Molecular mechanics calculations on cobalt phthalocyanine dimers

In order to obtain insight into the structure of cobalt phthalocyanine dimers, molecular mechanics calculations were performed on dimeric cobalt phthalocyanine species. Molecular mechanics calculations are first presented on monomeric cobalt(II) phthalocyanine. Using the Tripos force field for the organic part of the molecule and parameters derived from the literature and subsequently optimized to describe the CoII force field resulted in a geometry that is in very good agreement with experimental data from the literature. Optimization of the dimeric structure leads to a geometry in which both phthalocyanines are separated by 3.2 Å and one of the molecules is shifted 2.38 Å in both the X- and Y-directions with respect to the other. This geometry is in excellent agreement with literature data on ß-Co(pc) crystals and with other calculated and experimental data on similar systems. All calculations were performed with three possible charge distributions in the phthalocyanine molecule and it was shown that varying the charge distribution had no significant effect on the final dimeric structure. This method provides valuable insight into the most important energetic interactions leading to dimer formation

Role of polycation promoters in the cobalt phthalocyanine-catalyzed autoxidation of thiols

The promotion effect of 2,4-ionene on the cobalt phthalocyanine-catalyzed autoxidn. of thiols was studie

Preparation and co-catalytic properties of amphiphilic diblock copolymers consisting of polystyrene and ionene

Contains fulltext : 17073.pdf (publisher's version ) (Open Access

Synthesis of amphiphilic polystyrene-ionene diblock copolymers with controlled block lengths

Contains fulltext : 17074.pdf (publisher's version ) (Open Access

Influence of the molecular weight of ionenes on the cobaltphthalocyanine-catalysed autoxidation of mercaptoethanol

In order to study the promoting effect of polycations on the cobalt(II)phthalocyanine-tetrasodiumsulfonate [CoPc(NaSO3)4]-catalyzed autoxidn. of thiols, it is imperative to know the mol. wt. dependence of the polymer. Monodisperse oligomers can often supply a lot of information. To elucidate the mechanism of the promoting effect of 2,4-ionene, a poly(quaternary ammonium)salt, on the CoPc(NaSO3)4-catalyzed autoxidn. of 2-mercaptoethanol, a series of monodisperse 2,4-ionene oligomers were prepd. Trimeric 2,4-ionenes, contg. two quaternary ammonium groups sepd. by four methylene groups, showed a high co-catalytic activity, and active Co-aggregates were detected with visible light spectroscopy. The spectroscopic behavior was in close agreement with that of high mol. 2,4-ionene/CoPc(NaSO3)4 complexes. In order to achieve this aggregation several oligomeric ionenes have to act concertedly. If the distance between the ionic sites is short, the trimer acts as a simple salt in stabilizing the aggregates. With respect to the catalytic activity the optimum polycation/catalyst ratio, expressed as the N+/Co ratio, decreased with increasing chain length and reached a const. level of 50 at a 2,4-ionene nonamer. For the trimers and pentamer this ratio is affected by the type of end-group. All synthesized 2,4-ionene oligomers exhibited excellent co-catalytic properties at the optimum N+/Co ratio, with max. turnover frequencies of 4600 mol thiol/(mol Co s), i.e. 50 times higher than those obtained for the polymer-free system. In the case of monodisperse 2,4-ionene pentamer with bromo end-groups, double Michaelis-Menten kinetics were obsd., as also was exhibited by high mol. wt. ionen

Influence of molecular weight of ionenes on the cobalt phthalocyanine-catalyzed oxidation of 1-dodecanethiol

The cocatalytic properties of monodisperse 2,4-ionene oligomers were tested in the cobalt(II) phthalocaninetetrakis(sodium sulfonate) (CoPc(NaSO3)(4))-catalyzed autoxidation of 1-dodecanethiol. A tremendous rate increase in the dodecanethiol oxidation by a factor of 100, as compared with the polymer-free system, was observed for monodisperse ionene oligomers, with four quaternary ammonium groups and with 4-bromobutyl end groups. By contrast, the same oligomers terminated with the more hydrophilic dimethylamino end groups showed no enhancement in the catalytic activity. These differences can be ascribed to very effective interactions between the hydrophobic 4-bromobutyl end groups with the hydrophobic thiol, resulting in an enormous increase of the thiol-water interface, due to a decrease in dodecanethiol droplet size. The effects of the end groups decrease with increasing number of N+. 2,4-Ionenes with at least eight quaternary ammonium groups showed similar cocatalytic properties as the high molecular weight 2,4-ionenes. Moreover, the effect of end-capping of polymeric 2,4- and 3,3-ionenes even with long n-alkyl bromides is limited

Effects of complexation of oppositely charged water-soluble cobaltphthalocyanines on catalytic mercaptoethanol autoxidation

In order to elucidate the different promoting effects polycations have on cobalt(II) phthalocyanine-catalyzed autoxidn. of 2-mercaptoethanol, the properties of mixts. of oppositely charged water-sol. cobalt(II) phthalocyanines were studied. The contribution of polycation-induced dimerization of the catalyst was investigated with combinations of cobalt(II) phthalocyanine-tetrakis(trimethylammonium) iodide (CoPc[N(CH3)3I]4) and cobalt(II) phthalocyanine-tetrasodium sulfonate [CoPc(NaSO3)4]. A mixt. of equimolar amts. of both phthalocyanines shows an increase in reaction rate for 2-mercaptoethanol autoxidn. as compared with an equal amt. of one of the catalyst species sep. The highest activities are achieved when the pos. charges of the pos. phthalocyanine just match the charges of the neg. CoPc(NaSO3)4. A mixt. of cobalt(II) phthalocyanineoctacarboxylic acid (CoPc(COOH)8) and CoPc[N(CH3)3I]4 exhibits its max. activity at a ratio of 1:2, indicating the formation of a trimeric catalyst species. Visible light spectroscopy showed that these effects can be ascribed to the formation of aggregates of the phthalocyanines. Addn. of a poly(quaternary ammonium) salt, a so-called ionene, to a stoichiometric complex of oppositely charged phthalocyanines results in an increase in the catalytic activity due to substrate enrichment. The activities of an ionene-contg. equimolar CoPc[N(CH3)3I]4/CoPc(NaSO3)4 system were never as high as those achieved for a conventional CoPc(NaSO3)4/2,4-ionene system, probably as a result of the strong bonding between the two oppositely charged mols., which prevents a break-up of the dimeric species. In order to achieve a high catalytic activity, one should enhance the formation of aggregates of CoPc(NaSO3)4, which probably will break up after the first reaction ste