Ferrocene-based Derivatives Research Articles

A green synthesis and antibacterial activity of ferrocene-based thiazole derivatives in choline chloride/glycerol eutectic solvent.

In this work, a green Hantzsch synthesis of 4-ferrocenylthiazole derivatives has been accomplished successfully. The Hantzsch reaction between bromoacetylferrocene and various aryl thioureas, 1-alkylindole-3- or 9-alkylcarbazole-3-carbothioamides proceeded efficiently in a deep eutectic solvent (DES) that is, choline chloride/glycerol (ChCl/Gly) (1 : 2 molar ratio) at 80 °C, avoiding the use of common volatile organic solvents. Moreover, the DES media could be reused up to three times without any appreciable decrease in the yield. The synthetic strategy has the attractive features such as mild and environmentally benign reaction conditions, experimental simplicity, easy work-up procedure and good yields. Subsequently, a preliminary screening for in vitro antibacterial activities of all these newly-synthesized compounds revealed that the halo-substituted (F, Cl, Br) compounds 3f–h showed significant antibacterial activities against Gram (+) bacterial B. subtilis and Gram (−) E. coli, among which the fluoro-substituted 3f possessed the best activity with the MIC value of 7.8125 μg mL−1, being higher than the reference drug ciprofoxacin (15.625 μg mL−1).

Tunable Redox Potential, Optical Properties, and Enhanced Stability of Modified Ferrocene-Based Complexes.

We report a series of ferrocene-based derivatives and their corresponding oxidized forms in which the introduction of simple electron donating groups like methyl or tert-butyl units on cyclopentadienyl-rings afford great tunability of Fe+III/Fe+II redox potentials from +0.403 V down to −0.096 V versus saturated calomel electrode. The spin forbidden d–d transitions of ferrocene derivatives shift slightly toward the blue region with an increasing number of electron-donating groups on the cyclopentadienyl-rings with very little change in absorptivity values, whereas the ligand-to-metal transitions of the corresponding ferricinium salts move significantly to the near-IR region. The electron-donating groups also contribute in the strengthening of electron density of Fe+III d-orbitals, which therefore improves the chemical stability against the oxygen reaction. Further, density functional theory calculations show a reducing trend in outer shell reorganization energy with an increasing number of the electron donating units.

Synthesis of ethylene diamine-based ferrocene terminated dendrimers and their application as burning rate catalysts

Ferrocene-based derivatives are widely used as ferrocene-based burning rate catalysts (BRCs) for ammonium perchlorate (AP)-based propellant. However, in long storage, small ferrocene-based derivatives migrate to the surface of the propellant, which results in changes in the designed burning parameters and finally causes unstable combustion. To retard the migration of ferrocene-based BRCs in the propellant and to increase the combustion of the solid propellant, zero to third generation ethylene diamine-based ferrocene terminated dendrimers (0G, 1G, 2G and 3G) were synthesized. The synthesis of these dendrimers was confirmed by 1H NMR and FT-IR spectroscopy. The electrochemical behavior of 0G, 1G, 2G and 3G was investigated by cyclic voltammetry (CV) and the burning rate catalytic activity of 0G, 1G, 2G and 3G on thermal disintegration of AP was examined by thermogravimetry (TG) and differential thermogravimetry (DTG) techniques. Anti-migration studies show that 1G, 2G and 3G exhibit improved anti-migration behavior in the AP-based propellant.

Synthesis, crystal structure and redox properties of dihydropyrazole-bridged ferrocene-based derivatives

Dihydropyrazole-bridged ferrocene-based derivatives were prepared by corresponding chalcones with hydrazine hydrate, then acylation with 3-(ethoxycarbonyl)propionyl chloride directly in high yields and purity. All of these compounds were characterized by MS, IR, 1H NMR, 13C NMR and elemental analysis. The relationship between the structure and redox properties was investigated based on the results of single crystal X-ray structure determinations and cyclic voltammetry. The mechanism of the electron transfer for representative compound 4b was verified by density functional theory (DFT) calculations.

Strategies for the development of enantioselective catalysts

Novel C2-symmetric diiminosphosphoranes and diketimines are useful ligands for Pd-and Cu-catalyzed C-C bond forming reactions, Angermund's molecular modeling based on accessible molecular surface serving as a guide in predicting catalyst activity. The first highly enantioselective diphosphites as ligands in Rh-catalyzed hydrogenation are also described, the selectivity principle being based on in situ selection of conformational enantiomers. Finally, a systematic study of chiral diphosphonites reveals that ferrocene-based derivatives are ideal in hydrogenation and certain conjugate addition reactions. These methods are compared to biocatalytic strategies based on the creation of enantioselective biocatalysts by in vitro evolution, a rational process which is independent of the catalyst structure or mechanism.

Thermotropic properties of monosubstituted ferrocene derivatives bearing bidentateN-benzoyl-N′-arylthiourea ligands—novel building blocks for heterometallic liquid crystal systems

Ferrocene-based derivatives such as 4-{3-[4-(octyloxy)benzoyl]thioureido}phenyl 4-ferrocenylbenzoate and other higher homologues (n=12,16 and 18; n=length of alkoxy chain) were prepared by reacting 4-alkoxybenzoyl isothiocyanates with the corresponding amines containing the ferrocenyl moiety. Their mesomorphic properties were investigated by means of polarized optical microscopy and differential scanning calorimetry. All the compounds exhibit enantiotropic nematic phases and the nematic range increases with increasing terminal alkyl chain length. On cooling, the nematic phase persists below 0 °C in the first three compounds and in the case of n=18, a phase transformation, possibly to the SCphase, around 72 °C during cooling was observed. In all cases, a glass transition was observed around Tg=18–35 °C, which is remarkable for low molecular mass calamitic metallomesogen systems.