Pyrrole-thiazole based push-pull chromophores: An experimental and theoretical approach to structural, spectroscopic and NLO properties of the novel styryl dyes

Theoretical investigation of substitution effect on the sixth and seventh positions of coumarin derivatives

The linear and non-linear optical properties of 6-donor and 7-donor substituted coumarins were compared using density functional theory (DFT) and time-dependent-DFT (TD-DFT). Charge transfer characteristics were investigated through natural bond order analysis, frontier molecular orbital, and molecular electrostatic potential plots. TD-DFT results suggested that the 6-donor substituted coumarins (PS1, PS3, and PS5) showed red-shifted absorption than the 7-donor substituted coumarins (PS2, PS4, and PS6). The chemical potential (μ) and electrophilicity index (ω) showed direct relation with the band gap and an inverse relation with chemical hardness (η) and hyperhardness (Γ). The global reactivity descriptors μ and ω showed direct and η and Γ showed an inverse correlation with first-order hyperpolarizability (β0) and second-order hyperpolarizability (γ). The β0 and γ for 7-donor substituted coumarin are higher than for 6-donor substituted coumarin.

Fused ring effect on optical nonlinearity and structure property relationship of anthracenyl chalcone based push-pull chromophores

The Ultraviolet-visible (UV-Vis) spectra indicate that anthracenyl chalcones (ACs) have high maximum wavelengths and good transparency windows for optical applications and are suitable for optoelectronic applications owing to their HOMO–LUMO energy gaps (2.93 and 2.76 eV). Different donor substituents on the AC affect their dipole moments and nonlinear optical (NLO) responses. The positive, negative, and neutral electrostatic potential regions of the molecules were identified using molecular electrostatic potential (MEP). The stability of the molecule on account of hyperconjugative interactions and accompanying charge delocalization was analyzed using natural bond orbital (NBO) analysis. Open and closed aperture Z-scans were performed using a continuous-wave frequency-doubled diode-pumped solid-state (DPSS) laser to measure the nonlinear absorption and nonlinear refractive index coefficients, respectively. The valley-to-peak profile of AC indicated a negative nonlinear refractive index coefficient. The obtained single crystals possess reverse saturation absorption due to excited-state absorption. The structural and nonlinear optical properties of the molecules have been discussed, along with the role of anthracene substitution for enhancing the nonlinear optical properties. The calculated third-order susceptibility value was 1.10 x10^-4 esu at an intensity of 4.1 kW/cm², higher than the reported values for related chalcone derivatives. The NLO response for both ACs offers excellent potential in optical switching and limiting applications.

The second-order NLO property of a photoswitchable heteroditpioc ion-pair receptor based on 2-pyridyl acylhydrazone linking with 2,6-pyridine bisamide: The impacts of metal cations and anions

A photoswitchable heteroditpioc ion-pair receptor E-1 and its isomeride Z-1 (without the anion binding site), that are based on the 2-pyridyl acylhydrazone linking 2,6-pyridine bisamide, have brought our attention to systematically explore the second-order nonlinear optical (NLO) properties by the density functional theory (DFT). In this work, we mainly studied the influences of metal cations (M = Na⁺, K⁺, Mg²⁺, Ca²⁺, Hg²⁺ and Pb²⁺), anions (X = Cl^-, Br^- and I^-) and ion-pair (NaCl, NaBr and NaI) on NLO responses for the receptor. In addition, the impacts of isomerization and poto-switching processes on NLO response for these systems also have been discussed detailedly. The results show that the isomerization process does not effectively adjust the NLO properties for our studied systems. But the poto-switching process that was triggered by light to capure or release ions plays an important role in improving the NLO properties. The receptors E-1 and Z-1 are excellent candidates to effectively detect metal cation Pb²⁺, because the first hyperpolarizability (β_tot) values of E∗Pb²⁺ and Z∗Pb²⁺ increased by 13 times and 20 times relative to that of receptors E-1 (188.06 a.u.) and Z-1 (270.21 a.u.), respectively. In addition, the receptor E-1 has the possibility to detect anion I^- due to the larger β_tot values compared with other anion-complexes. However, the changes of NLO responses for ion-pair complexes are not obvious compared with corresponding anion-complexes. We are looking forward to the research would be beneficial for further theoretical and experimental studies on recognizing metal cations and anions based on large second-order NLO difference.

Vibrational spectral analysis, XRD-structure, computation, exo⇔endo isomerization and non-linear optical crystal of 5-((5-chloro-1H-indol-2-yl)methylene)-1,3-diethyl-2-thioxodihy-dropyrimidine-4,6 (1H,5H)-dione

This work deals with the synthesis and characterization of the novel 5-((5-chloro-1H-indol-2-yl)methylene)-1,3-diethyl-2-thioxodihydro-pyrimidine-4,6(1H,5H)-dione π-bridge (D–A–D) donor–acceptor–donor compound. Its exo-isomer structure has been proven by XRD-single-crystal analysis for the first time. The IR, UV–Vis., MS, CHN-, ¹H and ¹³C NMR analysis were also carried out. The DFT-optimized structural-parameters were matched with the XRD-crystallographic data. The experimental-XRD-interactions in the lattice were compared to the computed Hirshfeld analysis (HSA), MEP map and Mulliken charge population. The DFT/6-311G(d) calculations like IR/B3LYP, TD-SCF, HOMO–LUMO, GRD and GIAO-NMR have been compared to their corresponding experimental parameters. Non-linear optical (NLO) crystal theoretical-analysis was carried out then compared to urea reference. The compound thermal activity was evaluated in an open-atmosphere by TG/DTG analysis.

NLOphoric Triphenylamine Derived Donor-π-Acceptor-π-Donor Based Colorants: Synthesis, Spectroscopic, Density Functional Theory and Z-scan Studies

Three Donor-π-Acceptor-π-Donor type styryl dyes (5a-c) with different secondary donors are synthesized and characterized to study their nonlinear and linear optical properties. The structure-property relationships of the dyes are described in the light of systematic photophysical and theoretical investigations. The photophysical characteristics of 5a-c are influenced by the polarity of the medium, with an appreciable bathochromic shift in emission (5b = 81 nm) and large Stoke shifts (5b = 104-173 nm) in polar solvents. 5a-c showed intramolecular charge transfer characteristics recognized with the help of emission solvatochromism, solvent polarity graphs, natural bond orbital analysis and HOMO-LUMO energy difference. The optimized geometry and frontier molecular orbitals reveal that the electron donation takes place from secondary donors and not from a fixed donor (triphenylamine) which is more twisted. The nonlinear optical properties obtained using solvent induced spectral shift and computational methods are found within the limiting values. Z-scan results reveal saturable kind of behavior for 5a, 5b and 5c, whereas 5a and 5b show reverse saturable kind of behavior in acetone and ethanol and hence give optical limiting values. The two-photon absorption cross section described by two-level approximation is highest for 5b (251-300 GM).

Theoretical insights into the structural, photophysical and nonlinear optical properties of phenoxazin-3-one dyes

Here we investigate the structural, photophysical and nonlinear optical (NLO) properties of phenoxazin-3-one dyes, resazurin (Rz) and resorufin (Rf), by performing quantum chemical calculations using the DFT and TDDFT methods.

Synthesis, structural characterization and computational study of NLO-responsive chromophores and second-order coefficients of thermally crosslinked polymers

The HOMO and LUMO structures of compounds 2, 4 and 6 with their band gap values.

Synthesis, thermal behavior and optical characterizations of thin films of a novel thiazole azo dye and its copper complexes

In the present paper, a novel dye of 4-methyl-5-(4-acetylphenyldiazenyl)thiazol-2-amine (L) and its corresponding copper complexes are synthesized and characterized using different techniques including elemental analysis, thermal analysis, ¹H NMR, Mass, and FT-IR spectra. The thermal behavior of L and its complexes is carried out and discussed using thermogravimetric analysis, and it observed that the type of copper substituent affects the thermal decomposition of complexes. Homogenous thin films of L and its complexes are successfully grown onto quartz substrates using spin coating technique. Optical features and spectral phenomena of the thin films are studied using spectrophotometric measurements of absorbance, transmittance and reflectance. The optical constants such as refractive index, extinction coefficient, optical conductivity and energy loss functions of the thin films of L and its complexes are calculated. The refractive index curves for all films show a normal dispersion behavior in the non-absorbing region of spectra, from which the dispersion parameters can be calculated using Wemple-DiDomenico model. The type of optical transition bands shows indirect allowed. The values of the optical energy gap are calculated in the range from 2.13 to 2.33 eV, depending on the nature of Cu(II) substituent. Indeed, the present results show that the complexes as organic semiconductors acquired good characterizations better than metal free ligand (L) such as more thermal stability, reducing in the optical band gap and increasing in the absorption coefficient that refers to light harvesting capacity.

Synthesis of Phlorin Analogues of Dithiacorrphycene and Their Use as Specific Chemodosimetric Sensors for Fe3+ Ions

The first examples of stable phlorin analogues of dithiacorrphycene were synthesized by treating appropriate tetrapyrranes with two equivalents of trifluoroacetic acid in CH₂ Cl₂ followed by oxidation with p-chloranil. The oxidative coupling of tetrapyrrane resulted in the formation of two unexpected phlorin analogues of dithiacorrphycenes that differed from each other at the meso-sp³ -carbon, and the two macrocycles were easily separated and isolated by column chromatography. The novel macrocycles were confirmed by X-ray crystallography and characterized by HRMS, 1D and 2D NMR spectroscopy, absorption spectroscopy, cyclic voltammetry, and time-dependent DFT studies. X-ray structure analysis revealed the highly strained and distorted nature of the macrocycles. The macrocycles showed one ill-defined absorption band at λ≈315 nm and a broad band at λ≈530 nm. Because both macrocycles possess two thiophene and two pyrrole rings with one ionizable inner NH, the cation-sensing properties of the phlorin analogues of dithiacorrphycenes have been investigated. The phlorin analogues of dithiacorrphycenes act as specific chemodosimetric sensors for Fe³⁺ ions by converting phlorin analogues of dithiacorrphycenes into dithiacorrphycene.

2,2′-[(Disulfanediyl)bis{5-[(1E)-(2-hydroxybenzylidene)amino]-1,3-thiazole-4,2-diyl}]diphenol: synthesis, crystal structure and calculation of molecular hyperpolarizability

The title Schiff base compound {systematic name: 2-[5-[(E)-(2-hydroxybenzylidene)amino]-4-(2-{5-[(E)-(2-hydroxybenzylidene)amino]-2-(2-hydroxyphenyl)-1,3-thiazol-4-yl}disulfanyl)-1,3-thiazol-2-yl]phenol}, C32H22N4O4S4, incorporating a disulfanediyl (dithio) linkage, was obtained from the condensation reaction between two equivalents of salicylaldehyde and one equivalent of dithiooxamide in dimethylformamide, and was characterized by elemental analysis, IR spectroscopic analysis and single-crystal X-ray diffraction. A one-dimensional chain is formed along the b axis via double intermolecular C—H...S hydrogen bonds. The HOMO (highest occupied molecular orbital) and LUMO (lowest unoccupied molecular orbital) energies and some related molecular parameters were calculated at the B3LYP/6-311G(d,p) level of theory. The molecular hyperpolarizability was also calculated.