Adam P. Cole

A Trinuclear Intermediate in the Copper-Mediated Reduction of O2: Four Electrons from Three Coppers

The reaction of metal complexes with dioxygen (O2) generally proceeds in 1:1, 2:1, or 4:1 (metal:O2) stoichiometry. A discrete, structurally characterized 3:1 product is presented. This mixed-valence trinuclear copper cluster, which contains copper in the highly oxidized trivalent oxidation state, exhibits O2 bond scission and intriguing structural, spectroscopic, and redox properties. The relevance of this synthetic complex to the reduction of O2 at the trinuclear active sites of multicopper oxidases is discussed.

Synthesis and characterization of [TiF2(NMe2)2]4 and its use for olefin polymerizations

Abstract An equimolar mixture of TiF4 and Ti(NMe2)4 in CH3CN gave orange crystals of [TiF2(NMe2)2]4 in good yield. This complex is a cyclic tetramer of TiF2(NMe2)2, where each titanium atom is bonded to one terminal fluoride and terminal amide ligands and to two pairs of bridging fluoride and bridging amide ligands. This complex was employed as a catalyst for polymerizations of ethylene, propylene, and styrene in the presence of methylaluminoxane (MAO); the activity was relatively low for these olefin polymerizations.

Synthesis and molecular structure of titanium complexes containing a reduced TEMPO radical

Two titanium compounds containing monoanionic ligands derived from TEMPO were synthesized and structurally characterized, demonstrating the flexibility of the coordination modes adopted by the ligand.

United We Fail: Group versus Individual Strength in the California Sea Mussel, Mytilus californianus

The mussel Mytilus californianus is a dominant competitor for space on wave-swept rocky shores, where it forms dense beds. Byssal threads anchor each mussel both to the substratum and to neighbors, allowing mussels to resist the onslaught of waves. When incident hydrodynamic stress exceeds a mussel’s tenacity, the threads are broken, the mussel is dislodged, and a gap is opened in the bed. Here, we show that when groups of contiguous bed mussels experience similar hydrodynamic forces, they collectively have a lower tenacity than when force is applied to a single individual. Lowered group tenacity leads to greater probabilities of dislodgment, with ramifications for community dynamics and species diversity.

Modification of a commercially available photoacoustic imaging system for the use of 1064nm and 532nm wavelengthsto assess photoacoustic contrast agents

The use of near-infrared wavelengths for photoacoustic (PA) imaging takes advantage of the relatively low inherent absorption of tissues and has encouraged the development of agents which show high contrast in this range. Here, we describe the modification of a commercially available PA imaging system (Vevo LAZR, VisualSonics, Toronto) to take advantage of the 532nm and 1064nm wavelengths inherent in the generation of the currently tuneable range of 680 to 970nm and in the use of these two wavelengths to assess contrast agents. The photoacoustic imaging system generated light from a Nd/YAG laser modified to extract the 532 and 1064nm wavelengths in addition to its OPO-derived tuneable range (680 - 970 nm) and deliver this light through a fiber integrated into a linear array transducer (LZ400, VisualSonics). Gold nanorods (UT Austin), carbon nanotubes (Stanford U), DyLight 550 (Thermo Fisher) and blood were imaged in a phantom (PE20 tubing) and in a hindlimb subcutaneous tumor in vivo to determine their photoacoustic signal intensity at all wavelengths. In the phantom and in vivo, all agents caused an enhancement of the photoacoustic signal at their respective peak absorbance wavelengths. These results show that the 532nm and 1064nm wavelengths could prove useful in biomedical imaging due to the contrast agents customized for them. The 1064nm wavelength in particular has the advantage of having very low generation of endogenous signal in vivo, making agents tuned to this wavelength ideal for targeted contrast imaging.