synthesis and characterization of metallo-tetraarylazadipyrromethene complexes anne lam damali...
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Synthesis and Characterization of Metallo-tetraarylazadipyrromethene Complexes
Anne LamDamali Greenaway
Mentors: Dr. Chris Hansen and Dr. Jianguo Shao
July 05, 2013
Objectives• To synthesize a ligand and metal complexes
• To characterize complexes using Electro-chemistry, IR, and UV-visible Spectroscopy
NH N
NPh Ph
Ph Ph
N N
NPh Ph
Ph PhM
N N
NPh Ph
Ph Ph
Causes for Study• Metallo-tetraarylazadipyrromethene
complexes exhibit potential application as – fluorescent chemosensors - molecules that
change their fluorescence in response to substrate binding
– in vitro fluorophores – molecules employed in biochemistry, protein studies, and cell analysis
– photosensitive drugs in Photodynamic Therapy
Jablonski Diagram for the PDT process
Our compounds exhibit strong absorption in the visible range (400 – 780 nm).
1,4 Michael Addition
Reflux with CH3CO2NH4
Synthesis of Free-base Ligand
Products confirmed by H-NMR
Synthesis of Metallo-complexes
Reflux with Ni(CH3CO2)2 ·
4H2O 22 h
Reflux with
CH 3CO 2NH 4 and
CoCl 2 · 6H 2O
22 h
N N
NPh Ph
Ph PhCu
N N
NPh Ph
Ph Ph
N N
NPh Ph
Ph PhCo
N N
NPh Ph
Ph Ph
N N
NPh Ph
Ph PhNi
N N
NPh Ph
Ph Ph
Reflux with Cu(CH
3 CO2 )
21 h
Product purities tested with TLC
Ni Co Cu (pure)
(free-base ligand)
IR Spectra
Cpd Strong IR Peaks (cm-1)
FB1 1557, 1543, 1351, 1264, 1242, 962, 904, 762
Co 1520, 1476, 1448, 1367, 1248, 1131, 982, 930
Ni 1521, 1476, 1448, 1367, 1249, 1131, 985, 930
Cu 1521, 1476, 1448, 1366, 1250, 1131, 987,928
Ni complex
1Free Base (tetraarylazadipyrromethene)
NH N
NPh Ph
Ph Ph
UV-Visible Spectra in CH2Cl2
Wavelength (nm)
Cu
FB
Co
Ni
CpdB-Band
(nm)Q-Band (nm)
ΔQ (nm)
FB1 302 597
Co 305 604 672 68
Ni 306 607 652 45
Cu 304 565 641 76
300 400 500 600 700 8001Free Base (tetraarylazadipyrromethene)
NH N
NPh Ph
Ph Ph
UV-Visible Spectra in DMF
300 400 500 600 700 800
Wavelength (nm)
CpdB-Band
(nm)Q-Band (nm)
ΔQ (nm)
FB1 303 600
Co 305 607 676 69
Ni 307 611 653 42
Cu 303 569 641 72
Cu
FB
Co
Ni
1Free Base (tetraarylazadipyrromethene)
NH N
NPh Ph
Ph Ph
Electrochemical Introduction• A potential is applied to an electrode
immersed in a solution, forcing the oxidation/reduction of the analyte.
• The concentration ratio of the Oxidized and Reduced species (near the electrode) adopts a value consistent with the Nernst Equation.
• The magnitude of the current is then determined by – Electron-Transfer – the oxidation or
reduction of analyte– Mass- Transfer- the transport
(diffusion) of analyte to or from the electrode surface in an attempt to equalize the concentrations
11
(+)OxidationReduction
E1/2
E1/2
(-)
Cyclic Voltammetry (Theory)
(Electron Withdrawal)(Electron Addition)
A- A+A A+ e-
- e-
OxidationReduction
Cyclic Voltammetry CH2Cl2,0.1M TBAP
-2.00 -1.50 -1.00 -0.50 0.00
Potential (V vs SCE)
*
*
0.50 0.75 1.00 1.25 1.50
Potential (V vs SCE)
N N
NPh Ph
Ph PhCu
N N
NPh Ph
Ph Ph
NH N
NPh Ph
Ph Ph
N N
NPh Ph
Ph PhCo
N N
NPh Ph
Ph Ph
N N
NPh Ph
Ph PhNi
N N
NPh Ph
Ph Ph
Oxidations in CH2Cl2, 0.1M TBAP
0.50 0.75 1.00 1.25 1.50
Potential (V vs SCE)
N N
NPh Ph
Ph PhCu
N N
NPh Ph
Ph Ph
NH N
NPh Ph
Ph Ph
N N
NPh Ph
Ph PhCo
N N
NPh Ph
Ph Ph
N N
NPh Ph
Ph PhNi
N N
NPh Ph
Ph Ph
Reductions in CH2Cl2, 0.1M TBAP
-2.00 -1.50 -1.00 -0.50 0.00Potential (V vs SCE)
*
*
N N
NPh Ph
Ph PhCu
N N
NPh Ph
Ph Ph
NH N
NPh Ph
Ph Ph
N N
NPh Ph
Ph PhCo
N N
NPh Ph
Ph Ph
N N
NPh Ph
Ph PhNi
N N
NPh Ph
Ph Ph
Reductions in Pyridine, 0.1M TBAP
-2.00 -1.50 -1.00 -0.50 0.00
Potential (V vs SCE)
*
*
N N
NPh Ph
Ph PhCu
N N
NPh Ph
Ph Ph
NH N
NPh Ph
Ph Ph
N N
NPh Ph
Ph PhCo
N N
NPh Ph
Ph Ph
N N
NPh Ph
Ph PhNi
N N
NPh Ph
Ph Ph
Copper Reductions
-1.50 -1.00 -0.50 0.00
Potential (V vs SCE)
N N
NPh Ph
Ph PhCu
N N
NPh Ph
Ph Ph
DPV
DPV
CV
CV
a) In Pyridine
b) In CH2Cl2
Different Scan Rates, CH2Cl2, 0.1 M TBAP
0.0 0.4 0.8 1.2Potential (V vs SCE)
300250200150100 50
mV/s
-1.6 -1.2 -0.8 -0.4 0.0Potential (V vs SCE)
N N
NPh Ph
Ph PhNi
N N
NPh Ph
Ph Ph
7 12 1710
20
30
ν1/2 (mV/s)
ip (µ
A)
D
E
7 12 1710
20
30
40
ν1/2 (mV/s)
ip (µ
A)
A
B
C
AB
C ED
Diffusion-Controlled
Different Scan Rates, CH2Cl2, 0.1 M TBAP
N N
NPh Ph
Ph PhCo
N N
NPh Ph
Ph Ph
0.0 0.4 0.8 1.2Potential (V vs SCE)
300250200150100 50
mV/s
-1.6 -1.2 -0.8 -0.4 0.0Potential (V vs SCE)
7 12 1710
20
30
40
ν1/2 (mV/s)
ip (µ
A)D
E
7 12 175
15
25
35
ν1/2 (mV/s)
ip (µ
A)
A
B
C
AB
C ED
Diffusion-Controlled
Conclusion• All three metallo-complexes exhibit two common
reversible oxidations with greater relative ease as compared to the free base ligand.
• Ni and Co complexes share reductive properties from 1st and 2nd pyrrole electron additions and 3rd (and likely 4th) phenyl electron additions.
• Cu complex displays unique electro-reduction properties and the first reduction takes place on the Cu(II) center.
• All redox processes are diffusion-controlled.
Future Work• Purification is needed for Co and Ni complexes.• Fluorescence spectra will be examined.• Are Co, Ni and Cu complexes active catalysts for
the DDT reductive dechlorination?• To find the solution why Cu complex has a
special electro-reduction behavior as respect to Ni and Co complexes.
• Different substituted groups can be introduced into phenyl rings to fine-tune the properties.
Acknowledgments
• This research was supported by Midwestern State University’s UGROW program and funded by the Welch Foundation.
• Thanks to MSU chemistry department, Dr. Rincon, program director, and Drs. Hansen and Shao for advice and mentorship.
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Questions?