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The electrochemiluminescent (ECL) performance of three ruthenium-based metallopolymer platforms with different homogeneous charge transfer diffusion coefficients ( D CT ) is reported. Significantly, simultaneous detection of light and current in tandem with steady-state photoluminescence studies demonstrate that increasing the rate of Ru 3 + production via enhanced charge transport results in a decrease in ECL intensity of up to 82% when the concentration of the co-reactant, sodium oxalate, is low, i.e., sub-mM. Spectroelectrochemical studies demonstrate that for maximum sensitivity to be obtained, the electroactive properties of the polymeric support matrix need to be considered in tandem with luminophore, analyte and co-reactant concentrations. [ABSTRACT FROM AUTHOR]

The electrochemiluminescent (ECL) properties of a luminescent metal centre, [Ru(bpy)3]2+, can be significantly modulated through its electronic interaction with neighbouring centres and the polymer backbone used to confine it on an electrode surface. From the perspective of ECL based sensing devices, an increase in the ECL efficiency of a metallopolymer film can result in enhanced sensor sensitivity and selectivity. This work probes the ECL properties of both conjugated, [Ru(bpy)2(PPyBBIM)10]2+, and non-conjugated, [Ru(bpy)2(PVP)10]2+, ruthenium based metallopolymer films based on a well documented reaction with sodium oxalate, where bpy is 2,2′-bipyridyl, PPYBBIM is poly[2-(2-pyridyl)-bibenzimidazole] and PVP is poly(4-vinylpyridine). Through a combination of ground state electrochemical studies and ECL measurements, the ECL efficiency for each film is determined. This study reveals that despite a dramatic influence in charge transfer rates between metal centres, as observed for the conducting polymer, mediated through the conducting polymer backbone, a corresponding increase in ECL efficiency is not always observed. The degree of communication between the adjacent excited state metal centres are an important consideration for ECL enhancement however self quenching, luminophore distribution and film porosity must also be considered. [ABSTRACT FROM AUTHOR]

The photophysical and electrochemical properties of a novel metallopolymer containing [Re(bpy)(CO)3]+ moieties coordinated to a poly(4-vinylpyridine) polymer chain are reported. Significantly, the release of the metal complexes can be triggered by oxidation or reduction of the rhenium complex. Solvent rapidly binds to the vacant coordination site to give a luminescent product. The redox and photophysical properties of the parent metallopolymer and the released solvated complex are compared. Along with photoemission, the metallopolymer generates significant electrogenerated chemiluminescence upon reduction in the presence of benzoyl peroxide as coreactant. [ABSTRACT FROM AUTHOR]

Emission spectroscopy and electrochemistry has been used to probe the electronic communication between adjacent metal centres and the conjugated backbone within a family of imidazole based metallopolymers, [Ru(bpy)2(PPyBBIM)n]2, in the ground and excited states, bpy is 2,2′-bipyridyl, PPyBBIM is poly[2-(2-pyridyl)-bibenzimidazole] and n= 3, 10 or 20. Electronic communication in the excited state is not efficient and upon optical excitation dual emission is observed, i.e., both the polymer backbone and the metal centres emit. Coupling the ruthenium moiety to the imidazole backbone results in a red shift of approximately 50 nm in the emission spectrum. Luminescent lifetimes of up to 120 ns were also recorded. Cyclic voltammetry was also utilized to illustrate the distance dependence of the electron hopping rates between adjacent metal centres with ground state communication reduced by up to an order of magnitude compared to previously reported results when the metal to backbone ratio was not altered. DCTand Devalues of up to 3.96 × 10−10and 5.32 × 10−10cm2S−1were observed with corresponding conductivity values of up to 2.34 × 10−8S cm−1. [ABSTRACT FROM AUTHOR]

Abstract: The electrochemical and photochemical properties of [Ru(bpy)2dcb]Cl2 monolayers and their subsequent use for the detection of amino acids, e.g., proline, is reported; dcb is 4,4′-dicarboxy-2,2′-bipyridine and bpy is 2,2′-bipyridine. The ability of such a complex to form stable monolayers enables its utilization for the detection of oxalate and several amino acids, producing significant ECL. The electrochemical response of the Ru2+/3+ couple is electrochemically reversible and the monolayers show excellent stability with the response decreasing by less than 8% after continuous scanning over 4h. The ECL and current responses increase linearly with increasing analyte concentration 0.2⩽[Proline]⩽1nM while for hydroxy-proline the dynamic range is from 1 to 10nM. The ECL signal was monitored at ∼644nm, representing the λ max for the [Ru(bpy)2dcb]Cl2 monolayers. This wavelength is shifted by approximately 28nm compared to the photoexcited λ max for the same system. This technique is simple, rapid, selective and sensitive, and shows potential for the high-throughput quantitation of amino acids if adapted with other techniques such as FIA or LC systems. [Copyright &y& Elsevier]

The cover picture shows the release of the luminescent rhenium coordination complex (yellow spheres) in solution. This release is triggered by electrochemical stimulus applied through the cable to the metallopolymer, which is represented by the splash of blue paint. The irreversibility of the electrochemical release is highlighted by holes in the graph paper. G. Valenti, F. Paolucci, R. J. Forster, and co‐workers outline the photophysical and electrochemical properties of a novel metallopolymer containing [Re(bpy)(CO)3]+ moieties coordinated to a poly(4‐vinylpyridine) polymer chain in their Full Paper on page 55 ff. Release of the metal complexes can be triggered by oxidation or reduction of the rhenium complex. [ABSTRACT FROM AUTHOR]

Amorphous solid dispersion (ASD) is one of the most promising strategies for improving the solubility of active pharmaceutical ingredients (APIs) with low aqueous solubility. Solvent-based techniques such as electrospinning (ES), spray-drying (SD) and rotary evaporation (RE), have all previously been shown to be effective techniques for formulating ASDs. To date however, the effect of these processing techniques on the physicochemical properties and ASD homogeneity or "quality of ASD" produced remains largely unexplored. This work uses ibuprofen (IBU) as a model BCS class II API with two cellulosic excipients, HPMCAS and HPMCP-HP55 to produce ASDs by employing ES, SD and RE processing techniques. The physicochemical, morphological and dissolution properties of each sample were evaluated and the ASD forming strengths of each of the polymers were assessed using Differential Scanning Calorimetry (DSC). Principal |Component Analysis (PCA) of Raman spectra of crystalline and amorphous IBU was employed for qualitative analysis of ASD homogeneity and subsequent ASD stability during long-term storage. Results show that while ASD formation is predominantly dependent on API:excipient ratio, the ASD homogeneity is highly dependent on processing technique. Dissolution studies show that electrospun samples had the highest API release rate due to their fibrous morphology and higher specific surface area. However, these samples were the least homogenous of all ASDs produced thereby potentially influencing sample stability during long term storage. In addition, the higher melting point depression, higher T g , and increased abundance of functional groups suitable for hydrogen bonding, show HPMCAS to be a significantly better ASD co-former when compared with HPMCP-HP55. [ABSTRACT FROM AUTHOR]