Mustafa T. Ahmet

Measurement of the rate of uptake and subcellular localization of porphyrins in cells using fluorescence digital imaging microscopy.

Abstract A fluorescence imaging system incorporating a cooled slow‐scan charge‐coupled device camera was used to study the rate of uptake and subcellular localization of porphyrins in living cells. Measurements were carried out on human dermal fibroblasts (D532) using two different porphyrins meso‐tetra(4‐N‐methylpyridyl)porphine (TMPP) and meso‐tetra(4‐N‐hexylpyridyl)porphine (THPP). It was observed that TMPP was rapidly taken up by cells and principally located in the nucleus. The THPP, on the other hand, internalized more slowly and exhibited a particulate distribution in the cytoplasm.

Electrochromism in the transition-metal phthalocyanines. Part 2.—Structural changes in and properties of [Cr(pc)] and [Mn(pc)] films

The electrochromic properties observed in manganese and chromium phthalocyanine thin films are reported. Schemes are proposed to explain the chemistry involved in the electrochromic changes. Both chromium and manganese are shown to undergo changes in their valence states during oxidation and reduction of the phthalocyanine films. The phthalocyanine rings also undergo oxidation and reduction with cycling between reduced and oxidised states but the latter were not stable. Although changes in colour were observed in both materials on oxidation, the films degraded and so the results were not useful. The films have been found to cycle reversibly a few thousand times between neutral and reduced states. However, their cycling properties and colour range are greatly inferior to the metal bisphthalocyanine films.

Electrochromism in titanyl and vanadyl phthalocyanine thin films

The electrochromic behaviour of titanyl phthalocyanine [Ti(O)(pc)] and vanadyl phthalocyanine [V(O)(pc)] thin films are reported. These materials manifest a reversible electrochromic change when reduced, but upon oxidation they show evidence of immediate destructive breakdown. The behaviour of the films is discussed in relation to the α- and β-phase structures of the films. It is found that the phase of [Ti(O)(pc)] changes during the electrochromic process owing to ion incorporation. This is the first report of an electrochromically induced phase change in metal phthalocyanine materials. The structure of the phase present in a metal phthalocyanine material is found to dictate whether or not it is electrochromic. If the structure is too closely packed to allow ion penetration, it will not be electrochromic. The implications of the irreversible oxidations are discussed in relation to the behaviour of metal bisphthalocyanine electrochromic materials.

Electrochromism in the transition-metal phthalocyanines. Part 3.—Molecular organisation, reorganisation and assembly under the influence of an applied electric field. Response of [Fe(pc)] and [Fe(pc)Cl]

The electrochromic behaviour of α-[Fe(pc)] and [Fe(pc)Cl] has been studied, using cyclic voltammetry, electronic absorption spectroscopy and Mossbauer spectroscopy, the latter on 57Fe-enriched [Fe(pc)] films. [Fe(pc)] films have been shown to cycle reversibly ca. 103 times between neutral (blue) and reduced (purple-red) states (negative voltages), but decompose when oxidised repeatedly (positive voltages) in aqueous KCI electrolytes. When oxidised then reduced in < ca. 1 s [Fe(pc)Cl] is formed. This indicates that the Cl– ion adds as a ligand during the electrochromic oxidation and this takes place concomitantly with a lattice reorganisation. [Fe(pc)] films on oxidation produce red [FeIII(pc˙)Cl2] and contain a (pc˙) phthalocyanine radical anion. On reduction to neutral they become [Fe(pc)Cl].[Fe(PC)Cl] films have been shown to reduce electrochromically from an initial green film to a purple reduced film without first becoming [Fe(pc)]. However, on reoxidation to neutral, a blue [Fe(pc)] film is formed; this then behaves like a normal [Fe(pc)] film. These studies show that the axial Cl–on [Fe(pc)Cl], once removed, passes out of the lattice during the electrochromic reduction, and that under the influence of the field the lattice reorganises, assembling predominantly as the α-[Fe(pc)] phase.This is the first attempt to explain widespread lattice reorganisation that involves metallophthalocyanines with axial ligands attaching and detaching under controlled voltage.

Electrochromic behaviour and X-ray structure analysis of a Pechmann dye, (E)-5,5′-diphenyl-3,3′-bifuranylidene-2,2′-dione

Studies on the title compound have established that, although it could be oxidised with a concomitant change in its visible spectrum, this process is not reversible. This is discussed in the light of the crystal structure which is also reported in this paper. The title compound crystallises in the monoclinic space group P21/n, a= 27.033(6)A, b= 4.988(2)A, c= 5.372(2)A, β= 94.59(2)°. The molecules have close intermolecular contacts along stacks packing in the c direction. The packing is compared to that found in two other Pechmann dyes.

A potential iron pharmaceutical composition for the treatment of iron-deficiency anaemia. The crystal and molecular structure of mer-tris-(3-hydroxy-2-methyl-4H-pyran-4-onato)iron(III)

mer-Tris(3-hydroxy-2-methyl-4H-pyran-4-onato)iron(III) has potential use in the treatment of iron-deficiency anaemia. It displays the ideal properties that a new iron chelation complex must possess to be an effective treatment. These properties are discussed. The crystal and molecular structure of this complex has been determined from single-crystal X-ray diffraction data and refined by least squares to R= 0.0649 for 2 735 independent reflections. The compounds crystallizes in the monoclinic space group P21/c with cell dimensions a= 7.369(1), b= 14.720(3), and c= 19.964(5)A, β= 100.41(2)°, and Z= 4. The iron atom lies in a distorted octahedral environment with the three ligands bonded through the hydroxy and ketone oxygen atoms to give the mer configuration. Variable-temperature 57Fe Mossbauer data for the complex are reported and the results are discussed in relation to the structure.

The synthesis and characterization of organoimido- Re(V) complexes. The x-ray crystal structures of [ReCl(NC6H4Me-4) (OMe)(tBuNC)2(PPh3)][BPh4] and [ReCl2(NC6H4Me-4)(PPh3)4-ClC6H4(O)CNNCHPh-O,N]

Abstract Reaction of [ReCl 3 (NAr)(PPh 3 ) 2 ] (NAr = NC 6 H 4 Me-4, NC 6 H 3 Me 2 -2,6) with excess tertiary -butyl isocyanide, ( t BuNC), in methanol yielded the red--brown Re(V) arylimido- complexes, [ReCl(NAr)(OMe)( t BuNC) 2 (PPh 3 )][BPh 4 ] where NAr = NC 6 H 4 Me-4, ( 1 ) or NAr = NC 6 H 3 Me-2,6, ( 2 ). The X-ray crystal structure of ( 1 ) revealed a distorted octahedral configuration about the central rhenium atom. The isocyanide ligands are disposed in a cis configuration and the chloride and phosphine ligands trans . The remaining sites are occupied by the tolylimido- and methoxide ligands. The Re—N(I) bond length of 1.739(3) A and Re—N(1)—C(11) angle of 164.8(3) are consistent with the imido- ligand functioning as a linear four-electron donor (assuming the imido-ligand to be neutral). The reaction between the tolylimido- Re(V) complex, [ReCl 3 (NC 6 H 4 Me-4)(PPh 3 ) 2 ], and aroylhydrazones, Ar(O)CNHNCRR′(Ar = Ph, R = R 1 = Me: Ar = 4-ClC 6 H 4 , R = H, R 1 = Ph), in a 1 : 1 toluene/ethanol mixture under reflux yielded the green Re(V) complexes [ReCl 2 (NC 6 H 4 Me-4)(PPh 3 )Ar(O)CNNCRR′-O,N], where Ar = Ph, R = R′= Me ( 3 ) or Ar = 4-ClC 6 H 4 , R = H, R′ = Ph ( 4 ). Complex ( 3 ) can also be synthesized from the reaction of [ReCl 3 (NC 6 H 4 Me-4)(PPh 3 ) 2 ] and the hydrazone generated in situ from benzoic hydrazide in a 1:1 toluene/acetone mixture. The X-ray crystal structure of ( 4 ) showed a distorted octahedral geometry with the oxygen and nitrogen atoms of the chelated hydrazone (1-) ligand being mutually cis . The nitrogen atom of the tolylimido- ligand is trans to the chelated oxygen and the phosphorus atom of the triphenylphosphine ligand is trans to the chelated nitrogen. The remaining sites are filled by the two chloride ligands. The Re—N(3) bond length of 1.706(5) A and Re—N(3)—C(11) angle of 175.7(5) are consistent with the imido- ligand functioning as a linear four-electron donor.

1H and 13C NMR spectral and X-ray crystallographic study of 3-methyl-2,4-diphenylquinoline. Sterically hindered phenyl groups and the ‘pseudo peri-proximity’ effect

Abstract A study of the rotation of the sterically hindered phenyl groups in 3-methyl-2,4-diphenylquinoline by 1 H and 13 C NMR spectroscopy, supported by CP-MAR solid state NMR measurements and X-ray crystallography is presented. The 53° dihedral angle of the C 6 H 5 -2 ring results in a reduced electrostatic field effect and a residual ‘pseudo- peri proximity’ effect is proposed to operate. The rotation of the C 6 H 5 -4 ring to a near orthogonal position causes anisotropic shielding effects at 5-H and the ortho -protons. The NMR spectral assignments are supported by 2D studies and the results have been compared with the unhindered compound, 2,4-diphenylquinoline.

Optical absorption in metal bisphthalocyanine sublimed films

Visible optical absorption and reflection spectra are obtained for 50 nm thick sublimed films of heavy fraction rare-earth [HF(pc) (pc*)], gadolinium [Gd(pc) (pc*)] and thulium [Tm(pc) (pc*)] bisphthalocyanine compounds when they have undergone the post-deposition treatments of voltage-cycling to blue, voltage cycling to red and annealing at 393 K for 1 h. The different post-deposition treatments produce different effects on the absorption spectra; annealing generates phase changes in the films. The changes due to the voltage cycling are believed to be a result of oxidation/reduction processes taking place in the materials. The absorption data yield information on the dispersion of refractive index and dielectric constants within the optical frequency range. The energies of transition are found to be 1.9 and 2.8 eV, respectively for Q- and Soret bands of all untreated samples. The concentration of electrons involved in resonant oscillation is estimated to be in the order of 1031 m−3 for all types of samples, both fresh and treated.

Influence of crystal environment on molecular conformation: p-bromo-N-(p-dimethylaminobenzylidene)aniline

p-Bromo-N-(p-dimethylaminobenzylidene)aniline, C15H15BrN2, (1), comprises two independent molecules with markedly different conformations. Molecule A is essentially planar along its entire length (including the dimethylamino group) whereas molecule B deviates considerably from planarity with an interplanar angle of 145.8 (3) ° between the two phenyl rings and the NMe2 group twisted by 10 (2) ° out of the plane of the phenyl ring to which it is bound. While polymorphism and crystal packing effects are well documented for benzylidene derivatives, this is an interesting example with two quite distinct conformations in the same crystal phase. The differences are accounted for in terms of crystalpacking effects. The structure highlights the ability of particular molecular arrangements to stabilize a less favourable molecular conformation.