Electronic absorption spectroscopy and time-dependent density functional theory calculations on the nickel(II) complex of 1,4-bis(pyrrol-2-ylmethyleneamino)butane

Synthesis of (Tricyanofuran-3-ylmethylene)hydrazinyl thiazole-containing chromophore, study of its photophysical properties, solvatochromism and TD-DFT computations

The chromophore 2-2-(3-cyano-5,5-dimethyl-4-((2-(thiazol-2-yl)hydrazono)methyl)-furan-2(5H)-ylidene)malononitrile (TzHTCF) was prepared by diazo-coupling of diazotized 2-aminothiazole with 3-cyano-2-(dicyanomethylene)-4,5,5-trimethylfuran (TCF). The TzHTCF absorption solvatochromism, in different polarity solvents, offered ΔE_max = +4.74 where the positive sign implied red shift occurrence and the TzHTCF lowest excited state was more polar than its ground one. While, the TzHTCF fluorescence spectrum afforded λ_em , in 416-670 nm range, and was more dependent on the solvent polarity than the absorption λ_max , despite both exhibited red shift by 24 and 254 nm, respectively. To discover the Stokes' shift ( ∆ ν ¯ ) behaviour of TzHTCF derivative, Lippert-Mataga and linear solvation-energy relationship (LSER) formulations have been utilized where the LSER displayed better results than the Lippert-Mataga (R² = 0. 9931). Furthermore, the LSER showed that the absorption and fluorescence solvatochromic behaviours were dependent on the solvent's hydrogen-bond donor (α) and acceptor (β), along with the solvent's polarizability (π*). Moreover, DFT calculations showed that TzHTCF has a planar configuration and its simulated absorption and emission spectra in DMSO revealed that λ_max was primarily originated from HOMO→LUMO and HOMO-1→LUMO transitions, respectively.

Luminescence feature of new 3,6-di(thiazolidin-5-one-2-yl)-carbazole derivative: synthesis, photophysical properties, density functional theory studies, and crystal shape effect

A new carbazole chromophore conjugated with substituted thiazolidine-4-one (CzPT) was synthesized by applying the Knoevenagel reaction between 3,6-diformyl-N-hexylcarbazole and ethyl 2-aceto-2-(5-oxo-3-phenylthiazolidin-2-ylidene)acetate. The chemical structure of the new derivative (CzPT) was elucidated by spectral studies. The CzPT absorption spectra in different solvents exhibited a red shift for λ_max by increasing solvent polarity. Bands at 430-474 nm appeared and were attributed to intramolecular charge transfer with high π-π* characteristics. CzPT fluorescence spectra exhibited a red shift after increasing the solvent polarity. To understand the Stokes' shift ( ∆ ν ¯ ) behaviour of the CzPT derivative referring to the polarity of solvents, Lippert-Mataga and linear solvation-energy relationship (LSER) models were employed in which the LSER exhibited respectable results compared with Lippert-Mataga (r² = 0.9707). Moreover, time-dependent density functional theory absorption spectra in hexane and dimethylformamide showed that λ_max had a major contribution in the highest occupied molecular orbital to lowest unoccupied molecular orbital transition in both solvents. In addition, the reduced uniformity of crystal features may lead to dislocation or anomalous arrangement of crystals with irregular spacing, which automatically enhances the optical properties of such crystals.

Synthesis, modelling, and solvatochromic properties of a phenothiazine derivative

A new A-π-D-π-A phenothiazine derivative, 2,2'-((10-octyl-10H-phenothiazine-3,7-diyl)bis (ethene-2,1-diyl))bis(1-ethyl-3,3-dimethyl-3H-indol-1-ium)iodide (PTZ-BEI) was prepared and fully characterized using infra-red (IR), ¹ H nuclear magnetic resonance (NMR), ¹³ C NMR, ultraviolet-visible light and mass spectra. Electronic spectra of PTZ-BEI solutions in solvents with different polarities displayed absorption bands (λ_max ) related to intramolecular charge transfer. In addition, the emission spectra of PTZ-BEI solutions were strongly solvent dependent for both wavelength and intensity. Stokes' shift ( Δ ν ¯ ) increased with increasing solvent polarity up to 4105 cm^-1 in the most polar solvent, dimethylformamide. The linear solvation-energy relationship was utilized to investigate solvent dependency of the Stokes' shifts. Relative quantum yield (φ) of PTZ-BEI was calculated. Finally, density functional theory was employed at the B3LYP level for geometrical optimization and simulation of electron spectra for the PTZ derivative in gaseous and solvated states to explore the solvent effect.

Synthesis, photophysical properties, and density functional theory studies of phenothiazine festooned vinylcyclohexenyl-malononitrile

A novel phenothiazine derivative conjugated with vinylcyclohexenyl-malononitrile (PTZ-CDN) was synthesized through the Knoevenagel reaction of 10-octyl-10H-phenothiazine-3,7-dicarbaldehyde with 2-(3,5,5-trimethylcyclohex-2-en-1-ylidene)-malononitrile and fully characterized. The UV-vis absorption spectra of PTZ-CDN in different solvents showed a λ_max band at 497-531 nm with a high molar extinction coefficient attributed to intramolecular charge transfer (ICT) with the characteristics of a π-π* transition. Increasing the solvent polarity resulted in a bathochromic shift of λ_max . The PTZ-CDN fluorescence emission spectra were more sensitive to increasing the solvent polarity than the absorption spectra; they displayed a blue shift of λ_em by 85 nm. To understand the behaviour of the PTZ-CDN derivative, Stokes' shift ( Δ ν ¯ ) with respect to the solvent polarity, Lippert-Mataga and linear solvation-energy relationship (LSER) models were applied in which the LSER showed better regression than the Lippert-Mataga plots (r² = 0.9627). Finally, the TD-density functional theory (DFT) electronic transition spectra in dioxane and dimethyl formamide (DMF) were calculated. The DFT data showed that λ_max resulted from the support of the highest occupied molecular orbital to the lowest unoccupied molecular orbital transition with 74% and 99% in dioxane and DMF, respectively.

Synthesis and photophysical studies on a new fluorescent phenothiazine-based derivative

A new typical phenothiazine compound functionalized with thienyl-indandione derivative (PTZTID) was synthesized and characterized using spectral analysis (ultraviolet-visible (UV-vis) light, infrared (IR), ¹ H nuclear magnetic resonance (NMR) and ¹³ C NMR tools). The UV-vis absorption spectra of the PTZTID solution in 1,4-dioxane showed two absorption bands attributed to localized aromatic π-π* transitions of conjugated aromatic moieties and intramolecular charge transfer with the characteristics of a π-π* transition. The fluorescence spectra exhibited a maximum emission wavelength at 580 nm. The effect of concentration on photophysical properties took the form of a minor hypsochromic shift, which was attributed to some extent to the occurrence of H-type aggregation of the PTZTID derivative. Binary solvent effects on the spectroscopic behaviour of PTZTID were measured at different H₂ O/1,4-dioxane ratios. Similarly, when increasing the water content, a hypsochromic shift was observed that resulted from H-type aggregation. Furthermore, geometry and electronic configurations of PTZTID were studied at density functional theory /B3LYP level and indicated that the compound had a nonplanar (butterfly structure).

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.

Encapsulation of a Ni salen complex in zeolite Y: an experimental and DFT study

A planar diamagnetic Ni-complex when encapsulated in zeolite Y adopts a nonplanar geometry and shows a pragmatic change in its magnetic properties.