On the impact of a phosphoryl group in the recognition capabilities of 2-aminopyridines toward carboxylic acids

Abstract

Inspired by natural molecular recognition processes, many research efforts have been routed in recent years toward the design of new host–guest molecular systems based on non-covalent interactions. Within this field, 2-aminopyridines (2APs) have been widely studied due to their tunable spectroscopic response in the presence of carboxylic acids. Herein, we present and analyze a novel family of 2AP core compounds based on 2-phosphorylamidopyridine (2PAP). Linear response time-dependent density functional theory (TD-DFT) has been used to characterize and model several spectroscopic properties of 2PAP. Our results, validated through experiments, show that TD-DFT can provide a reliable description of the electronic excited states of these aromatic systems. In addition, we have also studied the amino–imino tautomerization of 2AP and 2PAP in light of TD-DFT tools. We show that the presence of a carboxylic acid has a catalytic effect on the tautomerization reaction, which otherwise does not occur spontaneously at room temperature. These results suggest that this low-cost computational approach can be applied to more complex organic systems derived from 2-aminopyridine, paving the way for the development of potentially useful sensing materials and organic species for molecular recognition.