Synthesis,characterization, coordination and antibacterial properties of novel asymmetric 1,1′‐disubstituted ferrocene‐derived Schiff‐base ligands and their Co(II), Cu(II) Ni(II) and Zn(II) complexes

Some new asymmetric 1,1 ′‐disubstituted ferrocene‐derived Schiff‐bases have been prepared and used as ligands in the preparation of their Co(II), Cu(II), Ni(II) and Zn(II) metal chelates. These synthesized ligands and their metal chelates have been characterized by their physical, analytical and spectral data. These have also been used for screening against pathogenic bacterial species, e.g. Escherichia coli, Staphylococcus aureus, Pseudomonas aeruginosa and Klebsiella pneumonae and have been found to be a novel class of organometallic‐based antibacterials. Copyright © 2001 John Wiley & Sons, Ltd.     

Aminocarbonylation of 1,1′-diiodoferrocene, two-step synthesis of heterodisubstituted ferrocene derivatives via homogeneous catalytic carbonylation/coupling reactions

Detailed investigation of the catalytic carbonylation of 1,1′-diiodoferrocene has been carried out. The importance of the 1′-iodo-ferrocenecarboxamide- or 1′-iodo-ferroceneglyoxylic amide-type products as starting materials for the synthesis of various heterodisubstituted ferrocenes, that can serve as starting materials for ferrocene-based biosensors, was also proved. The potential of this reaction sequence was shown by the high-yielding synthesis of 1′-vinyl ferrocenecarboxamide/glyoxylic amide and 1′-acyl ferrocencarboxamide derivatives.     

Solvent effects of ionic liquids: investigation of ferrocenes as electrochemical probes

The redox potentials of ferrocene and decamethylferrocene were determined in a number of molecular and ionic solvents and used as a probe for polarity of room temperature ionic liquids (ILs). No macroscopic solvent property is simply related to redox potentials. Single empirical solvent parameters also are not able to describe the differences in potentials. Instead, Kamlet–Taft multiparameter relationship fits well ferrocenes redox potentials variation, with both molecular solvents and ILs, well describing specific solvent–solute interactions with the two probes. Copyright © 2010 John Wiley & Sons, Ltd.     

Self-Immolative Amphiphilic Poly(ferrocenes) for Synergistic Amplification of Oxidative Stress in Tumor Therapy

Amphiphilic self-immolative polymers (SIPs) can achieve complete degradation solely through one triggerable event, which potentially optimize the blood clearance and uncontrollable/inert degradability for therapeutic nanoparticles. Herein, we report self-immolative amphiphilic poly(ferrocenes), BP ^nbs -Fc , composed by self-immolative backbone and aminoferrocene (AFc) side chains as well as end-capping poly(ethylene glycol) monomethyl ether. Upon triggering by tumor acidic milieu, the BP ^nbs -Fc nanoparticles readily degrade to release azaquinone methide (AQM) moieties, which can rapidly deplete intracellular glutathione (GSH) to cascade release AFc. Furthermore, both AFc and its product Fe²⁺ can catalyze intracellular hydrogen peroxide (H₂O₂) into highly reactive hydroxyl radicals (⋅OH), thus amplifying the oxidative stress of tumor cells. Rational synergy of GSH depletion and ⋅OH burst can efficiently inhibit tumor growth by the SIPs in vitro and in vivo. This work provides an elegant design to adopt innate tumor milieu-triggerable SIPs degradation to boost cellular oxidative stress, which is a promising candidate for precision medicine.     

Flame-retardancy and Smoke-suppression Studies on Ferrocene Derivatives in PVC

A range of substituted ferrocenes has been synthesized and studied for flame retardancy and smoke suppression on incorporation into plasticized PVC at 0.1–5.0 phr. Smoke suppression by up to 50 and enhancement of the limiting oxygen index by up to 4 units were observed. The differences in performance could not be correlated with char formation, thermal analysis or chemical structure of the additive. A negative correlation was found between smoke suppression and flame retardancy. The most effective smoke suppressant additive appears to accelerate the rate of dehydrochlorination of PVC while the most effective flame retardant appears to have little effect on the dehydrochlorination process.     

Synthesis and Characterization of Multiferrocenyl‐Substituted Group 4 Metallocene Complexes

The reaction of different metallocene fragments [Cp₂M] (Cp=η⁵‐cyclopentadienyl, M=Ti, Zr) with diferrocenylacetylene and 1,4‐diferrocenylbuta‐1,3‐diyne is described. The titanocene complexes form the highly strained three‐ and five‐membered ring systems [Cp₂Ti(η²‐FcC₂Fc)] ( 1 ) and [Cp₂Ti(η⁴‐FcC₄Fc)] ( 2 ) (Fc=[Fe(η⁵‐C₅H₄)(η⁵‐C₅H₅)]) by addition of the appropriate alkyne or diyne to Cp₂Ti. Zirconocene precursors react with diferrocenyl‐ and ferrocenylphenylacetylene under C? C bond coupling to yield the metallacyclopentadienes [Cp₂Zr(C₄Fc₄)] ( 3 ) and [Cp₂Zr(C₄Fc₂Ph₂)] ( 5 ), respectively. The exchange of the zirconocene unit in 3 by hydrogen atoms opens the route to the super‐crowded ferrocenyl‐substituted compound tetraferrocenylbutadiene ( 4 ). On the other hand, the reaction of 1,4‐diferrocenylbuta‐1,3‐diyne with zirconocene complexes afforded a cleavage of the central C? C bond, and thus, dinuclear [{Cp₂Zr(μ‐η¹:η²‐C?CFc)}₂] ( 6 ) that consists of two zirconocene acetylide groups was formed. Most of the complexes were characterized by single‐crystal X‐ray crystallography, showing attractive multinuclear molecules. The redox properties of 3 , 5 , and 6 were studied by cyclic voltammetry. Upon oxidation to 3 ⁿ⁺, 5 ⁿ⁺, and 6 ⁿ⁺ (n=1–3), decomposition occured with in situ formation of new species. The follow‐up products from 3 and 5 possess two or four reversible redox events pointing to butadiene‐based molecules. However, the dinuclear complex 6 afforded ethynylferrocene under the measurement conditions.     

Synthesis and characterisation of aromatic ethynyl-bridged ferrocenes

A series of aromatic ethynyl-bridged ferrocenes with the general formula Fc-CC-R-CC-Fc (Fc=ferrocenyl, R=C₆H₂(-p-CH₃)₂ (1), C₆H₄-p-C₆H₄ (2), C₅H₃N (3), 9,10-C₁₄H₈ (4), C₄H₂S (5), (C₄H₂S)₂ (6) and (C₄H₂S)₃ (7)) has been synthesised by the reaction of ethynyl ferrocene with the appropriate dibromo-arenes. The new complexes have been characterised by spectroscopic techniques. The structures of 3 and 7 were determined via X-ray crystallography, and both show the trans-trans configuration of the two ethynyl ferrocene groups with respect to the central R group. The electronic properties of the compounds have been studied via optical spectroscopy and cyclic voltammetry.     

Ruthenium Complexes with Dendritic Ferrocenyl Phosphanes: Synthesis,Characterization, and Application in the Catalytic Redox Isomerization of Allylic Alcohols

An efficient system for the catalytic redox isomerization of the allylic alcohol 1‐octen‐3‐ol to 3‐octanone is presented. The homogeneous ruthenium(II) catalyst contains a monodentate phosphane ligand with a ferrocene moiety in the backbone and provides 3‐octanone in quantitative yields. The activity is increased by nearly 90 % with respect to the corresponding triphenyl phosphane ruthenium(II) complex. By grafting the catalyst at the surface of a dendrimer, the catalytic activity is further increased. By introducing different spacers between ferrocene and phosphorus, the influence on the electronic properties of the complexes is shown by evaluating the electrochemical behavior of the compounds.     

Synthesis,spectral characterization and electrochemical properties of (2-alkylthiobenzoyl)ferrocenes. Crystal structures of 2-methylthio, 2-ethylthio and 2-isopropylthio derivatives

The one-pot synthesis of seven new (2-alkylthiobenzoyl)ferrocenes has been achieved by Friedel–Crafts acylation of ferrocene with acid chlorides generated in situ from the corresponding carboxylic acids and phosphorous trichloride. The obtained compounds were characterized by spectroscopic data (UV, IR, ¹H and ¹³C NMR), whereas their electrochemical properties have been investigated by cyclic voltammetry. The single-crystal X-ray structure determinations for three of them are also reported. Each of the three derivatives exhibits the intramolecular C–H…O interaction which involves the donor from the cyclopentadienyl (Cp) ring and the carbonyl oxygen as acceptor. This interaction favors the coplanar arrangement of the two moieties. The angles between the vectors coinciding the C–O bonds and the corresponding Cp planes are all below 6.4°. Conventional hydrogen bonds do not exist in any of the three crystal structures but some weak intermolecular interactions of the C–H…O, C–H…S and C–H…π types have been found and analyzed in detail. Different geometrical parameters for these crystal structures as well as for 22 similar ones extracted from Cambridge Structural Database (CSD) have been compared and analyzed.