The field of organic electronics has been heavily impacted by the discovery and development of π-conjugated conducting polymers. These polymers show great potential for integration into future optical and electronic devices due to their capacity to transition between semiconducting and conducting states as well as the ability to alter mechanical properties by controlled doping, chemical modification, and stacking or creating composites with other materials. Among π-conjugated polymers, polythiophene and its derivatives has been one of the most extensively studied and is widely investigated computationally and experimentally for use in electronic devices such as light-emitting diodes, water purification devices, hydrogen storage, and biosensors. Various theoretical modeling studies of polythiophene ranging from an oligothiophene approach to infinite chain lengths (periodic boundary conditions) have been undertaken to study a variety of electronic and structural properties of these polymers. In this review, we discuss the recent advances in the understanding of pristine polythiophene and its derivatives from fundamental perspectives to device applications.

Integration of bipolar membranes (BPMs) into electrochemical cells is an established method for acid and base generation, as well as desalinization methods. More recently, BPMs have been recognized for their ability to control the environment of half-reactions, including the maintenance of a pH gradient, without significant loss in efficiency. Over the past few years, significant advances have been made in BPM design, resulting in rapid deployment of BPMs into a wide range of applications, from mineral extraction, to energy storage and conversion frameworks, to ionotronics. Here, we explore the fundamentals of BPM operation and recent methods that have improved the performance and stability of BPMs and provide an overview of the limitations inherent to current BPM-based technologies, with a focus on future directions. Finally, we highlight research areas where BPM integration has enhanced, or is essential for, device operation, showing the versatility, potential, and broad range of research areas impacted by BPMs.

Dihydropyridines (DHPs) have been postulated as active intermediates in the pyridine-mediated electrochemical conversion of CO2 to methanol, however the ability of isolated DHPs to facilitate methanol production in a similar fashion to their parent aromatic N-heterocycles (ANHs) has not been tested. Here, we use bulk electrolysis to show that 1,2-and 1,4-DHPs (1,2-dihydrophenanthridine and 9,10dihydroacridine) can mediate the sub-stoichiometric electrochemical reduction of CO2 to methanol and formate with similar Faradaic efficiencies as the corresponding ANHs at Pt electrodes. 1,2-dihydrophenanthridine furthermore exhibits improved CO2 reduction activity compared to its parent ANH (phenanthridine) at glassy carbon electrodes. These results provide the first experimental evidence for the participation of DHPs as additives in electrochemical CO2 reduction. TOC GRAPHIC Pt or Glassy CarbonCO 2 HCOO -CH 3 OH (DHP) pH ~ 5 E app

Proligands based on bis(8-quinolinyl)amine (L1) were prepared containing one (L2) and two (L3) benzo-fused N-heterocyclic phenanthridinyl (3,4-benzoquinolinyl) units. Taken as a series, L1-L3 provides a ligand template for exploring systematic π-extension in the context of tridentate pincer-like amido complexes of group 10 metals (1-M, 2-M, and 3-M; M = Ni, Pd, Pt). Inclusion of phenanthridinyl units was enabled by development of a cross-coupling/condensation route to 6-unsubstituted, 4-substituted phenanthridines (4-Br, 4-NO, 4-NH) suitable for elaboration into the target ligand frameworks. Complexes 1-M, 2-M, and 3-M are redox-active; electrochemistry and UV-vis absorption spectroscopy were used to investigate the impact of π-extension on the electronic properties of the metal complexes. Unlike what is typically observed for benzannulated ligand-metal complexes, extending the π-system in metal complexes 1-M to 2-M to 3-M led to only a moderate red shift in the relative highest occupied molecular orbital (HOMO)-lowest unoccupied molecular orbital (LUMO) gap as estimated by electrochemistry and similarly subtle changes to the onset of the lowest-energy absorption observed by UV-vis spectroscopy. Time-dependent density functional theory calculations revealed that benzannulation significantly impacts the atomic contributions to the LUMO and LUMO+1 orbitals, altering the orbital contributions to the lowest-energy transition but leaving the energy of this transition essentially unchanged.

A synthetic route to 4-bromophenanthridine has been devised, enabling the construction of (4-diphenylphosphino)phenanthridine (1), a heterobifunctional Lewis base containing both phosphine and phenanthridine donors. The coordination chemistry of 1 with ions of late first-row transition metals nickel, copper and zinc has been explored, leading to the isolation and characterization of an organometallic Ni(II) complex, chloro(1-naphthyl)[(4diphenylphosphino)phenanthridine]nickel (2), a halide-bridged copper(I) complex, bromo[(4-diphenylphosphino)phenanthridine]copper dimer (3), and a Zn(II) complex, bis(chloro) [(4-diphenylphosphino)phenanthridine]zinc (4). The solid-state structures of 2-4 demonstrate the ability of 1 to support both square planar and tetrahedral geometries. Electrochemical and luminescence studies revealed both metal and ligand-based redox activity and emissive properties.

Diiminepyridines are a well-known class of "non-innocent" ligands that confer additional redox activity to coordination complexes beyond metal-centred oxidation/reduction. Here, we demonstrate that metal coordination complexes (MCCs) of diiminepyridine (DIP) ligands with iron are suitable anolytes for redox-flow battery applications, with enhanced capacitance and stability compared with bipyridine analogs, and access to storage of up to 1.6 electron equivalents. Substitution of the ligand is shown to be a key factor in the cycling stability and performance of MCCs based on DIP ligands, opening the door to further optimization.

Vapor-fed electrolysis of water has been performed using membrane-electrode assemblies (MEAs) incorporating earth-abundant catalysts and bipolar membranes (BPMs).

The electrochemistry of pyridines in acidic solution is dominated by a 'weak acid' reduction on the cyclic voltammetry timescale. Here we show that electrochemical hydrogenation of a benzannulated pyridine, phenanthridine (1), to the biomimetic hydride donor 1,2-dihydrophenanthridine (1-H2) can occur selectively at glassy carbon electrodes over longer timescales of potentiostatic electrolysis.