Photon Factory Activity Report 2022 #40 (2023)

BL-27A/2021G042

X-ray decomposition of tin (IV) phthalocyanine dichloride
Yudai IZUMI,* Maki OHARA, and Akinari YOKOYA
Institute for Quantum Life Science, Quantum Life and Medical Science Directorate,
National Institutes for Quantum Science and Technology (QST),
4-9-1 Anagawa, Inage-ku, Chiba 263-8555, Japan
1 Introduction
Phthalocyanine derivatives of which axial ligands arebioactive molecules, such as drugs, are candidates for
prodrugs. If the ligand releases can be induced by X-rayirradiations, phthalocyanine based prodrugs allow us to theselective release of medical ingredients at the target
locations via localized X-irradiations.
In this study, we irradiated a pellet of tin (IV)phthalocyanine dichloride (SnCl2Pc; Fig. 1), as a simple
model of the phthalocyanine based prodrugs, with 3 keV
X-rays and confirm whether the bond breakages between
Sn and Cl can be induced using photoemission
spectroscopy.

Fig. 1. Molecular structure of SnCl2Pc
2 Experiment
The reagents of SnCl2Pc and tin (II) phthalocyanine(SnPc), which is a molecule with the chlorine atoms
removed from SnCl2Pc, were purchased from Tokyo
Chemical Industries (Japan) and used without further
purification. Powder of the reagent (~0.1 g) was pelletizedat a pressure of ~0.3 GPa for 10 min.
Photoemission spectra of SnPc and SnCl2Pc weremeasured at the BL-27A of the PF. The excitation photon
energy was set at 3 keV. The pass energy was set at 44 eV.
The binding energies of SnPc and SnCl2Pc were comparedwith the literature data [1] in the N 1s region and calibrated.
The SnCl2Pc pellet was irradiated with 3 keV photons for
5 hours. After that, the photoemission spectra weremeasured again to confirm dissociation of SnCl2Pc. The
intensities of the photoelectrons were normalized for the N
1s peak intensity of each measurement without any
subtraction of baselines.
3 Results and Discussion
Figure 2(a) shows the N 1s photoemission spectra ofpristine SnCl2Pc and SnPc. The spectra were similar to
those found in the literature [1]. Peak shifts toward thelower binding energy side were induced by the irradiations(Fig. 2(b)). The peak of irradiated SnCl2Pc was fitted wellwith three Voigt functions after subtracting the background.
Comparing with the peak energies, the components wereassigned to the SnCl2Pc, SnPc, and triazines (C3N3H3) [2]from the higher energy side. These results show that thebond breakages between the Cl atoms and SnPc framework
were induced.
In Fig. 2(c), the photoemission spectra of pristine
SnCl2Pc and SnPc in the Sn 3d5/2 region are shown. The
spectrum of SnCl2Pc after irradiation also shifted toward
the lower binding energy side (Fig. 2(d)). The peakenergies of fitted Voigt functions were similar to those ofpristine SnCl2Pc and SnPc, indicating that the SnCl2PC andSnPc coexisted at the sample surface after the 5 h ofirradiation. It is consistent with the spectral changes
observed in the N 1s region.
Figure 2(e) shows the Cl 1s photoemission spectra ofpristine SnCl2Pc and SnPc. No peak was observed for SnPc
because it contains no chlorine atom. The pristine SnCl2Pc
showed a peak originating from Cl-Sn at around 2821.5 eV.
After the 5 h of irradiation, the peak shifted toward thelower binding energy side, suggesting a new component
originating from the decomposition product arose (Fig.
2(f)). The peak was fitted with two Voigt functions after
subtracting the background. The main component
originated from the SnCl2Pc. The other component of
which peak energy was ~2820.9 eV was assigned tochloride ions, comparing with the literature data [3]. It
clearly shows that the bond breakages of Cl-Sn wereinduced by irradiation.
Thus, the N 1s, Sn 3d5/2, and Cl 1s photoemission spectra
showed the production of chloride ions and SnPc from theSnCl2Pc after the X-ray irradiations, indicating that thebond breakages between ligands (Cl) and SnPc
frameworks were induced by the photoionizations.
4 Conclusions
Ligand cleavages of SnCl2Pc were induced by the 3 keV
X-ray irradiations. It suggests that the SnPc framework canbe used as X-ray dissociative prodrugs. Appropriate
molecular design and its application are future prospects.
Acknowledgement
This work was supported by JST, CREST Grant Number
JPMJCR1902, Japan.
References[1] C. Song et al., Mater. Lett. 270, 127666 (2020).
[2] J. -K. Sun et al., J. Materials Chem. C 6, 9065 (2018).
[3] J. S. Gibson et al., Phys. Rev. B 98, 165402 (2018).

Photon Factory Activity Report 2022 #40 (2023)

Research Achievement
Y. Izumi et al., Chem. Phys. Lett. 822, 140508 (2023).

* izumi.yudai@qst.go.jp

Fig. 2. (a, c, e) The N 1s, Sn 3d5/2, and Cl 1s photoemission spectra of pristine SnCl2Pc (black) and SnPc (red), respectively.
(b, d, f) The N 1s, Sn 3d5/2, and Cl 1s photoemission spectra of SnCl2Pc after 5 h irradiations (blue), respectively. Opencircles: the measurement data; Thick solid lines: the fitting curves; Thin solid lines: the divided components assigned toSnCl2Pc (black), SnPc (red), triazines (green), and Cl− (light blue).