Summer Science Research at Bryn Mawr

'Goldsmith, Dr. Jonas' Archive

“Synthesis and Characterization of Ruthenium Bipyridine-Pyrene Complexes

Posted July 10, 2011

Abstract: Maggie Ahrens Mentor: Dr. Jonas Goldsmith Iridium complexes have been shown to be able to harvest light energy to create hydrogen by reduction of the protons found in water. Though iridium complexes can catalyze this reaction independent of any other catalysts, they are often inefficient and slow. Similar ruthenium complexes have the potential to […]

Gas Chromatography Measurements of Photocatalytic Hydrogen Production Using Multimetallic Ruthenium and Iridium Complexes

Posted June 17, 2011

Abstract: Anna Melker Mentor: Jonas I. Goldsmith To impede the acceleration of global climate change and relieve our dwindling oil supplies, the development of other energy sources is imperative. Hydrogen fuel stands out as a zero emissions, clean alternative. One way to make hydrogen gas involves the photocatalytic reduction of water using transition metal complexes […]

Synthesis of Ruthenium Bipyridine-Pyrene Ligands

Posted June 22, 2010

My project involves the synthesis of synthesizing bipyridine-pyrene ligands that will facilitate the attachment of transition metals onto carbon nanotubes. The ligand will be synthesized via a nucleophilic substitution reaction between bipyridine acid chloride and an amine group, resulting in an amide to which the pyrene can subsequently be added.

Functionalization of a Variety of Carbon Surfaces with Transition Metal Complexes: Glassy Carbon, HOPG and SWNT

Posted May 14, 2010

The behavior of several carbon surface types functionalized with the compound below (1) will be explored.

A sample of complex 1 was synthesized and re-crystallized to obtain a workable powder. Polished glassy carbon, highly oriented pyrolytic graphite, and single-walled carbon nanotubes (SWNT), were functionalized using 1 by dissolving the complex in acetonitrile and exposing the carbon surface to a dilute solution of 1. The HOPG and glassy carbon functionalized surfaces were characterized by the observed redox behavior on an electrode surface using cyclic voltammetry. Experiments used a range of concentrations from 0.1μM to 2.0μM, and were conducted over the period of 1.5 hours. For each data point the reduction peak height was recorded. The equation was used to obtain the electrode coverage for each data point. The kinetics and thermodynamics of the adsorption process can be determined by an analysis of coverage (Γ) versus time and coverage versus concentration. In order to study the adsorption behavior of 1 on SWNT, an additional step was required to disperse and separate the SWNT material. Suspensions of SWNT were created using several solvents, including Milli-Q water, chloroform, ethanol, and isopropanol. A range of surfactants, SDS, PVP, PVA, and Triton X-100, were also used and compared as to their relative utilities for suspension formation. Suspensions that appeared to be well-distributed were diluted and filtered. Atomic force microscopy was used to characterize the appearance of the SWNT suspensions. The dispersions will also be cast onto metal electrodes to study their adsorption behavior.

Functionalizing Surfaces with Transition Metal Complexes

Posted May 13, 2010

The nanotechnology field is growing rapidly thus novel methods in modulating behavior on the nanoscale is necessary for the development of nanoelectronics. In order to control the behavior of this technology, one must appeal to redox chemistry. Adding functionality to surfaces is possible through the synthesis of metal complexes with the appropriate substituents, allowing adsorption to various surfaces.

The focus of this research is to achieve the synthesis of a transition metal complex capable of the aforementioned functionalization. First, a bromoalkyl chain of varying lengths is to be added to a 4,4’-dimethyl-2,2’-bipyridine molecule giving 4-bromobutyl-4-methyl-2,2’-bipyridine or 4-bromononyl-4-methyl-2,2’-bipyridine. The added bromine will then be replaced with a thiol, an SH group, which has the capability of adsorbing to gold surfaces. The bipyridine portion of the molecule also enables the formation of a stable metal complex. In this case the transition metal is ruthenium as shown in Figure 1.

The second goal is to synthesize a molecule with the capability of adsorbing to varying carbon surfaces. The first step is the same as the formation of the previous molecule. Once the molecule has a bromoalkyl substituent, the bromine will be converted to an amine. This NH2 group will allow the coupling of polyaromatic groups resulting in a ligand with an extended pi system. The ligands will then form a complex with a transition metal giving a product as seen in Figure 2 where the polyaromatic group shown is pyrene. The manner of how these molecules adsorb to gold, platinum surfaces, or carbon surfaces will then be observed by using electrochemistry.

Synthesis and Electrochemical Analysis of Transition Metal Complexes with Various Functionalities for Surface Modification

Posted May 13, 2010

It is possible to functionalize various surfaces by attaching various different types of organic ligands to them. The organic ligands are able to form complexes with transition metals, and an electrode composed of the surface material in question is placed into a solution containing a low concentration of the aforementioned metal complex. The interactions of various ligands with metal and carbon surfaces can be analyzed electrochemically, and in this manner the rate at which these ligands adhere to the surface, based on varying concentration, can be examined.

Examining the Role of Photosensitizers in Hydrogen Gas Production

Posted May 10, 2010

Fossil fuels are limited resources that form CO2 when burned. Carbon dioxide acts as a greenhouse gas, contributing further to global warming. Hydrogen is an ideal alternative fuel. It is high energy and combusts to form water. This lab’s research focuses on harnessing the energy in sunlight to convert water into hydrogen gas.

This research will utilize a photosensitizer to activate an electron relay and produce hydrogen gas. A photosensitizer (in this case Ru(4-(5-thiopentyl)-2,2’-bipyridine)3 ) is a metal complex that will absorb the energy from sunlight and transfer it to the electron relay, another metal complex. The electron relay will react with the protons in water and make H2.

Investigation of Synthesis and Adsorption Kinetics of a Family of Aromatic Functionalized Transition Metal Complexes

Posted May 10, 2010

In a technological society where smaller is better (think about the new nano-ipod), there has been increasing interest in nano-circuits, that is electronics at the molecular level. The focus of this research is to study transition metal complexes and their building block, ligands, because of their potential nanotechnology application.

Transition metals, such as iridium, ruthenium, rhodium, and cobalt, have the ability to complex with organic ligands. The focus of this research is to synthesis a library of transition metal complexes and characterize their electrochemical and physical properties. Two such complexes are diagramed below, where M represents a transition metal complex and one ligand is highlighted in red.

Ligands and Transition metals: A Complex Relationship

Posted May 10, 2010

The relatively recent discovery of carbon nano tubing, microscale tubes consisting of rings of carbon atoms, opens up new opportunities for research as to the potential uses of these tiny little conductors. One way of creating new uses for the nano tubing is by using transition metal complexes to “funtionalize” them, in other words, make it so they can respond to a chemical stimulus in a specific manner. The research done here involves synthesizing various organic ligands and reacting these compounds with transition metals, such as cobalt, to produce a complex. The resulting complex has a central metal ion that has little aromatic “appendages” which can adhere by non-covalent bonding to the carbon surface. The idea is that these ligands can “tag” the nano tubing so that it performs in the desired way, and the more soundly they adhere, the better. The research of this lab focuses mainly on creating many different variations of these complexes to see which are the most effectual in achieving this goal.