Speakers   Dr. Jing XIANG
Date and Time   8 February 2017 (Wednesday) 1:00 pm – 1:30 pm
Venue   D3-G-05, Tai Po Campus
Language   English (aided with Mandarin)

Abstract

Nitric oxide (NO) is synthesized in our body by the heme enzyme nitric oxide synthase (NOS). NOS catalyzes the two-step oxidation of arginine to NO and citrulline using O2 and NADPH. The mechanisms, especially for the second step, are unclear. The oxidation of arginine/guanidine and N-hydroxyarginine/N-hydroxyguanidine derivatives to give NO using various chemical reagents has been studied as models for NOS; however, no related work on oxidation of coordinated guanidine compounds has been done. We demonstrate here that N-hydroxyguanidine and guanidine bound to an osmium-(III) center readily undergoes oxidation at ambient conditions to give NO. The oxidation of (γ-OsGOH) is found to be pH dependent. At neutral pH, the NO is bound to the osmium center; however, at high pH, free NO is generated. In contrary, the oxidation of guanidine (OsG) gives rise to different products, depending on the nature of the oxidant. When the oxidant is a potential O-atom transfer reagent such as m-CPBA, the reaction gives mer-OsNO; when the oxidant is a one-electron oxidant, metal-centered oxidation occurs initially, and the product is a nitrido complex.

About the Speaker

Dr. Jing Xiang was born in China in 1981. He received his MSc. (2006) and Ph.D. (2010) degrees (under Professor T. C. Lau) from the City University of Hong Kong. He spent about two years (2010-2012 ) as a Postdoctoral Fellow with Professor T. C. Lau at City University of Hong Kong. He is an Associate Professor in Yangtze University. He was selected into ChuTian Scholar Plan (HuBei Province) in 2013. His main research interests lie in the chemistry of Synthesis and reactivity of coordination organic molecules, photochemistry and magnetic materials.

Enquiry: Melissa Tong (Email: mtwtong@eduhk.hk or Tel: 2948 8390)