Speaker
Description
The increasing interest in photoactive organic molecules for solar energy conversion systems, photocatalysis, and photodynamic therapy, requests a deep understanding of their photophysical and photochemical properties and how the microenvironment affects them. Metal phthalocyanines (MPcs), a class of highly conjugated macrocyclic compounds, are particularly promising due to their strong light absorption, tunable electronic properties, and high chemical stability.
In this study, we present experimental and theoretical spectroscopic investigations of metal phthalocyanine cations in the UV/Vis wavelength range, focusing on the influence of the central metal atom on electronic transitions. Using helium nanodroplets as a cryogenic environment, we form MPc monomer cations in their electronic ground states. For spectroscopic studies, the molecular ions are extracted from the helium matrix with a few helium atoms still attached, serving as gentle tag. Upon photoabsorption, the helium evaporates, and the resulting photofragments are analysed via time-of-flight mass spectrometry [1]. In addition, we exploit the advantages of helium nanodroplets to form tailored cluster ions via sequential pick-up, enabling the controlled attachment of individual atoms and molecules such as water to investigate environmental effects [2]. We present high-resolution laser absorption spectra of various MPcs, show that the hydration of the ions has only a minor influence on the electronic spectra, and discuss the advantages of our experimental method.
References:
[1] S. Bergmeister et al., Rev. Sci. Instrum. 94, 055105, (2023)
[2] S. Bergmeister et al., Adv. Sci. 11, 2307816, (2024)
