Vefa Ahsen

Synthesis and characterization of metal-free and metal derivatives of a novel soluble crown-ether-containing phthalocyanine

A straightforward and generalizable synthesis of metal-free and metal (Cu, Co, Ni, or Fe) derivatives of a symmetrically tetrasubstituted phthalocyanine derived from 15,16-dicyano-2,3,5,6,8,9,11,12-octahydro-benzo[1,4,7,10,13]pentaoxacyclopentadecine is described. The new compounds have been characterized by elemental analyses, and i.r., 1H n.m.r., u.v.–visible, and fast atom bombardment mass spectra. The alkali metal ions (sodium and potassium) bound to crown ether groups of the metal complexes force dimerization of the phthalocyanine units in solution as observed in the electronic spectra by the broadening of the Q-band transition at ca. 630 nm. The solubilities of the metal phthalocyaninates in chloroform were determined to be ca. 10–3 mol dm–3. The thermal stabilities of the compounds were determined by thermogravimetric and differential thermal analysis. The high affinity of the cobalt(II) derivative for the potassium ion was observed in solvent extraction experiments.

Preparation of a novel, soluble copper phthalocyanine with crown ether moieties

A novel, soluble copper phthalocyanine containing four benzo-15-crown-5 moieties was synthesized and characterized by elemental analysis, i.r. and u.v. spectroscopy, and its alkali cation-complexing capability and selectivity studied.

Separation and mesogenic properties of tetraalkoxy-substituted phthalocyanine isomers

The main aim of this paper is to describe the separation and properties of four possible structural isomers of non-peripherally substituted nickel(II) phthalocyanine. Two isomers (C4h and D2h) of this compound were separated by preparative thin layer chromatography; however the other two isomers (C2v and Cs) were separated by HPLC only with an analytical chiral column. The individual isomers and symmetry were assigned on the basis of the 1H NMR signals of the aromatic protons of the phthalocyanine ring system. The pure C4h isomer exhibited liquid crystalline properties at room temperature while the isomeric mixture containing four structural isomers was liquid. The other three isomers were liquid under the same conditions. The mesogenic properties of pure C4h isomer were determined by differential scanning calorimetry, optical polarizing microscopy and X-ray diffractometry. This is the first report of the separation of a liquid crystalline pure isomer in the field of phthalocyanine chemistry.

Water-soluble cationic gallium(III) and indium(III) phthalocyanines for photodynamic therapy.

The new tetra-non-peripheral and peripheral 2-mercaptopyridine substituted gallium(III) and indium(III) phthalocyanine complexes (np-GaPc, p-GaPc, np-InPc and p-InPc) and their quaternized derivatives (Qnp-GaPc, Qp-GaPc, Qnp-InPc and Qp-InPc) have been synthesized and characterized. The quaternized complexes show excellent solubility in water, which makes them potential photosensitizer for use in photodynamic therapy (PDT) of cancer. Photophysical and photochemical properties of these phthalocyanines were investigated. General trends are described for quantum yields of photodegradation, fluorescence and fluorescence lifetimes as well as singlet oxygen quantum yields of these compounds. In this study, the effects of the position of the substituents, the nature of the metal ion and quaternization of the substituents on the photophysical and photochemical parameters of the gallium(III) and indium(III) phthalocyanines are also reported. This study also presented the ionic gallium(III) and indium(III) phthalocyanines strongly bind to bovine serum albumin (BSA).

Light-Triggered Liposomal Release: Membrane Permeabilization by Photodynamic Action

Photosensitized damage to liposome membranes was studied by using different dye-leakage assays based on fluorescence dequenching of a series of dyes upon their release from liposomes. Irradiation of liposomes with red light in the presence of a photosensitizer, trisulfonated aluminum phthalocyanine (AlPcS(3)), resulted in the pronounced leakage of carboxyfluorescein, but rather weak leakage of sulforhodamine B and almost negligible leakage of calcein from the corresponding dye-loaded liposomes. The same series of selectivity of liposome leakage was obtained with chlorin e6 that appeared to be more potent than AlPcS(3) in bringing about the photosensitized liposome leakage. Electrically neutral zinc phthalocyanine tetrasubstituted with a glycerol moiety (ZnPcGlyc(4)) was less effective than negatively charged AlPcS(3) in provoking the light-induced liposome permeabilization. On the contrary, both ZnPcGlyc(4) and AlPcS(3) were much more effective than chlorin e6 in sensitizing gramicidin channel inactivation in planar bilayer lipid membranes, thus showing that relative photodynamic efficacy of sensitizers can differ substantially for damaging different membrane targets. The photosensitized liposome permeabilization was apparently associated with oxidation of lipid double bonds by singlet oxygen as evidenced by the mandatory presence of unsaturated lipids in the membrane composition for the photosensitized liposome leakage to occur and the sensitivity of the latter to sodium azide. The fluorescence correlation spectroscopy measurements revealed marked permeability of photodynamically induced pores in liposome membranes for such photosensitizer as AlPcS(3).

Electrochemistry of lutetium crowned ether diphthalocyanine films

Films of crown-ether substituted diphthalocyanine of lutetium (CR-Pc2Lu) have been studied by cyclic voltammetry. In contact with K+ or Na+ aqueous electrolyte, two reversible one-electron steps lead to the formation of the orange cation CR-Pc2Lu+ and to the blue anion CR-Pc2Lu−. With other alkali metal cations, the irreversibility of both steps increases in the order K+, Na+ ⪡ Li+ < Rb+, Cs+. In acid medium (HCl or HClO4), voltammetry cannot be performed in the absence of alkali cation added simultaneously to the solution, and destruction of the films occurs. In contact with a KCl + HCl or a KClO4 + HClO4 solution, disproportionation of CR-Pc2 Lu proceeds and a two-electron voltammetric peak takes the place of the two one-electron steps. A E-pH “Pourbaix” diagram is established.

Mesomorphic phthalocyanine as chemically sensitive coatings for chemical sensors

Abstract Octa(13,17-dioxanonacosane-15-sulfanyl)-substituted mesomorphic nickel(II) phthalocyanine (Pc) at room temperature is investigated for the detection of organic solvent vapors by utilizing quartz crystal microbalance (QCM). Determined by polarized Raman spectroscopy, the Ni(II) Pc layers as coated were disordered and the Ni(II) Pc layers thermally treated were ordered. The ordered films on QCM-devices show higher sensitivity and partition coefficient for all solvent molecules investigated such as ethanol, dichloromethane, acetone, n -hexane. The Raman Spectroscopy investigation results show that the molecules with saturated CC bonds such as ethanol interact with phthalocyanine films predominantly by formation of hydrogen bonds and the sensor response to π bond containing compounds such as acetone is the result of their π–π interaction with conjugated phthalocyanine ring.

ABAB homoleptic bis(phthalocyaninato)lutetium(III) complex: toward the real octupolar cube and giant quadratic hyperpolarizability.

The concept of octupolar molecules has considerably enlarged the engineering of second-order nonlinear optical materials by giving access to 2D and 3D architectures. However, if the archetype of octupolar symmetry is a cube with alternating donor and acceptor groups at the corners, no translation of this ideal structure into a real molecule has been realized to date. This may be achieved by designing a bis(phthalocyaninato)lutetium(III) double-decker complex with a crosswise ABAB phthalocyanine bearing alternating electron-donor and electron-acceptor groups. In this communication, we present the first step toward this goal with the synthesis, crystal structure determination, and measurement of the molecular first-order hyperpolarizability β by harmonic light diffusion, of an original lutetium(III) sandwich complex displaying the required ABAB-type alternation for one face of the cube. This structure is characterized by an intense absorption in the near-IR due to an intervalence transition and exhibits the highest quadratic hyperpolarizability ever reported for an octupolar molecule, √ = 5750 × 10(-30) esu.

Synthesis of 1,3-Diphenyl-4,5-bis(hydroxyimino)imidazolidine and Its Complexes with Nickel(II), Cobalt(II), Copper(II), Palladium(II), and Uranyl(VI)

Abstract 1, 3-Dipheny1-4, 5-bis(hydroxyimino)imidazolidine (LH2) has been prepared from anti-dichloroglyoxime, N,N′-diphenylmethylenediamine, and sodium bicarbonate in ethanol. Complexes of Cu(II), Ni(II), Co(II), Pd(II), and UO2(VI) and LH2 give a metal-ligand ratio of 1:2. A tetrahedral complex is obtained for the Ni(II) complex by coordination through N and O atoms. The (LH2)Co. H2O complex is squarepyramidal while the Cu(II), Pd(II) and UO2(VI) complexes are square-planar. The structures of the ligand and complexes are proposed based on elemental analysis, mass spectral, 1H-n.m.r., i.r., u. v. -visible, and magnetic data.

Click chemistry: the emerging role of the azide-alkyne Huisgen dipolar addition in the preparation of substituted tetrapyrrolic derivatives

The review aims at being an exhaustive summary of the use of Huisgen azide-alkyne dipolar addition in the synthesis of tetrapyrrolic compounds, mainly porphyrins, phthalocyanines, chlorins and bacteriochlorins.