Thiazolothiazole-Based Luminescent Metal-Organic Frameworks with Ligand-to-Ligand Energy Transfer and Hg2+-Sensing Capabilities

Photoinduced electron and energy transfer through preorganized chromophore, donor, and acceptor arrays are key to light-harvesting capabilities of photosynthetic plants and bacteria. Mimicking the design principles of natural photosystems, we constructed a new luminescent pillared paddle wheel metal-organic framework (MOF), Zn₂(NDC)₂(DPTTZ), featuring naphthalene dicarboxylate (NDC) struts that served as antenna chromophores and energy donors and N,N'-di(4-pyridyl)thiazolo-[5,4-d]thiazole (DPTTZ) pillars as complementary energy acceptors and light emitters. Highly ordered arrangement and good overlap between the emission and absorption spectra of these two complementary energy donor and acceptor units enabled ligand-to-ligand Förster resonance energy transfer, allowing the MOF to display exclusively DPTTZ-centric blue emission (410 nm) regardless of the excitation of either chromophore at different wavelengths. In the presence of Hg²⁺, a toxic heavy metal ion, the photoluminescence (PL) of Zn₂(NDC)₂(DPTTZ) MOF underwent significant red-shift to 450 nm followed by quenching, whereas other transition metal ions (Mn²⁺, Fe²⁺, Co²⁺, Ni²⁺, Cu²⁺, and Cd²⁺) caused only fluorescence quenching but no shift. The free DPTTZ ligand also displayed similar, albeit less efficient, fluorescence changes, suggesting that the heavy atom effect and coordination of Hg²⁺ and other transition metal ions with the DPTTZ ligands were responsible for the fluorescence changes in the MOF. When exposed to a mixture of different metal ions, including Hg²⁺, the MOF still displayed the Hg²⁺-specific fluorescence signal, demonstrating that it could detect Hg²⁺ in the presence of other metal ions. The powder X-ray diffraction studies verified that the framework remained intact after being exposed to Hg²⁺ and other transition metal ions, and its original PL spectrum was restored upon washing. These studies demonstrated the light-harvesting and Hg²⁺ sensing capabilities of a new bichromophoric luminescent MOF featuring a seldom-used photoactive ligand, which will likely spark an explosion of TTZ-based MOFs for various optoelectronic applications in near future.

Ultrahigh Proton Conduction in Two Highly Stable Ferrocenyl Carboxylate Frameworks

Nowadays, although research of proton conductive materials has been extended from traditional sulfonated polymers to novel crystalline solid materials such as MOFs, COFs, and HOFs, research on crystalline ferrocene-based carboxylate materials is very limited. Herein, we selected two hydrogen-bonded and π-π interactions-supported ferrocenyl carboxylate frameworks (FCFs), [FcCO(CH₂)₂COOH] (FCF 1) and [FcCOOH] (FCF 2) (Fc = (η⁵-C₅H₅)Fe(η⁵-C₅H₄)) to fully investigate their water-mediated proton conduction. Their excellent thermal, water, and chemical stabilities were confirmed by the means of thermogravimetric analyses, PXRD, and SEM determinations. The two FCFs indicate temperature- and humidity-dependent proton conductive features. Intriguingly, their ultrahigh proton conductivities are 1.17 × 10^-1 and 1.01 × 10^-2 S/cm, respectively, under 100 °C and 98% RH, which not only are comparable to the commercial Nafion membranes but also rank among the highest performing MOFs, HOFs, and COFs ever described. On the basis of the structural analysis, calculated E_a value, H₂O vapor adsorption, PXRD, and SEM measurements, reasonable conduction mechanisms are highlighted. Our research provides a novel inspiration for finding new high proton conducting crystalline solid materials. Importantly, the outstanding conducting performance of 1 and 2 suggests their, hopefully, potential in fuel cells and related electrochemical fields.

A switchable iron-based coordination polymer toward reversible acetonitrile electro-optical readout

Efficient and low cost detection of harmful volatile organic compounds (VOCs) is a major health and environmental need in industrialized societies. For this, tailor-made porous coordination polymers are emerging as promising molecular sensing materials thanks to their responsivity to a wide variety of external stimuli and could be used to complement conventional sensors. Here, a non-porous crystalline 1D Fe(ii) coordination polymer acting as a porous acetonitrile host is presented. The desorption of interstitial acetonitrile is accompanied by magneto-structural transitions easily detectable in the optical and electronic properties of the material. This structural switch and therefore its (opto)electronic readout are reversible under exposure of the crystal to acetonitrile vapor. This simple and robust iron-based coordination polymer could be ideally suited for the construction of multifunctional sensor devices for volatile acetonitrile and potentially for other organic compounds.

Suspending Ion Electrocatalysts in Charged Metal-Organic Frameworks to Improve the Conductivity and Selectivity in Electroorganic Synthesis

Electroorganic synthesis is an environmentally friendly alternative to traditional synthetic methods; however, the application of this strategy is heavily hindered by low product selectivity. Metal-organic frameworks (MOFs) exhibit high selectivity in numerous catalytic reactions; however, poor conductivity heavily limits the application of MOFs in electroorganic synthesis. To realize the electrocatalytic application of MOFs in selective electroorganic synthesis, a practically applicable strategy by suspending ion electrocatalysts in charged MOFs is herein reported. This approach could markedly improve the product selectivity in electroorganic synthesis. In the electrocatalytic oxidative self-coupling of benzylamine experiments, the imine product selectivity is markedly improved from 61.3 to 94.9 %, when the MOF-based electrocatalyst is used instead of the corresponding homogeneous electrocatalyst under the identical conditions. Therefore, this work opens a new route to improve the product selectivity in electroorganic synthesis.

Prospects for electroactive and conducting framework materials

Electroactive and conducting framework materials, encompassing coordination polymers and metal-organic frameworks, have captured the imagination of the scientific community owing to their highly designable nanoporous structures and their potential applications in electrochromic devices, electrocatalysts, porous conductors, batteries and solar energy harvesting systems, among many others. While they are now considered integral members of the broader field of inorganic materials, it is timely to reflect upon their strengths and challenges compared with 'traditional' solid-state materials such as minerals, pigments and zeolites. Indeed, the latter have been known since ancient times and have been prized for centuries in fields as diverse as art, archaeology and industrial catalysis. This opinion piece considers a brief historical perspective of traditional electroactive and conducting inorganic materials, with a view towards very recent experimental progress and new directions for future progress in the burgeoning area of coordination polymers and metal-organic frameworks. Overall, this article bears testament to the rich history of electroactive solids and looks at the challenges inspiring a new generation of scientists. This article is part of the theme issue 'Mineralomimesis: natural and synthetic frameworks in science and technology'.

MX-type single chain complexes with an aromatic in-plane ligand: incorporation of aromatic interactions for stabilizing the chain structure

MX-type one-dimensional complexes [Pt^IV(amp)₂Br₂][Pt^II/IV(amp)₂Br]₂(HSO₄)₂(SO₄)₂·13H₂O (3) and [Pt^IV(amp)₂Br₂][Pt^II/IV(amp)₂Br]₂(H₂PO₄)₆·8H₂O (4) were synthesized as the first analogue containing only an aromatic in-plane ligand. The Pt-Br chain structures of 3 and 4 are stabilized by both the hydrogen-bond network along the chain and the π-stacking via intercalated Pt(iv) complexes. Structural and spectroscopic studies indicated that both 3 and 4 form the Pt(ii/iv) mixed valence state.

[Cu3(C6Se6)] n : The First Highly Conductive 2D π-d Conjugated Coordination Polymer Based on Benzenehexaselenolate

Nanocrystals of a 2D π-d conjugated copper bis(diselenolene) coordination polymer (Cu-BHS, BHS = benzenehexaselenolate) are synthesized via a simple homogeneous reaction between cupric ions and benzenehexaselenol (H6BHS). Its 2D extended hexagonal lattice is confirmed by powder X-ray diffraction, and further characterized by scanning electron microscopy, transmission electron microscopy, and X-ray photoelectron spectroscopy. The electrical conductivity measured on compressed powder sample reaches 110 S cm-1 at 300 K, which is among the highest value ever reported for coordination polymers. Furthermore, the intrinsic metallic characteristics of Cu-BHS are confirmed by ultraviolet photoelectron spectroscopy and band structure calculation.

Porous Molecular Conductor: Electrochemical Fabrication of Through-Space Conduction Pathways among Linear Coordination Polymers

The first porous molecular conductor (PMC), which exhibits porosity, a through-space conduction pathway and rich charge carriers (electrons), was prepared through electrocrystallization from Cd²⁺ and N, N'-di(4-pyridyl)-1,4,5,8-naphthalenetetracarboxdiimide (NDI-py). [Cd(NDI-py)(OH₂)₄](NO₃)_1.3±0.1· nDMA (PMC-1) was assembled by π-π stacking among one-dimensional (1D) linear coordination polymers. The NDI cores were partially reduced into radical anions to form conductive π-stacked columns, yielding (1.0-3.3) × 10^-3 S cm^-1 at room temperature. Moreover, the electrical conductivity was significantly enhanced by removing the solvent molecules from PMC-1, indicating that PMCs are promising as molecule-responsive conductive materials.

Integration of a (-Cu-S-)n plane in a metal-organic framework affords high electrical conductivity

Designing highly conducting metal–organic frameworks (MOFs) is currently a subject of great interest for their potential applications in diverse areas encompassing energy storage and generation. Herein, a strategic design in which a metal–sulfur plane is integrated within a MOF to achieve high electrical conductivity, is successfully demonstrated. The MOF {[Cu₂(6-Hmna)(6-mn)]·NH₄}_n (1, 6-Hmna = 6-mercaptonicotinic acid, 6-mn = 6-mercaptonicotinate), consisting of a two dimensional (–Cu–S–)_n plane, is synthesized from the reaction of Cu(NO₃)₂, and 6,6′-dithiodinicotinic acid via the in situ cleavage of an S–S bond under hydrothermal conditions. A single crystal of the MOF is found to have a low activation energy (6 meV), small bandgap (1.34 eV) and a highest electrical conductivity (10.96 S cm⁻¹) among MOFs for single crystal measurements. This approach provides an ideal roadmap for producing highly conductive MOFs with great potential for applications in batteries, thermoelectric, supercapacitors and related areas.

Metal–organic frameworks that contain metal–sulfur chains have been demonstrated to exhibit good electrical conductivity. Here, the authors integrate a 2D metal–sulfur plane into a metal–organic framework, reporting a single crystal with a high conductivity of 10.96 S/cm.

Reversible redox switching of magnetic order and electrical conductivity in a 2D manganese benzoquinoid framework

We report a 2D manganese benzoquinoid network that undergoes simultaneous redox switching of magnetic order and electrical conductivity.

Materials with switchable magnetic and electrical properties may enable future spintronic technologies, and thus hold the potential to revolutionize how information is processed and stored. While reversible switching of magnetic order or electrical conductivity has been independently realized in materials, the ability to simultaneously switch both properties in a single material presents a formidable challenge. Here, we report the 2D manganese benzoquinoid framework (Me₄N)₂[MnII2(L^2–)₃] (H₂L = 2,5-dichloro-3,6-dihydroxo-1,4-benzoquinone), as synthesized via post-synthetic counterion exchange. This material is paramagnetic above 1.8 K and exhibits an ambient-temperature electrical conductivity of σ_{295 K} = 1.14(3) × 10^–13 S cm^–1 (E_a = 0.74(3) eV). Upon soaking in a solution of sodium naphthalenide and 1,2-dihydroacenaphthylene, this compound undergoes a single-crystal-to-single-crystal (SC–SC) reduction to give Na₃(Me₄N)₂[Mn₂L₃]. Structural and spectroscopic analyses confirm this reduction to be ligand-based, and as such the anionic framework is formulated as [MnII2(L^3–˙)₃]^5–. Magnetic measurements confirm that this reduced material is a permanent magnet below T_c = 41 K and exhibits a conductivity value of σ_{295 K} = 2.27(1) × 10^–8 S cm^–1 (E_a = 0.489(8) eV), representing a remarkable 200 000-fold increase over the parent material. Finally, soaking the reduced compound in a solution of [Cp₂Fe]⁺ affords Na(Me₄N)[MnII2(L^2–)₃] via a SC–SC process, with magnetic and electrical properties similar to those observed for the original oxidized material. Taken together, these results highlight the ability of metal benzoquinoid frameworks to undergo reversible, simultaneous redox switching of magnetic order and electrical conductivity.

Chemiresistive Detection of Gaseous Hydrocarbons and Interrogation of Charge Transport in Cu[Ni(2,3-pyrazinedithiolate)2] by Gas Adsorption

The development of new chemiresistive materials for use in chemical sensors that operate near ambient conditions could potentially reduce the costs of implementation, encouraging their use in new areas. Conductive metal-organic frameworks represent one intriguing class of materials for further investigation in this area, given their vast structural diversity and the specificity of adsorbate interactions afforded by their crystallinity. Here, we re-examine the electronic conductivity of the desolvated and acetonitrile-solvated microporous framework Cu[Ni(pdt)₂] (pdt^2- = 2,3-pyrazinedithiolate), and find that the conductivity in the pristine material is 200-fold greater than in the solvated state, highlighting the sensitivity of sample conductivity to guest inclusion. Additionally, the desolvated material is demonstrated to selectively adsorb the gaseous hydrocarbons ethane, ethylene, acetylene, propane, propylene, and cis-2-butene at ambient temperature. Investigation of the effect of gas adsorption on conductivity using an in situ measurement cell reveals a chemiresistive response for each adsorbate, and the change in conductivity with adsorbate pressure closely follows an empirical model identical in form to the Langmuir-Freundlich equation. The relative sensitivity of the framework to each adsorbate is, surprisingly, not correlated with binding strength. Instead, the differences in chemiresistive response between adsorbates are found to correlate strongly with gas phase specific heat capacity of the adsorbate. Nanoconfinement effects, manifesting as a relative deviation from the expected chemiresistive response, may influence charge transport in the case of the largest adsorbate considered, cis-2-butene. Time-resolved conductance and adsorption measurements additionally show that the chemiresistive response of the sensor equilibrates on a shorter time scale than gas adsorption, suggesting that interparticle contacts limit conduction through the bulk material and that conductivity at the crystallite surfaces is most responsive to gas adsorption.

In-situ formation of one-dimensional coordination polymers in molecular junctions

We demonstrate the bottom-up in-situ formation of organometallic oligomer chains at the single-molecule level. The chains are formed using the mechanically controllable break junction technique operated in a liquid environment, and consist of alternating isocyano-terminated benzene monomers coordinated to gold atoms. We show that the chaining process is critically determined by the surface density of molecules. In particular, we demonstrate that by reducing the local supply of molecules within the junction, either by lowering the molecular concentration or by adding side groups, the oligomerization process can be suppressed. Our experimental results are supported by ab-initio simulations, confirming that the isocyano terminating groups display a high tendency to form molecular chains, as a result of their high affinity for gold. Our findings open the road for the controlled formation of one-dimensional, single coordination-polymer chains as promising model systems of organometallic frameworks.

Organometallic frameworks have raised considerable interest in the area of nanoelectronics, but they are usually prepared at the ensemble level resulting in limited control. Vladyka et al. control the formation of single oligomer chains, unit by unit, in a mechanically controllable break-junction setup.

Nonpyrolyzed Fe-N Coordination-Based Iron Triazolate Framework: An Efficient and Stable Electrocatalyst for Oxygen Reduction Reaction

Pyrolyzed base-metal-based metal-organic frameworks (MOFs) with FeN_x coordination are emerging as nonprecious metal catalysts for electrochemical oxygen reduction reaction (ORR). However, surprisingly, nonpyrolyzed MOFs involving Fe-N coordination have not been explored for the ORR. This study concerns the catalytic performance of a semiconducting nonpyrolyzed iron triazolate framework (FeTa₂ ) for ORR in alkaline electrolyte. The FeTa₂ catalyst is studied as composites with different amounts of conductive Ketjenblack carbon (KB). The performance of these FeTa₂ -x KB (x denotes the KB/FeTa₂ weight ratio) composites by onset and half-wave potentials of ORR appears to be superior to most previously documented nonpyrolyzed MOFs. Characterization by elemental analysis, FTIR spectroscopy, XPS, and cyclic voltammetry suggest that N-Fe^III -OH^- sites at the surface of FeTa₂ function as the catalytic active sites. This FeTa₂ also shows very stable activity during ORR, as supported by accelerated durability test of the FeTa₂ -x KB sample (20 000 cycles, ca. 90 h). The framework structure of FeTa₂ remains intact during the durability test, which would help to explain its excellent catalytic durability. This would be the first study demonstrating efficient and stable ORR catalysis by a nonpyrolyzed Fe-N coordination-based MOF material.

Azido bridged binuclear copper(ii) Schiff base compound: synthesis, structure and electrical properties

The structure, FESEM, Al/complex/ITO microstructure and the current–voltage characteristics of the copper(ii) azido bridged dimer.

A semiconducting supramolecular Co(ii)-metallohydrogel: an efficient catalyst for single-pot aryl–S bond formation at room temperature

A monoethanolamine based Co(ii)-metallohydrogel can act as a Schottky barrier diode device and a catalyst for single-pot aryl–S bond formation at room temperature.

Syntheses of mono and bimetallic cyamelurate polymers with reversible chromic behaviour

MOPs and MMOPs were synthesized in water and their crystals exhibit switchable chromic behaviour and reversible solid-state structural transformations.

Synthesis of coordination polymer thin films with conductance-response to mechanical stimulation

Synthesis of coordination polymer thin films which are tough and highly oriented is of vital importance for exploring electronic functions under mechanical stimulation.

Reversible transformation between Cu(i)-thiophenolate coordination polymers displaying luminescence and electrical properties

The direct self-assembly between CuI with thiophenol produces two different 1D coordination polymers (CPs) with multifunctional properties; the ratio CuI in acetonitrile is the key factor determining the reversible conversion between both CPs.

Highly Conductive 2D Metal-Organic Framework Thin Film Fabricated by Liquid-Liquid Interfacial Reaction Using One-Pot-Synthesized Benzenehexathiol

Metal-organic frameworks (MOF) are studied extensively in applications like catalysts, gas storage, and sensors due to their various functional groups and structures. Two-dimensional (2D) MOFs such as triphenylene-based materials show excellent charge transport properties, but thin-film fabrication and organic ligand synthesis are difficult. In this work, we synthesize thiol-based organic ligand, benzenehexathiol (BHT), by a simple one-pot reaction. This facile method is safer and faster than conventional synthesis procedure that requires using liquid ammonia as solvent. Two novel 2D MOF materials, Ag₃BHT₂ and Au₃BHT₂, are fabricated by coordinating BHT with either silver (Ag) or gold (Au) ions through liquid-liquid interfacial reaction. The Ag₃BHT₂ thin film reaches a high electrical conductivity of 363 S cm^-1, which has potential applications in electronic devices and sensors.

Smart composite films of nanometric thickness based on copper-iodine coordination polymers. Toward sensors

One-pot reactions between CuI and methyl or methyl 2-amino-isonicotinate give rise to the formation of two coordination polymers (CPs) based on double zig-zag Cu2I2 chains. The presence of a NH2 group in the isonicotinate ligand produces different supramolecular interactions affecting the Cu-Cu distances and symmetry of the Cu2I2 chains. These structural variations significantly modulate their physical properties. Thus, both CPs are semiconductors and also show reversible thermo/mechanoluminescence. X-ray diffraction studies carried out under different temperature and pressure conditions in combination with theoretical calculations have been used to rationalize the multi-stimuli-responsive properties. Importantly, a bottom-up procedure based on fast precipitation leads to nanofibers of both CPs. The dimensions of these nanofibres enable the preparation of thermo/mechanochromic film composites with polyvinylidene difluoride. These films are tens of nanometers in thickness while being centimeters in length, representing smaller thicknesses so far reported for thin-film composites. This nanomaterial integration of CPs could represent a source of alternative nanomaterials for opto-electronic device fabrication.

One-Pot Preparation of Mechanically Robust, Transparent, Highly Conductive, and Memristive Metal-Organic Ultrathin Film

The future of 2D flexible electronics relies on the preparation of conducting ultrathin films of materials with mechanical robustness and flexibility in a simple but controlled manner. In this respect, metal-organic compounds present advantages over inorganic laminar crystals owing to their structural, chemical, and functional diversity. While most metal-organic compounds are usually prepared in bulk, recent work has shown that some of them are processable down to low dimensional forms. Here we report the one-pot preparation, carried out at the water-air interface, of ultrathin (down to 4 nm) films of the metal-organic compound [Cu₂I₂(TAA)] _n (TAA= thioacetamide). The films are shown to be homogeneous over mm² areas, smooth, highly transparent, mechanically robust, and good electrical conductors with memristive behavior at low frequencies. This combination of properties, as well as the industrial availability of the two building blocks required for the preparation, demonstrates their wide range potential in future flexible and transparent electronics.

Formation of the layered conductive magnet CrCl2(pyrazine)2 through redox-active coordination chemistry

The unique properties of graphene, transition-metal dichalcogenides and other two-dimensional (2D) materials have boosted interest in layered coordination solids. In particular, 2D materials that behave as both conductors and magnets could find applications in quantum magnetoelectronics and spintronics. Here, we report the synthesis of CrCl₂(pyrazine)₂, an air-stable layered solid, by reaction of CrCl₂ with pyrazine (pyz). This compound displays a ferrimagnetic order below ∼55 K, reflecting the presence of strong magnetic interactions. Electrical conductivity measurements demonstrate that CrCl₂(pyz)₂ reaches a conductivity of 32 mS cm^-1 at room temperature, which operates through a 2D hopping-based transport mechanism. These properties are induced by the redox-activity of the pyrazine ligand, which leads to a smearing of the Cr 3d and pyrazine π states. We suggest that the combination of redox-active ligands and reducing paramagnetic metal ions represents a general approach towards tuneable 2D materials that consist of charge-neutral layers and exhibit both long-range magnetic order and high electronic conductivity.

Conductive two-dimensional metal-organic frameworks as multifunctional materials

Two-dimensional (2D) conductive metal-organic frameworks (MOFs) have emerged as a unique class of multifunctional materials due to their compositional and structural diversity accessible through bottom-up self-assembly. This feature article summarizes the progress in the development of 2D conductive MOFs with emphasis on synthetic modularity, device integration strategies, and multifunctional properties. Applications spanning sensing, catalysis, electronics, energy conversion, and storage are discussed. The challenges and future outlook in the context of molecular engineering and practical development of 2D conductive MOFs are addressed.

Electron delocalization and charge mobility as a function of reduction in a metal-organic framework

Conductive metal-organic frameworks are an emerging class of three-dimensional architectures with degrees of modularity, synthetic flexibility and structural predictability that are unprecedented in other porous materials. However, engendering long-range charge delocalization and establishing synthetic strategies that are broadly applicable to the diverse range of structures encountered for this class of materials remain challenging. Here, we report the synthesis of K _x Fe₂(BDP)₃ (0 ≤ x ≤ 2; BDP^2- = 1,4-benzenedipyrazolate), which exhibits full charge delocalization within the parent framework and charge mobilities comparable to technologically relevant polymers and ceramics. Through a battery of spectroscopic methods, computational techniques and single-microcrystal field-effect transistor measurements, we demonstrate that fractional reduction of Fe₂(BDP)₃ results in a metal-organic framework that displays a nearly 10,000-fold enhancement in conductivity along a single crystallographic axis. The attainment of such properties in a K _x Fe₂(BDP)₃ field-effect transistor represents the realization of a general synthetic strategy for the creation of new porous conductor-based devices.

Supramolecular Interactions Modulating Electrical Conductivity and Nanoprocessing of Copper-Iodine Double-Chain Coordination Polymers

Two coordination polymers (CPs), based on Cu(I)-I double zig-zag chains bearing isonicotinic acid or 3-chloroisonicotinic acid as terminal ligands with molecular recognition capabilities, have been synthesized and fully characterized. Both compounds present extended networks with supramolecular interactions directed by the formation of H-bonds between the complementary carboxylic groups, giving supramolecular sheets. The chloro substituent allows establishing additional Cl···Cl supramolecular interactions that reinforce the stability of the supramolecular sheets. These CPs are semiconductor materials; however, the presence of chlorine produces slight changes in the I-Cu-I chains, generating a worse overlap in the Cu-I orbitals, thus determining a decrease in its electrical conductivity value. These experimental results have also been corroborated by theoretical calculations using the study of the morphology of the density of states and 3D orbital isodensities, which determine that conductivity is mostly produced through the Cu-I skeleton and is less efficient in the case of the chloro derivative compound. A fast and efficient bottom-up approach based on the self-assembly of the initial building blocks and the low solutibility of these CPs has proved very useful for the production of nanostructures.

Electroactive polymers for tissue regeneration: Developments and perspectives

Human body motion can generate a biological electric field and a current, creating a voltage gradient of -10 to -90 mV across cell membranes. In turn, this gradient triggers cells to transmit signals that alter cell proliferation and differentiation. Several cell types, counting osteoblasts, neurons and cardiomyocytes, are relatively sensitive to electrical signal stimulation. Employment of electrical signals in modulating cell proliferation and differentiation inspires us to use the electroactive polymers to achieve electrical stimulation for repairing impaired tissues. Electroactive polymers have found numerous applications in biomedicine due to their capability in effectively delivering electrical signals to the seeded cells, such as biosensing, tissue regeneration, drug delivery, and biomedical implants. Here we will summarize the electrical characteristics of electroactive polymers, which enables them to electrically influence cellular function and behavior, including conducting polymers, piezoelectric polymers, and polyelectrolyte gels. We will also discuss the biological response to these electroactive polymers under electrical stimulation. In particular, we focus this review on their applications in regenerating different tissues, including bone, nerve, heart muscle, cartilage and skin. Additionally, we discuss the challenges in tissue regeneration applications of electroactive polymers. We conclude that electroactive polymers have a great potential as regenerative biomaterials, due to their ability to stimulate desirable outcomes in various electrically responsive cells.

Solvent-modulation of the structure and dimensionality in lanthanoid-anilato coordination polymers

We show the key role that the size and shape of the solvent molecules may play in the dimensionality and structure of a series of lanthanoid-chloranilato coordination polymers. We report the synthesis, structure and magnetic properties of six different coordination polymers prepared with Er(iii) and chloranilato (C6O4Cl22- = 3,6-dichloro-2,5-dihydroxy-1,4-benzoquinone) and six different solvents: [Er2(C6O4Cl2)3(H2O)6]·10H2O (1), [Er2(C6O4Cl2)3(FMA)6]·4FMA·2H2O (2) (FMA = formamide = NH2CHO), [Er2(C6O4Cl2)3(DMSO)4]·2DMSO·2H2O (3) (DMSO = dimethy sulfoxide = Me2SO), [Er2(C6O4Cl2)3(DMF)6] (4) (DMF = dimethylformamide = Me2NCHO), [Er2(C6O4Cl2)3(DMA)4] (5) (DMA = dimethylacetamide = Me2NC(Me)O) and [Er2(C6O4Cl2)3(HMPA)(H2O)3]·H2O (6) (HMPA = hexamethylphosphormamide = (Me2N)3PO). We show how the different solvent molecules modulate and determine important structural parameters such as the coordination number and geometry, the shape and distortions of the cavities, the presence of solvent molecules in these cavities, the interlayer space and even the dimensionality of the structure.