A library of novel pyridinophane tetra-aza macrocyclic molecules derived from 1,4,7,10-tetraaza-2,6-pyridinophane (pyclen) capable of chelating biologically relevant metal ions have been synthesized. Applications of these types of molecules currently being pursued are 1) therapeutic, focusing on radical scavenging and metal chelation and 2) diagnostic, focusing on magnetic resonance imaging (MRI) contrast agents when complexed with specific metal ions. Despite wide interest in these molecules, a full study of the electronic effects imparted by substitution to the pyridyl moiety and the subsequent impact on the metal center has not yet been conducted. The objective of the present study is to characterize metal complexes of four, new tetra-aza macrocyclic metal chelating molecules. The pyridyl functional groups studied include: A) unmodified pyridyl (L1), B) 14-hydroxyl (L2), C) 14-nitrile (L3), and D) 14--nitro (L4) modified pyclen structures. Procedures for metal ion chelation with copper (II) ion, followed by characterization and analysis of the electronic environments of each are presented.

The dye-sensitized solar cells (DSSCs) are a possible alternative tool to harvest solar energy instead of the traditional silicon-based solar cells. DSSCs offer various advantages, such as good energy conversion efficiencies in low-light condition, simple fabrication, low cost, and the ability to modify key properties of the solar cell such as the absorbance wavelengths. We are interested in developing new types of semiconductor supports for use in DSSCs based on tin(IV) oxide nanoparticles (NPs). Tin(IV) oxide offers a wide band gap and higher electron mobility as compared with the more widely used titanium dioxide. In this study, two morphologies of tin(IV) oxide, spherical and flower-like NPs, are synthesized. These two types of tin(IV) oxide NPs and mixtures of both at various ratios are used to fabricate DSSCs. We find that nanoflowers usually give the cells higher open circuit voltages but with lower photocurrent. Nanospheres give much higher photocurrent but with lower open circuit voltage. A mixture that has a 1:2 molar ratio of nanoflowers and nanospheres gave the best performance in terms of photocurrent and voltage. Furthermore, we are investigating the effect of a deposited layer of titanium(IV) oxide on top of the tin(IV) oxide to further enhance the photoperformace of the solar cells.

Amaryllidaceae isoquinoline alkaloids as well as their analogs have long been of interest as lead compounds in drug discovery due to their range of biological activity. Many of these alkaloids are cytotoxic anti-tumor agents. Moreover, there have also been studies showing the effectiveness of these molecules against yellow fever and other diseases caused by RNA- containing flaviviruses. The study of these compounds as pharmaceutical agents is hampered by their low natural abundance, which necessitates the development of laboratory syntheses of these alkaloids and their analogs.
This project focuses on the total syntheses of the Pancratistatin-type natural products that contain the phenanthridone ring system. In stage one, model systems are being investigated to develop the methodology required to introduce requisite functionality found in natural systems. Previous research from this laboratory gives the basic phenanthridone skeleton with several different functional groups, but there are no reported methods for converting these functions into polyhydroxycyclohexenes with stereochemical control. Two of the problems under investigation involve the ring expansion of a spiro ring containing an epoxide and the production of a specific trihydroxycyclohexene with control of stereochemistry. In stage two, a specific phenanthridone alkaloid will be targeted for total synthesis that uses the new methodology developed in stage one.

Organometallic catalysts are useful in many organic reactions by exploiting the Lewis acidity of the metal complex. Most catalysts available rely on precious metals like platinum and rhenium. These catalysts pose a financial and environmental barrier to many scientists. Thus, there is a need for catalysts that use less expensive and toxic metals, such as copper. A library of copper catalysts with different electronic functionalities have been synthesized and characterized by cyclic voltammetry, UV-VIS, NMR, and X-ray crystallography. It was found that the complexes with electron donating groups better stabilize the copper center, when compared to the complexes with electron withdrawing groups. However, the planar characteristics of each ligand makes them unsuitable candidates for copper catalysis because they cannot bind to the tetrahedral geometry of reduced copper. This work warrants the complexation of these ligands with other metals, like nickel or cobalt, to determine their viability as applicable organometallic catalysts.

Room-temperature ionic liquids and deep-eutectic solvents have become unique and almost indispensible materials for various areas of sciences, medicine and engineering. The ability to engineer media with desired properties favorably distinguishes these solvents from traditionally used molecular solvents.

This poster will describe our ongoing efforts on designing various types of ionic, eutectic systems as well as approaches towards modulating their phase transitions. Studies related to controlling the self-assembly process of various solutes in this type of media will also be presented.