Inorganic / Materials
A unifying theme of my research program is to utilize metallo-radical and organo-metal substrate reactions to obtain both energy relevant small molecule organometallic transformations and living radical polymerization for applications in block copolymer materials. These two current focal areas of research are briefly described below.
A broad based program in polymer chemistry sponsored by NSF spans areas from transition metal catalyst development and block copolymer synthesis to technological applications of self assembled nano-structured polymer arrays. Reactivity of metal-centered radical species and organometallic derivatives are used in the control of radical polymerization through both catalytic chain transfer and living radical polymerization. Organo-cobalt porphyrin complexes mediate a highly precise living radical polymerization of vinyl monomers such as acrylates and vinyl esters to form low polydispersity homopolymers and block co-polymer materials. This pathway to obtain living radical polymerization is a transition metal form of degenerative transfer that we refer to as radical interchange polymerization (RIP). Living radical polymerization provides access to a vast array of new classes of block copolymers. Self assembly of amphiphilic block copolymers into micelles and nano-structured arrays have many technological applications in nano-reactors, gene and drug delivery, dispersants, metal nanoparticle synthesis, water and fuel cell membranes, sensors, and solar cells which are being developed through collaborations with materials scientists and engineers. New materials design strategies are determined for each of the central topics along with the requisite approaches for polymer synthesis, morphology, and property evaluation.
Our energy related catalysis research supported by DOE is focused on developing new strategies to accomplish thermodynamically and kinetically challenging substrate reactions such as methane activation and carbon monoxide reductive coupling. Ligands are designed to achieve high selectivity through steric and electronic constraints on forming the transition states for substrate reactions. The primary focus is on group nine (Co, Rh, Ir) metal complexes where the importance of metallo-radicals is a recurring theme. Metallo-porphyrins, chlorophylls, and related macrocyclic complexes are prominent thermal and photocatalysts in biological systems and emerging as important catalyst materials for chemical manufacturing processes. The unique chemical and physical properties of metallo-porphyrins and macrocyclic complexes are used in producing thermal and photocatalytic cycles for small molecule reactions.Several important examples include hydrogenation of CO and CO2, activation of methane, oxidation of alkenes, photoreductions, and alkene polymerization. Tethered diporphyrin ligands have been designed and synthesized that are used in forming bimetalloradical complexes of Rh(II). Bimetalloradicals provide preorganization of transition states that involve two metalloradicals and give rapid highly selective substrate reactions. Structural, kinetic-mechanistic, thermodynamic, and reactivity studies are used in characterizing intermediates, anticipating new types of reactions, and guiding the design of strategies to produce selective catalyst materials.
Imler, George; Bhagan, Salome; Coffin, Virginia L; Wayland, Bradford B. "Reduction of Carbon Monoxide by [(TMTAA)Rh](2) to Form a Dimetal Ketone Complex" Inorganic Chemistry 2012 50m 6, 3352-3354.
Tangeysh, Behzad; Fryd, Michael; Hayik, Sara; Kamps, Amanda; Wayland, Bradford B. "Anionically cross linked homopolymer colloids applied in formation of platinum nanoparticles." Journal of Colloid and Interfaces Science 2012 369, 482-484.
Zhu, Xaiobo; Fryd, Michael; Tran, Benjamin D; Ilies, Marc A; Wayland, Bradford B. "Modifying the Hydrophilic-Hydrophobic Interface of PEG-b-PCL to Increase micelle Stability: Preparation of PEG-b-PBO-b-PCL Triblock Copolymers, Micelle Formation, and Hydrolysis Kinetics." Macromolecules 2012 45, 2, 660-665.
Imler, Gregory H; Lu, Zhi; Kistler, Kurt A; Carroll, Patrick J; Zdilla, Michael J; Wayland, Bradford B. "Complexes of 2,5-Bis(α-pyridyl)pyrrolate with Pd(II) and Pt(II): A Monoanionic Iso-π-Electron Ligand Analog of Terpyridine." Inorganic Chemistry 2012 51, (19), 10122-10128
Tangeysh, Behzad; Fryd, Michael; Ilies Marc A; Wayland, Bradford B. "Palladium metal nanoparticle size control through ion paired structures of [PdCl4]2− with protonated PDMAEMA." Chemical Communications 2012 48, 8955-8957
Bhagan, Salome; Wayland, Bradford B. " Formation and Reactivity of a Porphyrin Iridium Hydride in Water: Acid Dissociation Constants and Equilibrium Thermodynamics Relevant to Ir-H, Ir-OH, and Ir-CH2-Bond Dissociation Energetics." Inorganic Chemistry 2011 50, 21, 11011-11020.
Sanchez-Gaytan, Brenda L; Li, Shan; Kamps, Amanda C; Hickey, Robert J; Clarke, Nigel; Fryd, Michael; Wayland Bradford B; Park, So-Jung. "Controlling the Radial Position of the Nanoparticles in Amphiphillic Block-Copolymer Assemblies." Journal of Physical Chemistry C 2011 115, 16, 7863-7842.
Sarkar, Sounak; Li, Shan; Wayland, Bradford B. "Hydrogen and Methanol Exchange Processes for (TMP)Rh-OCH3(CH3OH) in Binary Solutions of Methanol and Benzene." Inorganic Chemistry 2011 50, 8, 3313-3319.
Chen, Xi-Jun; Sanchez-Gaytan, Brenda L; Hayik, Sara EN; Fryd, Michael; Wayland, Bradford B; Park, So-Jung. "Self-Assemblied Hybrid Structures of DNA Block-Coploymers and Nanoparticles with Enhanced DNA Binding Properties." Small 2010 6, 20, 2256-2260.
Sarkar, Sounak; Li, Shan; Wayland, Bradford B. "Comparison of Rh-OCH3 and Rh-Ch2OH Bond Dissociation Energetics from Methanol C-H and O-H Bond Reactions with Rhodium(II) Porphyrins." Journal of the American Chemical Society 2010 132, 39, 13569-13571.
Liu, Lianghui; Yu, Mengmeng; Wayland, Bradford B; Fu, Xuefeng. "Aerobic oxidation of alcohols catalyzed by rhodium(III) poryphin complexes in water: reactivity mechanistic studies" Chemical Communications. 2010, 46, 34, 6353-6355.
Bhagan, Salome; Sarkar, Sounak; Wayland, B. "Comparative Studies of Preferential Binding of Group Nine Metalloporphyrins (M = Co, Rh, Ir) with Methoxide/Methanol in Competition with Hydroxide/Water in Aqueous Solution" Inorganic Chemistry. 2010 49, 14, 6734-6739.
Hickey, Robert J.; Sanchez-Gaytan, Brenda L.; Cui, Weihong, Russell J.; Fryd, Mike; Wayland, Bradford B.; Park, So-Jung. "Morphological Transitions of Block-Copolymer Bilayers via Nanoparticle Clustering" Small. 2010 6, 1, 48-51.
Zhang, Jiadi; Wayland, Bradford B.; Yun, Lin; Li, Shan; Fu, Xuefeng; " Reactivity and kinetic-mechanistic studies of regioselective reactions of rhodium prophyrins with unactivated olefins in water that form beta-hyroxyalkyl complexes and conversions to ketones and epoxides" Dalton Transactions. 2010, 39, 2, 477-483.
Li, Shan; Sarkar, Sounak; Wayland, Bradford B.; " Methanol as a Reaction Medium and Reagent in Substrate Reactions of Rhodium Porphyrins" Inorganic Chemistry. 2009, 48, 17, 8550-8558.
Peng, Chi-How; Li, Shan; Wayland, Bradfor B.; "Formation and Interconversion of Organo-Cobalt Complexes in Reactions of Cobalt(II) Porphyrins with Cyanoalkyl Radicals and Vinyl Olefins" Inorganic Chemistry. 2009, 48, 11, 5039-5046.
Zhang, Jiadi; Li, Shan; Fu, Xuefeng; Wayland, Bradford B.; "Aerobic oxidation of alkenes mediated by prophyrin rhodium(III) complexes in water" Dalton Transactions. 2009, 19, 3661-3663.
de Bruin, Bas; Dzik, Wojciech I.; Li, Shan; Wayland, Bradford B.; "Hydrogen-Atom transfer in Reactions of Organic Radicals with [Coll(pori)]. (por=Porphyrinato) and in Subsequent Addition of [Co(H)(pori)] to Olefins" Chemistry--A European Journal. 2009, 15, 17, 4312-4320.