Maximum One-photon Absorption Research Articles

Optical and morphological properties of DCM thin films co-doped of Znq2 by PVD: Theoretical and experimental investigations

In this article, new experimental results of the morphological and optical properties of thin films of 4-(dicyanomethylene)-2-methyl-6-(4-dimethylaminostyryl)-4H-pyran co-doped by 8-hydroxyquinoline zinc (Znq2) for different concentrations were presented. The physical vapor deposition in a high vacuum was used to create the thin films on glass substrates with a thickness of 100 nm. The morphological properties of the samples were identified using the Atomic Force Microscopy (AFM) apparatus in tapping mode. TEM images show amorphous structures. The phase composition of the samples was assessed using FTIR methods. The Tauc plot approach was used to examine the measured transmittance spectra in order to estimate the energy gap. Analysis of the results showed that the co-doping of DCM thin film by Znq2 influenced the structural and optical properties of the samples. To evaluate the experimental results found, theoretical calculations based on the maximum one-photon absorption (OPA) wavelengths of DCM and Znq2 have been first measured through the UV–Vis spectral technique. Then, the experimental conclusions on values for DCM and Znq2 have been compared with their corresponding simulation data procured from the time-dependent self-consistent-field (TD-SCF) computation utilizing the density functional theory (DFT) at B3LYP/6-311G(d,p) level. Besides, we have explored the first and second frontier molecular orbitals (MOs) for title compounds and their energy gaps via the DFT procedure. The calculations of maximum OPA wavelengths and the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) contributions on both molecules have also been crosschecked with the results of already published data in the literature.

Supramolecular Approach to Tuning the Photophysical Properties of Quadrupolar Squaraines.

In the present study, the influence of the hydrogen bonding for the one- and two-photon absorption of the prototypical squaraine dye is investigated with quantum chemistry tools. The central squaraine unit is bound by strong hydrogen bonds with 4-substituted N,N′-diphenylurea and, alternatively, N,N′-diphenylthiourea molecules, which affects to a high extend the properties of the squaraine electron accepting moiety, thus shifting its maximum absorption wavelength and enhancing the TPA cross section. The replacement of oxygen by sulfur atoms in the squaraine central ring, known to affect its photophysical behavior, is considered here as the way of modifying the strength and nature of the intermolecular contacts. Additionally, the influence of the oxygen-by-sulfur replacement is also considered in the N,N′-diphenylurea moiety, as the factor affecting the acidity of the N–H protons. The introduction of the sequence of the substituents of varying electron-donating or electron-withdrawing characters in the position 4 of N,N′-diphenyl(thio)urea subsystems allows to finely tune the hydrogen bonding with the central squaraine unit by further modification of the N–H bond characteristics. All of these structural modifications lead to the controlled adjustment of the electron density distribution, and thus, the properties affected such as transition moments and absorption intensity. Ab initio calculations provide strong support for this way of tailoring of one- or two-photon absorption due to the obtained strong hypsochromic shift of the maximum one-photon absorption wavelength observed particularly for thiosquaraine complexes and an increase in the TPA wavelength together with the increase in the TPA cross section. Moreover, the source of the strong modification of the thiosquaraine OPA in contrast to the pristine oxosquaraine upon N,N′-diphenyl(thio)urea substitution is determined. Furthermore, for the first time, the linear dependence of the non-additivity in the interaction energy on the Hammett substituent constant is reported. The stronger the electron-donating character of the substituent, the larger the three-body non-additive components and the larger their percentage to the total interaction energy.

THE INVESTIGATION OF SECOND-ORDER NONLINEAR OPTICAL PROPERTIES OF P-NITROPHENYLAZOANILINE: SECOND HARMONIC GENERATION AND AB INITIO COMPUTATIONS

p-nitrophenylazoaniline (1) belongs to the family of compounds with conjugated bonds and delocalized π-electrons, structurally similar to the well known push-pull compound Disperse Red 1 (DR1).1 Due to the assembly of the molecule, nonlinear optical (NLO) properties are expectable and can be more or less accurately predicted. To estimate the potential for second-order NLO properties, the electric dipole moment (μ), dispersion-free dipole polarizabilities (α) and first hyperpolarizabilities (β) have been determined by density functional theory (DFT) quantum chemical calculations at B3LYP/ 6-311 + G(d, p) level. According to the computation results, the synthesized compound exhibits non-zero β values and it might have second-order NLO behavior. Title compound has been synthesized and characterized by FT-IR, 1H-NMR and UV-Vis spectroscopies. The maximum one-photon absorption (OPA) wavelengths were estimated to be shorter than 450 nm by quantum mechanical computations using the configuration interaction (CI) method. The same result was achieved by UV-Vis spectra measurements, whereas the compound exhibited good optical transparency to the visible light. Quantitative measurements of second harmonic generation (SHG) at 800 nm and 1064 nm have been performed. The relative efficiency comparable with that of KDP (kalium diphosphate) has been observed with the exciting wavelength of 1064 nm, while the other wavelength led to strong absorption of produced light by the sample. In the following more detailed study on frequency-dependent first hyperpolarizabilities using time-dependent Hartree–Fock (TDHF) method have been computed at the wavelengths used in SHG measurements.

Third-order nonlinear optical properties and structures of (E)-N-(4-nitrobenzylidene)-2,6-dimethylaniline and (E)-N-(4-nitrobenzylidene)-2,3-dimethylaniline

(E)-N-(4-Nitrobenzylidene)-2,6-dimethylaniline (1) and (E)-N-(4-nitrobenzylidene)-2,3-dimethylaniline (2) have been synthesized. The crystal structures of both compounds have been defined by X-ray diffraction analysis. The maximum one-photon absorption (OPA) wavelengths recorded by quantum mechanical computations using a configuration interaction (CI) method are estimated in the UV region to be shorter than 450nm, showing good optical transparency to the visible light. To provide an insight into the microscopic third-order nonlinear optical (NLO) properties of the investigated molecules, both dispersion-free (static) and also frequency-dependent (dynamic) linear polarizabilities (alpha) and second hyperpolarizabilities (gamma) at lambda=825-1125nm and 1050-1600nm wavelength areas have been computed using time-dependent Hartree-Fock (TDHF) method. According to the ab initio calculation results, the title molecules exhibit second hyperpolarizabilities with non-zero values, implying microscopic third-order NLO behavior.

Syntheses, Structures and Second-order Nonlinear Optical Behavior of (E)-N-(4-Nitrobenzylidene)-3,4-dimethylaniline and (E)-N-(3-Nitrobenzylidene)-3,4-dimethylaniline

(E)-N-(4-Nitrobenzylidene)-3,4-dimethylaniline (1) and (E)-N-(3-nitrobenzylidene)-3,4-dimethylaniline (2) have been synthesized, and their crystal structures have been determined by X-ray diffraction analysis. Linear optical characteristics have been evaluated experimentally using UV/Vis spectroscopy and theoretically using the configuration interaction (CI) method. The maximum onephoton absorption (OPA) wavelengths of the studied compounds are shorter than 450 nm, giving rise to good optical transparency in the visible and near IR regions. The ab initio quantum-mechanical calculations (finite field second-order Møller-Plesset perturbation theory) of the investigated molecules have been carried out to compute the electric dipole moment (μ) and the first hyperpolarizability (β ) values. The ab initio results suggest that the title compounds might have microscopic second-order nonlinear optical (NLO) behavior with non-zero values.

Theoretical studies of one- and two-photon absorption properties for two series of three-branched fluorenylene–vinylene compounds with different centers (B, N) and peripheral substituted groups

Two series of three-branched fluorenylene–vinylene compounds with different centers (B, N) and peripheral substituted groups were investigated. The equilibrium geometries and electronic structures were obtained by using the density functional theory B3LYP and 6-31G basis set. The one- and two-photon absorption properties of all the molecules were studied theoretically with a ZINDO–SOS method in detail. It can be seen that the maximum one-photon absorption (OPA) intensities and the maximum two-photon absorption (TPA) cross sections values δ max are gradually increased with the stronger electron-donating capability [H < OH < N(CH 3) 2] or electron-accepting one (H < CHO < NO 2). This indicates that intramolecular charge transfer from the center to the peripheral substituted groups (or vice versa) plays a very important role on the TPA.

Two-Photon Absorption Properties of Two Kinds of Compounds with Fluorene as Centre

The two-photon absorption properties of two newly synthesized compounds containing fluorene as a π centre(denoted SK-G1 and NT-G1) were calculated using a response function method with density functional theory.Results show that both compounds have large one-photon and two-photon absorption abilities.In the low energy region,the maximum one-photon absorption strength of NT-G1 is twice as much as that of SK-G1 and its maximum absorption is red shifted compared to that for SK-G1.The maximum two-photon absorption cross section of NT-G1 is about five times as large as that of SK-G1 and those are found for the second excited states.Furthermore,NT-G1 has a wider two-photon absorption energy band.The optical properties of the molecules are closely related to their charge transfer processes when they are excited.The solvent effect on their one-photon absorption properties was calculated using the Onsager model.The numerical calculation is found to be in good agreement with experimental measurements.

Structure, Spectroscopic Study and ab initio Calculations on Third-order Nonlinear Optical Behavior of N-(2-Hydroxy-4-methoxybenzylidene)-3- nitroaniline

Abstract N-(2-hydroxy-4-methoxybenzylidene)-3-nitroaniline (1) has been synthesized and characterized by X-ray diffraction analysis, FTIR and 1H NMR spectroscopy. The maximum one-photon absorption (OPA) wavelengths recorded by quantum mechanical computations using a configuration interaction (CI) method are estimated in the UV region to be shorter than 450 nm, showing good optical transparency to the visible light. We have computed both dispersion-free (static) and also frequency-dependent (dynamic) linear polarizabilities (α) and second hyperpolarizabilities (γ) by using the time-dependent Hartree-Fock (TDHF) method to provide an insight into the microscopic third-order nonlinear optical (NLO) behavior of the title compound. The ab initio calculation results with non-zero values on (hyper)polarizabilities indicate that the synthesized molecule might possess microscopic third-order NLO phenomena.

Ab initio study of one-photon and two-photon absorption properties of 2,5-bis[4-(2-arylvinyl)phenyl]-1,3,4-oxadiazoles

The one- and two-photon absorption properties of 2,5-bis[4-(2-arylvinyl)phenyl]-1,3,4-oxadiazoles are investigated using response theory at DFT level. It is found that both one- and two-photon absorption properties are extremely sensitive to the geometry of the molecules, and the two-photon absorption cross section is dramatically reduced by the geometrical conformation distortion. The HF geometry is shown to be more realistic. The π enters in the compounds play different roles closely related with their different optical performances. The strongest two-photon performances for the compounds are predicted at suitable excited wavelengths. The maximum one-photon absorption is found to be non-monotonously dependent on the electron-donating ability of the terminal groups.

Spiro-linked oligofluorenes and derivatives: Molecular design and theoretical study of one- and two-photon absorption properties

A series of spiro-linked oligofluorenes and derivatives have been theoretically studied with DFT/B3LYP/6-31 G(d) associated with Z indo/SOS method. The increase of two-photon absorption (TPA) cross-sections of spiro-linked oligofluorenes with chain length can be expressed by formula lg δ TPA( N) = αlg N + lg δ TPA( N = 1). ( N is the number of fluorene rings in the molecule). The effects of Si center and interconnection pattern of fluorene rings on TPA response are discussed. The introduction of ethyne and ethene conjugated-bridges can further increase TPA cross-sections in longer wavelength range. The maximum one-photon absorption wavelengths of all molecules are less than 400 nm, which demonstrate spiro-linked oligofluorenes and derivatives exhibit at the same time strong two-photon absorption and good transparency.

Third-order Nonlinear Optical Properties and Crystal Structures of N-(2-Nitrobenzalidene)-2,4-dimethylaniline and N-(3-Nitrobenzalidene)- 2,4-dimethylaniline

N-(2-nitrobenzalidene)-2,4-dimethylaniline (1) and N-(3-nitrobenzalidene)-2,4-dimethylaniline (2) have been synthesized and characterized by X-ray diffraction analysis. Linear optical characteristics have been evaluated theoretically using the configuration interaction (CI) method. The maximum one-photon absorption (OPA) wavelengths of the studied compounds are shorter than 450 nm, giving rise to good optical transparency in the visible and near IR regions. To provide an insight into the third-order nonlinear optical (NLO) behavior of the title molecules, both dispersion-free (static) and frequency-dependent (dynamic) linear polarizabilities (α) and second hyperpolarizabilities (γ) at λ = 825 - 1125 nm and 1050 - 1600 nm wavelength ranges have been computed using the time-dependent Hartree-Fock (TDHF) method. The ab initio computational results on (hyper)polarizabilities reveal that both compounds exhibit second hyperpolarizabilities with non-zero values, implying microscopic third-order NLO behavior.

Solvent effects on structure and optical properties of a D-π-A azobenzene dye

Time-dependent hybrid density functional theory in combination with Onsager reaction field model and super-molecular model has been applied to study solvent effects on the geometrical and electronic structures, as well as one/two-photon absorption properties, of 4-(N-(2-hydroxyethyl)-N-methyl)-amino-4'-nitroazobenzene. It is found that the short-range interaction has a large effect on the electronic structure of the solute molecule, namely, large red-shift of the maximum one-photon absorption is induced by hydrogen bonding. The solute molecule has a large two-photon absorption cross section, which is enhanced by the solvent effect. The computational results are in good agreement with measurements.

SYNTHESIS, CRYSTAL STRUCTURE, SPECTROSCOPIC STUDIES ANDAB-INITIOCALCULATIONS ON THIRD-ORDER OPTICAL NONLINEARITY OF A FIVE-COORDINATE CHLOROIRON(III) COMPLEX

A five-coordinate chloroiron(III) complex has been synthesized and characterized by X-ray diffraction analysis and UV-Vis spectroscopy. The maximum one-photon absorption (OPA) wavelengths recorded by both linear optical measurements and quantum mechanical computations using the configuration interaction (CI) method are estimated to be shorter than 400 nm in the UV region, showing good optical transparency to visible light. To investigate the microscopic third-order nonlinear optical (NLO) behavior of the title compound, we have computed both dispersion-free (static) and also frequency-dependent (dynamic) linear polarizabilities (α) and second hyperpolarizabilities (γ) at λ = 825–1125 nm and 1050–1600 nm wavelength areas using the time-dependent Hartree–Fock (TDHF) method. The ab-initio calculation results with non-zero values on (hyper)polarizabilities indicate that the synthesized molecule might possess microscopic third-order NLO phenomena.

Calculation on the one- and two-photon absorptions properties for two series of dimethylfluorene core derivatives

Two series of dimethylfluorene core derivatives, which have different conjugation length or different peripheral substituted groups, are theoretically investigated in the paper. Using the density functional theory B3LYP with 6-31G basis set, we have obtained the equilibrium geometries and electronic structures for all the studied molecules. On the basis of the geometrical and electronic structures, the one- and two-photon absorptions properties are studied theoretically with ZINDO-SOS method in detail. The computational results are in good agreement with the available experimental values. According to our calculations, from the series I molecule to the series II counterparts, the maximum one-photon absorption (OPA) intensities and the maximum two-photon absorption (TPA) cross sections values δ max are obviously increased as the conjugation length increases. And for both series the maximum OPA wavelength λ max ( 1 ) and δ max values are increased with the stronger electron-donating or electron-accepting capability. This demonstrates that the conjugation length and the different substituent groups play important roles in the OPA and the TPA cross section.

Theoretical investigation on dendritic molecules with large two-photon absorption cross section

The two-photon absorption (TPA) properties of a class of dendritic molecules have been theoretically investigated by using the AM1 and ZINDO methods. The calculated peak TPA cross section values ( δ max) are from 2615.36×10 −50 cm 4 s/photon to 102222×10 −50 cm 4 s/photon. To the best of our knowledge, the gained TPA cross sections are ones of the highest TPA cross section values reported so far. It is found that there is a linear relationship between the maximal TPA cross section and the number of repeated units in chromphores, however, the position of the maximum one-photon absorption peak nearly maintains a constant. This result suggests that it is possible to obtain larger TPA cross section values at no cost of the transparency by means of increasing the number of repeated units in molecules.