Timothy W. Hanks

Functionalization of Carbon Nanotubes with Bovine Serum Albumin in Homogeneous Aqueous Solution

Single-walled (SWNTs) and multiple-walled (MWNTs) carbon nanotubes were solubilized via the esterification of nanotube-bound carboxylic acids by oligomeric polyethylene glycol compounds. The water-soluble samples were used as starting materials in reactions with bovine serum albumin (BSA) protein in ambient aqueous solutions. The reaction conditions were designed for thermodynamically favorable transformation from ester to amide linkages, yielding SWNT-BSA and MWNT-BSA conjugates. The results show that the use of soluble starting nanotube materials in an indirect functionalization method represents a valuable approach to the biomodification of carbon nanotubes.

Complementary halogen and hydrogen bonding: sulfur⋯iodine interactions and thioamide ribbons

Complementary halogen bonding and hydrogen bonding coexist in co-crystals of organoiodines with molecules containing the thioamide functionality. Thiourea.organoiodine co-crystals are shown to exhibit a remarkably reliable synthon with complementary N-H...S ribbons and S...I interactions.

Tetraiodoethylene: a supramolecular host for Lewis base donors

Abstract Tetraiodoethylene (TIE) forms charge transfer complexes with diazine donors through N···I interactions, in which the structure of the complex is very similar to that of TIE. In TIE, two unique molecules form distinct “layers”, and in the complexes the donor molecules take the place of TIE molecules in one of the layers. I···I interactions within the remaining layer of TIE maintain the structure of the layer and yet allow enough flexibility to accommodate a wide variety of donor molecules. Phenazine, quinoxaline, 1,4–dicyanobenzene, and 2,2′–bipyridine all form complexes with TIE which have very similar structures. Phenazine and 2,2′–bipyridine donors sit on the same inversion center as the TIE molecules they replace, and the donor·TIE chains run in the (1 1 0) direction. 1,4–Dcb·TIE has a very similar structure to that of the previously determined pyrazine·TIE complex, but the donor molecules span TIE acceptors in the (1 −2 1) direction rather than (1 1 1). The asymmetric environment of the donor sites in quinoxaline result in a very distorted layered structure, and the I···I interactions between neighboring TIE molecules are the weakest of those reported here. Decomposition of TIE in its reaction with 2,2′–bipyridine gave the side product, [2,2′–bipyridine(H)]I3·TIE, in which I···I interactions link TIE molecules and I3− anions to form a pseudo–polyiodide layer.

Efficient Synthesis of a Complete Donor/Acceptor bis(Aryl)diyne Family

Abstract A facile route to a family of bis(aryl)diynes containing both an electron donating pyridine ring and an electron accepting iodobenzene has been developed. The convergent synthesis involves the coupling of 2-, 3-, or 4-bromopyridine with TMS-acetylene, followed by deprotection to form the first half of the molecule. Similarly, 2-, 3-, or 4-iodoaniline was coupled to TMS-acetylene after protection of the amine group as a diethyltriazine. After conversion of the triazine to an iodine, deprotection of the acetylene and formation of the corresponding bromophenylacetylene, the two halves of the molecule were coupled under Cadiot-Chodkiewicz conditions. Nine new compounds were prepared, each of which was found to thermally polymerize from the melt. None of the compounds underwent photochemical polymerization in the solid-state.

Surface modification of polypyrrole/biopolymer composites for controlled protein and cellular adhesion

The ability to control the interaction between proteins and cells with biomaterials is critical for the effective application of materials for a variety of biomedical applications. Herein, the surface modification of the biological dopant dextran sulphate-doped polypyrrole (PPy-DS) with poly(ethylene glycol) to generate a biomaterial interface that is highly resistant to protein and cellular adhesion is described. Thiolated poly(ethylene glycol) (PEG-thiol) was covalently bound to PPy-DS backbone via a thiol-ene reaction. The surface resistance to an extracellular matrix protein fibronectin increased with increasing molecular weight and concentration of PEG-thiol, and was further optimised via increasing the reaction temperature and the pH of the reactant aqueous solution. Optimised surface modification conditions substantially reduced interfacial protein adsorption, with the complete inhibition of adhesion and colonisation by primary mouse myoblasts. PEG-thiol-modified inherently conducting polymers are highly protein resistant multifunctional materials that are promising compounds for a range of biomedical and aquatic applications.

Study of the Halogen Bonding between Pyridine and Perfluoroalkyl Iodide in Solution Phase Using the Combination of FTIR and 19F NMR

Halogen bonding between pyridine and heptafluoro-2-iodopropane (iso-C3F7I)/heptafluoro-1-iodopropane (1-C3F7I) was studied using a combination of FTIR and 19F NMR. The ring breathing vibration of pyridine underwent a blue shift upon the formation of halogen bonds with both iso-C3F7I and 1-C3F7I. The magnitudes of the shifts and the equilibrium constants for the halogen-bonded complex formation were found to depend not only on the structure of the halocarbon, but also on the solvent. The halogen bond also affected the Cα-F (C-F bond on the center carbon) bending and stretching vibrations in iso-C3F7I. These spectroscopic effects show some solvent dependence, but more importantly, they suggest the possibility of intermolecular halogen bonding among iso-C3F7I molecules. The systems were also examined by 19F NMR in various solvents (cyclohexane, hexane, chloroform, acetone, and acetonitrile). NMR dilution experiments support the existence of the intermolecular self-halogen bonding in both iso-C3F7I and 1-C3F7I. The binding constants for the pyridine/perfluoroalkyl iodide halogen bonding complexes formed in various solvents were obtained through NMR titration experiments. Quantum chemical calculations were used to support the FTIR and 19F NMR observations.

Synthesis of “Acetylene-Expanded” Tridentate Ligands

Synthetic routes to four new tridentate ligands with large cavities have been developed. Each ligand features two halides at the termini of the molecules that could be used for further elaboration of the system. Such compounds are ideal for encapsulating organoiodide guests using charge-transfer interactions.

Functionalised inherently conducting polymers as low biofouling materials.

Diatoms are a major component of microbial biofouling layers that develop on man-made surfaces placed in aquatic environments, resulting in significant economic and environmental impacts. This paper describes surface functionalisation of the inherently conducting polymers (ICPs) polypyrrole (PPy) and polyaniline (PANI) with poly(ethylene glycol) (PEG) and their efficacy as fouling resistant materials. Their ability to resist interactions with the model protein bovine serum albumin (BSA) was tested using a quartz crystal microbalance with dissipation monitoring (QCM-D). The capacity of the ICP-PEG materials to prevent settlement and colonisation of the fouling diatom Amphora coffeaeformis (Cleve) was also assayed. Variations were demonstrated in the dopants used during ICP polymerisation, along with the PEG molecular weight, and the ICP-PEG reaction conditions, all playing a role in guiding the eventual fouling resistant properties of the materials. Optimised ICP-PEG materials resulted in a significant reduction in BSA adsorption, and > 98% reduction in diatom adhesion.

The reaction of iodine with 9-methylacridine: formation of polyiodide salts and a charge-transfer complex

The reaction of iodine and 9-methylacridine in methylene chloride results not in the formation of a charge-transfer complex as with acridine, but in the iodine-rich salt [ICH2C13H8N–H]4(I8)(I5)2, 8, where a proton on the methyl group has been replaced by an iodine. In toluene, the reaction produces both a charge-transfer complex ICH2C13H8N–I2, 9, and a salt [CH3–acridine(H)]2(I7)(I5), 10. Polyiodide salt formation can be explained by the availability of a facile reaction pathway from the aryl radical cation which results from initial oxidation by I2.

Syntheses and structures of two acridine orange polyiodide salts

Polyiodide salts of acridine orange were isolated from solutions of an acridine and I2 in methylene chloride, ethanol, and acetone. The products from all solutions were found to contain both amorphous and crystalline material. The isolated crystalline product from methylene chloride and ethanol were identical (1), but the product isolated from acetone was different (2). Complex 1 was formulated as [C17H19N3(H)]2(I)2ċ 3I2. It crystallizes in the monoclinic space group P21/n, with a = 9.082(2) Å, b = 24.027(4) Å, c = 10.683(1) Å, β = 107.20(1)○, and D(calc) = 2.31 Mg/m3. Complex 2 was formulated as [C17H19N3(H)]I3. It crystallizes in the triclinic space group P − 1, with a = 10.498(2) Å, b = 11.265(2) Å, c = 9.287(1) Å, αg 100.88(1)○, β = 94.57(1)○, γ = 102.10(1)○, and D(calc) = 2.05 Mg/m3.