Nonlinear absorption dynamics in tetrapyridyl metalloporphyrins.
Nonlinear absorption dynamics of Zn(2+), Cu(2+), and Ni(2+) tetrapyridyl porphyrins in chloroform/methanol solutions were investigated at 532 nm with the Z-scan technique. Additional techniques such as UV-vis absorption spectroscopy and time-resolved fluorescence were used to obtain parameters that are important for the analysis of the population dynamics. A marked difference was observed in the nonlinear absorption and excited-state dynamics of closed (ZnTPyP)- and open-shell metalloporphyrins (CuTPyP and NiTPyP). ZnTPyP presents a reverse saturable absorption whose dynamics can be completely described by means of a simple five-energy-level diagram. On the other hand, CuTPyP and NiTPyP have a different excited-state dynamics, presenting a saturable absorption behavior and faster relaxation rates that were attributed to the presence of unfilled d shells of the central ion.
Barbosa Neto
N M
NM
Instituto de Física de São Carlos, Universidade de São Paulo, Caixa Postal 369, 13560-970 São Carlos, SP, Brazil. newton@if.sc.usp.br
De Boni
L
L
Mendonça
C R
CR
Misoguti
L
L
Queiroz
S L
SL
Dinelli
L R
LR
Batista
A A
AA
Zilio
S C
SC
D008665:Metalloporphyrins / Q000737:chemistry*; D011725:Pyridines / Q000737:chemistry*; D013057:Spectrum Analysis / Q000379:methods
D008665:Metalloporphyrins; D011725:Pyridines; C023666:pyridine