Synthesis, crystal structures, spectroscopy, and quantum chemical studies on the 4-dimethylaminopyridinium-2,4-dinitrophenolate: an organic NLO material for optoelectronics.

CONTEXT: In this work, the 4-dimethylaminopyridinium-2,4-dinitrophenolate (4DMAP + 2,4DNP) by slow evaporation solution growth method has been presented. The Fourier transform infrared (FT-IR) (4000-400 cm-1) and FT-Raman (4000-50 cm-1) spectra were recorded for the grown crystal. METHODS: The computational calculation has been carried out with density functional theory (DFT) in ground state with Gaussian program package. Optimized geometrical parameters (bond distances, bond angles, and dihedral angles) have been obtained and compared with X-ray crystallography data. The calculated fundamental vibrational frequencies from DFT/B3LYP with 6-311 + + G(d,p) level of theory were scaled so as to agree with the observed results, and the scaling factors were reported. RESULTS: Experimental and computed ultraviolet-visible (UV-Vis) spectra in acetone and methanol solvents were found comparable to each other. Furthermore, the frontier molecular orbitals (FMOs) energies, molecular electrostatic potential (MEP), nonlinear optical (NLO), hirshfeld surface (HS), and global chemical descriptors of the molecule were also calculated. The thermal stability and the melting point of the title compound were analyzed by the thermogravimetric analysis/differential thermal analysis (TGA/DTA) techniques. The mechanical behavior of the organic single crystal was measured by Vickers micro-hardness method. The third-order nonlinear optical properties such as nonlinear refractive index (n2), nonlinear absorption coefficient (ß), optical nonlinear susceptibility Reχ(3), and optical nonlinear susceptibility Imχ(3) were calculated by using the open and closed aperture Z-scan technique. CONCLUSION: The theoretical and experimental NLO values clearly proposed that the nonlinearity of 4DMAP + 2,4DNP molecule could be helped as a potential candidate for optical limiting, frequency doubling, and optical switching applications.

Synthesis, photophysical, electrochemical, and DFT examinations of two new organic dye molecules based on phenothiazine and dibenzofuran.

New dyes were developed and produced utilizing distinct electron donors (phenothiazine and dibenzofuran), a π-spacer, and an electron acceptor of cyanoacetohydrazide, and their structures were studied using FT-IR and NMR spectroscopy. Following the synthesis of dye molecules, the photophysical and photovoltaic characteristics were investigated using experimental and theoretical methods. The photosensitizers have been exposed to electrochemical and optical property experiments in order to study their absorption performance and also molecular orbital energies. The monochromatic optical conversion efficiency of (Z)-N-((5-(10H-phenothiazin-2-yl)furan-2-yl)methylene)-2-cyanoacetohydrazide (PFCH) was found higher than that of (Z)-2-cyano-N'-((5-(dibenzo[b,d]furan-4-yl)furan-2-yl)methylene)acetohydrazide (BFCH), with IPCEs of 58 and 64% for BFCH and PFCH, respectively. According to the photosensitizer molecular energy level diagram, the studied dye molecules have strong thermodynamically advantageous ground and excited-state oxidation potentials for electron injection into the conduction band of titanium oxide. It was observed that the ability to attract electrons correlated favorably with molecular orbital energy. While density functional theory calculations were used to examine molecule geometries, vertical electronic excitations, and frontier molecular orbitals, experimental and computed results were consistent. Natural bond orbital and nonlinear optical properties were also calculated and discussed.

Structural and optical properties of Purpurin for dye-sensitized solar cells.

In this work, we reported a combined experimental and theoretical study on molecular structure, vibrational spectra and Homo-Lumo analysis of Purpurin and TiO2/Purpurin. The geometries, electronic structures, molecular orbital analysis of natural dye sensitizer Purpurin were studied based on density functional theory (DFT) using the hybrid functional B3LYP. Fourier transform infrared (FT-IR) and FT-Raman spectra have been recorded and extensive spectroscopic investigations have been carried out on Purpurin. The optimized geometries, wave number and intensity of the vibrational bands of Purpurin have been calculated using density functional level of theory (DFT/B3LYP) employing 6-311G (d,p) basis set. Based on the comparison between calculated and experimental results, assignments of the fundamental vibrational modes are examined. Features of the electronic absorption spectrum in the visible and near-UV regions were assigned based on TD-DFT calculations. The calculated results suggest that the three excited states with the lowest excited energies in 1,2,4, trihydroxy 9-10 anthraquinone was due to photo-induced electron transfer processes. Frontier molecular orbitals (FMO), LUMO, HOMO, and energy gap, of these dyes have been analyzed to show their effect on the process of electron injection and dye regeneration. Interaction between HOMO and LUMO of Purpurin are investigated to understand the recombination process and charge transfer process involving these dyes. We also performed analysis of I-V characteristics to investigate the role of charge transfer and the stability of the dye molecule.

DFT and TD-DFT study on geometries, electronic structures and electronic absorption of some metal free dye sensitizers for dye sensitized solar cells.

The geometries, electronic structures, polarizabilities and hyperpolarizabilities of 2-hydroxynaphthalene-1,4-dione (henna1), 3-(5-((1E)-2-(1,4-dihydro-1,4-dioxonaphthalen-3-yloxy) vinyl) thiophen-2-yl)-2-isocyanoacrylic acid (henna2) and anthocyanin dye sensitizers were studied based on density functional theory (DFT) using the hybrid functional B3LYP. The Ultraviolet-Visible (UV-Vis) spectrum was investigated by using a hybrid method which combines the properties and dynamics of many-body in the presence of time-dependent (TD) potentials, i.e. TDSCF-DFT (B3LYP). Features of the electronic absorption spectrum in the visible and near-UV regions were plotted and assigned based on TD-DFT calculations. Due to the absorption, bands of the metal-organic compound are n→π(*) present. The calculated results suggest that the three lowest energy excited states of the investigated dye sensitizers are due to photoinduced electron transfer processes. The interfacial electron transfer between semiconductor TiO2 electrode and dye sensitizer is owing to an electron injection process from excited dye to the semiconductor's conduction band. The role of linking the henna1 dye with a carboxylic acid via a thiophene bridge was analyzed. The results are that using a stronger π-conjugate bridge as well as a strong donator and acceptor group enhances the efficiency.

Effect of donor (tetradecyloxy) and acceptor (carboxamide) groups in trans-stilbene for DSSCs: quantum chemical investigations.

Incorporation of tetradecyloxy and carboxamide groups in trans-stilbene molecule (dye) has been investigated first time for Dye Sensitized Solar Cells (DSSCs) applications. To understand the changes in electronic structure, geometry, dipole moment and polarizability of the mentioned dye architecture has been carried out by using density functional theory (DFT) and time dependent DFT calculations using hybrid functional B3LYP method. Further, the semiconductor TiO2 is also used as a model to evaluate the photo conversion efficiency of the chosen dye architecture. Results reveal that tetradecyloxy and carboxamide groups act as an excellent donor and acceptor groups respectively which give rise to larger difference in excited state dipole moment than the ground state. This kind of stilbene based metal free organic dyes are act as a promising sensitizer for practical DSSCs applications.

Quantum chemical investigations on the effect of dodecyloxy chromophore in 4-amino stilbene sensitizer for DSSCs.

Stilbene based metal free organic dye sensitizer has been designed first time for dye sensitized solar cells applications. The geometries, electronic structures and dipole moment of the chosen 4-amino-4'-dodecyloxy-stilbene dye sensitizer has been analyzed by using Density Functional Theory (DFT) and Time Dependent DFT (TD-DFT) calculations (based on hybrid functional B3LYP). The HOMO and LUMO energies of the dye 4-amino-4'-dodecyloxy-stilbene are -4.95 and -0.87 eV respectively calculated by using TD-DFT. To understand the conversion efficiency of the chosen dye architecture unit we selected TiO2 as a model for semiconductor. The values of polarizability and hyperpolarizability are 165. 94 and 347.74 a.u respectively based on DFT calculations. Results reveal that the selected dye sensitizer exhibits large dipole moment difference between the ground and excited state which is comparable to that of metal based dye sensitizers. Further the large dipole moment would be expected to give high photo-current conversion efficiency in practical DSSCs and also it is a promising candidate as a sensitizer for DSSC applications.

Generation of sub wavelength super-long dark channel using high NA lens axicon.

We investigate the focusing properties of a double-ring-shaped azimuthally polarized beam by a high numerical aperture (NA) lens axicon based on vector diffraction theory. We observe that our proposed system generates a sub wavelength focal hole of 0.5λ having large uniform focal depth of 48λ without any annular aperture. We also observed that the distribution of the total intensity near the focus has little variation with the degree of truncation ß of the incident beam by the pupil. The authors expect such a super-long dark channel may find applications in optical, biological, and atmospheric sciences.

Quantum chemistry calculations of 3-Phenoxyphthalonitrile dye sensitizer for solar cells.

The geometries, electronic structures, polarizabilities, and hyperpolarizabilities of organic dye sensitizer 3-Phenoxyphthalonitrile were studied based on Hartree-Fock (HF) and density functional theory (DFT) using the hybrid functional B3LYP. Ultraviolet-visible (UV-vis) spectrum was investigated by time dependent DFT (TD-DFT). Features of the electronic absorption spectrum in the visible and near-UV regions were assigned based on TD-DFT calculations. The absorption bands are assigned to pi-->pi* transitions. Calculated results suggest that the three excited states with the lowest excited energies in 3-Phenoxyphthalonitrile is due to photoinduced electron transfer processes. The interfacial electron transfer between semiconductor TiO(2) electrode and dye sensitizer 3-Phenoxyphthalonitrile is due to an electron injection process from excited dye to the semiconductor's conduction band. The role of phenoxy group in 3-Phenoxyphthalonitrile in geometries, electronic structures, and spectral properties were analyzed.

Improvement of lens axicon's performance for longitudinally polarized beam generation by adding a dedicated phase transmittance.

The focal field of high NA lens axicon with a binary-phase optical component is calculated by using vector diffraction theory. Numerical results show that for a radially polarized Bessel Gaussian input field, the proposed system generates a subwavelength (0.395λ) longitudinally polarized beam with large uniform depth of focus (approximately 6 λ).

DFT simulations and vibrational analysis of FT-IR and FT-Raman spectra of 2,4-diamino-6-hydroxypyrimidine.

Quantum mechanical calculations of energies, geometries and vibrational wavenumbers of 2,4-diamino-6-hydroxypyrimidine (2,4DA6HP) were carried out by using ab initio HF and density functional theory (DFT/B3LYP) method using 6-311G(d,p) basis set. The optimized geometrical parameters obtained by B3LYP method show good agreement with experimental X-ray data. The best level of theory in order to reproduce the experimental wavenumbers is B3LYP method with the 6-311G(d,p) basis set. The difference between the observed and scaled wavenumber values of most of the fundamentals is very small. A detailed interpretation of the infrared spectra of 2,4DA6HP was also reported. The calculated HOMO and LUMO energies show that charge transfer occurs in the molecule. The entropy of the title compound is also performed at HF/6-311G(d,p) and B3LYP/6-311G(d,p) levels of theory. The theoretical spectrograms for FT-IR and FT-Raman spectra of the title molecule have been constructed.

FT-IR, NIR-FT-Raman and gas phase infrared spectra of 3-aminoacetophenone by density functional theory and ab initio Hartree-Fock calculations.

The gas phase infrared spectrum of 3-aminoacetophenone (3AAP) was measured in the range 5000-500 cm(-1) and with a resolution of 0.5 cm(-1). The Fourier transform Raman (FT-Raman) and Fourier transform infrared (FT-IR) spectra of 3AAP were recorded in the solid phase. Geometry optimizations were done without any constraint and several thermodynamic parameters were calculated for the minimum energy conformer at ab initio and density functional theory (DFT) levels invoking 6-311G(2df 2p) basis set and the results are compared with the experimental values. Harmonic-vibrational wavenumber was also calculated for the minimum energy conformer at ab initio and DFT levels using 6-31G(d,p) basis set and the results are compared with related molecules. With the help of specific scaling procedures, the observed vibrational wavenumbers in gas phase, FT-IR and FT-Raman spectra were analyzed and assigned to different normal modes of the molecule. Most of the modes have wavenumbers in the expected range, the error obtained was in general very low. The appropriate theoretical spectrogram for the FT-IR spectra of the title molecule is also constructed.