الفهرس 
INTRODUCTION .Only 14 pages are availabe for public view
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Abstract
Clean and environmentally friendly energy resources that have the potential to meet the
needs of present and future generations are very necessary for the life on our planet. Cata-lytic water oxidation into oxygen and protons is a crucial reaction to many sustainable
energy storage schemes including water splitting for hydrogen production or the direct
conversion of carbon dioxide into fuel. For practical application, water oxidation catalysts
(WOCs) should be highly active, long-lived (i.e., stable under the reaction conditions), and
preferably made of earth-abundant elements. Further improvement of the artificial photo-synthetic cells mostly depends on improving its components. WOCs have special promi-nence for improving artificial photosynthesis systems as water oxidation is the most diffi-cult step of the whole process and considered to be the bottle-neck of making energy from
the sun. Molecular catalysts for water oxidation are advantageous for their possible struc-ture tuning aiming to catalyst activity optimization and most importantly the ability to study
the reaction mechanisms, which will give the chance for precise catalyst engineering.
Here, we have developed water oxidation systems that are based on both ruthenium and
cobalt metal ions. In ruthenium based molecular systems, the choice of a facial tridentate
capping ligand (1,4,7-triazacyclononane) along with some other bidentate ligands (neutral
and negatively charged) was found to be effective strategy to stabilize different ruthenium
oxidation states. Our ruthenium catalysts provide some interesting findings that are sum-marized as follow