Theoretical Study on Design and Feasibility of Novel Circumtrindene Derivatives to Remove Ionic Contaminants

Abstract

The structures and properties of Circumtrindene derivatives were studied at the M062X/6-31 + G(d,p) and M062X/LANL2DZ levels of theory in the gas phase and water as a solvent. Novel derivatives of Circumtrindene were designed by providing XH (X = NH, O, S) groups on the peripheral five-membered rings. Concave isomers were more stable (14.99–21.25 kcal/mol) than convex isomers. In these compounds, NH, OH, and SH groups were attached directly to the bowl and did not represent the proper size and flexibility to catch and hold ionic contaminants. Therefore, they could not be considered suitable for removing anions and cations. In the next series, the arms were extended to CH₂XH (X = NH, O, S). In these flexibility derivatives, the average distances of heteroatoms were sufficient (0.99–1.26 Å) in removing anionic (Cl⁻ and S2^-) and cationic (Hg²⁺) contaminants. A comparison of removal equilibrium constants showed that the amine-containing derivative (X = NH) (K = 43192, 99.52% removal) was more effective than the alcoholic derivative (X = O) (K = 10, 73.49% removal) in removing Cl⁻. The alcohol derivative (X = OH) was more effective in removing S²⁻ (K = 218530, 99.79% removal). On the other hand, the amine derivative (X = NH) possessed smaller energy barriers (ΔG^#) of 7.44 and 8.91 kcal/mol for Cl⁻ and S²⁻ uptake, respectively compared to the corresponding alcohol derivative. The thiol derivative (X = S) was effective in trapping Hg²⁺ (K = 1.35 × 10⁷), achieving a removal rate of 99.97%. Calculations in a PCM solvent (water) showed a decrease in Gibbs free energy barriers for ion removal, with values of 0.69 and 4.21 kcal/mol for Cl⁻ and S²⁻, respectively, compared to the gas phase.

KEYWORDS:

• DFT calculation
• circumtrindene
• ion removal
• polyaromatic

Disclosure statement

No potential conflict of interest was reported by the author(s).