Layer-by-Layer Assemblies of Coordinative Surface-Confined Electroactive Multilayers: Zigzag vs Orthogonal Molecular Wires with Linear vs Molecular Sponge Type of Growth

Abstract

Surface-anchored coordination-based molecular assemblies (CBMA) are very powerful tools for the design of modern materials. The CBMAs were created using bis-terpyridine–iron coordination chemistry by the alternation of linear or bent bis-terpyridine ligands and Fe­(II) metal centers. The coordination of the bent ligand results in the formation of zigzag structures that experience linear growth with each successive deposition step. Interestingly, the deposition of the linear ligand has two distinct steps. During the first four deposition cycles, the thickness and iron uptake (surface coverage) of the multilayer change similarly to ones of the bent ligand based multilayer. However, during the following deposition cycles, the linear ligand based multilayer demonstrates significantly higher growth rate. This unusual behavior might be attributed with the reorganizational transformations leading to a higher organizational level of the assembly. As a result, a part of templating layer molecules, which due to sterical reasons cannot seed a molecular wire growth, and successfully formed molecular wires begin acting as by-holders or molecular sponges able to trap extra metal ions and provide these ions to the system during the next deposition step, thus speeding up the growth of the molecular wires. Indeed, incubation of linear assemblies in solutions of Zn­(II) or Cd­(II) demonstrates significant trapping abilities for the ions. During electrochemical cycling, both assemblies show high stability, fast response times, and sufficient coloration efficiencies that make them valuable building blocks for the design of novel electrochromic materials.

Rapidly sequence-controlled electrosynthesis of organometallic polymers

“…Electrosynthesis is rapid (1 min for each addition), and possibly independent of metal species and organic ligands of complexes, thus they provide significantly high controllability toward uniform synthesis, compared to well-known method based on coordination chemistry. To date, the iterative synthesis of organometallic polymers were mostly achieved by the metal coordination between almost Fe 2+ and terpyridine on solid substrate, which took up to 24 h for each addition of single monomer at room temperature [26][27][28] . Absorption laying at 505 nm is attributed to metal-to-ligand [Os II (dπ) to tpy(π*)] charge transfer (MLCT) transition, while the additional band at 680 nm seems to be owing to spin-forbidden MLCT transition from 1 [Os II (dπ) 6 ] to 3 [Os II (dπ) 5 tpy(π*) 1 ] 29 .…”

“…29). Usual chemical coordination for synthesis of organometallic wires [26][27][28] requires the high-quality solvents without external ions for synthesis and purification, and its controllability and reproducibility still remain stagnant and challenge in general metal and ligand species, and following coordination types for further sequence-controlled synthesis. Each addition of monomer for stepwise chemical coordination generally took very long time up to 24 h, which could cause the depolymerization and exchange of ligands and metal cores during the synthesis of organometallic polymers 34 .…”

Effect of Transition Metals on the Oxygen Reduction Reaction Activity at Metal‐N3/C Active Sites

“…V‐tpy‐Mn N1s spectrum (Figure S3B) displays a signal at 399.2 eV characteristic to the pyridinic nitrogen atoms in the metal‐tpy mono‐complexes [33,45,49] . Mn2p 1/2 and Mn2p 3/2 peaks were observed at 654.0 eV and 641.9 eV that is typical for Mn 2+ [50] .…”

“…[33] V-tpy-Mn N1s spectrum ( Figure S3B) displays a signal at 399.2 eV characteristic to the pyridinic nitrogen atoms in the metal-tpy mono-complexes. [33,45,49] Mn2p 1/2 and Mn2p 3/2 peaks were observed at 654.0 eV and 641.9 eV that is typical for Mn 2 + . [50] The atomic ratio of C : N : Mn is 95:0.79:0.24, this is close to the expected ratio of 3 : 1 of N:metal that would be expected for the mono-complex (1 : 1 metal-to-ligand stoichiometry).…”

Probing the Influence of Counter Electrode Structure on Electrochromic‐Device Operating Potentials and Performance Using Electrochemical Impedance Spectroscopy

“…Previously, it was demonstrated that 2,2':6',2''terpyridine (terpy) moiety can form stable complexes with a variety of metals in different oxidation states. [17][18] This moiety as a part of different ligands can be used to covalently anchor and grow electrochromic (EC) molecular wires on a flat surface [19][20] or to form EC coatings or separate nanosheets of metallo-supramolecular polymers. [21][22][23] Our group has developed ECDs that utilize just a monolayer of EC terpy-based metal complexes deposited on enhanced surface area conductive supports [24] to form the working electrode.…”