Evolution of Chain Dynamics and Oxidation States with Increasing Chain Length for a Donor–Acceptor-Conjugated Oligomer Series

The oxidation state of the transition metal (Mt) active centre is the most disputable question in the polymerization of olefins by Ziegler-Natta (ZN) and metallocene complexes. In this paper the importance and the changes of the Mt active centers are presented and discussed on the basis of a charge percolation mechanism (CPM) of olefin polymerization. Mt atoms can exist in different oxidation states and can be easily transformed from one to another state during activation. In all cases, the Mt atoms are present in several oxidation states, i.e., Mt+(n-1), Mt+(n) to Mt+(n+1), producing an irregular charge distribution over the support surface. There is a tendency to equalize the oxidation states by a charge transfer from Mt+(n-1) (donor) to Mt+(n+1) (acceptor). This cannot occur since the different oxidation states are highly separated on the support. However, monomer molecules are adsorbed on the support producing clusters with stacked ?-bonds, making a ?-bond bridge between a donor and an acceptor. Once a bridge is formed (percolation moment), charge transfer occurs. The donor and acceptor equalize their oxidation states simultaneously with the polymerization of the monomer. The polymer chain is desorbed from the support, freeing the surface for subsequent monomer adsorption. The whole process is repeated with the oxidation-reduction of other donor-acceptor ensembles.

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Interaction of manganese corroles with TCNQ and related acceptor molecules

Journal of Porphyrins and Phthalocyanines ◽

10.1142/s1088424619501359 ◽

2020 ◽

Vol 24 (05n07) ◽

pp. 705-711

Author(s):

Benedikt Wolfram ◽

Çağla Baş ◽

Christian Kleeberg ◽

Martin Bröring

Keyword(s):

Charge Transfer ◽

Single Crystals ◽

High Reactivity ◽

Geometric Parameters ◽

Oxidation States ◽

Stacking Interactions ◽

Oxygenated Compounds ◽

Axial Ligands ◽

Donor Acceptor ◽

New Compounds

Manganese corroles with the Mn atom in the oxidation states +III and +IV have been probed as donor moieties for supramolecular stacked donor–acceptor complexes with the typical acceptor units TCNQ (tetracyanoquinone), TCNP (tetracyanopyrazine), and TCNB (tetracyanobenzene). Four new compounds formed as single crystals from different co-crystallization attempts. In those cases where a Mn(III) corrole was used as the donor component, hydrolyzed and/or oxygenated compounds [(cor)Mn(TCNQ*)] and [(cor*)Mn(TCNP*)] were obtained as the exclusive products. With chloridomanganese(IV) corroles, sandwich-like 2:1 complexes [(cor)MnCl][Formula: see text][TCNQ] and [(cor)MnCl][Formula: see text][TCNB] form, with both components left intact. Crystallographic analyses reveal partial or complete charge transfer to unusual axial ligands and thus prove the high reactivity of Mn(III) corroles in the first two cases. For the sandwich arrangements, almost-unaltered geometric parameters of the Mn(IV) corroles are observed, pointing to negligible structural consequences for metal corroles when engaged in stacking interactions.

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