The conversion of light energy into chemical energy is a focus of much research. Solar energy is of sufficient energy
to drive water splitting to generate hydrogen and oxygen. The splitting of water involves multi-electron reactions and
the breaking and formation of chemical bonds. Light driven water splitting has therefore proven elusive.
Supramolecular complexes that contain ruthenium or osmium polyazine units can efficiently absorb visible light and
generate charge transfer excited states. While many supramolecular complexes can absorb solar light efficiently, few are
able to convert this energy into chemical energy via the conversion of a readily available chemical feedstock into a fuel.
One process that is proposed as applicable for light to energy conversion is photoinitiated electron collection.
Photoinitiated electron collection is a multi-step process whereby light energy is used to collect reducing equivalents.
The collection of reducing equivalents is an essential step in the use of light energy to drive multi-electron reactions such
as water splitting. The development of mixed-metal complexes as photoinitiated electron collectors is described,
including the factors impacting device function. The use of Rh based electron collectors allows for the reducing
equivalents generated by photoinitiated electron collection to be transferred to substrates, such as the reduction of water
to produce hydrogen.
In the investigation of alternative energy sources, specifically, solar hydrogen production from water, the ability to
perform experiments with a consistent and reproducible light source is key to meaningful photochemistry. The design,
construction, and evaluation of a series of LED array photolysis systems for high throughput photochemistry have been
performed. Three array systems of increasing sophistication are evaluated using calorimetric measurements and
potassium tris(oxalato)ferrate(II) chemical actinometry and compared with a traditional 1000 W Xe arc lamp source. The
results are analyzed using descriptive statistics and analysis of variance (ANOVA). The third generation array is
modular, and controllable in design. Furthermore, the third generation array system is shown to be comparable in both
precision and photonic output to a 1000 W Xe arc lamp.
Mixed-metal supramolecular complexes coupling Ru and Os light absorber units to a central, reactive Rh site have been designed of the type [{(bpy)2M(dpp)}2RhCl2]5+. These complexes possess intense metal-to-ligand charge transfer transitions when excited at 500-700 nm making them good light absorbers. The presence of the Rh site introduces low lying metal-to-metal charge transfer states that are capable of visible light induced photocleavage of DNA via an oxygen independent pathway.1 We report here a study of the photodynamic action of supramolecular mixed-metal complexes showing that these systems inhibit cell replication after exposure to light while displaying no impact on cell replication in the dark. This photodynamic action has been studied using cultured Vero cells with a pre-incubation with the complexes, rinsing to remove complex from the media, followed by photo-activation and cell growth assay. The photodynamic action of this new series of complexes can be tuned as a function of components of the supramolecular assembly and complexes capable of coupling to targeting proteins and fluorescent reporter groups have been synthesized.
The high binding affinity of cisplatin toward DNA has led to its popularity as an anticancer agent. Due to cumulative drug resistance and toxic side effects, researchers are exploring related metallodrugs. Our approach involves the use of supramolecular complexes. These mixed-metal complexes incorporate a reactive platinum moiety bridged by a polyazine ligand to a light absorbing metal-based chromophore. The presence of the light absorber allows excitation of these systems, opening up the possibility of photoactivation. The use of a supramolecular design allows components of the assembly to be varied to enhance device function and light absorbing properties. Aspects of our molecular design process and results on the DNA binding properties for a number of these mixed-metal complexes will be discussed.
Mixed-metal supramolecular complexes are of interest in that they link multiple structural components into a large supramolecular array. Each subunit is designed to perform a simple act and those acts combine together to give rise to more complicated device functions. By variation of the nature or type of components used and their structural position within the supramolecular assembly, the type of functioning of the molecular device can be controlled. Our molecular design uses transition metal polyazine light absorbers (LA) and couples them through bridging ligands (BL) to other metal centers of interest. These additional metals can function as bioactive sites (BAS), electron acceptors (EA) and electron collectors (EC). An overview of our work in this area will be described with a focus on how component modulation allows these systems to be applicable to a large array of problems of interest including multifunctional DNA binding agents and photochemical molecular devices for light energy conversion.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.