AUTHOR=Manna Utsab , Portis Bobby , Egboluche Tochukwu K. , Nafis Muhammad , Hossain Md. Alamgir 

TITLE=Anion Binding Studies of Urea and Thiourea Functionalized Molecular Clefts

JOURNAL=Frontiers in Chemistry

VOLUME=8

YEAR=2021

URL=https://www.frontiersin.org/journals/chemistry/articles/10.3389/fchem.2020.575701

DOI=10.3389/fchem.2020.575701

ISSN=2296-2646

ABSTRACT=<p>Two rationally designed 4-nitrophenyl-based molecular clefts functionalized with thiourea (<bold>L</bold><sub><bold>1</bold></sub>) and urea (<bold>L</bold><sub><bold>2</bold></sub>) have been synthesized and studied for a variety of anions by UV-Vis and colorimetric techniques in DMSO. Results from the binding studies suggest that both <bold>L</bold><sub><bold>1</bold></sub> and <bold>L</bold><sub><bold>2</bold></sub> bind halides showing the order: fluoride &gt; chloride &gt; bromide &gt; iodide; and oxoanions showing the order: dihydrogen phosphate &gt; hydrogen sulfate &gt; nitrate &gt; perchlorate. Each receptor has been shown to form a 1:1 complex with an anion <italic>via</italic> hydrogen bonding interactions, displaying distinct color change for fluoride and dihydrogen phosphate in solution. As compared to the urea-based receptor <bold>L</bold><sub><bold>2</bold></sub>, the thiourea-based receptor <bold>L</bold><sub><bold>1</bold></sub> exhibits stronger affinity for anions due the presence of more acidic thiourea functional groups.</p>