Solution and Solid-State Characterization of Alq₃-Functionalized Polymers

Poly(norbornene) has been functionalized with aluminum tris(8-hydroxyquinoline) (Alq3), the emission and electron-transport layer of choice in organic light-emitting diodes. The resulting polymer can be spin coated onto surfaces thereby overcoming fabrication problems associated with pure Alq3. The Alq3-polymers, both in solution and in the solid-state, show outstanding emission properties, clearly indicating that the polymer backbone does not interfere with the optical properties of the pendant Alq3 side-chain. The ligand sphere around the aluminum center on the polymer can be functionalized with electron-donating or -withdrawing groups, thereby allowing the emission of the polymer to be tuned from blue to yellow (430−549 nm). The results demonstrate the potential of the Alq3-polymer system as emission layer in organic light-emitting diodes

Investigations of Metal-Coordinated Peptides as Supramolecular Synthons

This article describes the synthesis and controlled assembly of four model biological-hybrid scaffolds via coordination of a metal complex to four new tripeptides. Each model tripeptide investigated has either a central pyridyl glycyl or a pyridyl alanyl residue between two terminally protected glycines. All tripeptides were coordinated to their complementary recognition unit, a p-methoxy SCS−Pd pincer complex. The assembly events were fully characterized and investigated by 1H NMR, ES-MS, and isothermal titration calorimetry (ITC) to elucidate how the substitution and spatial distance of the pyridyl moiety to the peptide backbone affects the metal coordination. Using these characterization techniques, we have shown that the metal-coordination events in all cases are fast and quantitative and that the peptide backbones do not interfere with the self-assembly. The ITC analyses showed that the 4-pyridyl tripeptides are the tightest binding ligands toward the palladated pincer complexes with the alanyl derivative being the strongest overall, demonstrating the superiority of the 4-pyridyl peptides over their 3-pyridyl analogues. The measured association constants are comparable to other pincer−pyridine systems in DMSO suggesting that the controlled coordination of the metalated pincer/pyridine interaction is an interesting biological synthon and will allow for the future development of important noncovalent peptide-based hybrid materials

Design and Synthesis of Alq₃-Functionalized Polymers

Design and Synthesis of Alq3-Functionalized Polymer

Modular Approach for the Development of Supported, Monofunctionalized, Salen Catalysts

We report a modular approach toward polymer-supported, metalated, salen catalysts. This strategy is based on the synthesis of monofunctionalized Mn− and Co−salen complexes attached to a norbornene monomer via a stable phenylene−acetylene linker. The resulting functionalized monomers can be polymerized in a controlled fashion using ring-opening metathesis polymerization. This polymerization method allows for the synthesis of copolymers, resulting in an unprecedented control over the catalyst density and catalytic-site isolation. The obtained polymeric manganese and cobalt complexes were successfully used as supported catalysts for the asymmetric epoxidation of olefins and the hydrolytic kinetic resolution of epoxides. All polymeric catalysts showed outstanding catalytic activities and selectivities comparable to the original catalysts reported by Jacobsen. Moreover, the copolymer-supported catalysts are more active and selective than their homopolymer analogues, providing further proof that catalyst density and site isolation are key toward highly active and selective supported salen catalysts

Noncovalently Functionalized Poly(norbornene)s Possessing both Hydrogen Bonding and Coulombic Interactions

Random copolymers containing both hydrogen bonding and charged ionic sites have been synthesized by the ring-opening metathesis polymerization of norbornene monomers containing either an ionic quaternary ammonium group or a 2,6-diaminopyridine functionality. All copolymers were functionalized subsequently via self-assembly using hydrogen bonding and Coulombic interactions. The hydrogen bonding interactions between 2,6-diaminopyridine and N-butylthymine were studied in the presence of the ionic quaternary ammonium group and its subsequent self-assembly with three different charged anionic species to investigate the influence of the Coulombic interactions on the strength of hydrogen bonding. It was found that hydrogen bonding was independent of the nature and presence of the Coulombic interactions. These results prove that the studied hydrogen bonding interactions are orthogonal to the Coulombic interactions and that both interactions can be used independently of each other in the same system to noncovalently functionalize polymer backbones

Patterned Polymeric Multilayered Assemblies through Hydrogen Bonding and Metal Coordination

Patterned polymeric multilayered assemblies were formed using a combination of metal coordination and hydrogen bonding interactions. We proved that the hydrogen bonding interaction between diamidopyridine and thymine can be employed for polymeric multilayer assemblies. We then combined this strategy along with a second supramolecular interaction, metal coordination. These interactions proved to be orthogonal to one another on the surface, making each discrete region individually responsive to external stimuli

Bridged Coordination Polymer Multilayers with Tunable Properties

Coordination multilayers consisting of Pd(II) pincer-type complexes and poly(vinyl pyridine) were synthesized and characterized. Film properties were found to be dependent on and could be tuned by varying bath deposition concentrations, polymer molecular weight, and solution additives that compete with binding. Generally, smoother, thinner films were obtained with lower poly(vinyl pyridine) deposition bath concentrations. Likewise, film thickness and roughness could be reduced by employing a higher-molecular-weight poly(vinyl pyridine). Film properties could also be influenced by using acetonitrile as a solution additive, effectively driving the binding equilibrium slightly toward the free species

Investigations of Metal-Coordinated Peptides as Supramolecular Synthons

This article describes the synthesis and controlled assembly of four model biological-hybrid scaffolds via coordination of a metal complex to four new tripeptides. Each model tripeptide investigated has either a central pyridyl glycyl or a pyridyl alanyl residue between two terminally protected glycines. All tripeptides were coordinated to their complementary recognition unit, a p-methoxy SCS−Pd pincer complex. The assembly events were fully characterized and investigated by 1H NMR, ES-MS, and isothermal titration calorimetry (ITC) to elucidate how the substitution and spatial distance of the pyridyl moiety to the peptide backbone affects the metal coordination. Using these characterization techniques, we have shown that the metal-coordination events in all cases are fast and quantitative and that the peptide backbones do not interfere with the self-assembly. The ITC analyses showed that the 4-pyridyl tripeptides are the tightest binding ligands toward the palladated pincer complexes with the alanyl derivative being the strongest overall, demonstrating the superiority of the 4-pyridyl peptides over their 3-pyridyl analogues. The measured association constants are comparable to other pincer−pyridine systems in DMSO suggesting that the controlled coordination of the metalated pincer/pyridine interaction is an interesting biological synthon and will allow for the future development of important noncovalent peptide-based hybrid materials

Investigations of Metal-Coordinated Peptides as Supramolecular Synthons

This article describes the synthesis and controlled assembly of four model biological-hybrid scaffolds via coordination of a metal complex to four new tripeptides. Each model tripeptide investigated has either a central pyridyl glycyl or a pyridyl alanyl residue between two terminally protected glycines. All tripeptides were coordinated to their complementary recognition unit, a p-methoxy SCS−Pd pincer complex. The assembly events were fully characterized and investigated by 1H NMR, ES-MS, and isothermal titration calorimetry (ITC) to elucidate how the substitution and spatial distance of the pyridyl moiety to the peptide backbone affects the metal coordination. Using these characterization techniques, we have shown that the metal-coordination events in all cases are fast and quantitative and that the peptide backbones do not interfere with the self-assembly. The ITC analyses showed that the 4-pyridyl tripeptides are the tightest binding ligands toward the palladated pincer complexes with the alanyl derivative being the strongest overall, demonstrating the superiority of the 4-pyridyl peptides over their 3-pyridyl analogues. The measured association constants are comparable to other pincer−pyridine systems in DMSO suggesting that the controlled coordination of the metalated pincer/pyridine interaction is an interesting biological synthon and will allow for the future development of important noncovalent peptide-based hybrid materials

Facile Functionalization of Gold Nanoparticles via Microwave-Assisted 1,3 Dipolar Cycloaddition

This contribution describes a simple and facile method for the functionalization of thiol-coated gold nanoparticles using microwave-assisted 1,3 dipolar cycloadditions. The developed procedure allows for the attachment of terminal alkynes onto azide-containing gold nanoparticles in nearly quantitative conversions within minutes. The utility of the method has been demonstrated by attaching a library of substituted alkynes onto gold nanoparticles in nearly quantitative yields. In a proof of principle study, we demonstrate the potential use of this methodology in catalysis by attaching palladium catalysts to the azide-containing gold nanoparticles and investigate the resulting materials as supported catalysts in Suzuki couplings. Activities that rival the nonsupported analogues were observed, demonstrating that the nanoparticle support does not interfere with the catalytic activity