Photophysics and Nonlinear Absorption of Peripheral-Substituted Zinc Phthalocyanines

Abstract

The photophysical properties, such as the UV-vis absorption spectra, triplet transient difference absorption spectra, triplet excited-state extinction coefficients, quantum yields of the triplet excited state, and lifetimes of the triplet excited state, of 10 novel zinc phthalocyanine derivatives with mono- or tetraperipheral substituents have been systematically investigated in DMSO solution. All these complexes exhibit a wide optical window in the visible spectral range and display long triplet excited-state lifetimes (140-240 mus). It has been found that the complexes with tetrasubstituents at the alpha-positions exhibit a bathochromic shift in their UV-vis absorption spectra, fluorescence spectra, and triplet transient difference absorption spectra and have larger triplet excited-state absorption coefficients. The nonlinear absorption of these complexes has been investigated using the Z-scan technique. It is revealed that all complexes exhibit a strong reverse saturable absorption at 532 nm for nanosecond and picosecond laser pulses. The excited-state absorption cross sections were determined through a theoretical fitting of the experimental data using a five-band model. The complexes with tetrasubstituents at the alpha-positions exhibit larger ratios of triplet excited-state absorption to ground-state absorption cross sections (sigma T/sigma g) than the other complexes. In addition, the wavelength-dependent nonlinear absorption of these complexes was studied in the range of 470-550 nm with picosecond laser pulses. All complexes exhibit reverse saturable absorption in a broad visible spectral range for picosecond laser pulses. Finally, the nonlinear transmission behavior of these complexes for nanosecond laser pulses was demonstrated at 532 nm. All complexes, and especially the four alpha-tetrasubstituted complexes, exhibit stronger reverse saturable absorption than unsubstituted zinc phthalocyanines due to the larger ratio of their excited-state absorption cross sections to their respective ground-state absorption cross sections.

Long-lifetime reverse saturable absorption in a bipyridyl platinum(II) complex bearing naphthalimidylethynyl-substituted fluorenylacetylide ligands

“…The differential equations for the populations of the relevant electronic states and for the attenuation and propagation of the beam are solved numerically using the procedure described in [26]. We analyze the Z-scan data in Fig.…”

Study of the Effect of Substitution on Phtalocyanine Based Compounds for Photovoltaic Application

“…Moreover, the structures of Pc and MPc can be easily modified without significantly changing their stability and processability. The photophysical and photochemical properties of these complexes can be altered by introducing different substituents into the peripheral positions of the macrocyclic ring, varying the central metal ions, alternating the axial ligands, or changing the substituted of the macrocycle to strengthen the capacity and solubility of the material [14][15][16][17][18].…”

Aluminum Phthalocyanine on Silica Nanoparticles: Aggregation and Excited States

“…The obtained value is in good agreement with the lifetime of the triplet state of phthalocyanines in DMSO. [26] Flash photoexcitation of deoxygenated aqueous solutions of AlClPc on the silica surface leads to the appearance of difference absorption spectrum with maximum at 465 and 720 nm ( Figure 7a). This absorption spectrum is markedly different from the absorption spectrum of T m in solution (Figure 7b) in the absence of bleaching of the absorption bands of the ground state of the monomer AlClPc and the presence of intense absorption in the longer wavelengths.…”