Ümit İşci

Preparation of N-bridged diiron phthalocyanines bearing bulky or small electron-withdrawing substituents

The synthesis of novel μ-nitrido diiron phthalocyanine with electron-withdrawing substituents is reported: μ-nitrido tetra-methylsulfonylphthalocyanine (13), μ-nitrido tetra-ethylsulfonylphthalocyanine (14), μ-nitrido tetra-adamantylsulfonylphthalocyanine (15), μ-nitrido tetra-cyclohexylsulfonylphthalocyanine (16). These complexes were characterized by ESI-MS, UV-vis, FT-IR and EPR techniques. The state of these complexes depends on the size of the substituents. Complexes 13 and 14 bearing small methylsulfonyl and ethylsulfonyl substituents are cationic (PcFeIVNFeIVPc)+N3- complexes while complexes 15 and 16 with bulkier adamantylsulfonyl and cyclohexylsulfonyl substituents are formally neutral PcFeIIINFeIVPc complexes which can be represented as PcFe(+3.5)NFe(+3.5)Pc.

Methylsulfonyl Zn phthalocyanine: A polyvalent and powerful hydrophobic photosensitizer with a wide spectrum of photodynamic applications

BACKGROUND The biomedical photodynamic principle is based on the light-induced and photosensitizer-mediated killing of unwanted or harmful cells by overproduction of reactive oxygen species. Motivated by the success of photodynamic therapy (PDT) against several types of tumors, further applications of this approach are constantly identified which require the design and synthesis of novel photosensitizers with specifically tailored properties for a particular clinical application. METHODS Hydrophobic photosensitizers are currently gaining attention and hence a tetramethylsulfonyl Zn(II) phthalocyanine (2) was designed with respect to the desired photoproperties. The photodynamic potential of 2 was assessed by the determination of its photophysical and photochemical properties, and by a large range of biological tests including its phototoxicity against cancer cells and Gram(+) bacteria. Unsubstituted ZnPc was used as a reference compound for comparison purposes. RESULTS Phthalocyanine 2 has a better oxygen generation and is more photostable than ZnPc. 2 is a polyvalent and powerful hydrophobic photosensitizer with a wide spectrum of photodynamic applications against cancer (tested on A431 cells) and for Gram(+) PDI. Against Staphylococcus aureus, a maximum photokilling efficiency of more than 6 log10 steps was induced by a 5μM concentration of 2, outperforming the 3 log10 criterion for an antimicrobial effect (according to the recommendation of the American Society for Microbiology) by more than three orders of magnitude. CONCLUSIONS Phthalocyanine 2 has attractive photophysical and -chemical characteristics. Initial evaluation of its application in anti-tumor PDT and PDI suggest potential for further pre-clinical and clinical development of this compound.

Comparative structural analysis of 4,5- and 3,6-dialkylsulfanylphthalonitriles of different bulkiness

Phthalonitriles disubstituted by alkylsulfanyl moieties of different bulkiness (tert-butyl, adamantly, cyclohexyl and hexyl) and in 4,5- or 3,6-positions, respectively, set A and set B, have been prepared for comparative structural analyses. Miscellaneous parameters such as melting points and related polarity of the compounds are summarized. Substituents position and bulkiness effects on NMR and IR spectroscopy as well as refined X-ray structural data were examined.

A library of dimeric and trimeric phthalonitriles linked by a single aromatic ring: comparative structural and DFT investigations

A library of five phthalonitriles, dimeric or trimeric, all connected by an aromatic spacer (catechol, resorcinol, hydroquinone, phloroglucinol and catechol with two tert-butyl moieties), was selected to be comparatively studied from a structural point of view. Hirshfeld surface analysis and DFT calculations were performed as well.

Dihydroxylated Alkylsulfanyl Phthalonitriles

Complete crystallographic characterizations of three phthalonitriles disubstituted by hydroxylated alkynylsulfanyl moieties have been performed with a comparative approach.Graphical Abstract

The first push-pull μ-nitrido iron phthalocyanine dimer

The first push-pull μ-nitrido diiron phthalocyanine complex was prepared and characterized. The EPR spectrum confirms the Fe+3.5–N–Fe+3.5 formalism. The stability of this dimer in oxidant media (up to 1000 equivalent of H2O2) was studied by UV-vis spectroscopy. The push-pull μ-nitrido diiron phthalocyanine exhibited excellent stability because of the delocalization of an unpaired electron.

Subtle variations of the behavior of a silylated tetraethylene glycol-substituted Zn phthalocyanine towards acids

An organosoluble phthalocyanine substituted by four silylated tetraethyleneglycol chains was designed. This phthalocyanine become water-soluble after acid-promoted removal of the TBDMS moieties (which does not occur in acetonitrile), and is therefore a naked-eye observation system of acid aqueous media. Fluoride anion sensitivity based on the same principle proved unfortunately unsuccessful.

Photophysical properties of palladium/platinum tetrasulfonyl phthalocyanines and their application in triplet–triplet annihilation upconversion

Triplet photosensitizers showing strong absorption in the red/deep red spectral region, high intersystem crossing, a long-lived triplet state and a high triplet state energy level are crucial for triplet–triplet annihilation upconversion. Herein we selected two tetrasulfonyl-substituted phthalocyanine (Pc) Pt(II) and Pd(II) complexes (Pd-Pc and Pt-Pc) likely to meet the above criteria. The complexes showed prolonged triplet state lifetimes (15.9 μs and 3.03 μs) and high triplet state energy levels (1.5 eV) as compared to a Pc complex bearing electron donating groups (triplet lifetimes <3.0 μs; triplet energy levels ≈1.2 eV). Weak fluorescence was observed for Pd-Pc, whereas a fluorescence/phosphorescence dual emission feature was observed for Pt-Pc. Based on the phosphorescence emission, intermolecular triplet–triplet-energy-transfer (TTET) experiments and TD–DFT computations, the T1 state energy levels of Pd-Pc and Pt-Pc were determined as 1.25 eV and 1.5 eV, respectively. The two complexes were used for triplet–triplet-annihilation upconversion, with deep red excitation at 658 nm, upconversion with a quantum yield of 0.63% and an anti-Stokes shift of 3996 cm−1 was achieved.

Comparative X-ray structure analyses of 4,5- and 3,6-dialkylsulfanylphthalonitriles of different bulkiness

Phthalonitriles are synthetic precursors of phthalocyanines which are used as high-tech materials in important application areas such as photodynamic theraphy (PDT), catalysis, liquid crystal, chemical sensors, nonlinear optics (NLO) [1]. We have recently established the X-ray crystal structures of phthalonitriles and phthalocyanines of interest in our researches [2,3]. In this study, we comparatively studied the set of eight phthalonitriles shown in Fig. 1, constitute two groups of molecules: 4.5peripherally substituted phthalonitriles, and corresponding 3,6non peripherally substituted phthalonitriles. Crystallographic data regarding the tertbutyl derivatives are compared to those of the adamantyl, cyclohexyl and hexylthio derivatives in terms of the influence of the position of the substituents on structural parameters [4].