Platinum(II) olefin hydroarylation catalysts: tuning selectivity for the anti-Markovnikov product Tandem catalytic ester hydrogenation and deoxygenation of polyethylene terephthalate

Thesis (Master's)--University of Washington, 2016-06

Tuning the metal-to-metal charge transfer energy of cyano-bridged dinuclear complexes

The metal-to-metal charge transfer (MMCT) transitions of a series of Class II mixed valence dinuclear complexes bearing cyano bridging ligands may be varied systematically by variations to either the hexacyanometallate(II) donor or Co-III acceptor moieties. Specifically, the new dinuclear species trans-[(LCoNCFe)-Co-14S(CN)(5)](-) (L-14S = 6-methyl-1,11-diaza-4,8-dithia- cyclotetradecane-6-amine) and trans-[(LCoNCRu)-Co-14(CN)(5)]-(L-14 = 6-methyl-1,4,8,11-tetraazacyclotetradecane-6-amine) have been prepared and their spectroscopic and electrochemical properties are compared with the relative trans-[(LCoNCFe)-Co-14(CN)(5)](-). The crystal structures of Na{trans-[(LCoNCFe)-Co-14S(CN)(5)]}.51/2H(2)O.1/2EtOH, Na{trans-[(LCoNCRu)-Co-14(CN)(5)]}.3H(2)O and Na{trans-[(LCoNCRu)-Co-14(CN)(5)]}.8H(2)O are also reported. The ensuing changes to the MMCT energy have been examined within the framework of Hush theory, and it was found that the free energy change between the redox isomers was the dominant effect in altering the energy of the MMCT transition.

No-switching quantum key distribution using broadband modulated coherent light

We realize an end-to-end no-switching quantum key distribution protocol using continuous-wave coherent light. We encode weak broadband Gaussian modulations onto the amplitude and phase quadratures of light beams. Our no-switching protocol achieves high secret key rate via a post-selection protocol that utilizes both quadrature information simultaneously. We establish a secret key rate of 25 Mbits/s for a lossless channel and 1 kbit/s for 90% channel loss, per 17 MHz of detected bandwidth, assuming individual Gaussian eavesdropping attacks. Since our scheme is truly broadband, it can potentially deliver orders of magnitude higher key rates by extending the encoding bandwidth with higher-end telecommunication technology.

Tuning the photophysical behavior of luminescent cyclam derivatives by cation binding and excited state redox potential

The emission from two photoactive 14-membered macrocyclic ligands, 6-((naphthalen-1-ylmethyl)-amino)trans-6,13-dimethyl- 13-amino- 1,4,8,11 -tetraaza-cyclotetradecane (L-1) and 6-((anthracen-9-ylmethyl)-amino)trans-6,13 -dimethyl - 13 -amino- 1,4,8, 1 1-tetraaza-cyclotetradecane (L-2) is strongly quenched by a photoinduced electron transfer (PET) mechanism involving amine lone pairs as electron donors. Time-correlated single photon counting (TCSPC), multiplex transient grating (TG), and fluorescence upconversion (FU) measurements were performed to characterize this quenching mechanism. Upon complexation with the redox inactive metal ion, Zn(II), the emission of the ligands is dramatically altered, with a significant increase in the fluorescence quantum yields due to coordination-induced deactivation of the macrocyclic amine lone pair electron donors. For [ZnL2](2+), the substituted exocyclic amine nitrogen, which is not coordinated to the metal ion, does not quench the fluorescence due to an inductive effect of the proximal divalent metal ion that raises the ionization potential. However, for [ZnL1](2+), the naphthalene chromophore is a sufficiently strong excited-state oxidant for PET quenching to occur.

Problems with the argument from fine tuning

The argument from fine tuning is supposed to establish the existence of God from the fact that the evolution of carbon-based life requires the laws of physics and the boundary conditions of the universe to be more or less as they are. We demonstrate that this argument fails. In particular, we focus on problems associated with the role probabilities play in the argument. We show that, even granting the fine tuning of the universe, it does not follow that the universe is improbable, thus no explanation of the fine tuning, theistic or otherwise, is required.

Chemical and structural disorder in eumelanins: A possible explanation for broadband absorbance

We report the results of an experimental and theoretical study of the electronic and structural properties of a key eumelanin precursor-5,6,-dihydroxyindole-2-carboxylic acid ( DHICA) - and its dimeric forms. We have used optical spectroscopy to follow the oxidative polymerization of DHICA to eumelanin and observe red shifting and broadening of the absorption spectrum as the reaction proceeds. First principles density functional theory calculations indicate that DHICA oligomers ( possible reaction products of oxidative polymerization) have the gap between the highest occupied molecular orbital and the lowest unoccupied molecular orbital red-shifted gaps with respect to the monomer. Furthermore, different bonding configurations ( leading to oligomers with different structures) produce a range of gaps. These experimental and theoretical results lend support to the chemical disorder model where the broadband monotonic absorption characteristic of all melanins is a consequence of the superposition of a large number of nonhomogeneously broadened Gaussian transitions associated with each of the components of a melanin ensemble. These results suggest that the traditional model of eumelanin as an amorphous organic semiconductor is not required to explain its optical properties and should be thoroughly reexamined. These results have significant implications for our understanding of the physics, chemistry, and biological function of these important biological macromolecules. Indeed, one may speculate that the robust functionality of melanins in vitro is a direct consequence of its heterogeneity, i.e., chemical disorder is a "low cost" natural resource in these systems

Diel 'tuning' of coral metabolism: physiological responses to light cues

Hermatypic-zooxanthellate corals track the diel patterns of the main environmental parameters temperature, UV and visible light - by acclimation processes that include biochemical responses. The diel course of solar radiation is followed by photosynthesis rates and thereby elicits simultaneous changes in tissue oxygen tension due to the shift in photosynthesis/respiration balance. The recurrent patterns of sunlight are reflected in fluorescence yields, photosynthetic pigment content and activity of the two protective enzymes superoxide dismutase (SOD) and catalase (CAT), enzymes that are among the universal defenses against free radical damage in living tissue. All of these were investigated in three scleractinian corals: Favia favus, Plerogyra sinuosa and Goniopora lobata. The activity of SOD and CAT in the animal host followed the course of solar radiation, increased with the rates of photosynthetic oxygen production and was correlated with a decrease in the maximum quantum yield of photochemistry in Photosystem H (PSII) (Delta F'/F-m'). SOD and CAT activity in the symbiotic algae also exhibited a light intensity correlated pattern, albeit a less pronounced one. The observed rise of the free-radical-scavenger enzymes, with a time scale of minutes to several hours, is an important protective mechanism for the existence and remarkable success of the unique cnidarian-dinoflagellate associations, in which photosynthetic oxygen production takes place within animal cells. This represents a facet of the precarious act of balancing the photosynthetic production of oxygen by the algal symbionts with their destructive action on all living cells, especially those of the animal host.

An examination of the antecedents of readiness for fine-tuning and corporate transformation changes

This study examined employee readiness for fine-tuning changes and for corporate transformation changes. It was proposed that employees would report different degrees of readiness for these two types of change and that different variables would be associated with readiness for the two types of change. Results of regression analyses indicated that trust in peers and logistics and system support displayed strong positive relationships with readiness for fine-tuning changes, while trust in senior leaders and self-efficacy displayed strong positive relationships with readiness for corporate transformation changes. The implications of this study focus on the appropriateness of traditional change management strategies in light of findings that multiple change readiness attitudes exist within an organization.