Photophysics and Nonlinear Optical Properties of Tetra- and Octabrominated Silicon Naphthalocyanines
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- 作者：Yunjing Li ; Danilo Dini ; Mario J. F. Calvete ; Michael Hanack ; Wenfang Sun
- 刊名：Journal of Physical Chemistry A
- 出版年：2008
- 出版时间：January 24, 2008
- 年：2008
- 卷：112
- 期：3
- 页码：472 - 480
- 全文大小：176K
- 年卷期：v.112,no.3(January 24, 2008)
- ISSN：1520-5215
文摘
The effect of the number of bromide substituents on the photophysical and nonlinear optical properties of thetetrabrominated naphthalocyanine Br4(tBu2PhO)4NcSi[OSi(Hex)3]2 (1) and the octabrominated naphthalocyanineBr8NcSi[OSi(Hex)3]2 (2) has been investigated through various spectroscopic techniques. Absorption andemission of 1 and 2 have been studied at room temperature and 77 K to determine the spectral properties ofthe ground and the excited states and the lifetimes and quantum yields of formation of the excited states.There is a moderate increase of the quantum yield of the triplet excited-state formation (
T = 0.10 vs 0.13)and a decrease of the triplet excited-state lifetime (
T 
70 vs 50 
s) from 1 to 2. These can be attributed tothe stronger heavy atom effect produced by the larger number of peripheral bromide substituents in 2 consideringthat an excited state with a triplet manifold is involved in the excitation dynamics of both complexes 1 and2. The quantum yields of the singlet oxygen formation (
) upon irradiation of 1 and 2 at 355 nm were alsoevaluated, and a value of (1) = (2) = 0.16 was obtained. In addition to that, octabrominated complex2 displays a larger decrease of nonlinear optical transmission for nanosecond pulses at 532 nm with respectto the tetrabrominated complex 1. The nanosecond Z-scan experiments reveal that 1 and 2 exhibit both areverse saturable absorption and a nonlinear refraction at 532 nm. However, both the sign and the magnitudeof the nonlinear refraction change from 1 to 2. For picosecond Z-scan in the visible spectral region, these twocomplexes exhibit only reverse saturable absorption, and the excited-state absorption cross-section increasesat longer wavelengths.
T = 0.10 vs 0.13)and a decrease of the triplet excited-state lifetime (T 70 vs 50 s) from 1 to 2. These can be attributed tothe stronger heavy atom effect produced by the larger number of peripheral bromide substituents in 2 consideringthat an excited state with a triplet manifold is involved in the excitation dynamics of both complexes 1 and2. The quantum yields of the singlet oxygen formation () upon irradiation of 1 and 2 at 355 nm were alsoevaluated, and a value of (1) = (2) = 0.16 was obtained. In addition to that, octabrominated complex2 displays a larger decrease of nonlinear optical transmission for nanosecond pulses at 532 nm with respectto the tetrabrominated complex 1. The nanosecond Z-scan experiments reveal that 1 and 2 exhibit both areverse saturable absorption and a nonlinear refraction at 532 nm. However, both the sign and the magnitudeof the nonlinear refraction change from 1 to 2. For picosecond Z-scan in the visible spectral region, these twocomplexes exhibit only reverse saturable absorption, and the excited-state absorption cross-section increasesat longer wavelengths.