Mixed-ligand copper© polymer

Luminescent coordination compounds continue to attract considerable attention. Zink recently reported a new mixed-ligand copper(I) polymer that shows interesting photoluminescence (232). The complex [CuCl(L44)Ph3P] consists of a one-dimensional chain lattice of metal ions bridged by both Cl" ions and pyrazine molecules. The compound shows conductivity of less than 10-8 S cm 1. The absorption spectrum of the complex shows a band at 495 nm, which could be interpreted as the promotion of an electron from the valence band to the conduction band. On the basis of resonance Raman spectra, the lowest excited state in the polymer is assigned to the Cu(I)-to-pyrazine metal-to-ligand charge-transfer excited state. 

This category of polymers is interesting because of the possible structural diversity for such materials and the mixed-Ugand nature of the excited state. As for the structures, both the diphosphines and diisocyanides can act as assembling ligands for the metal. The mixed-nature of the excited state in the poly-chromophore is easy to predict from EHMO calculations on the luminescent mixed-ligand di-copper and disilver models such as 34-37 [42,43], which can serve as useful polymer models for polymer (38) [44], In complex 34, the atomic contributions for the HOMO are mainly the P-lone pairs and Cu d-orbitals, whereas for the LUMO, these were the CO ... 

When G2-OH is mixed with a fourfold molar excess of Cu + ions the spectrum in Fig. 9b results. These data indicate that each G2-OH can sorb at least four Cu + ions. Moreover, the separation between adjacent copper adducts is 62.5, which indicates that the oxidation state of Cu inside dendrimer during the MALDI-MS experiments is -1-1. Reflectron-mode MS also confirms this assignment the mass differences between the monoisotopic peaks of protonated dendrimers, singlecopper adducts, and double-copper adducts are 61.96 and 61.93, respectively, which is consistent with the assignment of the adduct ions as [Mis + Cu(l)]+ and [Mis + 2Cu(I)-H] +. We speculate that the presence of Cu+ is a consequence of the photochemical reduction of Cu + during ionization. Such photoreduction in MALDI MS measurements has been observed previously when polymers or peptides are used as ligands for Cu + [117,118]. 

Interesting results have been obtained in studies of the catalytic activity for oxidation by phthalocyanine polymers, containing different metal ions in the same molecule 87-90>. If Fe was mixed with a series of other transition metal ions, differences in activity were found to be dependent on the metal ion, and correlations between the catalytic activity and the thermal activation energy of semiconductivity were found. With copper as the second metal ion, maximum activities were found at a ratio Fe/Cu = 1. Many other chelate polymers have been tested for their oxidation activity, and a dependence of the catalytic activity on the donor properties of the ligand was found 91>92). 

Thus the catalytic activity of amine complexes of copper (II) reaches a maximum after full replacement of Cl -bridged ligands by OH -bridged ones (Fig. 12). However, for copper complexes of polyamidoamines, the maximum of the rate of DMP oxidation has been achieved at a NaOH/Cu ratio of 0.5 instead of 1 as is the case for other polymer ligands [128]. The authors attribute this to the fact that mixed complexes of PAA-Cu(OH)Cl Cu-PAA-type behave as catalyticcdly active species. 

Problem 11,6 Styrene (St) was polymerized by ATRP using a copper(I) bromide (CuBr) catalyst, com-plexed with A, A, A, A, iV"-pentamethyldiethylenetriamine (PMDETA) ligand, and methyl 2-bromopropion-ate (MBrP) as initiator. Experiments were performed in 1 E mixed vessel at 110°C with excellent temperature control using a monomer to solvent (toluene) ratio of 70 30 wt% and molar ratios of 50 1 1 1 for St/MBrP/CuBr/PMDETA. Under these reaction conditions, only a portion of the catalyst species was soluble and 90% monomer conversion was obtained in 6 h. Calculate a theoretical molecular weight (MW) of the polymer obtained. How would you explain if the experimental MW is found to be higher than the theoretical... 

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