Spectral and Redox Properties

FIGURE 4. Absorption spectra of the different redox forms of MADH. 

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Complexes with ligands bearing alkylpyridine pendant arms attached to an ethylenediamine framework were prepared, and their spectral and redox properties were studied (238), (239), and (240) (r = 0.10).222... 

A few thioether-ligated copper(II) complexes have been reported, however (cf. Section 6.6.3.1.2) (417) (essentially square planar), (418) (two crystalline forms one TBP and other SP),361 (419) (SP),362 (420) (SP),362 (421) (TBP),362 (422) (SP),363 (423) (SP),363 (424) (two independent complexes SP and octahedral),364 (425) (TBP).364 In the complexes (420) and (421), EPR spectra revealed that the interaction between the unpaired electron and the nuclear spin of the halogen atom is dependent on the character of the ligand present. For (424) and (425), spectral and redox properties were also investigated. Rorabacher et al.365 nicely demonstrated the influence of coordination geometry upon CV/Cu1 redox potentials, and reported structures of complexes (426) and (427). Both the Cu1 (Section 6.6.4.5.1) and Cu11 complexes have virtual C3v symmetry. 

For the cytochrome c-plastocyanin complex, the kinetic effects of cross-linking are much more drastic while the rate of the intracomplex transfer is equal to 1000 s in the noncovalent complex where the iron-to-copper distance is expected to be about 18 A, it is estimated to be lower than 0.2 s in the corresponding covalent complex [155]. This result is all the more remarkable in that the spectroscopic and thermodynamic properties of the two redox centers appear weakly affected by the cross-linking process, and suggests that an essential segment of the electron transfer path has been lost in the covalent complex. Another system in which such conformational effects could be studied is the physiological complex between tetraheme cytochrome and ferredoxin I from Desulfovibrio desulfuricans Norway the spectral and redox properties of the hemes and of the iron-sulfur cluster are found essentially identical in the covalent and noncovalent complexes and an intracomplex transfer, whose rate has not yet been measured, takes place in the covalent species [156]. 

JC Goedheer (1960) Spectral and redox properties of bacteriaochlorophyll in its natural state. Biochim Biophys Acta 38 389-399... 

In the primary reactions of photosynthesis, the light-induced charge separation and stabilization involves the generation of a radical cation and of radical anions at the various steps of electron transfer. In the reaction centers, specialized pigment molecules and redox components act as primary electron donors and electron acceptors. They are embedded in the protein matrix and provided with very specific interactions that seem to be responsible for the spectral and redox properties of the pigments as well as for the efficiency and specificity of electron transfer. 

Huang C-Y, Su YO (2010) Spectral and redox properties of zinc porph5nin core dendrimers with triarylamines as dendron. Dalton Trans 39(35) 8306-8312... 

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