Complex indicator

When equal amounts of solutions of poly(ethylene oxide) and poly(acryhc acid) ate mixed, a precipitate, which appears to be an association product of the two polymers, forms immediately. This association reaction is influenced by hydrogen-ion concentration. Below ca pH 4, the complex precipitates from solution. Above ca pH 12, precipitation also occurs, but probably only poly(ethylene oxide) precipitates. If solution viscosity is used as an indication of the degree of association, it appears that association becomes mote pronounced as the pH is reduced toward a lower limit of about four. The highest yield of insoluble complex usually occurs at an equimolar ratio of ether and carboxyl groups. Studies of the poly(ethylene oxide)—poly(methacryhc acid) complexes indicate a stoichiometric ratio of three monomeric units of ethylene oxide for each methacrylic acid unit. 

Similarity with cobalt is also apparent in the affinity of Rh and iH for ammonia and amines. The kinetic inertness of the ammines of Rh has led to the use of several of them in studies of the trans effect (p. 1163) in octahedral complexes, while the ammines of Ir are so stable as to withstand boiling in aqueous alkali. Stable complexes such as [M(C204)3], [M(acac)3] and [M(CN)5] are formed by all three metals. Force constants obtained from the infrared spectra of the hexacyano complexes indicate that the M--C bond strength increases in the order Co < Rh < [r. Like cobalt, rhodium too forms bridged superoxides such as the blue, paramagnetic, fCl(py)4Rh-02-Rh(py)4Cll produced by aerial oxidation of aqueous ethanolic solutions of RhCL and pyridine.In fact it seems likely that many of the species produced by oxidation of aqueous solutions of Rh and presumed to contain the metal in higher oxidation states, are actually superoxides of Rh . ... 

A number of quinoxalines carrying substituents in the benzene ring base have been quaternized, including 5-ethoxy,6-methyl, 6-chloro, and some 2-phenyl derivatives, but in none of these cases has the position of quatemization been ascertained. 5-Hydroxy-quinoxaline gives a methiodide which can still form metal complexes, indicating that salt formation occurred on N-1. ... 

Figure 1 shows the pH-rate profiles of some active complexes. Both Ni2 + and Zn2 + ion complexes of 8 afford saturation curves with inflection at around pH s 6 and 8, respectively, which represent, most likely, the ionization of the hydroxyl group complexed with a Ni2+ or a Zn2+ ion. The pKa = 8.6 was assigned for the ionization of the hydroxyl group of the latter complex 12). The lower pH for the ionization of the Ni2+ ion complex in respect to that of the Zn2+ ion complex indicates that the ligand 8 coordinates to Ni2+ ion more tightly than to Zn2+ ion, which is in conformity with a larger K value (1120 M) for the Ni2 + ion than for the Zn2 + ion complex (559 M) at pH 7.05 (Table 2). 

In a regime of strong interaction between the chains no optical coupling between the ground slate and the lowest excited state occurs. The absence of coupling, however, has a different origin. Indeed, below 7 A, the LCAO coefficients start to delocalize over the two chains and the wavefunclions become entirely symmetric below 5 A due to an efficient exchange of electrons between the chains. This delocalization of the wavcfunclion is not taken into account in the molecular exciton model, which therefore becomes unreliable at short chain separations. Analysis of the one-electron structure of the complexes indicates that the... 

Bis complexes of pyrrole-A -carbodithiolate (L) with Pt(II), Pd(II), and Co(II), as well as Cu(II), have been reported. A mixed chlorine-ligand complex of Pt(IV), [PtCl2L2], was also prepared. Infrared spectra of these complexes indicated an exocyclic single C-N bond, as opposed to similar complexes containing other dithiocarbamate ligands (407). 

Fig. 9. The structure of the Rieske fragment from bovine heart bc complex, indicating positions where deficient mutations have been selected in yeast (see text).

Mossbauer spectroscopy of AvF clearly demonstrated the presence of P clusters (174). The EPR spectra of dithionite-reduced VFe proteins are complex, indicating the presence of several paramagnetic species. Avl exhibits broad EPR signals, with g values of 5.8 and 5.4 integrating to 0.9 spins per V atom, which have been assigned to transitions from the ground and first excited state of a spin S = system (175). EPR data for AcF are more complex, with g values at 5.6, 4.3, and 3.77 that appear to arise from a mixture of S = species (176). The signals were associated with a midpoint potential of... 

CTien contraction of muscle is stimulated (via events involving Ca +, troponin, tropomyosin, and actin, which are described below), actin becomes accessible and the S-1 head of myosin finds it, binds it, and forms the actin-myosin-ADP-P complex indicated. 

The rate sequence is determined by the entropy term and correlates with the oxidation potential of the chelate complex, indicating an outer-sphere electron transfer. 

Bertz, S.H. (2003) Complexity of Synthetic Reactions. The Use of Complexity Indices to Evaluate Reactions, Transforms and Disconnections. New Journal of Chemistry, 27, 860-869. 

The cyclophosphazene ring assumes a highly puckered conformation in both the zinc and aluminum complexes, indicating its remarkable flexibility to adapt to the coordination requirement of the metals. 

The redox properties of complexes with hexaaza monocyclic ligands (e.g., (568)-(570)) are similar to those of the cyclam complex, indicating that the electrochemical properties of the complexes are only slightly affected by the presence of uncoordinated tertiary nitrogen atoms,... 

In total the analysis of protein complexes indicates that methionine is the most likely group to bind to [PtCU]2 and [PtenClfc] probably by a displacement reaction. However a specific attachment to another residue such as histidine or sulphydryl can not be ruled out. Furthermore the antitumour activity is that of cis- [Pt (NH 3) 2CI2] and the di-functional character of this reagent has not been revealed so far by the above studies. In fact no attempt has been made to uncover the difference between [PtCl2(NH3)2] in its cis and fraMS-forms. 

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