Redox-Responsive Colloidal Particles Based on Coordination Polymers Incorporating Viologen Units

Abstract

Colloidal particles based on supramolecular polymers are emerging as promising functional materials because of their intrinsic dynamic features and the possibility of stimuli responsivity. In this work, ≈200 nm self-assembled redoxresponsive colloidal particles made of 1D-coordination polymers were readily prepared. In these metallopolymers, organic entities made of bis(viologen) groups covalently associated with terpyridine units are spontaneously bridged by Zn 2+ cations through the formation of coordination bonds. The properties of these particles were analyzed and their redox activities investigated. Upon reduction of the viologen units, the formation of π-dimers between the reduced viologen moieties was demonstrated by spectroscopic experiments. It was shown that intermolecular π-dimers (i.e., between different polymer chains) that do not exist in homogeneous polymer solutions were, nevertheless, formed in the particle's structure because of the effects of confinement. The presence of these π-dimers allows stabilization of the charge in the colloids.

Light-controlled aggregation and gelation of viologen-based coordination polymers

“…As mentioned in a recent report, the formation of inter-chain dimers (5 in Fig. 1) in the gel phase can also not be ruled out [36]. Following these initial findings, we have carried out detailed microscopy and rheological investigations to provide further insights into the gelation mechanism.…”

Light-Controlled Aggregation and Gelation of Viologen-Based Coordination Polymers

“…At this stage, the exact structure of the π-dimerized structure(s) still remains hypothetical, but all available data suggest the formation of either box-shaped discreet complexes ( 3 in Figure ) or of accordion-shaped folded polymers ( 4 in Figure ). As mentioned in a recent report, the formation of inter-chain dimers ( 5 in Figure ) in the gel phase can also not be ruled out . Following these initial findings, we have carried out detailed microscopy and rheological investigations to provide further insights into the gelation mechanism.…”

“…As mentioned in a recent report, the formation of inter-chain dimers (5 in Figure 1) in the gel phase can also not be ruled out. 36 Following these initial findings, we have carried out detailed microscopy and rheological investigations to provide further insights into the gelation mechanism.…”

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“…On the other hand, the absorption spectrum of mixture of 0.5 mM CuA-Cl with 2eq V2 2+ .2PF6revealed a new band at 382 nm and a blue shift for the d-d transition from 816 nm to 611 nm. These observations are attributed to the formation of πdimer among two viologen radicals that latter occurred after reduction by two electrons of V2 2+ .2PF6 -within the structure of the adducts [38,39].…”