Photophysics and spectroscopic properties of zinc phthalocyanine revisited using quantum chemistry

Abstract

Este estudo fornece uma avaliação teórica do comportamento fotofísico da ftalocianina de zinco (FtZn) usando teoria do funcional da densidade (DFT) e a sua abordagem dependente do tempo (TD-DFT), baseado na combinação do funcional híbrido B3LYP e o conjunto de base 6-311+G(d,p). A influência da solvatação foi estimada utilizando o método IEFPCM (modelo do contínuo polarizável) e considerando DMSO (dimetilsulfóxido) como solvente. Os espectros de absorção simulados foram baseados no cálculo dos primeiros 40 estados excitados sendo que os oito picos mais intensos podem ser atribuídos às bandas Q e Soret (B). Comprimento de onda de emissão de fluorescência e tempo de vida radiativo foram calculados utilizando a abordagem TD-DFT e comparados com dados experimentais. O fenômeno de cruzamento intersistema (CIS) da FtZn foi atribuído ao acoplamento spin-órbita induzida pelo Zn 2+ pelo fato dos estados singlete e triplete adjacentes possuirem a mesma simetria orbital. Os dados de fosforescência em fase gasosa também foram comparados.This study provides a theoretical evaluation of the photophysical behavior of zinc phthalocyanine (ZnPc) using density functional theory (DFT) and its time-dependent (TD-DFT) approach, based on the combination of the B3LYP hybrid functional and the 6-311+G(d,p) basis set. The influence of solvation was estimated using IEFPCM (integral equation formalism approach of polarizable continuum model) considering DMSO (dimethyl sulfoxide) as solvent. The simulated absorption spectra were based in the calculation of the first 40 excited states being that the eight most intense peaks could be assigned to the Q and Soret (B) bands. Fluorescence emission wavelength and radiative lifetime were calculated using the TD-DFT approach and compared to experimental data. The ZnPc intersystem crossing (ISC) phenomena was attributed to spin-orbit coupling induced by Zn 2+ since the adjacent singlet and triplet states have the same orbital symmetry. The phosphorescence data in gas phase were also compared.

Theoretical investigation of the substituent effects on the electronic and optical properties of 6-substituted coumarin derivatives

“…It is found that time-dependent density functional theory (TD-DFT) at the B3LYP/6-311+G (d, p) level correctly reproduced the absorption wavelength and intensity of many organic molecules [33][34][35][36]. And as you can see in our previous work, in the case of 6-fluoro coumarin, the calculated absorption and emission spectrum at this level were found to be in good agreement with the experimental values [37].…”

Kinetic model for the molecular system of Zinc(II)-2,9,16,23-phthalocyanine tetracarboxylate

“…Similar findings were also obtained for some MPcs. 73 As well-known, the spin-orbit coupling enhances the intersystem crossing, resulting in long-lived |T 1 state with considerable population of |T 1 state. 1,4,18,25 The long-lived |T 1 sate should lead to an effective sensitization of triplet oxygen to singlet oxygen by energy transfer.…”

Evaluation of photodynamic activity, photostability and in vitro drug release of zinc phthalocyanine-loaded nanocapsules

“…1) has been attracting great interest as photosensitizer in PDT due to its exceptional photophysical properties such as high triplet yields and long lifetime of triplet excited state (Tedesco et al, 2003;Durmus and Nyokong, 2007), and high capacity to produce singlet oxygen by energy transfer (Fadel et al, 2010). The ZnPc presents an intense absorption band at around 670 nm (called Q band) and a much broader and less defined absorption band in the range of 300 to 400 nm (called Soret or B bands) (Ueno et al, 2012).…”