Synthesis of Neopentoxy Boron Dipyrromethene Ethylene Probe-4 (Neo BEP-4) and Evaluation of its Optical Characterizations

Ethylene is an important plant hormone responsible for plant growth and development due to which several current ethylene detection techniques have been developed but are not suitable for its detection at the cellular level. Michel Lab at DU has synthesized two pro-fluorescent BODIPY Ethylene Probes (BEP) i.e., BEP-4 and BEP-5 to quantify ethylene gas through fluorescence. These 1st gen probes, however, have relatively slow turn-on rates which limits their sensitivity. We hypothesized that varying R group attached to the chelating O atom can develop more sensitive ethylene detection probes. BEP-4 analogues such as MBEP-4 and Phenoxy BEP-4 have already been developed, but their higher reactivity with ethylene decreases probe stability. Probes with faster turn-on rates and better stability are preferred since they have an improved limit-of-detection (LOD), and many biological activities in plants respond to a low level of ethylene. Specifically, my research project is focused on synthesizing Neo BEP-4 following the synthetic route comprised of six steps. After its synthesis, this faster probe analogue will be evaluated for its quantum yield, LOD, and turn-on rates in response to ethylene gas. We predict that a neopentyl group will maintain a faster reaction rate, and the increased group size will limit probe decomposition. Additionally, this work will show the structure-activity relationship (SAR) which could be utilized to help design better and more sensitive probes.