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Ulrich S Schubert - One of the best experts on this subject based on the ideXlab platform.
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catalytic applications of terpyridines and their transition metal complexes
ChemInform, 2012Co-Authors: Andreas Winter, George R Newkome, Ulrich S SchubertAbstract:The coordination compounds of the tridentate oligopyridine ligand 2,2′:6′,2′′-terpyridine (tpy) are utilized in very different fields of research, such as materials science (e.g. photovoltaics), biomedicinal Chemistry (e.g. DNA intercalation), and organometallic catalysis. Applications in the latter area have arisen from initial reports on electro- or photochemical processes and, today, a broad range of reactions—from artificial photosynthesis (water splitting) to biochemical and organic transformations as well as polymerization reactions—have been catalyzed by terpyridines and their transition metal complexes. In this review, the scope and the limitations of these applications, which emerged particularly in organic and Macromolecular Chemistry, will be evaluated.
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new 4 functionalized 2 2 6 2 terpyridines for applications in Macromolecular Chemistry and nanoscience
European Journal of Organic Chemistry, 2003Co-Authors: P Philip R Andres, Ralph Lunkwitz, Gunther Pabst, Karlheinz Bohn, Daan D Wouters, Stefan S Schmatloch, Ulrich S SchubertAbstract:The well-known reaction of 4′-chloro-2,2′:6′,2′′-terpyridine with alkoxide nucleophiles leads to 4′-functionalized 2,2′:6′,2′′-terpyridines. This reaction allows the easy introduction of different functional groups onto the terpyridine at the 4′-position, i.e. opposite to the metal binding site, in one reaction step. Among the functionalized 2,2′:6′,2′′-terpyridines reported here are amines (including chiral examples), carboxylic acids, simple alkoxy-chain terpyridines with different chain lengths, and a stilbene-functionalized terpyridine. Moreover, the synthesis of two important already known substances was significantly improved. One example of a sequential functionalization of the (aminopentoxy)terpyridine with a dithiolane functionality is also reported. For two of the alkyl-chain-functionalized terpyridines, single-crystal X-ray crystallographic data were obtained. Finally, ordered monolayers of alkyl-substituted terpyridines on HOPG were visualized using STM. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)
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syntheses of functionalized 2 2 6 2 terpyridines
ChemInform, 2003Co-Authors: Marcel Heller, Ulrich S SchubertAbstract:2,2′:6′,2′′-Terpyridine compounds are important chelating ligands in a multitude of applications in the fields of supramolecular and Macromolecular Chemistry as well as electroChemistry. Therefore, a “pool” of functionalized terpyridine derivatives is essential. Classical and modern synthetic strategies towards terpyridine systems and novel functional 2,2′:6′,2′′-terpyridine compounds that originated in the last seven years are reviewed comprehensively. (© Wiley-VCH Verlag GmbH & Co KGaA, 69451 Weinheim, Germany, 2003)
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macromolecules containing bipyridine and terpyridine metal complexes towards metallosupramolecular polymers
Angewandte Chemie, 2002Co-Authors: Ulrich S Schubert, Christian EschbaumerAbstract:The ability of a broad range of N-heterocycles to act as very effective and stable complexation agents for several transition metal ions, such as cobalt(II), copper(II), nickel(II), and ruthenium(II), has long been known in analytical Chemistry. This behavior was later utilized in supramolecular Chemistry for the construction of highly sophisticated architectures, such as helicates, racks, and grids. The discovery of macromolecules by Staudinger in 1922 opened up avenues towards sophisticated materials with properties hitherto completely unknown. In the last few decades, the combination of Macromolecular and supramolecular Chemistry has been attempted by developing metal-complexing and metal-containing polymers for a wide variety of applications that range from filtration to catalysis. The stability of the polymer-metal complex is a fundamental requirement for such applications. In this respect, the use of bi- and terpyridines as chelating ligands is highly promising, since these molecules are known to form highly stable complexes with interesting physical properties with transition-metal ions. A large number of different structures have been designed for many different applications, but polymers based on the application of coordinative forces have been prepared in a few cases only. Furthermore, the synthetic procedures applied frequently resulted in low yields. During the last few years, strong efforts have been made in the direction of self-assembling and supramolecular polymers as novel materials with "intelligent" and tunable properties. In this review, an overview of this active area at the interface of supramolecular and Macromolecular Chemistry is given.
Nakul C Maiti - One of the best experts on this subject based on the ideXlab platform.
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cα h carries information of a hydrogen bond involving the geminal hydroxyl group a case study with a hydrogen bonded complex of 1 1 1 3 3 3 hexafluoro 2 propanol and tertiary amines
Journal of Physical Chemistry A, 2014Co-Authors: Uttam Pal, Sudeshna Sen, Nakul C MaitiAbstract:Experimental measurement of the contribution of H-bonding to intermolecular and intramolecular interactions that provide specificity to biological complex formation is an important aspect of Macromolecular Chemistry and structural biology. However, there are very few viable methods available to determine the energetic contribution of an individual hydrogen bond to binding and catalysis in biological systems. Therefore, the methods that use secondary deuterium isotope effects analyzed by NMR or equilibrium or kinetic isotope effect measurements are attractive ways to gain information on the H-bonding properties of an alcohol system, particularly in a biological environment. Here, we explore the anharmonic contribution to the C–H group when the O–H group of 1,1,1,3,3,3-hexafluoro-2-propanol (HFP) forms an intermolecular H-bond with the amines by quantum mechanical calculations and by experimentally measuring the H/D effect by NMR. Within the framework of density functional theory, ab initio calculations wer...
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Cα–H Carries Information of a Hydrogen Bond Involving the Geminal Hydroxyl Group: A Case Study with a Hydrogen-Bonded Complex of 1,1,1,3,3,3-Hexafluoro-2-propanol and Tertiary Amines
2014Co-Authors: Uttam Pal, Sudeshna Sen, Nakul C MaitiAbstract:Experimental measurement of the contribution of H-bonding to intermolecular and intramolecular interactions that provide specificity to biological complex formation is an important aspect of Macromolecular Chemistry and structural biology. However, there are very few viable methods available to determine the energetic contribution of an individual hydrogen bond to binding and catalysis in biological systems. Therefore, the methods that use secondary deuterium isotope effects analyzed by NMR or equilibrium or kinetic isotope effect measurements are attractive ways to gain information on the H-bonding properties of an alcohol system, particularly in a biological environment. Here, we explore the anharmonic contribution to the C–H group when the O–H group of 1,1,1,3,3,3-hexafluoro-2-propanol (HFP) forms an intermolecular H-bond with the amines by quantum mechanical calculations and by experimentally measuring the H/D effect by NMR. Within the framework of density functional theory, ab initio calculations were carried out for HFP in its two different conformational states and their H-bonded complexes with tertiary amines to determine the 13C chemical shielding, change in their vibrational equilibrium distances, and the deuterium isotope effect on 13C2 (secondary carbon) of HFP upon formation of complexes with tertiary amines. When C2–OH was involved in hydrogen bond formation (O–H as hydrogen donor), it weakened the geminal C2–H bond; it was reflected in the NMR chemical shift, coupling constant, and the equilibrium distances of the C–H bond. The first derivative of nuclear shielding at C2 in HFP was −48.94 and −50.73 ppm Å–1 for anti and gauche conformations, respectively. In the complex, the values were −50.28 and −50.76 ppm Å–1, respectively. The C–H stretching frequency was lower than the free monomer, indicating enhanced anharmonicity in the C–H bond in the complex form. In chloroform, HFP formed a complex with the amine; δC2 was 69.107 ppm for HFP–triethylamine and 68.766 ppm for HFP-d2–triethylamine and the difference in chemical shift, the ΔδC2 was 341 ppb. The enhanced anharmonicity in the hydrogen-bonded complex resulted in a larger vibrational equilibrium distance in C–H/D bonds. An analysis with the Morse potential function indicated that the enhanced anharmonicity encountered in the bond was the origin of a larger isotope effect and the equilibrium distances. Change in vibrational equilibrium distance and the deuterium isotope effect, as observed in the complex, could be used as parameters in monitoring the strength of the H-bond in small model systems with promising application in biomacromolecules
Matthew I Gibson - One of the best experts on this subject based on the ideXlab platform.
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redox sensitive materials for drug delivery targeting the correct intracellular environment tuning release rates and appropriate predictive systems
Antioxidants & Redox Signaling, 2014Co-Authors: Daniel J Phillips, Matthew I GibsonAbstract:Abstract Significance: The development of responsive drug delivery systems (DDS) holds great promise as a tool for improving the pharmacokinetic properties of drug compounds. Redox-sensitive systems are particularly attractive given the rich variety of redox gradients present in vivo. These gradients, where the circulation is generally considered oxidizing and the cellular environment is substantially more reducing, provide attractive options for targeted, specific cargo delivery. Recent Advances: Experimental evidence suggests that a “one size fits all” redox gradient does not exist. Rather, there are subtle differences in redox potential within a cell, while the chemical nature of reducing agents in these microenvironments varies. Recent works have demonstrated an ability to modulate the degradation rate of redox-susceptible groups and, hence, provide new tools to engineer precision-targeted DDS. Critical Issues: Modern synthetic and Macromolecular Chemistry provides access to a wide range of redox-susc...
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redox sensitive materials for drug delivery targeting the correct intracellular environment tuning release rates and appropriate predictive systems
Antioxidants & Redox Signaling, 2014Co-Authors: Daniel J Phillips, Matthew I GibsonAbstract:Abstract Significance: The development of responsive drug delivery systems (DDS) holds great promise as a tool for improving the pharmacokinetic properties of drug compounds. Redox-sensitive systems are particularly attractive given the rich variety of redox gradients present in vivo. These gradients, where the circulation is generally considered oxidizing and the cellular environment is substantially more reducing, provide attractive options for targeted, specific cargo delivery. Recent Advances: Experimental evidence suggests that a “one size fits all” redox gradient does not exist. Rather, there are subtle differences in redox potential within a cell, while the chemical nature of reducing agents in these microenvironments varies. Recent works have demonstrated an ability to modulate the degradation rate of redox-susceptible groups and, hence, provide new tools to engineer precision-targeted DDS. Critical Issues: Modern synthetic and Macromolecular Chemistry provides access to a wide range of redox-susc...
Uttam Pal - One of the best experts on this subject based on the ideXlab platform.
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cα h carries information of a hydrogen bond involving the geminal hydroxyl group a case study with a hydrogen bonded complex of 1 1 1 3 3 3 hexafluoro 2 propanol and tertiary amines
Journal of Physical Chemistry A, 2014Co-Authors: Uttam Pal, Sudeshna Sen, Nakul C MaitiAbstract:Experimental measurement of the contribution of H-bonding to intermolecular and intramolecular interactions that provide specificity to biological complex formation is an important aspect of Macromolecular Chemistry and structural biology. However, there are very few viable methods available to determine the energetic contribution of an individual hydrogen bond to binding and catalysis in biological systems. Therefore, the methods that use secondary deuterium isotope effects analyzed by NMR or equilibrium or kinetic isotope effect measurements are attractive ways to gain information on the H-bonding properties of an alcohol system, particularly in a biological environment. Here, we explore the anharmonic contribution to the C–H group when the O–H group of 1,1,1,3,3,3-hexafluoro-2-propanol (HFP) forms an intermolecular H-bond with the amines by quantum mechanical calculations and by experimentally measuring the H/D effect by NMR. Within the framework of density functional theory, ab initio calculations wer...
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Cα–H Carries Information of a Hydrogen Bond Involving the Geminal Hydroxyl Group: A Case Study with a Hydrogen-Bonded Complex of 1,1,1,3,3,3-Hexafluoro-2-propanol and Tertiary Amines
2014Co-Authors: Uttam Pal, Sudeshna Sen, Nakul C MaitiAbstract:Experimental measurement of the contribution of H-bonding to intermolecular and intramolecular interactions that provide specificity to biological complex formation is an important aspect of Macromolecular Chemistry and structural biology. However, there are very few viable methods available to determine the energetic contribution of an individual hydrogen bond to binding and catalysis in biological systems. Therefore, the methods that use secondary deuterium isotope effects analyzed by NMR or equilibrium or kinetic isotope effect measurements are attractive ways to gain information on the H-bonding properties of an alcohol system, particularly in a biological environment. Here, we explore the anharmonic contribution to the C–H group when the O–H group of 1,1,1,3,3,3-hexafluoro-2-propanol (HFP) forms an intermolecular H-bond with the amines by quantum mechanical calculations and by experimentally measuring the H/D effect by NMR. Within the framework of density functional theory, ab initio calculations were carried out for HFP in its two different conformational states and their H-bonded complexes with tertiary amines to determine the 13C chemical shielding, change in their vibrational equilibrium distances, and the deuterium isotope effect on 13C2 (secondary carbon) of HFP upon formation of complexes with tertiary amines. When C2–OH was involved in hydrogen bond formation (O–H as hydrogen donor), it weakened the geminal C2–H bond; it was reflected in the NMR chemical shift, coupling constant, and the equilibrium distances of the C–H bond. The first derivative of nuclear shielding at C2 in HFP was −48.94 and −50.73 ppm Å–1 for anti and gauche conformations, respectively. In the complex, the values were −50.28 and −50.76 ppm Å–1, respectively. The C–H stretching frequency was lower than the free monomer, indicating enhanced anharmonicity in the C–H bond in the complex form. In chloroform, HFP formed a complex with the amine; δC2 was 69.107 ppm for HFP–triethylamine and 68.766 ppm for HFP-d2–triethylamine and the difference in chemical shift, the ΔδC2 was 341 ppb. The enhanced anharmonicity in the hydrogen-bonded complex resulted in a larger vibrational equilibrium distance in C–H/D bonds. An analysis with the Morse potential function indicated that the enhanced anharmonicity encountered in the bond was the origin of a larger isotope effect and the equilibrium distances. Change in vibrational equilibrium distance and the deuterium isotope effect, as observed in the complex, could be used as parameters in monitoring the strength of the H-bond in small model systems with promising application in biomacromolecules
P Philip R Andres - One of the best experts on this subject based on the ideXlab platform.
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new 4 functionalized 2 2 6 2 terpyridines for applications in Macromolecular Chemistry and nanoscience
European Journal of Organic Chemistry, 2003Co-Authors: P Philip R Andres, Ralph Lunkwitz, Gunther Pabst, Karlheinz Bohn, Daan D Wouters, Stefan S Schmatloch, Ulrich S SchubertAbstract:The well-known reaction of 4′-chloro-2,2′:6′,2′′-terpyridine with alkoxide nucleophiles leads to 4′-functionalized 2,2′:6′,2′′-terpyridines. This reaction allows the easy introduction of different functional groups onto the terpyridine at the 4′-position, i.e. opposite to the metal binding site, in one reaction step. Among the functionalized 2,2′:6′,2′′-terpyridines reported here are amines (including chiral examples), carboxylic acids, simple alkoxy-chain terpyridines with different chain lengths, and a stilbene-functionalized terpyridine. Moreover, the synthesis of two important already known substances was significantly improved. One example of a sequential functionalization of the (aminopentoxy)terpyridine with a dithiolane functionality is also reported. For two of the alkyl-chain-functionalized terpyridines, single-crystal X-ray crystallographic data were obtained. Finally, ordered monolayers of alkyl-substituted terpyridines on HOPG were visualized using STM. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)
