A. Houlton

Studies on the anti-tumour activity of some iron sandwich compounds

Abstract Four types of water-soluble iron sandwich compounds, ferrocenes bearing charged side chains (Ia), ferrocenium salts (Ib), (η-arene) 2 Fe 2+ salts (II) and (η-cyclopentadienyl)Fe + salts (III), have been tested in in vitro against experimental tumours, L1210, Walkers and Chinese hamster lung (V.79). Some activity was observed for all the types of complex; though that of only two, Ib and II, was good. Of special interest is that the iron(II) sandwich type II compounds display anti-tumour activity, since previous active complexes have contained type Ib or other known cytotoxic groups that would account for their activity. Examples of complexes of type Ib and II were further tested against improved cell lines L1210, PC6 and CHl. The results show the two types to be similar in their effect and specificity. An attempt is made to rationalise the data.

Molecular materials for non-linear optics. Second harmonic generation and the crystal and molecular structure of the 4-nitrophenylimine of ferrocenecarboxaldehyde

Abstract Ferrocenyl derivatives of the form [(η-C 5 H 5 )Fe(η-C 5 H 4 )CHN-( p -C 6 H 4 X)], where XNO 2 , F, Br, were tested for second harmonic generation (s.h.g.). Only when XNO 2 was such activity observed. This was not large, however, at 1/3 times that of the urea standard. X-ray analysis confirms that the material is non-centrosymmetric, crystallizing in the space group P 2 1 2 1 2 1 . This dictates that despite being acentric the crystal arrangement essentially ensures a cancelling of the dipolar nature of the molecule. The residual s.h.g. must arise from intermolecular effects . This is only the second structural report of such a metallocene derivative to display s.h.g. The possible influence of the molecular shape of 1 and of related compounds is also discussed.

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.

Mössbauer studies on ferrocene complexes: XVII. Ferrocenylamines and ferrocenylphosphines☆

Abstract 57Fe Mossbauer data are reported for some ferrocene derivatives in which the ferrocenyl group is bonded to N And P, and are considered in the light of 13C NMR and cyclic voltammetry (CV) data. They highlight the difference in the interaction between the ferrocenyl unit and the exocyclic nitrogen or phosphorus atom.

Studies on gold(I) complexes of 1,1'-bis(diphenylphosphino)ferrocene

Abstract The synthesis and 197Au, 57Fe Mossbauer and 31P NMR spectroscopic data for a series of Au1 complexes of 1,1′-bis(diphenylphosphino)ferrocene (fdpp) are reported. Two different Au1 coordination geometries are apparent in the solid state, linear and trigonal. There is no evidence in the solid state for a tetrahedral species[fdpp2Au]+, but 31P NMR spectroscopy indicates its existence in solution. Chemical oxidation of the complexes does not yield the expected ferrocenium derivatives. In accord with this, cyclic voltammetry reveals there to be no observable electrochemical processes in the timescales investigated (500–20 mV/s).

Mössbauer studies on ferrocene complexes: XVIII. A comparative study of azaferrocenes and phosphaferrocenes and their derivatives by 57Fe Mössbauer and 13C NMR spectroscopy☆

Abstract The 13C NMR chemical shifts (δ) for azaferrocenes, phosphaferrocenes and their precursor ligands have been used to determine coordination shifts, Δδ ( = δcomplex −δligand) for the complexes. For azaferrocenes, Δδ values were similar to that of ferrocene, but the phosphaferrocenes showed much larger coordination shifts. These observations are discussed in terms of the difference in bonding in these complexes. The 57Fe Mossbauer data are reported for a number of azaferrocene derivatives and compared with those for the phosphaferrocene analogues in terms of orbital contributions to the electric field gradient that governs the quadrupole splitting (QS). An excellent correlation is found between QS and the orbital population parameter (2P2 - p1), where p2 and p2 are electronic populations of the e2 and e1 iron-based orbitals, respectively. Protonation and quaternisation of azaferrocene causes a lowering of QS, in contrast to the slight increase observed for monophosphaferrocene in CF3CO2H solution. The results confirm that protonation at the N atom takes place for azaferrocene. The W(CO)5 adduct of azaferrocene shows little change in QS from that for azaferrocene, which is interpreted as evidence for back bonding by the tungsten.

Ferrocenyl ligands—II. In search of redox-active ferrocenyl ligands. The preparation and characterization of two schiff's base derivatives of 1,1′-

Abstract With the aim of producing redox-active ferrocenyl ligands, the synthesis and characterization of two arylhydrazones, phenyl (1) and pyridyl (2)

An iron-57 mössbauer study of (η6-arene)(η5-cyclopentadienyl)iron(II) salts

57Fe Mossbauer spectra have been obtained for a series of (η6-arene)(η5-cyclopentadienyl)iron(II) complexes (ArFe+Cp). Simple Hammett plots of quadrupole splittings (Δ) for Ar ring substituents are sigmoidal, indicating limits to electron withdrawal and donation. For these simple plots the data are best fitted by use of σ−R constants, in keeping with the proposed ϵ2-π* back-bonding in the iron—arene interaction. The correlations are improved by use of a dual parameter approach with a 40% inductive component. A plot of Δ for (ArFe+Cp) complexes versus those of corresponding ferrocenes is approximately linear buth with a slope of 2.3, indicating enhanced substituent effects in the former series due to the positive charge on Fe. Substituent effects on the Cp ring are directly opposite to those found in ferrocenes, and Hammett correlations follow σ+R rather than the σ−R constants found to apply for the arene substituents. Electron-releasing groups in the arene ring have been shown to cause marked attenuation of the substituent effects on Δ for both arene and Cp substituents. Mossbauer parameters are also presented and discussed for polysubstituted complexes, polycyclic systems, and novel phosphacyclopentadienyl complexes and adducts. Finally, some tetracyanoquinodimethane complexes (TCNQ) have been synthesised and their Mossbauer parameters are discussed in terms of population of a conduction band.

A spectroscopic study of bis(η6-arene)iron(II) salts

Abstract A number of bis(η 6 -arene)iron(II) salts have been synthesised from the following ligands: benzene, toluene, ethylbenzene, ortho, meta and para xylenes, mesitylene, 1,2,3,4-tetramethylbenzene, 1,2,3,5-tetramethylbenzen, 1,2,4,5-tetramethylbenzene, pentamethylbenzene, and hexamethylbenzene. The stabilities of these complexes in solution vary considerably both with solvent basicity and the degree of alkyl substitution. 1 H and 13 C NMR data are reported. The observed large upfield shifts of ligand 13 C signals is discussed in terms of shielding by the d z 2 electrons of the central iron atom. 13 C shifts correlate reasonably well with the total charge density at the relevant carbon atom for a variety of sandwich complexes, including those discussed in this work. 57 Fe Mossbauer data are presented; quadrupole splittings increase systematically with the number of methyl substituents on the ligands. These changes are explained in terms of imbalances in the electronic population of metal-based e 2 and ligand-based e 1 orbitals.

A six-coordinate high spin protoporphyrin IX iron(III) complex as a model for ferric haemproteins: Mössbauer spectrum of bisaquo(protoporphyrinato IX)iron(III) encapsulated in aqueous detergent micelles

Abstract The Mossbauer spectrum is reported for a six- coordinate high spin iron(III) protoporphyrin complex, [(PPIX)Fe(H 2 O) 2 ] + , which is monodispersed in an aqueous frozen solution of sodium dodecyl sulphate micelles. The isomer shift of 0.46 mm −1 and the quadrupole splitting of 1.19 mm 1 are similar to those of aquo met myoglobin. These results are compared with the literature results on other high spin six-coordinated models and with those of some proteins. This is the first report of a Mossbauer study on a haem encapsulated in a detergent micelle.