Solvent Effects on the Photophysicochemical Properties of Tetra(tert-butylphenoxy)phthalocyaninato Zinc(II)

Abstract

The solvent viscosity dependence of the photophysical and photochemical properties of tetra(tert-butylphenoxy)phthalocyaninato zinc(II) (ZnTBPPc) is presented. The fluorescence quantum yields (ΦF) and Stern-Volmer′ s constant (KSV) for ZnTBPPc fluorescence quenching by benzoquinone in all the solutions followed a semi-empirical law that depends only on the solvent viscosity. ΦF values vary between 0.08 in tetrahydrofuran (THF) and 0.14 in dimethylsulphoxide (DMSO). Triplet quantum yields (ΦT) and lifetimes (τT) also exhibit clear solvent viscosity dependence with the values being higher in the most viscous solvents. The interaction of the ZnTBPPc triplet state with oxygen was found to be diffusioncontrolled, but higher rate constants were observed in low-viscosity solvents like THF and toluene. Absolute values of singlet oxygen quantum yields (ΦΔ) were determined, and the values are comparable in all the solvents, which is attributed to the proximity of the ZnTBPPc triplet energies in different solvents.

Measuring non-radiative relaxation time of fluorophores with biomedical applications by intensity-modulated laser-induced photoacoustic effect

“…This E-type delayed fluorescence is attributed to enhanced intersystem crossing in presence of dissolved oxygen [ 34 ]. It also has been shown that triplet lifetime increases with the increase in solvent viscosity [ 37 ]. Gratz et al [ 38 ] have found that dwell time, which is a measure of efficiency for triplet-state accumulation, for indocyanine green sodium iodide (ICG-NaI), in N2-bubbled solutions of dye in DMSO is in the range of 35 ns while this value for solutions of this dye in N2-bubbled water is only 1.2 ns.…”