Microscale SynthesisMicroscale Synthesisof

Porphyrin Complexes

The Porphyrin Chromophore

Porphyrins are particularly attractive for many applications due to their

rigid planar geometry rigid-planar geometry

redox stability

intense electronic absorption

strong emission

small HOMO-LUMO energy gap

tunable optical and redox properties

Zinc‐5,10,15,20‐tetraphenylporphyrin

UV‐Vis absorption, Fluorescencese Emission and Cyclic Voltammetry of ZnTPP

Photosynthesis( 6CO2 + 6H2O + hv → (CH2O)6 + 6O2 )( 6CO2 + 6H2O + hv → (CH2O)6 + 6O2 )

Light-Harvesting(energy transfer) Reaction Center

(charge-separation via e- transfer)

From Photosynthesis to Dye Sensitized Solar Cells (DSC’s)

OTE TiO2 Dye-sensitizer Electrolyte Counter-electrode

CB -0.5S*charge

separatione-

E0.0

0vsN

HE

hv e-

Red Oxe-

Voc

charge

recombination

EF

0.5

1.0

E(V

)v

S0/S+

e- Mediator

dif f usion

e-

• Chare separation and charge recombination competitive processes

O’Regan B.; Graetzel M. Nature 1991, 353, 737.Graetzel M. Nature 2001, 414, 338.

Porphyrins and Semiconductor Sensitization

ETCPP* ~ -0.6 eV vs. ECB TiO2

Maximum 3 % IPCE = 55 % ff = 70 %Maximum ~ 3 % , IPCE = 55 % , ff = 70 %

Isc = 6 mAcm-2 , Voc = 485 mV

Cherian S.; Wamser C. C. J. Phys. Chem. B 2000, 104, 3624.

Effect of the Spacer Length and Anchoring Group Position

p-ZnTCPP-[S] m-ZnTCPP-[S] m-ZnTCP2P-[S]m-ZnTC(PEP)P-[S]In

tens

ity

ZrO2/Glass

( ) [ ]

mal

ised

Em

issi

on

550 600 650 700 750 800

Nor

m

Wavelength (nm)

40

50

60

on TiO /FTO

p-ZnTCPP-[S] m-ZnTCPP-[S] m-ZnTCP2P-[S] m-ZnTC(PEP)P-[S]

E (%

)

0

10

20

30 on TiO2/FTO

IPC

E

Rochford J.; Chu D.; Hagfeldt A.; Galoppini E. J. Am. Chem. Soc. , 2007, 129, 4655.

400 500 600 700 8000

Wavelength (nm)

Porphyrin Catalysts for CO2 Reduction

• The metalloporphyrins and related metallo‐macrocycles studied for CO2 reduction reactivity includemetalloporphyrins (MP), metallocorrins (MN), metallophthalocyanines (MPc), and metallocorroles(MC), Figure 4, where M = Fe or Co.

• The active catalytic states as identified by cyclic voltametry have the metal in the formal oxidation• The active catalytic states as identified by cyclic voltametry have the metal in the formal oxidationstate of zero for porphyrins [M0P]2‐ and corrins [M0N]2‐, +1 for corroles [MIC]2‐, and +1 with areduced phthalocyanine ring [MIPc•‐]2‐.

Morris et. al Acc. Chem. Res., 2009, 42 (12), pp 1983–1994

Mechanism for CO2 Reduction

Porphyrin Catalysts for O2 Activation

Matsui et. al Inorg. Chem., 2010, 49 (8), pp 3602–3609

Halime et. al Inorg. Chem., 2010, 49 (8), pp 3629–3645

Synthetic Methods

NH

R

R NHNH

Ph

PhPh

R

R R

R

+Propionic acid, Ar

CHO

NH NHPh

Ph

Ph

R

RR

R

+relux, 30 min

PhR R

R = H, Me R = H - meso-TetraphenylporphyrinogenR = Me - -octamethyl-meso-tetraphenylporphyrinogen

N NH

NNHPhPh

R

R R

R

O2

N NH

Ph

R

RR

R

R = H - meso-TetraphenylporphyrinR H meso Tetraphenylporphyrin R = Me - -octamethyl-meso-tetraphenylporphyrin

A.D. Adler, F.R. Longo, J.D. Finarelli, J. Goldmacher, J. Assour, L. Korsakoff, J. Org. Chem. 1967, 32, 476.

Synthetic Methods

NH NH

NHNH

H

H

H

Ph

Ph

Ph

NH

+TFA or BF3.OEt, Ar

CH2Cl2 250C

4

+ 4 H20NH

H Ph

CHO

5,10,15,20-Tetraphenylporphyrinogen

4

O

O

Cl

Cl

CN

CNCH2Cl2 250C

3

NNH

PhOH

Cl CN

DDQ

3

N NHPh

Ph

PhOH

Cl CN

DDQH2

5,10,15,20-Tetraphenylporphyrin (TPP)

J. S. Lindsey, I. C. Schreiman, H.C. Hsu, P. Kearney, A. M. Marguerettaz, J. Org. Chem. 1987, 52, 827