Stimuli-Responsive Metal-Ligand Assemblies.

The Engineering and Physical Sciences Research Council and the European Research Council are acknowledged for financial support.This is the accepted manuscript of a paper published in Chemical Reviews (McConnell AJ, Wood CS, Neelakandan PP, Nitschke JR, Chemical Reviews (2015) 115(15):7729-7793. doi:10.1021/cr500632f). The final version is available at http://dx.doi.org/10.1021/cr500632

State-of-the-Art of (Bio)Chemical Sensor Developments in Analytical Spanish Groups

(Bio)chemical sensors are one of the most exciting fields in analytical chemistry today. The development of these analytical devices simplifies and miniaturizes the whole analytical process. Although the initial expectation of the massive incorporation of sensors in routine analytical work has been truncated to some extent, in many other cases analytical methods based on sensor technology have solved important analytical problems. Many research groups are working in this field world-wide, reporting interesting results so far. Modestly, Spanish researchers have contributed to these recent developments. In this review, we summarize the more representative achievements carried out for these groups. They cover a wide variety of sensors, including optical, electrochemical, piezoelectric or electro-mechanical devices, used for laboratory or field analyses. The capabilities to be used in different applied areas are also critically discussed

Ion-Sensing Systems Based on Mesoporous Carbon: from Bulk Electrodes to Paper-Based Ion Sensors

University of Minnesota Ph.D. dissertation. August 2017. Major: Chemistry. Advisors: Andreas Stein, Philippe Buhlmann. 1 computer file (PDF); xxvii, 206 pages.Potentiometric sensors, comprising ion-selective electrodes (ISEs) and reference electrodes, are a large subgroup of electrochemical ion sensors. In view of affordable and portable analytical devices, all-solid-state ISEs and reference electrodes, in which a solid contact is used as an ion-to-electron transducer, are highly desirable. Compared with conventional ISEs, all-solid-state ISEs offer comparable electrochemical performance with the distinct advantages of simple maintenance and miniaturization. This dissertation focuses on the development of robust all-solid-state potentiometric ion-sensing systems. It starts with the investigation of colloid-imprinted mesoporous (CIM) carbon as a novel solid contact material. CIM carbon exhibits desirable properties as a solid contact material, including a low content of redox-active impurities and a high double layer capacitance. Therefore, sensors based on CIM carbon can be constructed with superior electrochemical performance, including excellent ionic response, reproducibility, signal stability, and resistance to common interfering agents. These outstanding characteristics make CIM carbon-based potentiometric sensors promising candidates for the next generation of commercial ion sensors. To develop low-cost and simple ion sensors for point-of-care applications, this dissertation also involves the development of disposable ion-sensing platforms based on paper. The use of ISEs can be significantly simplified by embedding a conventional potentiometric cell into paper. Paper-based Cl– and K+ sensors are fabricated with highly reproducible and linear responses towards different concentrations of analyte ions in aqueous and biological samples. To further simplify the use of these paper-based ion sensors, CIM carbon-based ISEs and reference electrodes can be integrated into the paper substrate, thus constructing all-solid-state paper-based ion-sensing platforms. Finally, the dissertation explores the possibility of constructing robust calibration-free ion sensors by covalently attaching a redox buffer to CIM carbon. Click chemistry and amide coupling reactions are evaluated for the attachment, and the cobalt-based redox buffer can be attached to CIM carbon. It is found that the open circuit potential of modified CIM carbon films can be affected by the oxidation states of the redox buffer, but a higher redox buffer loading is required to achieve high electrode-to-electrode reproducibility. Possible approaches to achieving such high redox buffer loading are discussed at the end of this dissertation

Electrocatalytic and Photoelectrosynthetic Hydrogen Production using Metalloporphyrins and Molecular-modified Gallium Phosphide Photocathodes

abstract: Metalloporphyrins represent a class of molecular electrocatalysts for driving energy relevant half-reactions, including hydrogen evolution and carbon dioxide reduction. As electrocatalysts, they provide a strategy, and potential structural component, for linking renewable energy sources with the production of fuels and other value-added chemicals. In this work, porphyrins are used as structural motifs for exploring structure-function relationships in electrocatalysis and as molecular building blocks for assembling photoelectrochemical assemblies leveraging the light capture and conversion properties of a gallium phosphide (GaP) semiconductor. These concepts are further covered in Chapter 1. A direct one-step method to chemically graft metalloporphyrins to GaP surfaces is described in Chapter 2. Structural characterization of the hybrid assemblies is achieved using surface-sensitive spectroscopic methods, and functional performance for photoinduced hydrogen production is demonstrated via three-electrode electrochemical measurement combined with product analysis using gas chromatography. In Chapter 3, preparation of a novel cobalt porphyrin modified with 3-fluorophenyl groups at all four meso-positions of the porphyrin ring and a single 4-vinylphenyl surface attachment group at one of the β-positions is described. Electrochemical measurements show the 3-fluorophenyl groups perturb the reduction potentials of the complex to more positive values as compared to non-fluorinated analogs, illustrating synthetic control over the redox properties of the catalysts. The use of grazing angle attenuated total reflectance Fourier transform infrared spectroscopy to characterize chemically modified GaP surfaces containing grafted cobalt fluoro-porphyrins is presented in Chapter 4. In these hybrid constructs, porphyrin surface attachment is achieved using either a two-step method involving coordination of cobalt fluoro-porphyrin metal centers to nitrogen sites on an initially applied thin-film polypyridyl surface coating, or via a direct modification strategy using a cobalt fluoro-porphyrin precursor bearing a covalently bonded 4- vinylphenyl surface attachment group. Finally, Chapter 5 describes binuclear copper porphyrins in which two copper porphyrin macrocycles are doubly fused at the meso-β positions are shown to be active electrocatalysts for the hydrogen evolution reaction. The enhancement in catalytic performance over analogous non-fused copper porphyrins indicates extended macrocycles provide an advantageous structural motif and design element for preparing electrocatalysts that activate small molecules of consequence to renewable energy.Dissertation/ThesisDoctoral Dissertation Chemistry 201

Calixpyrroles, calixpyridinopyrroles and calixpyridines

The present invention provides calixpyrrole, calixpyridinopyrrole, and calixpyridine macrocycles, having 4, 5, 6, 7, or 8 heterocyclic rings, as well as syntheses, derivatives, conjugates, multimers, and solid supports thereof. Such macrocycles have proved to be effective and selective ion- and neutral molecule-binding agents forming supramolecular ensembles, and ion- and neutral molecule-separation agents. The macrocycles are fully meso-non-hydrogen-substituted porphyrinogens, a few molecules of which were previously known but not recognized as possessing anion- or molecule-binding properties. The binding mode is noncovalent, primarily that of hydrogen-bonding, thereby providing a new mode for liquid chromatography, that of Hydrogen Bonding Liquid Chromatography. Further useful applications of the macrocycles provided herein include environmental remediation by removal of undesired ions or neutral molecules, and removal of phosphate for kidney dialysis.Board of Regents, University of Texas Syste

Halogenated calixpyrroles and uses thereof

The present invention provides halogenated calixpyrrole, calixpyridinopyrrole, and calixpyridine macrocycles having 4–12 pyrrolic rings with greater stability, enhanced anion and neutral molecule binding affinity, and different binding selectivites as compared to their non-halogenated congeners as judged from 1H NMR, 19F NMR and fluorescence emission spectroscopic analyses.Board of Regents, University of Texas Syste

Development and Application of Synthetic Lipid Probes to Study and Mimic Lipid Function

Lipids are biologically important molecules as they regulate a litany of key cellular processes that, when aberrant, result in disease. Since lipids control these regulation pathways, it is imperative to understand their properties and exploit them for use in advancing therapeutic strategies. The complex environments in which lipids exist have historically complicated their understanding, but recent advancements have facilitated this effort. In the chapters that follow, we have used synthetic lipid probes to investigate the role of signaling lipids as site-specific ligands in the binding of protein effectors and developed a high-throughput platform that can be used to rapidly classify protein-binding partners to phosphoinositide lipids. Using microarray analysis, we have achieved high-throughput binding results for the Akt-PH domain to phosphatidylinositol-(3,4,5)-trisphosphate. In addition, preliminary results from an investigation of how multivalency affects profilin binding to phosphatidylinositol-(4,5)-bisphosphate are discussed. We have also developed the first known example of liposome modification via copper-free click chemistry as an ideal bioorthogonal approach to intact membrane derivatization towards targeting applications. Using a microplate surface-based immobilization technique, we have reported the derivatization of intact azido-liposomes with a biotinylated cyclooctyne by copper-free click chemistry and performed various control reactions to ensure labeling is specific and reliable. Additionally, we have reported initial findings for the advancement of this liposome immobilization strategy to be performed in high-throughput fashion via microarray. In the final chapter, we briefly discuss our involvement in a few collaborative efforts including the optimization of a non-lipid autotaxin inhibitor, synthesis of porphyrin-lipid conjugates for use in photocurrent generation systems, and synthesis of several rhodamine dyes for use in surface enhanced hyper Raman spectroscopy (SEHRS)

The synthesis and anion coordination chemistry of novel mono- and multi-functional borylmetallocenes

The synthesis, characterisation and anion binding properties of a series of mono-, tris- and tetiukis-functional boronic esters of ferrocene are reported. Mono- borylated systems: (n5C5H5)Fe(ri5C5H4B02R) where 02R = ethane-1,2-diolato (la) and pinanediolato (lb) , tris-functional borylated systems: (r 5-C5H3EtB02R)Fe(r 5- C5H3(B02R)2 where 02R = ethane-1,2-diolato (3a), stilbenediolato (3b) and pinanediolato (3c) and tetrakis-functional borylated systems: (rj5-C5H3(B02R)2) 2Fe where 02R = ethane-1,2-diolato (4a), stilbenediolato (4b), pinanediolato (4c) and napthalenediolato (4d) have been synthesised and characterised by NMR, UV/Vis and IR spectroscopy, mass spectrometry and in most cases by X-ray diffraction. Electrochemical analyses of most of the above-mentioned boronic esters of ferrocene have demonstrated the influence of the number of boronic ester groups on the redox potential of the ferrocene backbone, and have allowed a comparison of the different substituents. The anion-binding properties of the above-mentioned boronic esters have been monitored by spectroscopic (including NMR and UV/Vis) and electrochemical methods. Bis-functionalised boronic esters of ferrocene have previously shown a colorimetric response to fluoride, and have been shown to bind two equivalents of fluoride per receptor. An analogous colorimetric response to fluoride is observed with the tris- and tetrakis-functionalised boronic esters, which also display a particular affinity for fluoride. The kinetics of the colorimetric response have been probed using time-resolved UV/Vis experiments, with the tris- and tetrakis-functionalised compounds shown to effect a more rapid response to fluoride. Kinetic experiments have revealed that the response to fluoride is greatly enhanced with tris- and tetrakis- functionalised receptors, and also revealed a binding stoichiometry of 2:1 (anion: receptor) in all cases thus the binding of more than two equivalents of fluoride by the additional boryl groups is not responsible for enhanced kinetics. The synthesis and characterisation of a range of dimeric, macrocyclic and polymeric ferroceneboronic esters has been undertaken. Dimeric ferrocene boronic esters (ti5-C5H5)Fe(r 5-C5H4)R(Ti5-C5H4)Fe(ri5-C5H5) where R = B02C8H1202B (7a), B(OCH2)2C(CH20)2B (8a) and B02(C6H2)02B (9a) , macrocyclic ferrocene boronic esters: (Ti5-C5H4)Fe(Ti5-C5H4)BRB 2 where R = B02C8Hi202B (7b) and B(OCH2)2C(CH20)2B (8b) , and the polymeric ferrocene boronic ester (rj5- C5H4)B02CgHi202B(r 5-C5H4)Fe n polymer (7c) have been synthesised and characterised by NMR and UV/Vis spectroscopy, mass spectrometry and in some cases by X-ray diffraction. Electrochemical analyses of some of the above-mentioned boronic esters of ferrocene have demonstrated the lack of electronic communication between iron centres with the saturated pentaerythritol and cyclooctanetetraol linker groups. Investigation into the factors controlling assembly of boronic ester units into poly-, oligomeric or macrocyclic products has been possible. The two different linker groups have revealed very different product distributions under analogous reaction conditions with ferrocene-bis-boronic acid. The pentaerythritol linker favours macrocycle formation, whilst the cyclooctanetetraol linker favours polymer formation. Thus reactions can be driven with high selectivity towards either macrocyclic or polymeric products depending on choice of linker group