Recognition of Melamine by Chromium Tricarbonyl (Thio)barbituric Acid Derivatives: Theoretical Insight into Multiple Hydrogen-Bond Modes

摘要

Melamine-contaminated milk products continually emerge in recent years and cause disease. Therefore, how to swiftly and efficiently differentiate melamine from protein becomes an urgent issue. In this work, three neutral receptors p-dimethylaminobenzaldehyde-barbituric acid chromium tricarbonyl (PBC), p-dimethylaminobenzaldehyde-2-thiobarbituric acid chromium tricarbonyl (2-PTC), and p-dimethylaminobenzaldehyde-4-thiobarbituric acid chromium tricarbonyl (4-PTC) were constructed for recognition of melamine, and their non-covalent interactions were systematically studied using density functional theory and several theoretical analysis methods. Our results suggest that melamine can be theoretically recognized by receptors PBC and 2-/4-PTC due to the formation of multiple hydrogen bonds upon complexation, indicating the good detecting capability of the Cr(CO)(3)-based (thio)barbituric acid moiety. Nevertheless, the IR analysis results show the receptors 2-/4-PTC cannot distinctly detect melamine by evident frequency shift of metal carbonyl. Therefore, we further proposed a structural modification strategy by introducing the cyano group into the (thio)barbituric acid moiety, and the corresponding IR analysis exhibits large frequency shift of metal carbonyl, indicating the potential of modified receptors in the infrared neutral molecular recognition of melamine. The results reported herein will be very useful in the design of potent receptors distinguishing melamine from protein.