Yazar "Nadeem, Sohail" seçeneğine göre listele

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    Öğe
    Novel pull–push organic switches with D–?–A structural designs: computational design of star shape organic materials
    (Springer, 2022) Hassan, Abrar U.; Mohyuddin, Ayesha; Güleryüz, Cihat; Nadeem, Sohail; Nkungli, Nyiang K.; Hassan, Sadaf U.; Javed, Mohsin
    The structural alteration with π-linkers was used to design a donor–acceptor type series of 2,2′-(pyrimidine-4,6-diyl)bis(2,3-dihydro-1,3-benzothiazole) (PB)-based chromophores (AH1–AH7) to exploit the adjustments in their optical characteristics. To investigate the electronic geometries, absorption wavelengths, charge transfer processes, and the efect of structural alterations on nonlinear optical (NLO) characteristics, density functional theory (DFT) simulations have been used. During the UV–visible study, several long-range and range separated functionals like B3LYP, CAM-B3LYP, B97XD, and APFD with the 6-311G+(d,p) basis set were used to select the efcient level at DFT. As a response, UV–vis data indicated an intriguing consistency at the B3LYP level across experimental and TD-DFT-based values of PB. All the designed molecules had a smaller energy band gap (0.84–3.67 eV) and wide absorption spectra inside the visible region. Natural bond orbital (NBO) results indicated a signifcant push–pull operation, with donors and π-conjugates exhibiting positive values and most acceptors exhibiting the minimum values. Electronic transformations between electron donors to acceptor moiety, Trifuoromethyl (TFM) via π-conjugated linkers were shown to have a superior linear ˂α>and nonlinear (βtotal) NLO values of 306–474 and 40–230 Debye-Angstrom−1 respectively. When chromophores with one phenyl π-linker were compared to those with the two π-linkers, the chromophores with the higher π-linker showed increased hyperpolarizability. The highest second-order hyperpolarizability (β) was found to be 230.11 DebyeAngstrom−1 which was about fve times higher than urea (standard). This research has shown that by manipulating the kind of π-spacers, novel metal-free NLO compounds may be created, which might be used for high-tech NLO purposes.
  • [ X ]
    Öğe
    Structural and electronic (Absorption and fluorescence) properties of a stable triplet diphenylcarbene: A DFT Study
    (2022) Hassan, Abrar; Mohyuddin, Ayesha; Nadeem, Sohail; Güleryüz, Cihat; Hassan, Sadaf; Javed, Mohsin; Muhsan, Muhammad Salman
    A triplet diphenylcarbene, bis[3-bromo-5-(trifuoromethyl)[1,1'-biphenyl]-4-yl]methylidene (B3B), with exceptional stability was discovered by chemists from Japan's Mie University. To investigate its diferent quantum chemical features, a theoretical analysis was predicated on Density Functional Theory (DFT) and Time Dependent-DFT (TD-DFT) based technique. According to the fndings, the singlet–triplet energy gap (ES-T), as well as HOMO–LUMO energy bandgap (EH-L), was found to be diminished when nucleophilicity (N) rose. We looked at the geometrical dimensions, molecular orbitals (MOs), electronic spectra, electrostatic potential, molecular surfaces, reactivity characteristics, and thermodynamics features of the title carbene (B3B). Its electronic spectra in diferent solvents were calculated using TD-DFT and Polarizable Continuum Model (PCM) framework. The estimated absorption maxima of B3B were seen between 327 and 340 nm, relying on the solvents, and were attributed to the S0→ S1 transition. Estimated fuorescence spectral peaks were found around 389 and 407 nm with the S1 and S0 transitions being identifed. Its fuorescence/absorption intensities revealed a blue shift change when the solvent polarity was increased. The least exciting state has been discovered to be the π→π* charge-transfer (CT) phase. According to the Natural Bonding Orbital (NBO) exploration, ICT ofers a signifcant role in chemical system destabilization. Furthermore, several hybrid features were used to determine the NLO (nonlinear optical) features (polarizability, frst-order hyperpolarizability, and dipole moment). The calculated values suggest that B3B is a promising candidate for further research into nonlinear optical properties.