Open Access Kent State (OAKS)

While liquid crystals (LCs) possess diverse structures, they are often oversimplified as requiring a “hard” ring/core component and a “soft” acyclic/tail component as well as some sufficient degree of spacial anisotropy (rods/calamitic or disks/discotic). Small molecule rod-like calamitic LCs without tails are well known but small molecule disc-like LCs without tails are extremely rare. The technical goal of this project is to design, prepare and characterize simple aromatic molecules with no tails that display discotic/columnar behavior. Such materials are potentially important as organic semiconductor materials.

We have prepared triphenylene compounds with careful control of fluorination and other substitution. These molecules were prepared using a series of organometallic C-C bond forming reactions and a final photochemical photocyclodehydrofluorination (PCDHF) reaction; specifically developed for the controlled preparation of selectively fluorinated polynuclear aromatics. New materials have been routinely characterized by standard chemical/physical techniques (NMR, GC-MS, DSC, POM). A subset of materials identified as potentially discotic are subjected to further additional characterization methods (TOF, XRD).

This approach has led to the discovery of a growing class of tail-free triphenylene discotic materials. We are in the process of systematically modifying the structure of the triphenylenes (varying the number, identity and location of small substituents) in order to understand the underlying molecular features required to deliver discotic behavior in the absence of soft segments. As we continue to identify the specific molecular and intermolecular contributions involved we can then selectively turn them on and off to deliver a well-controlled set of phase transitions including columnar phases.

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Antibiotic resistant bacteria strains have come into focus in recent years; these bacteria are unable to be treated by normal antibiotics and have resulted in an increase in the number of mortalities by infectious diseases for the first time in decades. The antibiotic properties of gallium have been studied in recent years. Bacterial cells require iron to function; gallium, which has very similar ionic size and charge, travels through the body by the same mechanisms (i. e. siderophores) and is delivered to the cell by the same uptake pathways. Gallium attacks the cell by a “Trojan horse” method: it takes the place of iron in the metabolic pathway of the cell, but since it does not possess iron’s redox properties, gallium cannot do iron’s job, and the cell is forced to undergo apoptosis (programmed self-death). Gallium has also been shown to penetrate biofilms, self-produced matrices created by bacteria to protect themselves. Gallium was utilized in therapy as Ganite®, a gallium nitrate solution; however, 12.5% of patients had renal failure because gallium precipitated as gallium hydroxide and prevented proper kidney function. Our plan is to utilize gallium cysteinate nanoparticles to kill antibiotic-resistant strains of bacteria such as Staphylococcus aureus and Pseudomonas aeruginosa that will not cause aggregation and kidney death. In addition, properties of a copper-bound gallium cysteinate nanoparticle in these therapies will be explored.

https://docs.google.com/document/d/1pXGvprxPTlu5zuM2orvPikc2Bp-KNvub9O_…

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