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Density Functional Theory Calculation on the Structural, Electronic, and Optical Properties of Fluorene-Based Azo Compounds.

ABSTRACT: In the present work, a theoretical study was carried out to study the molecular structure, harmonic vibrational frequencies, normal force field calculations, and Raman scattering activities for fluorene ?-conjugation spacer containing azo-based dye named trans- and cis-bis(9H-fluoren-2-yl)diazene (AzoFL) at density functional theory using B3LYP (Becke-3-Lee-Yang-Parr) functional and 6-31+G(d,p) basis set. The theoretical calculations have also been performed with fluorene and the trans- and cis-isomers of diazene, difluorodiazene by the same method DFT-B3LYP/6-31+G(d,p) and basis set. The present DFT calculation shows that the trans-AzoFL is more stable than the cis-AzoFL by 16.33 kcal/mol. We also report the results of new assignments of vibrational frequencies obtained on the basis of the present calculations. Time-dependent DFT (TD-DFT) and ZIndo calculations have been performed to study the UV-vis absorption behavior and frontier molecular orbitals for the above-mentioned compounds. The UV-vis spectrum from TD-DFT calculation shows the ?-?* transition bands at ?max 423.53 nm (?max 6.0 × 104 M-1 cm-1) and at ?max 359.45 nm (?max 1.7 × 104 M-1 cm-1), respectively, for trans- and cis-AzoFL. Compared to parent trans-diazene (?max 178.97 nm), a significant variation to longer wavelength (?245 nm) is observed due to the incorporation of the fluorene (FL) ring into the -N=N- backbone. The co-planarity of the two FL rings with the longer N=N bond length compared to the unsubstituted parent diazene indicates the effective red shift due to the extended ?-conjugation in trans-AzoFL. The nonplanarity of cis-AzoFL (48.1° tilted about the C-N bond relative to the planar N=N-C bond) reflects its ?64 nm blue shift compared to that of trans-counterpart.

SUBMITTER: Khayer K

PROVIDER: S-EPMC7066559 | biostudies-literature | 2020 Mar

REPOSITORIES: biostudies-literature

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Density Functional Theory Calculation on the Structural, Electronic, and Optical Properties of Fluorene-Based Azo Compounds.

Khayer Khurshida K Haque Tahmina T

ACS omega 20200227 9

In the present work, a theoretical study was carried out to study the molecular structure, harmonic vibrational frequencies, normal force field calculations, and Raman scattering activities for fluorene π-conjugation spacer containing azo-based dye named trans- and cis-bis(9H-fluoren-2-yl)diazene (AzoFL) at density functional theory using B3LYP (Becke-3-Lee-Yang-Parr) functional and 6-31+G(d,p) basis set. The theoretical calculations have also been performed with fluorene an ...[more]

PMID: 32175498

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Project description:The significance of strontium oxide (SrO) and strontium peroxide (SrO2) is currently being investigated as one of the countless potential uses for green energy. However, few studies have examined the distinctive properties of several phases of SrO and SrO2. In order to fill this research gap, we have conducted a study on their various properties through "density functional theory (DFT)" under ideal conditions. This includes the study of electronic, optical, thermodynamic, and thermoelectric properties of the above-mentioned materials. For this study, the "Quantum Espresso" tool in DFT using Perdew-Burke-Ernzerhof-generalized-gradient approximation (PBE-GGA) as the exchange-correlation functional and "Optimized Norm-Conserving Vanderbilt (ONCV)" as the pseudopotential has been used. The face-centered cubic (FCC), body-centered cubic (BCC), hexagonal-1, and hexagonal-2 phases of SrO and the tetragonal and orthorhombic phases of SrO2 have been selected for the aforesaid study, for which some structural information has already been available. During this study, the energy band gap as an electronic property; the dielectric constant, refractive index, absorption coefficient, reflectivity, and energy loss function as optical properties; entropy, heat capacity, Debye temperature, and Debye sound velocity as thermodynamic properties; and the Seebeck coefficient, thermal conductivity, electrical conductivity, and figure of merit as thermoelectric properties have been investigated. In addition, phonon dispersion curves and formation energies have been used to confirm the dynamical stability and thermodynamic stability, respectively, for all of the materials mentioned above. The curve showed that the FCC, hexagonal-1, and hexagonal-2 phases of "SrO" are dynamically stable. These materials have good optoelectronic properties and can be used in ultraviolet sensors due to their intermediate band gap and highest material response in the ultraviolet range. In terms of thermoelectric property, the maximum value of "figure of merit" for the above material has been achieved up to 0.5. Satisfactory agreement has been found between the current findings and the known theoretical and experimental findings.

Dataset Information

Density Functional Theory Calculation on the Structural, Electronic, and Optical Properties of Fluorene-Based Azo Compounds.

Publications

Density Functional Theory Calculation on the Structural, Electronic, and Optical Properties of Fluorene-Based Azo Compounds.

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