Enhanced luminescence efficiency of structurally tailored new coumarin-based heterocyclic organic materials: a DFT/TD-DFT study

Cross-over from pyrene to acene optical and electronic properties: a theoretical investigation of a series of pyrene derivatives fused with N-, S, and O-containing heterocycles

Pyrene and acene derivatives are an important source of materials for optoelectronic device applications both as emitters and organic semiconductors. The mobility of major charge carriers is correlated with the coupling constants of the respective major charge carrier as well as the relaxation energies. Herein, we have applied range-separated density functionals for the estimation of said values. A series of five alkylated derivatives of pyrene laterally extended by heteroaromatic or phenyl groups were explored and contrasted to nascent pyrene, alkylated pyrene and tetracene. The ground state geometries along with absorption properties and relaxation energies are presented as well as a discussion of the suitability of the material toward hole and electron transport materials.

Theoretical Insights into the Structural and Optical Properties of D-π-A-based Cyanostilbene Systems of α and β Variants

The π-conjugated organic molecules containing cyanostilbene motifs have been extensively investigated due to their great potential applications in several optoelectronic and biological fields. Developing efficient molecules in this respect requires strategic structural engineering and a deep understanding of the structure-property relationship at the molecular level. In this context, understanding the impact of positional isomerism in cyanostilbene systems is a fundamental aspect of designing desired materials with improved photophysical properties. Herein, we designed ten donor-π-acceptor (D-π-A) type cyanostilbene derivatives (P1 - P10) with different π linkers and compared their structural and optoelectronic properties arising from the positional variations of the -CN group (α and β- variations) through the utilization of density functional theory (DFT) and time-dependent DFT (TDDFT) methods. The topological analyses of the electron density are used to explain the relatively high stability of α isomer compared to that of β. Frontier molecular orbital analysis reveals that 17 molecules tend to show a reduced highest occupied molecular orbital-lowest unoccupied molecular orbital gap, and most of them showed a greater nonlinear optical (NLO) character compared to the parent molecule. TDDFT calculations indicate that β isomers show higher absorption maxima compared to their α counterparts. Among all the scrutinized molecules, the absorption maximum extended up to 602 nm for P9 and it possesses the highest first-order hyperpolarizability. This study sheds light on positional isomers and their reactivity, absorption spectra, and NLO properties of D-π-A type architecture that can be suitably tuned by appropriating the π-bridge for practical applications.

Designing and theoretical study of benzocarbazole-based D-π-D type small molecules donor for organic solar cells

Seven new molecules (S1-S7) of D-π-D type have been designed for organic photovoltaic applications. The DFT and TD-DFT methods were used to investigate the effect of different central bridge groups on the geometric, optoelectronic, and charge transport properties of the constructed molecules. Among them, S4 and S6 have the lowest energy band gap and a red shift in the absorption spectra, revealing the perfect relationship between the central bridge and the strong electron withdrawal character through extended conjugation. Similarly, S6 explored the lowest reorganization energy (RE) value for electron and hole revealing its enhanced charge transition, also shows better ICT characteristics with its highest NLO properties. Compound S4 showed the smallest value of ΔE_L-L and E_b, and the highest V_oc due to its low HOMO, which improves the photocurrent density of the devices. Thus, the results suggest that bridge modification is a practical strategy to improve the efficiency of OSCs.

Structural, Electronic, and Charge Transport Properties of New Materials based on 2-(5-Mercapto-1,3,4-Oxadiazol-2-yl) Phenol for Organic Solar Cells and Light Emitting Diodes by DFT and TD-DFT

This work reports on the density functional theory (DFT) and its time-dependent extension (TD-DFT) study of the structural, electronic, and charge transport properties of 2-(5-mercapto-1,3,4-oxadiazol-2-yl) phenol (MODP) and some of its transition M2+ complexes (M = Fe, Co, Cu, Ni, Zn, Pd, Pt). Reorganization energy, integral charge transfer, mobility, open circuit voltage, and electronic properties of these compounds have been calculated by employing the global hybrid functional PBE0 in conjunction with the Karlsruhe basis set def2-TZVP. Results show that MODP and its transition metal complexes are good electron donors for organic solar cells (OSC) owing to their relatively higher HOMO and LUMO energies compared to the prototypical (6, 6)-phenyl-C61-butyric acid methyl ester (PCBM). Energy gaps ranging between 2.502 and 4.455 eV, energy driving forces (∆EL-L) ranging between 2.08 and 2.44 eV, and large open circuit voltages ( $V_{\text{OC}}$ ) ranging from 1.12 to 2.05 eV were obtained. The results also revealed that MODP and its Pd(II) and Pt(II) complexes could serve as ambipolar charge transport materials owing to their very small reorganization energies, integral charge transfers, high rate charge transfers, and mobilities. All studied molecules showed OSC donor and hole/electron transport characteristics required by organic light-emitting diodes (OLEDs). Based on these results, new ways for designing charge transport materials for OLEDs as well as donor materials in OSCs are proposed.

Piperazine-substituted derivatives of favipiravir for Nipah virus inhibition: What do in silico studies unravel?

Favipiravir is found to show excellent in-vitro inhibition activity against Nipah virus. To explore the structure-property relationship of Favipiravir, in silico designing of a series of piperazine substituted Favipiravir derivatives are attempted and computational screening has been done to evaluate its bimolecular interactions with Nipah virus. The geometrical features of all the molecules have been addressed from Density Functional Theory calculations. Chemical reactivity descriptor analysis was carried out to understand various reactivity parameters. The drug-likeness properties were estimated by a detailed ADMET study. The binding ability and the mode of binding of these derivatives into the Nipah virus are obtained from molecular docking studies. Our calculations show greater binding ability for the designed inhibitors compared to that of the experimentally reported molecule. Overall, the present work proves to offers new insights and guidelines for synthetic chemists to develop new drugs using piperazine substituted Favipiravir in the treatment of Nipah virus.

SUPPLEMENTARY INFORMATION

The online version contains supplementary material available at 10.1007/s42452-020-04051-9.