Electroactive Metal Complexes Covalently Attached to Conductive PEDOT Films: A Spectroelectrochemical Study

Abstract

The successful covalent attachment, via copper­(I)-catalyzed azide alkyne cycloaddition (CuAAC), of alkyne-functionalized nickel­(II) and copper­(II) macrocyclic complexes onto azide (N3)-functionalized poly­(3,4-ethylenedioxythiophene) (PEDOT) films on ITO-coated glass electrodes is reported. To investigate the surface attachment of the selected metal complexes, which are analogues of the cobalt-based complex previously reported to be a molecular catalyst for hydrogen evolution, first, three different PEDOT films were formed by electropolymerization of pure PEDOT or pure N3-PEDOT, and last, 1:2N3-PEDOT:PEDOT were formed by co-polymerizing a 1:4 mixture of N3-EDOT:EDOT monomers. The successful surface immobilization of the complexes on the latter two azide-functionalized films, by CuAAC, was confirmed by X-ray photoelectron spectroscopy (XPS) and electrochemistry as well as by UV–vis–NIR and resonance Raman spectroelectrochemistry. The ratio between the N3 groups, and hence, the number of surface-attached metal complexes after CuAAC functionalization, in pristine N3-PEDOT versus 1:2N3-PEDOT:PEDOT is expected to be 3:1 and seen to be 2.86:1 with a calculated surface coverage of 3.28 ± 1.04 and 1.15 ± 0.09 nmol/cm2, respectively. The conversion, to the metal complex attached films, was lower for the N3-PEDOT films (Ni 74%, Cu 76%) than for the copolymer 1:2N3-PEDOT:PEDOT films (Ni 83%, Cu 91%) due to the former being more sterically congested. The Raman and UV–vis–NIR results were simulated using density functional theory (DFT) and time-dependent DFT (TD-DFT), respectively, and showed good agreement with the experimental data. Importantly, the spectroelectrochemical behavior of both anchored metal complexes is analogous to that of the free metal complexes in solution. This proves that PEDOT films are promising conducting scaffolds for the covalent immobilization of metal complexes, as the existing electrochromic features of the complexes are preserved on immobilization, which is important for applications in electrocatalytic proton and carbon dioxide reduction, optoelectronics, and sensing.

Light-Responsive Conductive Surface Coatings on the Basis of Azidomethyl-PEDOT Electropolymer Films

“…The electropolymerization of EDOT-N 3 was carried out either by continuous cyclic voltammetry or chronoamperometrically at 1.50 V versus Ag|AgCl (sat.). The shape of the recorded cyclic voltammogram for EDOT-N 3 electropolymerization is similar to that reported previously (Figure a). After finishing the polymerization, the resulting polymer films were kept at 0.00 V versus Ag|AgCl (sat.)…”

“…To address the reactivity behavior of similar substrates with active azide groups of lower surface density toward the modification with AAP-alkyne , the application of co-polymers of EDOT and EDOT-N 3 was investigated. Regardless of a slightly lower oxidation potential of unsubstituted EDOT , EDOT-N 3 incorporates more readily into the copolymer films due to its higher electropolymerization rate . As a result, the relative difference between absorbance values correlates well with the azide group content in the starting monomer solution used for electropolymerization (Figure c).…”

Spectroelectrochemistry of Electroactive Polymer Composite Materials

“…The electrochromic characteristics of a number of composites of PEDOT with different carbon materials were compared [ 23 ]. The successful covalent attachment, via copper(I)-catalyzed azide-alkyne cycloaddition, of alkyne-functionalized nickel(II) and copper(II) macrocyclic complexes onto azide (N3)-functionalized PEDOT films was reported by Rodriguez-Jimenez et al [ 132 ]. The spectroelectrochemical studies revealed that nickel-containing films demonstrated more pronounced bipolaron absorption then PEDOT films with Cu.…”

Mono-copper far more active than analogous di-copper complex for electrocatalytic hydrogen evolution

“…1), 18 was shown to have a reversible redox process at −1.39 V versus 0.01 M AgNO 3 /Ag, in dry MeCN with 0.10 M Bu 4 NPF 6 , and to have high and long lived electrocatalytic HER activity in the presence of 80 equivalents of acetic acid as the proton source ( E applied = −1.60 V for 6 hours gave TON = 12.5, but activity remained high so this is an underestimate of the true TON). 19,20…”