Monomer complexes

Expressions for predicting monomer sequence distribution with higher order models and for monomer complex and other models have also been proposed. 

The formation of monomer and dimer of (salen)Co AIX3 complex can be confirmed by Al NMR. Monomer complex la show Al NMR chemical shift on 5=43.1 ppm line width =30.2 Hz and dimer complex lb 5=37.7 ppm line width =12.7 Hz. Further instrumental evidence may be viewed by UV-Vis spectrophotometer. The new synthesized complex showed absorption band at 370 nm. The characteristic absorption band of the precatalyst Co(salen) at 420 nm disappeared (Figure 1). It has long been known that oxygen atoms of the metal complexes of the SchifT bases are able to coordinate to the transition and group 13 metals to form bi- and trinuclear complex [9]. On these proofs the possible structure is shown in Scheme 1. 

CXCL4 CTAP-III 1F9P X-ray (1.93A) Monomer Complex with heparin analogue... 

Komiyama at al. have prepared two oligonuclear Zn(II) complexes (22 and 23) and tested their hydrolytic activity toward different diribonucleotides [45,46] (catalytic turnover was not demonstrated). The dimer and trimer structures of the active species were confirmed by measuring the hydrolytic activity as a function of Zn/L ratio, which show sharp maxima at the expected 2/1 and 3/1 ratios, respectively. The oligomer complexes have high ribonuclease activity (e.g. the hydrolysis of UpU is accelerated more than 4 and 5 orders of magnitude by 22 and 23, respectively), whereas the effect of the monomer complex 24 was not... 

Komiyama et al. have described [65] enhanced hydrolysis of ApA by La(III) ion in presence of the tetrapyridine ligand 44. The complexation was followed by H NMR spectroscopy. Besides a 1/1 (La(DI)/L) complex, a 2/1 species is formed in the presence of excess metal. Both the 1/1 and 2/1 complexes are efficient promotors of ApA cleavage the monomer complex being ca. 7, the dimer ca. 70-fold more reactive than the metal ion alone under the same conditions (pH = 7.2, T = 323 K). 

Notes ak (dimer)/fcobs (monomer) where "dimer" is the dinuclear complex and monomer is a related monomer complex. bSeveral substrates were measured. cThe effect of monomer complex is too small to be detected. dlmportant regioselectivity was detected. eSelf-hydrolysis. 

The kinetic models for these reactions postulate fast complex-formation equilibria between the HA- form of ascorbic acid and the catalysts. The noted difference in the rate laws was rationalized by considering that some of the coordination sites remain unoccupied in the [Ru(HA)C12] complex. Thus, 02 can form a p-peroxo bridge between two monomer complexes [C12(HA)Ru-0-0-Ru(HA)C12]. The rate determining step is probably the decomposition of this species in an overall four-electron transfer process into A and H202. Again, this model does not postulate any change in the formal oxidation state of the catalyst during the reaction. 

The results presented here seem to indicate that 1) the local order about ruthenium centers in the polymers is essentially unchanged from that in the monomer complex and 2) that the interaction with the electrode surface occurs without appreciable electronic and structural change. This spectroscopic information corroborates previous electrochemical results which showed that redox properties (e.g. as measured by formal potentials) of dissolved species could be transferred from solution to the electrode surface by electrodepositions as polymer films on the electrode. Furthermore, it is apparent that the initiation of polymerization at these surfaces (i.e. growth of up to one monolayer of polymer) involves no gross structural change. 

In coordination polymerisation, the catalyst-monomer complex forms a heterogeneous system in which the metal ion is in the solid phase and the carbanion of the alkyl group is in the solvent phase. The monomer is inserted in between the metal ion and the carbanion and the Polymer chain formed is pushed out from the solid catalyst surface. Because of this coordination polymerisation is also known as insertion polymerisation. 

The present paper is an attempt to unravel a rather confused aspect of cationoid polymerisations. This concerns the phenomenon comprised in the term monomer complexation of the growing cation . The idea seems to have occurred for the first time in the work of Fontana and Kidder on the polymerisation of propene by AlBr3 and HBr in w-butane [3]. The kinetics indicated a reaction of zero order with respect to monomer, M to explain this, it was assumed that the growing end of the chain, written as a carbenium ion, Pn+, is complexed with M and that the rate-determining growth step is an isomerisation of this complex ... 

If we introduce the monomer-complexation by means of equation (1) and write the new charge and mass balances as... 

We now consider the polymerizations in bulk, i.e., without a solvent, of hydrocarbon monomers by ionizing radiations in the light of the monomer complexing of cations which has been noted for polymerizations in solution. If in a solvent of low polarity this... 

According to Fontana s theory, the rate-determining step in a polymerization involving a monomer-complexed cation is a unimolecular isomerization of the complex, which is kinetically of first order ... 

The monomer-complexing Equations (16) and (17) for unpaired ions [corresponding to... 

Monomer pool Equilibrating mixture of (monomer)-metal-(monomer) complexes... 

Chiral Self-Dimerization of V-Schiff-Base Monomer Complexes on Si02... 

Scheme 10.2 Chiral self-dimerization of V-Schiff-base monomer complexes on Si02. Two vanadium monomers are dimerized through two sets of hydrogen bonds between Ph-OH and COO.

The monomer complex participation (MCP) mechanism suggests that alternation results from homopolymerization of a 1 1 complex formed between donor and acceptor monomers [Cowie, 1989 Furukawa, 1986] ... 

Another model used to describe deviations from the terminal model involves the participation of a comonomer complex (Sec. 6-3b-3) [Cais et al., 1979 Coote and Davis, 2002 Coote et al., 1998 Seiner and Litt, 1971]. The comonomer complex competes with each of the individual monomers in propagation. The monomer complex participation model involves eight... 

A variation of the complex participation model, referred to as the monomer complex dissociation model, involves disruption of the complex during reaction with a propagating chain end [Hill et al., 1983 Karad and Schneider, 1978]. Reaction of the propagating center with... 

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