Effect of external electric field on the tautomeric equilibrium and structure of 2‐carbamido‐1,3‐indandione

Abstract

2‐Carbamido‐1,3‐indandione (CAID) is a new reliable fluorescent biomarker and it exists in two tautomeric forms: 2‐(hydroxyl‐aminomethylidene)‐indan‐1,3‐dione (A) and 2‐carboamide‐1‐hydroxy‐3‐oxo‐indan (B). The structures of the tautomers and the transition state for intramolecular proton transfer are located at MP2/6‐31+G(d) level for each magnitude and for opposite directions of the applied electric field. According to our SCS‐MP2/6‐31+G(d) field‐free calculations tautomer A prevails (59.3%) while variation of the electric field strength along the direction from the indandione moiety to the carbamido fragment (+x‐direction) leads to stabilization of tautomer B. The two tautomeric forms become isoenergetic at 2.571 V/Å when the applied electric field is parallel to the direction from amino to the hydroxyl group (−y‐direction) in CAID, and at 3.085 V/Å tautomer B (51.9%) is slightly favored. Apparently, an external electric field has a strong influence on the tautomeric equilibrium in the CAID molecule.

Effects and Influence of External Electric Fields on the Equilibrium Properties of Tautomeric Molecules

“…In [ 92 , 93 ], the authors propose a model Hamiltonian analysis, which is two-fold. On one hand, they intend to propose a simple and yet general approach with the main aim of predicting the tautomeric behavior of molecular systems immersed in external electrostatic fields of various origin, on the basis of analysis of permanent and induced molecular multipole moments.…”