Photophysical, thermal properties, solvatochromism and DFT/TDDFT studies on novel conjugated D-A-π-A-D form of small molecules comprising thiophene substituted 1,3,4-oxadiazole

Investigation of second-order NLO properties of novel 1,3,4-oxadiazole derivatives: a DFT study

CONTEXT

In this study, we have developed four new chromophores (TM1-TM4) and performed quantum chemical calculations to explore their nonlinear optical properties. Our focus was on understanding the impact of electron-donating substituents on 1,3,4-oxadiazole derivative chromophores. The natural bond orbital analysis confirmed the interactions between donors and acceptors as well as provided insights into intramolecular charge transfer. We also estimated dipole moment, linear polarizability molecular electrostatic potential, UV-visible spectra, and first hyperpolarizability. Our results revealed that TM1 with a strong and stable electron-donating group exhibited high first hyperpolarizability (β) 293,679.0178 × 10-34 esu. Additionally, TM1 exhibited a dipolar moment (μ) of 5.66 Debye and polarizability (α) of 110.62 × 10-24 esu when measured in dimethyl sulfoxide (DMSO) solvent. Furthermore, in a benzene solvent, TM1 showed a low energy band gap of 5.33 eV by using the ωB97XD functional with a 6-311 +  + G(d, p) basis set. Moreover, our study of intramolecular charge transfers highlighted N, N dimethyl triphenylamine and carbazole as major electron-donating groups among the four 1,3,4-oxadiazole derivative chromophores. This research illustrates the potential applications of these organic molecules in photonics due to their versatile nature.

METHODS

The molecules were individually optimized using different functionals, including APFD, B3LYP, CAM B3LYP, and ωB97XD combined with the 6-311 +  + G (d, p) basis set in Gaussian 16 software. These methods encompass long-range functionals such as APFD and B3LYP, along with long-range corrected functionals like CAM B3LYP and ωB97XD. The employed functionals of APFD, B3LYP, CAM B3LYP, and ωB97XD with the 6-311 +  + G (d,p) basis set were used to extract various properties such as geometrical structures, dipole moment, molecular electrostatic potential, and first hyperpolarizability through precise density functional theory (DFT). Additionally, TD-DFT was utilized for obtaining UV-visible spectra. All studies have been conducted in both gas and solvent phases.

CoII-catalysed synthesis of N-(4-meth-oxy-phen-yl)-5-(pyridin-4-yl)-1,3,4-oxa-diazol-2-amine hemi-hydro-chloride monohydrate

The title compound, C14H12N4O2·0.5HCl·H2O or H(C14H12N4O2)2 +·Cl-·2H2O, arose from the unexpected cyclization of isonicotinoyl-N-phenyl hydrazine carbo-thio-amide catalysed by cobalt(II) acetate. The organic mol-ecule is almost planar and a symmetric N⋯H+⋯N hydrogen bond links two of them together, with the H atom lying on a crystallographic twofold axis. The extended structure features N-H⋯O and O-H⋯Cl hydrogen bonds, which generate [001] chains. Weak C-H⋯Cl inter-actions cross-link the chains. The chloride ion has site symmetry 2. The major contributions to the Hirshfeld surface are from H⋯H (47.1%), Cl⋯H/H⋯Cl (total 10.8%), O⋯H/H⋯O (7.4%) and N⋯H/H⋯N (6.7%) inter-actions.

Photophysical and Electrochemical Properties of Highly π-Conjugated Bipolar Carbazole-1,3,4-Oxadiazole-based D-π-A Type of Efficient Deep Blue Fluorescent Dye

In this contribution, we have designed and synthesized a novel carbazole-1,3,4-oxadiazole based bipolar fluorophore (E)-2-(4-(4-(9H-carbazol-9-yl)styryl)phenyl)-5-(4-(tertbutyl) phenyl)-1,3,4-oxadiazole (CBZ-OXA-IV). Wittig reaction is utilised for the synthesis of the designed bipolar target compound CBZ-OXA-IV. ¹H NMR, ¹³C NMR, FT-IR and ESI-MS results confirmed the designed chemical structure of the fluorophore CBZ-OXA-IV. The photophysical properties have been investigated in detail using UV-Vis absorption, photoluminescence spectroscopy. Also, the photoluminescence studies on solid state samples (as thin films) were carried out. The CBZ-OXA-IV dye emits intense deep blue fluorescence with observed absorption and emission maxima occurring are at 353 nm and 470 nm, respectively. Fluorophore CBZ-OXA-IV has shown high Stokes shift of 7052 cm^-1. The experimentally measured optical band gap ([Formula: see text]) value is found to be 3.01 eV and the fluorescence quantum yields (Φ_f) is 0.40. The intramolecular charge transfer property of CBZ-OXA-IV dye was examined by using photophysical properties such as absorption, emission in different solvents of different varying polarities. In addition, Density Functional Theory computations are studied in detail including the MEP surface plots and natural bond orbital analysis. The electrochemical properties have been investigated in detail by using cyclic voltammetry measurements. Thermal gravimetric analysis (TGA) and differential scanning calorimetry (DSC) measurement results display a high thermal stability with decomposition temperature (T_d5%) 387 °C and a large glass transition temperature (Tg) of 98 °C. The obtained results demonstrated that the novel bipolar fluorophore CBZ-OXA-IV could play an important role in organic optoelectronics and possibly can be utilized as bipolar transport materials for electroluminescence applications in optoelectronic devices/OLEDs.