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.

References• Besette, A.; Ferreira, J. G.; Giguere, M.; Belanger, F., Desilets,

D.; Hanan, G. S. Inorg. Chem. 2012, 51, 12132-12141.• O’Connor, A.; Mc Gee, M.; Likar, Y.; ponomarev, V.; Callanan,

J. J.; O’shea, D. F.; Byrne, A.; Gallagher, W. Int. J. Canc. 2011, 130, 705-715.

• Aniello, P.; Gallagher, J.F.; Muller-Bunz, H.; Wolowska, J.; McInnes, E. J.L.; O’Shea, D. F. Dalton Trans. 2009, 273-273.

• Teets, T.; Partyka, J.; Updegraff III, J. J.; Gray, T.Inorg. Chem. 2008, 47, 2338-2346.

• Gorman, A.; Killoran, J.; O’Shea, C.; Kenna, T.; Gallagher,W.M.; O’Shea, D. F. J. Am. Chem. Soc. 2004, 126, 10619-10631.

• Kissinger, P. T.; Heineman, W. R.; J. Chem. Educ. 1983, 60, 702-706.

Questions?