Synthesis, spectral characterization, single crystal X-ray diffraction and DFT studies of 4-((2,4,5-triphenyl-1H-imidazol-1-yl)methyl)pyridine derivatives

Synthesis, crystal structure, spectroscopic and computational studies of NLO active 2-methylimdazolium 4-nitrobenzoic acid single crystal

In this report, we have presented the theoretical and experimental investigation of 2-Methylimdazolium 4-Nitrobenzoic Acid (2MI4NB) - an organic crystal. The good quality 2MI4NB single crystal was grown by slow evaporation technique. Both single and powder X-ray diffraction (XRD) analysis confirmed that the grown crystal structure is Triclinic with the P1 space group. The vibrational modes present in the chemical were validated through Fourier transform infrared (FT-IR) spectrum investigations. Density functional theory (DFT), a quantum chemical approach, has emerged as a potential or an effective tool for studying molecular structure and NLO properties and is being used frequently in applications involving NLO systems. HOMO-LUMO analysis and reactivity parameters were calculated. Molecular Electrostatic Potential (MEP), Natural Bond Orbital (NBO) analysis and first order hyper polarizability were studied by B3LYP theoretical level with 6-311++G(d,p) basic set. In addition, the Mulliken Atomic Charge was calculated with the same basic set. The thermal properties of the 2MI4NB crystal was analysed by TG-DTA studies. It shows that the two endothermic peaks were observed. The optical absorption spectrum shows that there is no absorption in the region of 430-1200 nm. The Z-scan analysis gives the third order NLO properties like refractive index and third-order NLO susceptibility of 2MI4NB crystals.

Crystal Structure and Theoretical Investigation of Thiobarbituric Acid Derivatives as Nonlinear Optical (NLO) Materials

Here we report on the crystal structure of three enamine/imine TBA derivatives (1–3). Since the derivatives can take the form of enamine or imine tautomers, theoretical calculations were made to confirm that the former predominates due to higher stability (thermodynamic calculations). The enamines’ form was further corroborated by high activation energy (ΔG≠; which is >60 kcal/mol in all the cases), thus requiring a large amount of energy to pass the barrier (kinetics calculations). Furthermore, 1–3 were found to show high static hyperpolarizability (βtot), thereby making them potential candidates as nonlinear materials for electro-optical devices and crystal engineering.

A comparison between observed and DFT calculations on structure of 5-(4-chlorophenyl)-2-amino-1,3,4-thiadiazole

The crystal and molecular structure of 5-(4-chlorophenyl)-2-amino-1,3,4-thiadiazole 3 was reported, which was characterized by various spectroscopic techniques (FT-IR, NMR and HRMS) and single-crystal X-ray diffraction. The crystal structure 3 (C₈H₆ClN₃S) crystallized in the orthorhombic space group Pna2₁ and the unit cell consisted of 8 asymmetric molecules. The unit cell parameters were a = 11.2027(2) Å, b = 7.6705(2) Å, c = 21.2166(6) Å, α = β = γ = 90°, V = 1823.15(8) ų, Z = 8. In addition, the structural geometry (bond lengths, bond angles, and torsion angles), the electronic properties of mono and dimeric forms of compound 3 were calculated by using the density functional theory (DFT) method at B3LYP level 6-31+ G(d,p), 6-31++ G(d,p) and 6-311+ G(d,p) basis sets in ground state. A good correlation was found (R² = 0.998) between the observed and theoretical vibrational frequencies. Frontier molecular orbitals (HOMO and LUMO) and Molecular Electrostatic Potential map of the compound was produced by using the optimized structures. The NBO analysis was suggested that the molecular system contains N-H…N hydrogen bonding, strong conjugative interactions and the molecule become more polarized owing to the movement of π-electron cloud from donor to acceptor. The calculated structural and geometrical results were in good rational agreement with the experimental X-ray crystal structure data of 1,3,4-thiadiazol-2-amine, 3. The compound 3 exhibited n→π* UV absorption peak of UV cutoff edge, and great magnitude of the first-order hyperpolarizability was observed. The obtained results suggest that compound 3 could have potential application as NLO material. Therefore, this study provides valuable insight experimentally and theoretically, for designing new chemical entities to meet the demands of specific applications.