Novel peripherally tetra substituted phthalocyanines: Synthesis, characterization, photophysical and photochemical properties

doi:10.1016/j.molstruc.2020.128082

Journal of Molecular Structure

Volume 1211, 5 July 2020, 128082

https://doi.org/10.1016/j.molstruc.2020.128082 Get rights and content

Highlights

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The substituted phthalonitrile was prepared.
•
Peripherally tetra substituted metallo-phthalocyanines were synthesized.
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The photophysical and photochemical properties of metallo-phthalocyanines were investigated.

Abstract

In this paper, phthalonitrile (3) and it’s zinc(II) (4) and magnessium (II) phthalocyanine (5) derivatives were prepared. The novel compounds (3–5) were characterized spectroscopically. The photochemical and photophysical properties compounds (4 and 5) were examined to determine whether they are suitable photosensitizers for PDT applications. The magnessium (II) phthalocyanine (5) produced low amount of singlet oxygen and high fluorescence quantum yield. However, the zinc(II) phthalocyanine (4) had potential to be used in PDT applications with it’s high singlet oxygen production and high photostability.

Graphical abstract

Introduction

Photodynamic therapy (PDT) has emerged in recent years as a clinical treatment method. The basis of the PDT is the activation of the photosensitizer agent to break down cancerous tissues [1]. In the first step of the PDT, the photosensitizer agent is injected into the patient and placed in cancerous tissues. Then, light is applied to the cancerous tissues and the photosensitizer is activated. Activated photosensitizer causes some chemical reactions and as a result of these reactions singlet oxygen is released. This highly singlet oxygen breaks down cancerous tissues [2]. In addition, PDT has some advantages such as low powered light, high selectivity of photosensitizer to cancerous tissues and having less side effects [3].

Because of their electrochemical, thermal and optical properties resulting from strong electron conjugation, phthalocyanines (Pcs) have been used in many different applications over the years [[4], [5], [6], [7], [8], [9], [10]]. Pcs are suitable photosensitizers for PDT applications with their high absorption in the visible region, high stability in solutions, high singlet oxygen yields and high selectivity to cancerous tissues [11,12].

In this work, it was planned to prepare novel photosensitizers which can be used in PDT applications and investigate their photophysical and photochemical properties to determine their PDT potential. For this purpose, tetra substituted zinc(II) and magnesium (II) phthalocyanines were prepared. After photosensitizer compounds were prepared, photochemical and photophysical parameters of them were examined.

Although there are many studies in this field in the literature [[13], [14], [15], [16], [17], [18]], the synthesized compounds are novel, the zinc (II) phthalocyanine showed higher singlet oxygen quantum yield than standard and the magnesium (II) phthalocyanine showed higher fluorescence quantum yield than the standard. Therefore, the obtained results are new and very important for further studies.

Section snippets

Experimental

The used chemicals, materials and methods, details and equations for photophysical/chemical studies were represented in Supplementary File.

Synthesis and characterization

The thieno [3,2-b]pyridin-7-ol (1) and 4-nitrophthalonitrile (2) were reacted in DMF to prepare compound (3) (Scheme 1). The appeared vibration band at 2236 cm⁻¹ and the ¹³C NMR signals at 107.19 and 111.60 ppm indicated that nitrile groups were added to target compound (3) successfully. In addition, the mass spectrum and ¹H NMR signals and elemental analysis results supported the proposed structure of compound (3) (Figs. S1–S3).

The compound (3) and related metal salt were reacted in n-pentanol

Conclusions

The phthalonitrile (3) was prepared using thieno [3,2-b]pyridin-7-ol (1). Phthalocyanines (4 and 5) prepared by the reaction of compound (3) in the presence of the related metal salt. The novel compounds (3–5) were characterized spectroscopically. Aggregation studies were performed to find out which solvent was the most suitable for the applications. Both compounds showed the highest absorbance in DMF and did not aggregate within the studied concentrations. For this reason, DMF was chosen as

CRediT authorship contribution statement

Ümit Demirbaş: Project administration, Visualization, Writing - original draft, Writing - review & editing, Resources, Investigation, Conceptualization, Resources.

Declaration of competing interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

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Novel peripherally tetra substituted phthalocyanines: Synthesis, characterization, photophysical and photochemical properties

Highlights

Abstract

Graphical abstract

Introduction

Section snippets

Experimental

Synthesis and characterization

Conclusions

CRediT authorship contribution statement

Declaration of competing interest

Photodiog Photodyn Ther

Biomed. Pharmacother.

Inorg. Chim. Acta.

Coord. Chem. Rev.

J Pharm Biomed

J. Organomet. Chem.

Dyes Pigments

J. Photochem. Photobiol., A

J. Mol. Struct.

J. Photochem. Photobiol., A

Inorg. Chim. Acta.

J. Organomet. Chem.

J. Photochem. Photobiol., A

J. Organomet. Chem.

J. Mol. Struct.

Inorg. Chim. Acta.

Synthetic Met J Organomet Chem

photophysical and photochemical properties

J. Organomet. Chem.

J. Organomet. Chem.

J. Mol. Struct.