Molecular, Electronic, Nonlinear Optical and Spectroscopic Analysis of Heterocyclic 3-Substituted-4-(3-methyl-2-thienylmethyleneamino)-4,5-dihydro-1H-1,2,4-triazol-5-ones: Experiment and DFT Calculations

Murat Beytur,Ihsan Avinca

doi:10.1515/hc-2020-0118

Abstract

Abstract In the present study, 3-p-methoxybenzyl/m-chlorobenzyl/phenyl-4-(3-methyl-2-thienylmethyleneamino)-4,5-dihydro-1H-1,2,4-triazol-5-ones were obtained from the reaction between 3-methylthiophene-2-carbaldehyde and three different 4-amino-(3-p-methoxybenzyl/m-chlorobenzyl/phenyl)-4,5-dihydro-1H-1,2,4-triazole-5-ones. In order to compare experimental and theoretical values, the geometric parameter, electronic, nonlinear optical properties, molecular electrostatic potentials and spectroscopic properties of 3-substituted-4-(3-methyl-2-thienylmethyleneamino)-4,5-dihydro-1H-1,2,4-triazol-5-ones have been simulated. The electronic properties of the newly synthesized compounds were calculated using DFT/B3LYP and DFT/B3PW91 methods revealing parameters such as ionization potential, electron affinity, energy gap, electronegativity, molecular hardness, molecular softness, electrophilic index, nucleophilic index and chemical potential, all obtained from HOMO and LUMO energies, dipole moments and total energies. UV-visible absorption spectra and the stimulation contributions in UV-visible transitions were obtained by using TD-DFT/B3LYP/6-311G(d,p) and TD-DFT/B3PW91/6-311G(d,p) methods in ethanol. The calculated absorption wavelengths, oscillator power and excitation energies were compared with experimental values. In line with DFT, the numbers of molecular vibration were analyzed through the basis set of 6-311G(d,p). The recording of FT-IR frequencies was done for the pertinent compound. The recorded frequencies through DFT/B3LYP and DFT/B3PW91 methods were compared to experimental values, with a result gained closest to the values of B3LYP. Finally, the Gaussian09W program package in DMSO phase, starting from the optimized structure, has been instrumental in calculating the 13C-NMR and 1H-NMR chemical shift values of the GIAO method.

Highlights

Heterocyclic compounds are considered important classes of molecules, and they have been found to be significant to the structural cores of many natural and synthetic drugs [1]
When the donor and acceptor substituents examined the effect on structures, LUMO/HOMO energies differences of 1a, 1b and 1c molecules are calculated as 4.166/4.178, 4.182/4.195 and 4.199/4.129 eV according to Density functional theory (DFT)/B3LYP and DFT/B3PW91, respectively (Table 4)
nuclear magnetic resonance (NMR) chemical shift values of the titled compounds were obtained, using B3LYP and B3PW91 methods, by using the GaugeIndependent Atomic Orbital (GIAO) NMR approach using 6-311G(d,p) basis set in DMSO

Summary

Introduction

Heterocyclic compounds are considered important classes of molecules, and they have been found to be significant to the structural cores of many natural and synthetic drugs [1]. The 1,2,4-triazole moiety and its derivatives are present in a variety of therapeutically important agents such as ribavirin (antiviral) [3], docetaxel (antineoplastic) [4] and rizatriptan (antimigraine) [5]. Heterocyclic derivatives containing sulfur possess essential biological properties too [6, 7]. Antiepileptic drugs including brotizolam [8], etizolam [9] and tiagabine [10], contain the thiophene moiety in the active pharmacophore structures. Schiff bases containing 1,2,4-triazole in their structure have been extensively studied for their applicability in various areas such as biological [11,12,13], chemical [14, 15] and pharmaceutical applications [16, 17].

Methods

Results

Conclusion