Università degli Studi di Roma “Tor Vergata” Facoltà di...
Transcript of Università degli Studi di Roma “Tor Vergata” Facoltà di...
Università degli Studi di Roma “Tor Vergata” Facoltà di Scienze Matematiche, Fisiche e Naturali
Dipartimento di Scienze e Tecnologie Chimiche
Prof. Pietro Tagliatesta
Reaction center of PSII
K. N. Ferriera; T. M. Iverson and coworkers Science 2004, 303, 1831
P680
Natural Photosystems
Photosystem II (PSII) from Thermosynecochoccus Elongatus
Absorption spectrum of Rhodobacter Sphaeroides reaction center
W. Zynth; J. Wachtveitl ChemPhysChem 2005, 6, 871
400 500 600 700 8000.0
0.2
0.4
0.6
0.8
1.0
1.2
Abs
Wavelength (nm)
500 550 600 650 700
Q bands
MgN
N
NN
O
O
O O
O
Natural Pigments
Chlorophylls
5,10,15,20-Tetraphenylporphyrin
NNH
N HN
R2
R1 R1
R2
R3
R4R4
R3
R
R
R
R
Tetrapyrrole macrocycle
R = aryl, alkyl R1, R2, R3, R4 = aryl, alkyl, alogen, nitro group, amino group…
UV-vis spectrum
D
C C
NHCO
CNH
O
Spacer:
Porphyrin-fullerene covalent systems: P spacer C60
kET (s-1) kBET (s-1) τ
2.2.1010 2.0 . 106 500 ns
1.3 .1010 3.7 . 105 2.7 µs
3.7 . 1010 1.5 . 106 666 ns
Multichromophoric systems: P C60 P
FeZn
NN
N N
NH
O
NNH
N HN
NH
O
NH
ON
CH3
Guldi, D. M.; Imahori, H.; Fukuzumi S. et al. J. Phys. Chem. A 2004, 108, 541.
e- + e-
NN
N N
Zn CH3
N
CH3
spacer
H. Imahori; D. M. Guldi; T. Okada; S. Fukuzumi and coworkers Angew. Chem. Int. Ed. 2002, 41, 2344
τRIP = 0.34 s
in DMF a 178 K
Oligomer as spacer: “molecular wires”
Zn
NN
N N
N
CH3O
On
n
n = 1, 2Guldi, D. M.; Martin, N. and coworkers Chem.Eur.J. 2005, 11, 1267
Zn
NN
N N
CH3
n = 2, 3, 4
n
D. I. Schuster; L. Echegoyen; D. M. Guldi; J. P. C. Tomè and coworkers Chem. Eur. J. 2005, 11, 3377
oligo-phenylenevinylenes
oligo-acetylenes
( )DAET Rkk β−= exp0
β = damping factor
n τ (ns) 2 555 3 625 4 714
In THF solution:
β = 0.06 Å-1
n = 1 PhCN τRIP = 230 ns THF τRIP = 830 ns
n = 2 PhCN τRIP = 370 ns THF τRIP = 1000 ns
β = 0.03 Å-1
H2-TPP
In our laboratory
New β-substituted porphyrins
Molecular wires directly linked to the β-pyrrole position
Use of oligo-phenyleneethynylenes as molecular wire
** n
Rigid structure between the chromophores
Extended π delocalization along the linker
1)
NNH
N NH
Br
HO
H
H
O
H
or
Pd(dba)2/AsPh3Toluene/NEt3 65 °C
H
ONN
H
N NH
n
n = 1 90%
n = 2 65%
n = 3 70%
HO
H
or
2)
3)
Rese:
Synthesis of new porphyrin-”wire”-fullerene systems
N
HNN
NHN
CH3
60%
N
HNN
NH
N
CH3
57%
N
HNN
NH
N
CH3
52%
C60, Toluene reflux
Steady state fluorescence studies
550 600 650 700 750 800 8500
1x108
2x108
3x108
4x108
5x108
n = 1 n = 2 n = 3
Inte
nsity
(cps
)
Wavelength (nm)
Free base Zinc complex
The fluorescence quencing efficiency is distance dependent
Compound Quencing efficiency Toluene THF Benzonitrile
H2P-EP1-C60 93% >99% >99%
ZnP-EP1-C60 98% >99% >99%
H2P-EP2-C60 47% 60% 71% ZnP-EP2-C60 81% 94% 95% H2P-EP3-C60 20% 23% 24% ZnP-EP3-C60 45% 58% 66%
550 600 650 700 750 800 8500
1x108
2x108
3x108
4x108
5x108
6x108
7x108
8x108
9x108
n = 1 n = 2 n = 3
Inte
nsity
(cps
)
Wavelength (nm)
N
HNN
NHN
CH3
n
n = 1, 2, 3