Reverse saturable absorption in 5,10,15,20-Tetra(4-pyridyl)-21H,23H-porphyrin with ruthenium outlying complexes

Abstract

Modificações no sinal de absorção de estado excitado da 5,10,15,20-tetra(4-piridil)-21H,23H-porfirina, provocadas tanto pela substituição do íon central quanto pela adição de grupos periféricos, são investigadas empregando-se pulsos laser de 5 ns com 532 nm, juntamente com medidas de absorção linear e tempo de decaimento da fluorescência. A absorção saturada reversa (RSA) aumenta consideravelmente quando os íons H + são substituídos pelo Zn 2+ na posição central do anel porfirínico. Contudo, esta diminui quando os grupos RuCl 2 (CO)(PPh 3 ) 2 e RuCl 2 (CO)(dppb) são ligados através dos anéis piridínicos às posições periféricas da porfirina, tanto para a base livre quanto para a zinco porfirina. Um modelo teórico baseado no diagrama de Jablonski foi usado para verificar qual a principal causa da diminuição do sinal de RSA provocada pelos grupos de rutênio.Investigations on the excited state absorption signal of 5,10,15,20-tetra(4-pyridyl)-21H,23H-porphyrin, modified by either changing the central ion or adding peripheral groups, were performed using 5 ns laser pulses at 532 nm, in association with linear absorbance and fluorescence decay time measurements. The reverse saturable absorption (RSA) increases remarkably when Zn 2+ replaces H + at the central position of the porphyrin ring. However, it decreases when RuCl 2 (CO)(PPh 3 ) 2 and RuCl 2 (CO)(dppb) groups are attached at outlying positions through the pyridine rings, for both the free base and zinc porphyrins. A theoretical model based on Jablonski diagram was used to verify the main reason for the decrease on the RSA signal caused by ruthenium groups.

Nonlinear Optical Properties of Porphyrins

“…[113] The available reports include studies on RSA [42c,e,53b,106] and the utility of porphyrins and phthalocyanines to limit optical radiation at 308 nm (XeCl laser)…”

Investigation of Ground- and Excited-State Photophysical Properties of 5,10,15,20-Tetra(4-pyridyl)-21H,23H-porphyrin with Ruthenium Outlying Complexes

“…The results presented up to now provided information about the ground-state absorption and the first singlet excited state decay, besides pointing to the necessity of understanding the real importance of the intersystem crossing mechanism to the quenching process. Moreover, we have recently observed that tetraruthenated porphyrins present sequential two-photon absorption at the nanosecond regime, 14 but no information about the excited-state absorption dynamics was obtained until now. In order to accomplish this task, we performed Z-scan measurements with single 70 ps pulses and with pulse trains (PTZ-scan), in association with laser flash a λ c is the band center position, Φ is the fluorescence quantum yield, and τ i \ i = 1,2,3 are the decay times.…”

Investigation of the photophysical and eletrochemical properties of a free base tetrapyridyl porphyrin with meso carbon linked ruthenium(II) groups

“…For instance, the combination of ruthenium complexes with porphyrin rings expands the spectral range for light harvesting, which could lead higher DSSCs in the cell efficiencies [19]. Furthermore, it is worth mentioning that porphyrins with peripheral ruthenium groups have demonstrated great potential for applications in a large branch of fields like photonics, sensors, and others [32][33][34]. However, to accomplish all of these possible technological applications, photophysical investigations are imperative as a starting point.…”