Modification of glassy carbon electrode with iron-terpyridine complex and iron-terpyridine complex covalently bonded to ordered mesoporous carbon substrate: Preparation, electrochemistry and application to H 2 O 2 determination

Polarity-Induced Morphological Transformation with Tunable Optical Output of Terpyridine-Phenanthro[9,10-d]imidazole-Based Ligand and Its Zn(II) Complexes with I-V Characteristics

Self-assembled nanostructures obtained from various functional π-conjugated organic molecules have been able to draw substantial interest due to their inherent optical properties, which are imperative for developing optoelectronic devices, multiple-color-emitting devices with color-tunable displays, and optical sensors. These π-conjugated molecules have proven their potential employment in various organic electronic applications. Therefore, the stimuli-responsive fabrication of these π-conjugated systems into a well-ordered assembly is extremely crucial to tuning their inherent optical properties for improved performance in organic electronic applications. To this end, herein, we have designed and synthesized a functional π-conjugated molecule (TP) having phenanthro[9,10-d]imidazole with terpyridine substitution at the 2 position and its corresponding metal complexes (TPZn and (TP)2Zn). By varying the polarity of the self-assembly medium, TP, TPZn, and (TP)2Zn are fabricated into well-ordered superstructures with morphological individualities. However, this medium polarity-induced self-assembly can tune the inherent optical properties of TP, TPZn, and (TP)2Zn and generate multiple fluorescence colors. Particularly, this property makes them useful for organic electronic applications, which require adjustable luminescence output. More importantly, in 10% aqueous-THF medium, TPZn exhibited H-type aggregation-induced white light emission and behaved as a single-component white light emitter. The experimentally obtained results of the solvent polarity-induced variation in optical properties as well as self-assembly patterns were further confirmed by theoretical investigation using density functional theory calculations. Furthermore, we investigated the I-V characteristics, both vertical and horizontal, using ITO and glass surfaces coated with TP, TPZn, and (TP)2Zn, respectively, and displayed maximum current density for the TPZn-coated surface with the order of measured current density TPZn > TP > (TP)2Zn. This observed order of current density measurements was also supported by a direct band gap calculation associated with the frontier molecular orbitals using the Tauc plot. Hence, solvent polarity-induced self-assembly behavior with adjustable luminescence output and superior I-V characteristics of TPZn make it an exceptional candidate for organic electronic applications and electronic device fabrication.

Metal-Terpyridine Assembled Functional Materials for Electrochromic, Catalytic and Environmental Applications

Molecular assembly induced by metal-terpyridine-based coordinative interactions has become an emergent research topic due to its ease of synthesis and diverse applications. This article highlights recent significant developments in the metal-terpyridine-based supramolecular architectures. At first, the design aspect of the molecular building blocks has been described, followed by elaboration on how the ligand backbone plays an important role for achieving different dimensionalities of the resulting assemblies which exhibit a wide range of potential applications. After that, we discussed different synthetic approaches for constructing these assemblies, and finally, we focused on their significant developments in three specific areas, viz., electrochromic materials, catalysis and a new application in wastewater treatment. In the field of electrochromic materials, these assemblies made important advancements in various aspects like sub-second switching time (<1 s), low switching voltage (<1 V), increased switching stability (>10000 cycles), tuning of multiple colors by using multimetallic systems, fabrication of charge storing electrochromic devices, utilizing and storing solar energy etc. Similarly, the catalysis field witnessed application of the metal-terpyridine assemblies in C-H monohalogenation, heterogeneous Suzuki-Miyaura coupling, photocatalysis, reduction of carbon dioxide, etc. Finally, the environmental application of these coordination assemblies includes capturing Cr(VI) from waste water efficiently with high capture capacity, good recyclability, wide pH independency etc.

Redox- and EPR-Active Graphene Diiron Complex Nanocomposite

A mixed valence diiron(II/III) complex with the ligand 2,6-bis{bis[(2-pyridinylmethyl)amino]methyl}phenol (bppH) has been covalently anchored onto graphene using a mild in situ microwave-assisted diazonium coupling through an aryl amino precursor and isoamyl nitrite. A dinuclear iron complex is then formed by complexation of the grafted bppH-graphene material with iron(II) in the presence of dioxygen. X-ray photoelectron spectroscopy (XPS), atomic force microscopy, cyclic voltammetry, scanning transmission electron microscopy, energy-dispersive X-ray spectroscopy, and electron paramagnetic resonance (EPR) spectroscopy confirm the formation of the anchored ligand and derivative diiron complexes. Semiquantitative XPS analysis shows an average bppH ligand bulk loading of 0.33 mmol/g, corresponding to a significant 20.7 wt % of the functionalized material consisting of grafted moieties. EPR measurements reveal the existence of a strong isotropic S = 1/2 spin center associated with the graphene lattice, together with a much weaker S = 5/2 signal, associated with the iron(III) center of the grafted complex. The grafted complex is redox-active with surface-confined Fe^IIFe^II → Fe^IIFe^III (+0.56 V vs NHE), Fe^IIFe^III → Fe^IIIFe^III (+0.73 V), and Fe^IIIFe^III → Fe^IIIFe^IV (+0.95 V) redox processes accessible, with an estimated surface coverage of 58 pmol cm^-2 established from the electrochemical measurements.

Recent Trends on Electrochemical Sensors Based on Ordered Mesoporous Carbon

The past decade has seen an increasing number of extensive studies devoted to the exploitation of ordered mesoporous carbon (OMC) materials in electrochemistry, notably in the fields of energy and sensing. The present review summarizes the recent achievements made in field of electroanalysis using electrodes modified with such nanomaterials. On the basis of comprehensive tables, the interest in OMC for designing electrochemical sensors is illustrated through the various applications developed to date. They include voltammetric detection after preconcentration, electrocatalysis (intrinsically due to OMC or based on suitable catalysts deposited onto OMC), electrochemical biosensors, as well as electrochemiluminescence and potentiometric sensors.