The synthesis of polyethyleneglycol substituted new macromolecules and investigation of their physical and biological properties

Macrocyclic compounds are defined as nine or more membered ring structures consisting of at least three potential donor heteroatoms. Among the macromolecular systems, phthalocyanine (Pc) molecules which have a wide range of application fields, are planar aromatic compounds with 18-π electrons. Numerous molecular syntheses have been carried out with the aim of studying that the coordination compounds containing metal atoms are capable of carrying out very different functions. It has been observed that the synthetic macromolecules coordinated with different metal ions can be model for biologically important species especially in the field of bioinorganic chemistry. Macrocyclic ligands have been studied intensively due to possessing superior and unique properties. One of these properties is defined as ring size effect. It describes the capacity of the macro compounds that have the ability to discriminate between the metal ions which are close to each other according to the metal ion radius. The second is defined as the macrocyclic effect which describes the high complex stability constants that macro compounds show when compared to their open-chain analogs. Phthalocyanines (Pcs) are macromolecules that have been the subject of research in many fields of application such as dyes, optic data storage, non-linear optics, sensors, catalysis, liquid crystal systems, solar cells, medical, etc. This diversity in their use is due to their unique structural properties. It is possible to synthesize desired targeted Pc molecules since they can form complexes with a large number of elements and can be substituted with multifarious organic structures. Unlike other tetrapyrrole derivatives, the conjugation of phthalocyanines is remarkable because of the benzene units in their chemical structures results in high absorption capacity in the low energy region of electromagnetic spectrum. The absorption spectra of Pc compounds contains two characteristic bands called as Q and B bands. When a molecule of Pc absorbs ultraviolet or visible light, an electron is excited to a high energy empty orbital from a low energy filled orbital. There are various conversions for the excited electron corresponding to the radiative and non-radiative transitions. The quantum yields of these transformations, which are called as fluorescence and phosphorescence, are used in the investigation of photophysical properties of Pcs. To determine the photochemical properties of Pcs, singlet oxygen quantum yields and photodegradation studies can be used. As a result of transferring the excited energy of the Pc molecule to another chemical quencher, a change in the UV-Vis absorption spectrum is observed resulting from the singlet oxygen oxidation of the chemical quencher. The singlet oxygen quantum yield is calculated using this change. The capability of forming singlet oxygen for Pcs is very important especially in medical applications such as photodynamic therapy (PDT). Molecular oxygen contains two electrons shared in external orbitals. These electrons are at the minimum energy level when their spins are in the same direction and in different orbitals. Singlet oxygen, on the contrary to molecular oxygen, has two electrons whose spins are opposite to each other and these electrons have higher energy and shorter lifespan than electrons in the ground state. The reactivity of singlet oxygen is quite high so it causes a destruction of existing tumorous tissue. Photodegradation of the Pc molecules are also important for medical applications. Changes in the intensity of characteristic absorption bands because of the light are followed by taking UV-Vis spectrum for the photodegradation studies of the Pcs. It is also important in many respects to determine the biological properties of phthalocyanines for medical applications. Unless some modifications are made, Pcs have some disadvantages resulting from their natural planar structure, which increases the limitations in biologicals applications. Aggregation and insolubility phenomena are the most important restrictions on the use of Pcs in many applications. The water solubility of Pc molecules plays a decisive role in biomedical research. Phthalocyanine compounds have to be soluble in water as well as organic solvents for physical and biological applications. The results of studies on Pc molecules substituted with chemical groups that interact easily with biological molecules are quite successful. For this purpose, the interaction of Pcs with biological materials such as DNA (deoxyribonucleic acid) and BSA (bovine serum albumin) has been investigated in various searches. Among the Pc compounds that have been gained solubility in water with the help of different methods, Pcs substituted with poly(ethylene glycol) (PEG) derivatives are the most important molecules in medical practices in terms of their water solubility and biocompatibility. Poly(ethylene glycol) (PEG) blocks are among the best yielding substituents in this sense. There are examples of Pcs substituted at axial or peripheral positions with different lengths of PEG derivatives in the literature. It has been observed that Pc compounds susbstituted with PEG blocks having a chain length of less than 1000 are synthesized with PEGME blocks with smaller chains. In the majority of publications, the studies that include the investigations of both physical and biological properties of PEG-substituted Pcs are not explored extensively. In the first part of this thesis, a novel poly(ethylene glycol)-conjugated silicon phthalocyanine (2) axially substituted with long PEG chains (average molecular weight is 1000) was synthesized by the condensation reaction between poly(ethylene glycol) blocks bearing hydroxyl functional units at both ends and silicon phthalocyanine dichloride. Therefore, in this study, PEG blocks with an average molecular weight of 1000 bearing OH groups at both ends was selected. The most important feature distinguishing this substance from its analogues is the presence of free OH groups at both ends. Because free OH functional groups can react with each other to form dimer, trimer or larger oligomeric structures. Thus, the reaction conditions should be optimized to obtain the expected product as well as to stop the polymerization at the same time. These conditions have been found with so many trials. The chemical structure of the novel compound (2) was characterized by 1H-NMR, FT-IR, and UV-Vis spectrophotometric methods. Elemental analysis data were also used to approve the number of PEG groups that exist in the structure. According to the 1H-NMR analysis result of novel PEG-conjugate silicon phthalocyanine, the peaks observed between 8.45 and 9.67 ppm are attributed to the peripheral hydrogen atoms on the Pc core. Signals belonging to the CH2 protons were perceived at a high field between 0.28–0.34 ppm for Si–O–CH2 because of magnetic anisotropy of the localized 18 π electrons in the Pc structure. The total number of ethylene glycol units was found as 44 which gives the ratio of silicon Pc and PEG1000 units as 1:2. As a result, apart from the other examples of PEG-substituted silicon phthalocyanine compounds in the literature, the novel silicon phthalocyanine engaged with two PEG 1000 blocks was accomplished successfully. The most important purpose of this study was to obtain the compound with the property of high water solubility. Incorporation of long-chain PEG units into Pc core increased water solubility due to the high hydrophilicity of the terminated OH functional groups on the main polymer backbone. The photophysical and photochemical properties of the novel compound such as fluorescence quantum yield, fluorescence lifetime, singlet oxygen quantum yield and photodegradation quantum yield were determined in both DMSO and water. According to analogues of the new compounds reported previously in the literature, the superiority of the new Pc compound over the previous ones is to have longer PEG blocks having OH at both ends. These axially substituted PEGME blocks decreased the aggregation to a minimum level which allowed high the singlet oxygen quantum yield. For biological studies, the photocytotoxicity of the compound against HeLa and HuH tumor cells was investigated. The results showed that HeLa cells are more responsive to PDT application. Considering all the physical and biological measurements, it has been found that the new silicon phthalocyanine compound may be a good potential photosensitizer for PDT. The second scope of this thesis focused on the synthesis of novel Pc molecules containing zinc, indium and lutetium metal ions which are substituted with poly(ethylene glycol) methyl ether (PEGME) blocks having an average molecular mass of 2000, peripherally. For this purpose, the tetraiodo-substituted metallophthalocyanines were prepared by the treatment of iodophthalonitrile derivatives with anhydrous zinc, indium and lutetium acetate salts in the presence of DBU. After obtaining of tetraiodo-zinc(II) phthalocyanine (3), tetraiodo-indium(III) acetate phthalocyanine (4) and tetraiodo-lutetium(III) acetate phthalocyanine (5), PEGME2000 tetra-substituted derivatives of them on the peripheral positions were obtained via Sonogashira Coupling Reaction with quite high yields. PEGME2000 blocks were firstly treated with propargyl bromide which corresponds to compound 6. Then these PEGME2000-propargyl derivative (6) reacted with compounds 3, 4, 5 to yield ZnPc(PEGME2000)4 (7), InPc(PEGME2000)4 (8), LuPc(PEGME2000)4 (9) respectively. Novel tetra-substituted Pc compounds were characterized by 1H-NMR, FT-IR, and UV-Vis spectrophotometric methods. These new macromolecules show high solubility in water and most of the organic solvents. The photophysical and the photochemical properties of the compounds were investigated in both DMSO and water. Because of the heavy atom effect of indium and lutetium elements, the fluorescence quantum yields of the 8 and 9 could not be measured. The biological properties of the compounds were determined by examining the interactions of molecules with biological molecules such as DNA and BSA. The solutions of molecules in water were titrated with the solution of CT-DNA and the changes in the Q bands were observed on UV-Vis spectrophotometer. To determine the effects of these molecules on the denaturation of double-strand DNA structure, the changes in absorptions at certain temperatures have been examined by using UV-vis spectra. Thermodynamic parameters were also used to clarify the types of binding modes. As a result, the fact that three new Pc molecules substituted with PEGME2000 blocks with high reaction yields did not show aggregation in water and DMSO which was proved with whose graphics fit the Lambert-Beer law. The singlet oxygen quantum yields were found to be higher when compared to the reference materials. They were found to be stable when exposed to light during time intervals used during the measurements, ie they did not degrade. The interactions with BSA and DNA have been demonstrated using UV-vis, fluorescence spectra, thermal denaturation plots and thermodynamic parameters (enthalpy, entropy, and Gibbs free energy). New Pc compounds bound to DNA with hydrophobic interactions via PEG blocks non-specifically and spontaneously. All thermodynamic parameters together with thermal denaturation values and Pc-DNA binding constants proved that the lutetium and indium-acetate Pcs have higher binding ability than the zinc derivative. These properties of new compounds have been shown to be promising for medical applications.