Binuclear Ferrocene Derivatives Research Articles

Synthesis and characterization of new mono and bi-nuclear ferrocene derivatives connected via a cross-conjugated prop-2-en-1-one bridge

In order to understand the influence of the carbonyl group proximity on the electronic behavior of organometallic terminal fragments, new binuclear ferrocenyl-alquinylruthenium based isomeric prop-2-en-1-ones, (η5C5H5)-Fe-(η5C5H4)-(E)CH2CH2COC6H4-pCC-trans-RuCl[κ2-(dppe)2], dppe=(diphenylphosphanyl)-ethane, 5 and (η5C5H5)-Fe-(η5C5H4)CO-(E)CH2CH2C6H4-pCC-trans-RuCl[κ2-(dppe)2], 6, have been synthesized. The electronic properties, evaluated through cyclic voltammetry, revealed the existence of an electronic communication in such compounds between the two metal centers, in spite of the cross conjugated prop-2-en-1-one bridge. Therefore, to better understand the influence of the alquinylruthenium donor fragments, two new compounds containing nitro groups located at the terminal positions were also synthesized, (η5C5H5)-Fe-(η5C5H4)-(E)CH2CH2COC6H4-pCCC6H4-p-NO2, 7, and (η5C5H5)-Fe-(η5C5H4)CO-(E)CH2CH2C6H4-pCCC6H4-p-NO2, 8. Likewise, a new series of isomeric p-ethynyl substituted chalcones containing a ferrocenyl unit (Fc), p-RCCC6H4COCH=CHFc, R = -Si(CH3)31, H 2, and p-RCCC6H4CH=CHCOFc, R = Si(CH3)33, H 4, were prepared to serve as precursors in the synthesis of the above mentioned compounds. Additionally, the X-Ray characterization of 1 was investigated.

Mixed-Valence States of 1′,1″′-Bis(2-phenylbutyl)-1,1″-biferrocenium(1+) Triiodides: Effects of the Cation Symmetry and Counter Anion on the Electron-Transfer Rate

Abstract The effects of cation symmetry and packing on the mixed-valence state of binuclear ferrocene derivatives are discussed by using chiral isomers and the racemic modification of 1′,1″′-bis(2-phenylbutyl)-1,1″-biferrocenium(1+) triiodide. Although the three chiral isomers showed trapped-valence states at 78 K, only the (R,S) isomer showed a perfect detrapped-valence state at room temperature in the three isomers. The racemic modification consisted of the (R,R) and the (S,S) isomers showed a perfect detrapped-valence state at room temperature. This shows that the packing effect overcomes the effect of cation asymmetry. The electron-transfer rate for each pentaiodide salt was faster than that of the corresponding triiodide salt. A comparison between the (S,S) triiodide and the (S,S) pentaiodide salts reveals an important packing effect. The polymeric pentaiodide skeleton forced the (S,S) cation to have pseudo-inversion center.

Mixed-valence state of optically active 1',1'"-bis(2-phenylbutyl)-1,1''-biferrocenium pentaiodide: effects of cation symmetry and intermolecular interaction on trapped-/detrapped-valence states.

The effects of cation symmetry and packing on the mixed-valence state of binuclear ferrocene derivatives are discussed separately by using chiral isomers and racemic modification of 1',1' "-bis(2-phenylbutyl)-1,1' '-biferrocenium pentaiodide. The pentaiodide anion has a polymeric structure and is composed of triiodide anion and iodine molecule units. The (R,S) isomer having an inversion center shows a detrapped-valence state even at 78 K. On the other hand, the (R,R) and the (S,S) isomers having no inversion center show a trapped-valence state at room temperature. The racemic modification, however, consisting of the (R,R) and the (S,S) isomers shows a perfect detrapped-valence state at room temperature. This finding shows that the packing effect overcomes the effect of cation asymmetry.

Division of the Effects of Cation Symmetry and Its Packing on the Mixed-Valence State of 1‘,1‘ ‘‘-Bis(2-methylbutyl)-1,1‘ ‘-biferrocenium Triiodide Having Asymmetric Carbon in the Substituent

The effects of the cation symmetry and packing on the mixed-valence state of binuclear ferrocene derivatives are discussed separately by paying attention on the differences between the racemic and (S,S) samples and between the salts from hexane and from dichloromethane in 1‘,1‘ ‘‘-bis(2-methylbutyl)-1,1‘ ‘-biferrocenium triiodide having asymmetric carbon. An (R,S) isomer can sit on the center of symmetry, while (S,S) and (R,R) isomers cannot. Such a difference plays an important role on the mixed-valence state in the samples from dichloromethane but not in the samples from hexane. Both the racemic and (S,S) salts in the disordered state showed the same temperature-dependent mixed-valence state. The disordered state of racemic and (S,S) salts from hexane changed to the ordered state by recrystallization from dichloromethane. The ordered state for (S,S) salts showed a typical temperature-independent trapped-valence state. The packing effect in the present salts appears different from that of the derivatives...

Even−Odd Character and Dynamic Electronic State in the Binuclear Ferrocene Derivatives with Long Alkyl Substituents

X-ray powder diffraction patterns revealed that 1‘,1‘‘‘-diheptyl- and 1‘,1‘‘‘-dioctyl-1,1‘‘-biferrocenium triiodides obtained from hexane and from dichloromethane have a layered structure with longer interlayer distances. 1‘,1‘‘‘-Diheptyl-1,1‘‘-biferrocenium triiodide falls under the category reported before, while 1‘,1‘‘‘-dioctyl-1,1‘‘-biferrocenium triiodide becomes exception; it shows a valence detrapping with increasing temperature despite the longer interlayer series. The difference in the crystal structure between longer and shorter interlayer distance series was reflected in the difference of the space group. 1‘,1‘‘‘-Diheptyl-1,1‘‘-biferrocenium triiodide (C34H46Fe2I3) crystallizes in the monoclinic space group P21/c with unit cell parameters a = 27.209(10) Å, b = 9.6480(6) Å, c = 14.042(10) Å, β = 98.572(4)°, and Z = 4, while 1‘,1‘‘‘-dioctyl-1,1‘‘-biferrocenium triiodide (C36H50Fe2I3) crystallizes in the monoclinic space group P21/c with a = 20.758(6) Å, b = 9.80(1) Å, c = 37.88(2) Å, β = 90.44(3)°, and Z = 8. Both salts in the present study have a space group of P21/c, which is different from the shorter interlayer series; 1‘,1‘‘‘-dihexyl- and 1‘,1‘‘‘-didodecyl-1,1‘‘-biferrocenium triiodides have a space group of P1̄. The difference in the structure between the 1‘,1‘‘‘-diheptyl derivative and the 1‘,1‘‘‘-dioctyl derivative is also discussed. There is a difference in the symmetry of the monocation between the two salts, while both show the unsymmetrical triiodide anion. The difference between them makes the difference of the cation−cation interaction. The structure of the cations agrees with the result of 57Fe Mössbauer spectroscopy. The cation−cation interaction in the stacking is observed in 1‘,1‘‘‘-dioctyl derivative, while such interaction is disturbed by the adjacent stacking in 1‘,1‘‘‘-diheptyl derivative.

Phase transition in triiodide salts of binuclear ferrocene derivatives having long alkyl chains accompanied by a change in mixed-valence state

The relation between the mixed-valence state and crystal structure of 1′,1‴-didecyl- and 1′,1‴-bis(undecyl)-1,1″-biferrocenium triiodide has been studied by means of 57Fe Mossbauer spectroscopy and X-ray powder diffraction. The salts with even numbers of carbon atoms in the alkyl chain show a phase transition between two types of layered structures, accompanied by a change in mixed-valence state. Iodine-129 Mossbauer spectroscopy was applied to determine the electronic state of the triiodide anion in the biferrocenium salts. A change in the electronic state accompanied by a phase transition was observed in the case of the 1′,1‴-didecyl derivative.

Iron-57 Mössbauer spectroscopic and X-ray diffraction studies on the mixed-valence state of binuclear ferrocene derivatives with long alkyl substituents

The mixed-valence states of biferrocene derivatives with long alkyl substituents, which have a layered structure, have been investigated by means of 57Fe Mossbauer spectroscopy and X-ray powder diffraction. An interesting even–odd character in the number of carbon atoms of the alkyl chain is found in the relationship between the crystal structure and the mixed-valence state. The mixed-valence states of 1′,1‴-bis(dodecyl)-1,1″-biferrocenium triiodide change in accordance with a transformation of the crystal structure in the solid state. An X-ray diffraction analysis for this salt obtained from dichloromethane at 0 °C showed that both the cation and the anion are situated at a centre of symmetry and the dodecyl substituent has the all-trans conformation. The layers are located in the ab plane.

Antitumor effects of binuclear ferrocene derivatives

AbstractOn the basis of an earlier model of chemical carcinogenesis, the antitumor activity of the mono‐, bi‐ and poly‐nuclear ferrocene derivatives ferricenium tri‐iodide (1), ferricenium tetrachloroferrate (2), 1, 1′‐diethylferricenium triiodide: (3), N‐(ferrocenylmethyl)hexamethylenetetramine tetrafluoroborate (4), bis(ferrocenylmethyl)benzotriazolium tetrafluoroborate (5), bis(ferrocenyl‐α‐ethyl)benzotriazolium tetrafluoroborate (6) and bis(ferrocenylmethyl)‐2‐methylbenzimidazolium tetrafluoroborate (7), and the oligomer (—Fc—CH2—Fc+˙—CH2—)7–8− (PF6)7–8 (8) was studied in vivo (FcC10H8Fe). The tumor models studied included MCH‐11 (mouse sarcoma induced by methylcholantrene), P‐815 (mouse mastocytoma of DBA/2 origin) and virus‐induced Raucher leukemia (RLV). The cytotoxic effects of these preparations were examined against in vitro cultured normal murine cells (line L‐929). The binuclear ferrocene derivatives 5, 6 and 7 inhibited the development of experimental tumors in mice. Ferricenium tri‐iodide (1) was effective in Rauscher leukemia. Kinetic dependencies for most complexes had a two‐phase character: the region of inhibition of tumorogenesis was followed by a region in which the complexes accelerated the development of this process. The link between the structure of compounds 1–8 and their antitumor effects is discussed.

Mixed-valence states of polynuclear iron complexes

The valence-delocalization in mixed-valence binuclear ferrocene derivatives is investigated by using several physicochemical results. It is demonstrated that the mixed-valence state is controlled by the environment in the solid state. The mechanism of the valence-delocalization in 1 ',1 '''-diethylbiferrocenium triiodide is discussed. The difference between the valence-delocalization accompanied by the symmetry change of the counter anion and the valence-delocalization without connection with the symmetry of the counter anion is discussed. The results are compared with those of oxo-centered trinuclear iron carboxylates.

Effects of counter anion on mixed-valence states of binuclear ferrocene derivatives

The mixed-valence states of iron atoms in 1′, 1‴-dialkylbiferrocenium cations were found to be affected by the kind of their counter anions. The TCNQ salts showed only an averaged-valence state from 78 K to room temperature, while the triiodide salts showed only a trapped-valence state or a temperature dependent trapped-to-averaged valence state depending on the kind of alkyl group.

Mixed-valence states of 11, 1111-dialkyl- and 11, 1111-bis(methylbenzyl)biferrocenium triiodides

It was found that the packing of cations and anions influences the electronic structures of mixed-valence binuclear ferrocene derivatives. Temperature-dependence of the mixed-valence state of 11, 1111-diisobutylbiferrocenium triiodide was observed in a crystalline state, whereas only a trapped-valence state was found in a dispersed state. The packing effect was also observed for a series of 11, 1111-dialkyl- and 11, 1111-bis(methylbenzyl)biferrocenium triiodides by means of ESR spectroscopy.

Crystal Structure of Mixed-valence Compound 1′,1'″-Dipropylbiferrocenium Triiodide with Averaged-valence Type Irons at 298 K and with Trapped-valence Type Irons at 110 K and Thermal Electron Transfer Process of Mono-oxidized Binuclear Ferrocene Derivatives

Abstract The crystal structure of 1′,1'″-dipropylbiferrocenium (PrFcFcPr)+I3−, which shows averaged-valence irons at 298 K and trapped-valence irons at 110 K, was determined by X-ray diffraction. The crystal at 298 K is triclinic, space group P\bar1, a=8.5148(8), b=8.5482(5), and c=10.9032(13) Å, α=89.546(9), β=115.582(9), and γ=108.488(7)°, U=671.10(9) Å3, and Z=1. The crystal at 110 K is triclinic, space group P1, a=8.431(2), b=8.478(2), and c=10.816(3) Å, α=88.58(3), β=117.39(2), and γ=108.65(2)°, U=643.4(3) Å3, and Z=1. Structures were refined to R=0.042 at 298 K and R=0.050 at 110 K. At 298 K cation (PrFcFcPr)+ sits on the symmetry center and the two Fc units are crystallographically equivalent, whereas at 110 K the symmetry center is lost and ferrocene-like and ferrocenium-like Fc units are distinguished. A three-dimensional hydrogen-bond network is clearly found between the cation and iodine atoms at 110 K, in contrast to the result at 298 K. Infrared spectra of 1′,1'″-diethyl- and 1′,1'″-dipropylbiferrocenium+I3− and μ-(as-indacenyl)-bis(cyclopentadienyliron)+I3−0.5I2 salts measured at 294 and 78 K indicate that a remarkable change in peak intensity is observed at 680 and 1525 cm−1 in the dialkyl salts, whereas no change is found in the remainder.