Conformational search, spectral analysis and electronic properties of 5-(4-Pyridinyl)-1,3,4-thiadiazol-2-amine

• Conformational search of 5-(4-Pyridinyl)-1,3,4-thiadiazol-2-amine using 3D PES scan.
• Most stable conformer optimized at B3LYP and M06-2X level and vibrational analysis performed.
• H- Bonding interaction between complexes of PTA with methanol has been investigated.
• Frequency-dependent first hyperpolarizability β(−2ω;ω,ω) has been evalua0074ed.

Comprehensive investigation of molecular geometry and electronic structure of 5-(4-Pyridinyl)-1,3,4-thiadiazol-2-amine in ground as well as in the first excited state has been carried out. The stable conformers of the title compound have been determined from the 3D potential energy scan by varying selected dihedral angles, responsible for conformational flexibility. As the energy difference between the conformers was very small, the relative stability has been confirmed at potentially high-level G2MP2 method. The most stable structure was optimized with B3LYP and M06-2X functional using polarized triple-zeta 6-311++G(d,p), to obtain the ground state structure and calculation of vibrational wavenumbers. Experimental FT-IR and FT-Raman spectra were compared with theoretical spectral data. Dipole moment, polarizability, first static hyperpolarizability and molecular electrostatic potential surface map have been calculated to get a better insight of the properties of title molecule. Frequency-dependent first hyperpolarizability β(−2ω;ω,ω) has also been evaluated to gauge the non-linear optical behavior of the title compound. Natural bond orbital (NBO) analysis has been done to study the stability of the compound arising from charge delocalization. UV–Vis spectrum, possible solvent-solute interaction and electronic properties such as frontier orbitals, band gap energies have been calculated by TD-DFT approach. 1H nuclear magnetic resonance chemical shifts of the title compound were calculated using the Gauge-Including Atomic Orbital (GIAO) method and compared with experimental data.

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