Executive Summary : | Increased use of fertilizer has caused continuous increases in reactive nitrogen in the environment. Nitrogen oxyanions such as nitrate is the major nitrogen-containing toxic waste in water. Nitrate contamination in water disturbs the nitrogen cycle and causes concern to environmental and health issues. Thus, managing the nitrogen cycle is one of the important concerns and it needs remediation of nitrogen oxyanions. In this context, nitrogen oxyanions reduction to useful products can be a useful strategy for water remediation. Reductions of nitrogen oxyanions involve use of acid. So, an effective catalyst for nitrogen oxyanion reduction should not perform efficient proton reduction. This requires study of proton reduction to understand when explicit nitrogen oxyanions can occur over proton reduction and vice versa. On the other hand, hydrogen production from water via proton reduction is considered as a captivating energy bearer. Thus, understanding proton reduction is also an important part of this proposed project. This project aims to develop molecular systems which can perform electrocatalytic reduction of nitrogen oxyanions, protons, and study their ease of selectivity. The criteria of ligand-framework for efficient and selective nitrogen-oxyanion reduction and understanding of mechanism needs further study. In this context second coordination sphere effects particularly activation of nitrate and nitrite via oriented electric fields induced by tailormade charged substituents in the complex have not been explored. For multielectron reduction of nitrate or nitrite to ammonia, metal complexes coordinated by redox-active ligand will be developed to facilitate multielectron transfer process. In this context, metal-ligand cooperativity vs ligand-ligand cooperativity will be investigated. For selectivity, oriented electric field caused by the charged substituents in the complex will be targeted. With additional positive charge, anionic nitrate/nitrite will be activated easily whereas with more negative/basic residues, positively charged protons will be activated easily. We have some preliminary results for selective nitrite reduction over proton utilizing this concept. We are in the process of establishing it with more experimental results. |