Ferrocenes modification

Monomers 1 and 2 have been synthesized starting from ferrocene, utilizing modifications of procedures outlined previously by Sonoda and MoritaniH and by Ratajczak et al. The intermediate diacid, l,l ferrocenedicarboxylic acid, was synthesized according to the more convenient procedure of Knobloch and Rauscher. Monomer JL was vacuum distilled prior to use (bp 120°C, 1 mm Hg). Details of the... 

However, because of the mostly very slow electron transfer rate between the redox active protein and the anode, mediators have to be introduced to shuttle the electrons between the enzyme and the electrode effectively (indirect electrochemical procedure). As published in many papers, the direct electron transfer between the protein and an electrode can be accelerated by the application of promoters which are adsorbed at the electrode surface [27], However, this type of electrode modification, which is quite useful for analytical studies of the enzymes or for sensor applications is in most cases not stable and effective enough for long-term synthetic application. Therefore, soluble redox mediators such as ferrocene derivatives, quinoid compounds or other transition metal complexes are more appropriate for this purpose. 

The conventional and efficient method for the synthesis of dithienyl-maleimide 185, according Scheme 56, was described by Chinese researchers (06TL9227). 2,3-Bis(5-bromo-2-methylthiophen-3-yl)fumaronitrile 184 was hydrolyzed with sodium methoxide-methanol followed by N-meth-ylation with potassium ferf-butoxide and iodomethane to give the target compound 2,3-bis(5-bromo-2-methylthiophen-3-yl)-N-methylmaleimide. Subsequent modification of the latter afforded 186 containing two ferrocene fragments. 

Ferrocenyl-based polymers are established as useful materials for the modification of electrodes, as electrochemical biosensors, and as nonlinear optical systems. The redox behavior of ferrocene can be tuned by substituent effects and novel properties can result for example, permethylation of the cyclopentadienyl rings lowers the oxidation potential, and the chaige transfer salt of decamethylfer-rocene with tetracyanocthylene, [FeCpJ]" (TCNE], is a ferromagnet below = 4.8 K, and electrode surfaces modified with a pentamethylferrocene derivative have been used as sensors for cytochrome c These diverse properties have provided an added impetus to studies on ferrocene dendrimers. 

Representative results are shown in Fig. 2.1.2.1. Both reactions with mixtures of diphenylzinc and diethylzinc and those with pure diphenylzinc are catalyzed by ferrocene 9 as indicated by the comparisons between curves A and C as well as B and D, respectively. Apparently the reaction becomes slower when the mixture of the zinc reagents is applied (curve A versus curve B). We presume that this effect is - as hoped - due to a less pronounced background reaction as well as to a modification of the aryl source (potentially PhZnEt or complexes thereof). Consequently, a better control of the enantioselectivity at the expense of the reaction rate is observed. 

Menke, K., Maub, J.B., Brehler, K.P., Jungbluth, H., and Kalischewski, W. (1995) New ferrocenes for bum-rate modification of composite propellants. Proc. ADPA Inti Symp. on Energetic Materials Technology, Phoenix, Arizona, US, Sept. 24-27, 1995. 

Boehnnein-Mauss,)., et al. (1993) Structural influences of ferrocenes on burn rate modification of composite rocket propellants. Proc. 24th Inti Ann. Conf. ICT, Karlsruhe, Germany June 29-July 02,1993, pp. 71/1-71/19. 

Additional information about this Fc GO preparation has been reported elsewhere (112). The intramolecular electron transfer rate constant kmirn calculated using Eq. (36) equals 40 s-1 and is by a factor of 50 higher than that for the randomly modified GO (104). The distance separating the ferrocene unit and FAD in Fc GO is believed to be ca. 19 A, by 2 A shorter than in the most effective electrically contacted enzyme generated by the random modification of GO by ferrocene units. This information supports the hypothesis about the key locations of ferrocene groups that play the dominant role in the electrocatalysis (104). 

The second topic of this chapter is the role of coordination compounds in advancing electrochemical objectives, particularly in the sphere of chemically modified electrodes. This involves the modification of the surface of a metallic or semiconductor electrode, sometimes by chemical reaction with surface groups and sometimes by adsorption. The attached substrate may be able to ligate, or it may be able to accept by exchange some electroactive species. Possibly some poetic licence will be allowed in defining such species since many interesting data have been obtained with ferrocene derivatives thus these organometallic compounds will be considered coordination compounds for the purpose of this chapter. 

If (23) is selected as the dihalosilane, a convenient way of modifying the nickel surface is available.64 The electrochemical properties of the treated nickel electrode are very similar to those of a similarly derivatized platinum electrode for example, both are equally effective in the elec-trocatalytic oxidation-reduction of solution ferrocene. Normally oxidation of the nickel surface would be a competing process ultimately rendering the electrode passive. The surface modification clearly eliminates this problem and opens up the possibility of using surface modified inexpensive metals as electrodes. 

J. Razumiene, V. Gureviien, A. Vilkanauskyt, L. Marcinkeviien, I. Bach-matova, R. Mekys and V. Laurinaviius, Improvement of screen-printed carbon electrodes by modification with ferrocene derivative, Sens. Actuators B Chem., 95 (2003) 378-383. 

---