Behavior of 1,8-Diaminonaphthalene

Report
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

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