member Oxygen
ring .
Its pours diameters
d1 = 12 Å
d2 = 7.4 Å
Y-zeolite
36
Calcination Process
Three forms of zeolite Y were used:
NaY, HY 34% and HY96%
NaY can be changed to HY of different concentrations
by ion exchange with NH4NO3
NH4NO3 + NaY
NH4Y
500 °C
HY + NH3(g)
37
Protonation Process
NH2
NH2
H
H
O
O
Si
Al
Si
Si
NH2
H
H
O
Si
O
NH2
O
Si
O
Al
Si
O
Si
Si
O
38
Why 1,8-DAN inside Zeolite Sieves ?
To do acidity characterization of solid acids
e.g. Zeolite Y
Acidity characterization can be done by:
1. Temperature-programmed desorption (TPD) Qualitative
2. Calorimetric methods
Qualitative
3. Fourier transformation infrared (FTIR)
Qualitative
4. Laser-induced spectroscopy (LI)
Introduced by El-Rayyes et al.
Quantitative
39
Emission Spectra of DAN /Zeolite Y
DAN/NaY shows the neutral band of 1,8-DAN.
However, under higher energy excitation it shows
the protonated band even there is no proton
Some interesting effects with Na+ ion
i.e. the lone pairs interact with Na+ to give the
higher energy band
40
Emission Spectra of NaY
Ex 340 nm
NaY
Ex 300 nm
8
Irel
6
4
2
0
300
350
400
450
500
550
600
nm
41
Emission Spectra of DAN /Zeolite Y
DAN/HY 34% shows both neural band and the
protonated band of 1,8-DAN.
DAN/HY 96% shows both the neural band and
the protonated band of 1,8-DAN.
However, under higher energy excitation it gives
low energy band.
Which need further studies
42
Emission Spectra of HY 34%
Irel
HY 34% Ex 300nm
5
4
3
2
1
0
300
350
400
450
500
550
nm
43
Conclusion
1,8-DAN shows a Diabatic Reaction Process
i.e. the reaction of the excited neutral form with H+
does not lead to the excited mono-protonated
form, rather it goes to the ground state.
There are three different forms of 1,8-DAN in the
ground state. Whereas, there are only two forms in
the excited state.
44
Proposed Scheme of 1,8-DAN
NH 2 NH 2
NH3 NH3
NH3 NH2
+ H+
kd
k'q [H2O]
+
kq[H ]
kf '
kf
Iabs
Iabs
Iabs
NH3 NH3
NH3 NH2
NH2 NH2
pk1
+ H+
4.0
+
+H
pk2
-0.1
45
Conclusion
The Mono-cation form has two transitions band,
rather than one transition as believed before, which
is supported by absorption spectra.
The Di-cation form has a bi-exponential decay
which suggest the existence of a new form X. i.e.
an adduct between the solvent molecules and the
fluorophore molecules as shown for 1-AN.
46
Conclusion
The excited state reactions is very sensitive
to the presence or absence of water
molecules and protons, which makes 1,8DAN possibly a good indicator for zeolite
acidity.
i.e. 1,8-DAN may be used as a probe
molecule to assess zeolite acidity.
47
Acknowledgement
All praise be to Allah for his limitless help and guidance.
Peace pleasing of Allah be upon his prophet
Mohammed.
To my advisor Prof. Uwe Klein
To other members: Prof. A. Ali and Dr. Than Htun
To helpful discussion: Dr. El-Rayyes
To helpful consultation: Dr. Fettouhi
To technicians help: M. Arab and Mr. Mazhar
To graduate advisor, chemistry chairman and dean of
science college
To all faculty, staff and students
48
Thank You All
49
NH 2
NH 2
50
NH 2 NH 2
51