Understanding the Effect of Metal Centers on Charge Transport and Delocalization in Conducting Metallopolymers

Abstract

A series of conducting polymers, formed from an electropolymerizable Schiff-base ligand, N,N ′-((2,2′-dimethyl)­propyl)­bis­(2-thiophenyl)­salcylidenimine, and the corresponding metal complexes (i.e., Ni­(II), Cu­(II), V­(IV)O, Co­(II), and Zn­(II)) have been prepared, characterized, and studied in detail. Our successful synthesis of the ligand polymer helps to make a direct comparison between the properties of metal-free conducting polymers and the corresponding metallopolymers. This enables the role of metal centers in these Schiff-base conducting metallopolymers (CMPs) in particular, and in Wolf type III CMPs in general, to be unambiguously elucidated. Vis–NIR absorption spectroelectrochemical studies show that longer distances for charge delocalization were found in the CMPs when compared to the metal-free counterpart, an indication of the contribution of the metal centers in extending the effective conjugation length of these electroactive polymers. The systematic use of both redox-active and redox-inactive first row transition metals helps to better understand the nature of charge transport and the specific role of the metal centers in these systems. Cyclic voltammetry and in situ conductivity show superior charge transport in the CMPs compared to the ligand polymer, especially in systems containing redox-active metal centers with redox potentials higher than, but similar to, that of the conjugated organic backbone. Our results indicate that inner-sphere charge transport within the organic backbone, which is serving as a hopping station, is the dominant mechanism of conductivity enhancement and favorable for efficient charge transport in Schiff-base CMPs.

Analysis of Conjugated Polymers Conductivity by in situ Electrochemical‐Conductance Method

“…In recent years using this technique, different polymer films derived from polyfurans, PTh, PPy, PANI, polyalcoxythiophenes to organometallics polymers, dendrimer structures and conjugated radical polymers, have been examined. [81,[92][93][94][95][96][97][98][99][100][101][102][103][104][105][106][107][108][109][110] Conductance behavior, charge/discharge process, n-doping and charge trapping are the most common phenomena studied. Commonly these studies have been carried out using low scan rate values (v � 10 mV s À 1 ) in order to obtain reliable data, because some structural changes during the charge/discharge process are slow and using higher scan rates unreproducible data could be obtained.…”

“…In recent years using this technique, different polymer films derived from polyfurans, PTh, PPy, PANI, polyalcoxythiophenes to organometallics polymers, dendrimer structures and conjugated radical polymers, have been examined . Conductance behavior, charge/discharge process, n ‐doping and charge trapping are the most common phenomena studied.…”

Molybdenum Carbonyl Complexes with a Polymerizable Phosphorus/Nitrogen/Phosphorus Ligand and Corresponding Conducting Metallopolymers

“…The conjugated polymers with redox‐active ligand sites have been investigated to control the reactivity and binding of transition metal complexes . The conjugated polymer matrix has a large number of available oxidation states.…”

“…[24][25][26] The conjugated polymers with redox-active ligand sites have been investigated to control the reactivity and binding of transition metal complexes. [27][28][29] The conjugated polymer matrix has a large number of available oxidation states. This wide Molybdenum-containing hybrid and coordination polymers have been reported for a variety of applications.…”

Metal-containing polymers bearing pendant nickel(ii) complexes of Goedken's macrocycle

“…[7][8][9][10][11][12][13][14][15][16][17][18] These polymers have shown utility, for example, as the functional component of redox-active capsules, 19 as antimicrobial surfaces, 20 and as precursors to nanostructured materials. [21][22][23] Nickel-containing polymers (e.g., 47) [24][25][26][27][28] remain relatively scarce throughout the literature when compared to polymers based on first row metals such as iron and cobalt. There are two primary reasons behind this scarcity.…”