Electronic structure, hydrogen bonding and spectroscopic profile of a new 1,2,4-triazole-5(4H)-thione derivative: A combined experimental and theoretical (DFT) analysis

• Structural and spectral analysis of C18H20ClN3S, a potential antimicrobial agent.
• The red shift in υ(NH) is related to the hydrogen bonded supramolecular structure.
• The H-bond strength at X3LYP/M06-2X are nearly 5%/20% larger than that of B3LYP.
• NLO properties and NBO analysis were performed.

Density functional theory has been implemented to study the electronic structure, molecular properties and vibrational spectra of 3-(adamantan-1-yl)-4-(4-chlorophenyl)-1H-1,2,4-triazole-5(4H)-thione, a novel 1,2,4-triazole-5(4H)-thione derivative. Hydrogen bonded dimer of the title molecule has been studied using B3LYP, M06-2X and X3LYP functionals at 6-311++ G(d,p) level of theory. The intermolecular hydrogen bonding has been studied using NBO analysis of the dimer. Bader’s AIM theory was also used to evaluate the strength as well as the hydrogen bonding characteristics. Experimental FT-IR and FT-Raman spectra of the title molecule were related with the spectral data obtained with DFT/B3LYP method. The 1H NMR chemical shifts of the title molecule were calculated by the GIAO method and compared with experimental results. Dipole moment, polarizability (α), first order static hyperpolarizability (β) along with molecular electrostatic potential surface have been calculated. Frequency-dependent first hyperpolarizabilities, β(−2ω;ω,ω) and β(−ω;ω,0) have also been evaluated to study the non-linear optical behavior of the title compound. UV–Vis spectrum of the title molecule was recorded and TD-DFT method has been used to calculate six lowest excited states and the corresponding excitation energies.

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