Crystal structure and DFT studies of (E)-1-(4-fluorophenyl)-3-(1H-indol-1-yl)-4-styrylazetidin-2-one

Linear and Nonlinear Optical Responses of Nitrobenzofurazan-Sulfide Derivatives: DFT-QTAIM Investigation on Twisted Intramolecular Charge Transfer

In this study, we report on the green fluorescence exhibited by nitrobenzofurazan-sulfide derivatives (NBD-Si, i = 1-4). The optical responses of these studied compounds in a polar methanol solvent were simulated by the use of time-dependent density functional theory (TD-DFT) employing the Becke-3-Parameter-Lee-Yang-Parr (B3LYP) functional along with the 6-31G(d,p) basis set. The computed energy and oscillator strength (f) results complement the experimental results. The band gap was calculated as the difference between the lowest unoccupied molecular orbital (LUMO) and the highest occupied molecular orbital (HOMO). Additionally, the density of states (DOS) was computed, providing a comprehensive understanding of the fundamental properties of these materials and further corroborating the experimental data. When the experimental data derived from ultraviolet/visible (UV/visible) and fluorescence spectroscopic techniques and those from simulated spectra are analyzed, the extracted values match up adequately. In addition, the NBD-sulfide compounds exhibit a large Stokes shift up to 85 nm in a polar methanol solvent. They are hypothesized to represent a novel paradigm of excited-state intramolecular charge transfer (ICT). To understand the intrinsic optical properties of NBD-Si materials, an ICT was identified, and its direction within the molecule was evaluated using the ratio of βvect and βtotal, values extracted from the computed nonlinear optical (NLO) properties. Moreover, the reduced density gradient (RDG)-based noncovalent interactions (NCIs) were employed to characterize the strength and type of NBD-Si interactions. Furthermore, noncovalent interactions were identified and categorized using the Quantum Theory of Atoms in Molecules (QTAIM) analysis. Ultimately, the combination of Hirshfeld surface analysis and DFT calculations was utilized to enhance the characterization and rationalization of these NCIs.

Synthesis of indole-tethered [1,3,4]thiadiazolo and [1,3,4]oxadiazolo[3,2-a]pyrimidin-5-one hybrids as anti-pancreatic cancer agents

New indole-tethered [1,3,4]thiadiazolo[3,2-a]pyrimidin-5-one (8a-j) and [1,3,4]oxadiazolo[3,2-a]pyrimidin-5-one hybrids (9a-e) were synthesized using [4+2] cycloaddition reactions of functionalized 1,3-diazabuta-1,3-dienes with indole-ketenes. All molecular hybrids were structurally characterized by spectroscopic techniques (IR, NMR, and HRMS) and screened for their anti-pancreatic cancer activity in vitro. The [1,3,4]oxadiazolo[3,2-a]pyrimidin-5-one hybrids (9a-e) showed stronger anti-pancreatic cancer activity than the [1,3,4]thiadiazolo[3,2-a]pyrimidin-5-one hybrids (8a-j) against the PANC-1 cell line. Compound 9d bearing an ortho-chlorophenyl moiety emerged as the most potent anti-pancreatic cancer agent with an IC50 value of 7.7 ± 0.4 µM, much superior to the standard drug Gemcitabine (IC50 > 500 µM). The discovery of these [1,3,4]thiadiazolo and [1,3,4]oxadiazolo[3,2-a]pyrimidin-5-one hybrids elicits their potentials as pursuable candidates for pancreatic cancer chemotherapy.

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.