Archive \ Volume.10 2019 Issue 5

A New Proton Transfer Complex OF 2-Amino-4,6-‎Dimethoxypyrimidine with 2,6-Dichloro-4-Nitrophenol: ‎Spectroscopic And DFT/TD-DFT Studies

Maram T. Basha , Saied M. Soliman , Reem M. Alghanmi , Nada M. Wafi
Abstract

A new proton transfer (PT) complex formed on the reaction between 2,6-dichloro-4-nitrophenol (DCNP) as a proton donor and 2-amino-4,6-dimethoxypyrimidine (ADMP) as a proton acceptor has been investigated and characterized experimentally and theoretically. The experimental work has been carried out in three different polar solvents, including methanol, ethanol, and acetonitrile as well as in the solid state. The molecular composition of the PT complex was determined employing Job’s and photometric titration methods to be 1:1 in all studied solvents confirming that the complex’s stoichiometry is solvent-independent. The PT formation constant (KPT) and the molar extinction coefficient () in the selective solvents were calculated using the modified Benesi-Hildebrand equation. The KPT values are highest in the protic solvent (EtOH) and lowest in the aprotic solvent (ACN). The spectroscopic physical parameters have been determined, where the more negative ΔG° was recorded in EtOH and was in good agreement with the PT formation constant. Furthermore, a sensitive spectrophotometric method for determining ADMP is proposed and validated statistically. The solid complex was synthesized and characterized, utilizing elemental analysis, 1H NMR, and FT-IR spectroscopy and they confirmed the formation of 1:1 PT complex. The optimized geometries of DCNP, ADMP, and the proton transfer DCNP-ADMP complexes were calculated using B3LYP and CAM-B3LYP methods as well as 6-31++G (d,p) basis sets. The reactivity descriptors were used to describe the electron transfer processes among the DCNP and ADMP molecules. The significant electron density of 0.142 e was transferred from ADMP to DCNP. The electronic spectra of DCNP-ADMP complex were predicted using Time-dependent density functional theory (TD-DFT) calculations and compared with the experimental data‎‎‎‎.


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