Absorption Spectra Of Derivatives Research Articles

Fine-tuning photophysical properties in pyrene derivatives: Unravelling the impact of substitution patterns with incorporation of a strong electron-donating group

To investigate the impact of substitution patterns on the photophysical properties of pyrene derivatives, six novel pyrene derivatives A1-A6 were synthesised by directly coupling anthracene with pyrene units. The objective was to explore the influence of strong electron-donating groups and substitution patterns on their photophysical behaviour. Experimental and theoretical studies were conducted to analyse the photophysical properties of these compounds, revealing a clear dependence on the position of substitution within the pyrene core. Analysis of molecular orbitals revealed significant contributions from both pyrene and anthracene moieties, with deviations from typical electronic distributions attributed to the presence of electron-donating groups. The energy gap values remained consistent across derivatives, contrary to previous findings involving acceptor motif substitutions. Structural analyses indicated deviations from planarity with significant changes in angles upon excitation. The emission spectra of mono- and disubstituted pyrene derivatives predominantly exhibited a single broad maximum with slight shoulders in each solvent. However, the emission spectra of the tetrasubstituted compound (A6) displayed a vibrational structure with three maxima in all solvents, reminiscent of pyrene itself but red-shifted by approximately 30 nm. Furthermore, the central maximum for compound A6 was around 20 nm blue-shifted compared to the other compounds, although its shoulder at around 440 nm corresponded to a maximum observed in other pyrene derivatives. Typically, 1,3,6,8-tetrasubstituted pyrene derivatives, compared to their disubstituted analogues, exhibited red-shifted emission maxima associated with increased π-conjugation due to additional units on the pyrene core. A comprehensive analysis was performed on the absorption and emission spectra of the pyrene derivatives in solvents of various polarities and in the solid state. The fluorescence intensity was influenced by solvent polarity, with A6 showing limited sensitivity (similar quantum efficiency of approximately 45 % in all solvents). Moreover, the quantum yield decreases with the increasing number of anthracene substituents, being the lowest for tetrasubstituted A6. Bi-exponential decay and shorter lifetimes were observed for A1-A6 compared to known compounds, with quantum yields decreasing as solvent polarity increased. In the solid state, emission peaks shifted towards longer wavelengths, with A1 exhibiting the highest quantum yield attributed to steric hindrance. At low temperatures (77 K), emission spectra displayed redshifts, and longer lifetimes were observed. Spectrometric tests in THF/water mixtures indicated luminescence quenching at higher water fractions.

DETERMINATION OF CHAMAZULENE BY REVERSED PHASE HPLC

A method for the determination of hamazulene in essential oils using reverse-phase high-performance liquid chromatography with diode-matrix detection has been developed. The possibility of qualitative determination of hamazulene from the electronic absorption spectra recorded in the detector cell and quantitative determination of this substance during detection at several different wavelengths is shown. To obtain chromatograms, it is proposed to use C18 stationary phase with a mobile phase containing 20 vol. % water in acetonitrile. Samples for the study were prepared by dissolving essential oils in acetonitrile. The chromatographic determination of hamazulene is not hindered by the accompanying components of the studied essential oils of four plants: Matricaria chamomilla, Achillea millefolium, Tanacetum annuum and Artemisia absinthium; the concentration of hamazulene in them was 0.184, 0.311, 0.299 and 0.0025 mol/l, respectively. The wavelength of 603 nm provides the most selective detection of hamazulene along a complex electron-vibrational band for a solution in the mobile phase. When the detection wavelength changes from 603 to 350 and up to 280 nm, the sensitivity of hamazulene detection increases by 15.5 and 187 times. The chromatographic method has a linear response of the detector despite the known features of the electronic absorption spectra of azulene derivatives. It was found that when a blue-colored spot of hamazulene is isolated from TLC plates, other nonpolar components of oils that are detected when recording a chromatogram under HPLC conditions at a detector wavelength of 210 nm also enter the extract. It was also found that when recording chromatograms at 200 nm, differentiation of oils is possible, since most of the components of these oils have at least one isolated double C=C bond in the structure, which allows detecting compounds at 190-200 nm. For citation: Deineka V.I., Salasina Ya.Yu. Determination of chamazulene by reversed phase HPLC. ChemChemTech [Izv. Vyssh. Uchebn. Zaved. Khim. Khim. Tekhnol.]. 2024. V. 67. N 6. P. 6-20. DOI: 10.6060/ivkkt.20246706.6989.

Absorption spectra of p-nitroaniline derivatives: charge transfer effects and the role of substituents.

Push-pull compounds are model systems and have numerous applications. By changing their substituents, properties are modified and new molecules for different applications can be designed. The work investigates the gas-phase electronic absorption spectra of 15 derivatives of push-pull para-nitroaniline (pNA). This molecule has applications in pharmaceuticals, azo dyes, corrosion inhibitors, and optoelectronics. Both electron-donor and electron-withdrawing groups were investigated. Employing machine learning-derived Hammett's constants σm, σm0, σR, and σI, correlations between substituents and electronic properties were obtained. Overall, the σm0 constants presented the best correlation with HOMO and LUMO energies, whereas the σR constants best agreed with the transition energy of the first band and HOMO-LUMO energy gap. Electron-donors, which have lower σR values, redshift the absorption spectrum and reduce the HOMO-LUMO energy gap. Conversely, electron-withdrawing groups (higher σR's) blueshift the spectrum and increase the energy gap. The second band maximum energies, studied here for the first time, showed no correlation with σ but tended to increase with σ. A comprehensive charge transfer (CT) analysis of the main transition of all systems was also carried out. We found that donors (lower σ's) slightly enhance the CT character of the unsubstituted pNA, whereas acceptors (higher σ's) decrease it, leading to increased local excitations within the aromatic ring. The overall CT variation is not large, except for pNA-SO2H, which considerably decreases the total CT value. We found that the strong electron donors pNA-OH, pNA-OCH3, and pNA-NH2, which have the smallest HOMO-LUMO energy gaps and lowest σ's, have potential for optoelectronic applications. The results show that none of the studied molecules is fluorescent in the gas phase. However, pNA-NH2 and pNA-COOH in cyclohexane and water reveal fluorescence upon solvation. We investigated theoretically employing the second-order algebraic diagrammatic construction (ADC(2)) ab initio wave function and time-dependent density functional theory (TDDFT) the gas-phase electronic absorption spectra of 15 derivatives of p-nitroaniline (pNA). The investigated substituents include both electron-donor (C6H5, CCH, CH3, NH2, OCH3, and OH,) and electron-withdrawing (Br, CCl3, CF3, Cl, CN, COOH, F, NO2, and SO2H) substituents.

Study of Geometrical, Electronic Structure, Spectral, and NLO Properties of Phenyl‐Based Azo Dyes of Dye Sensitizer for Solar Cells: A Theoretical Study

AbstractThe molecular geometry, electronic structure, and absorption spectra of some important phenyl derivatives are investigated by using DFT and TD‐DFT with B3LYP and CAM‐B3LYP functional. The highest HOMO–LUMO energy gap, Non‐linear optical properties of dipole moment, polarizability, and hyperpolarizability are calculated. In both methods hyperpolarizability PDP values (16.77 × 10−30 and 16.59 × 10−30 esu) are higher than PDNA, PDN, and MPAN dye. The Molecular electrostatic potential shows that PDNA dye has more electronegative potential. Comparing all the dyes, PDP dye shows a higher light harvesting efficiency in the UV–vis region. The vibrational frequencies are assigned based on the potential energy distribution (PED) using the VEDA‐4 program.

Unraveling environmental effects in the absorption and fluorescence spectra of p-methoxyphenylpiperazine derivatives

The p-methoxyphenylpiperazine motif can be found in many biologically active molecules, including approved drugs. It is characterized by a relatively weak fluorescence, which can be employed in different types of studies involving molecules with this motif. In this work, a thorough analysis of the absorption, excitation and emission spectra of the diphenyl(aminomethyl)phosphine and tris(aminomethyl)phosphine derivatives of p-methoxyphenylpiperazine, supported by the DFT calculations (ωB97XD/6-311++G(d,p)) with NBO and QTAIM analysis also for different model molecules (e.g. 1-(4-methoxyphenyl)-4-methylpiperazine) enabled determination of the mechanisms underlying beneath the electronic transitions and allowed to rationalize mixed solvent effects observed in electronic spectra of the studied compounds. Electronic transition from the ground state to the first excited state can be regarded as the n,π → π* transition with no solvatochromic effects, however the hydrogen bonds between the HBD solvent molecules and the nitrogen atom bound directly to the aromatic ring (N(4)) are shifting strongly the 1st absorption or excitation band maxima to the higher energies. Fluorescence band, as a result of the electron transition from the equilibrated 1st excited state to the ground state, can be described as the π*→π with positive solvatochromism. N(4) in the excited states adopts a sp2 hybridization and is no longer able to form HBs. On the other hand, increased electron density on the aromatic ring makes the emission processes vulnerable to its direct environment.

Density Functional Theory Simulation of Optical and Photovoltaic Properties of DRTB-T Donor-Based Organic Solar Cells

Using the density functional theory (DFT), the influence of substitution of electron-donating (OCH3 and OH) and electron-accepting (F and Cl) groups on the peripheral thiophene units of DRTB-T donor molecule is studied. By optimizing the geometric structure, HOMO and LUMO energies, reorganization energies, optical properties, and photovoltaic properties are simulated. It is found that the ionization potential of the electron-donating derivatives (DRTB-4OCH3 and DRTB-4OH) reduces, but it increases for the electron-accepting derivatives (DRTB-4F and DRTB-4Cl) in comparison with that of DRTB-T. It is also found that the absorption spectra of the electron-donating derivatives (DRTB-4OCH3 and DRTB-4OH) get redshifted, but these get blue shifted for the electron-accepting derivatives (DRTB-4F and DRTB-4Cl) in comparison with those of DRTB-T. These changes in the electronic and optical properties of the modified structures result in higher PCE in BHJ OSCs with the blended active layer of DRTB-4F: NITI, DRTB-4Cl: NITI, in comparison with that of OSC with the active layer of DRTB-T: NITI and the highest being 15.0% in DRTB-4Cl: NITI. Our results may be expected to provide valuable insights into design optimization, leading to the fabrication of more efficient OSCs.

NIR-Absorbing 1,1,4,4-Tetracyanobuta-1,3-diene- and Dicyanoquinodimethane-Functionalized Donor-Acceptor Phenothiazine Derivatives: Synthesis and Characterization.

A series of symmetrical and unsymmetrical donor-acceptor type phenothiazine derivatives 1-18 were designed and synthesized via Pd-catalyzed Sonogashira cross-coupling and [2 + 2] cycloaddition-retroelectrocyclization reactions. The incorporation of cyano-based acceptors 1,1,4,4-tetracyanobutadiene (TCBD) and dicyanoquinodimethane (DCNQ) in the phenothiazine derivatives resulted in systematic variation in the photophysical, thermal, and electrochemical properties. The electronic absorption spectra of the phenothiazine derivatives with strong acceptors 2, 3, 5, 6, 8, 9, 11, 12, 14, 15, 17, and 18 show red-shifted absorption as compared to phenothiazine derivatives 1, 4, 7, 10, 13, and 16 in the near-IR region due to a strong intramolecular charge transfer (ICT) transition. The electrochemical analysis of the phenothiazine derivatives 2, 3, 5, 6, 8, 9, 11, 12, 14, 15, 17, and 18 reveals two reduction waves at low potential due to the TCBD and DCNQ acceptors. The mono-TCBD-functionalized phenothiazine 2 shows higher thermal stability compared to other phenothiazine derivatives. The computational studies on phenothiazines 1-18 reveal the LUMO is substantially stabilized as acceptor strength increases, which lowers the HOMO-LUMO gap.

Substituent and solvent effects on UV‐visible absorption spectra of chalcones derivatives: Experimental and computational studies

The electronic spectra of the title compounds were measured in ethanol and cyclohexane. Three band systems are distinguished in the spectra of which the first and second band systems are attributed to local excitation of PhCH and PhCO rings. The third absorption band is assigned to a charge transfer (CT) band and is associated with the CO−CH=CH moiety. The solvent plays an important role in the absorption spectra and causes the CT band to consist of two electronic transitions. The effect of substituents on the phenyl rings on the charge transfer band of chalcone derivatives was also established in the two solvents.The converged gas-phase geometries of the studied chalcones was optimized using the DFT PBE0 functional with the basis set 6-311++G**. DFT calculations has been performed for an ethanol solution (using TD-PBE0/6-311++G**) level to understand electronic transitions on terms of energies and oscillator strengths to study the substituent effect on the electronic transitions of the chalcone derivatives. To consider the solvation effect of ethanol on the absorptions, the integral equation formalism variant of the polarizable continuum model (IEFPCM) was used. The calculated energies were in good agreement with experiment results.The molecular modelling technique was followed to monitor the effect of substitutions on the HOMO/LUMO energy and total dipole moment. Transitions between natural transition orbitals are also described as part of this study.

Calculation of the one- and two-photon absorption spectra of water-soluble stilbene derivatives using a multiscale QM/MM approach.

We calculated the one- (OPA) and two-photon absorption (TPA) spectra of two large water-soluble stilbene derivatives presenting TPA cross sections of about 400 GM. However, the reported experimental TPA spectra present a spectral gap region, and a theoretical study of these promising molecules seems now timely and relevant. These molecules are composed of 200 or more atoms, becoming a challenge to obtain the TPA spectra even using density functional theory at the time-dependent quadratic response formalism. Thus, both OPA and TPA were also calculated using the INDO-S semi-empirical method. We used explicit solvent molecules using the sequential-quantum mechanics/molecular mechanics to include the solvent effects. Our results show that different transitions are participating in the OPA and TPA processes and that exchange-correlation functionals, including larger Hartree-Fock contributions, provide a better description of the OPA spectra; however, the opposite trend is observed on the TPA spectra. Alternatively, INDO-S/CISD, including contributions from single and double excitations, systematically describes both OPA and TPA bands with similar shifts and better reproduces the relative intensities of the two TPA bands compared to the experimental ones. The OPA spectra are characterized by a Highest Occupied Molecular Orbital-Lowest Unoccupied Molecular Orbital (HOMO-LUMO) excitation, while the low-energy TPA band is ascribed to a single transition encompassing the (HOMO-1)-LUMO and HOMO-(LUMO+1) excitations and the high-energy one is a combination of several transitions. Thus, although more studies are required to better assess the capability of the INDO-S/CISD method in describing the TPA spectra of large molecules, our results corroborate that it is a promising alternative.

Effects of Two Electron-Donating and/or -Withdrawing Substituents on Two-Photon Absorption for Diphenylacetylene Derivatives.

Two-photon absorption for diphenylacetylene (DPA) derivatives with two substituents (-OMe and/or -NO2) at the 4,4'-position was investigated experimentally and theoretically. The two-photon absorption spectra and the two-photon absorption cross-sections σ(2) for DPA derivatives were obtained by optical-probing photoacoustic spectroscopy (OPPAS). The simulated two-photon absorption spectra of the DPA derivatives, obtained with the time-dependent density functional theory within the Tamm-Dancoff approximation, agreed well with the experimental ones. The mechanisms for enhancement of the σ(2) for centrosymmetric and non-centrosymmetric DPA derivatives were found to be different. The large σ(2) for centrosymmetric molecules (DPA-OMeOMe and DPA-NO2NO2) results from the magnitude of the transition dipole moment, while for non-centrosymmetric molecules (DPA-OMeNO2), it is enhanced by the smaller detuning energy. Information on two-photon absorption properties of DPA derivatives obtained in this study will be important for the molecular design of two-photon absorption materials.

Copper‐Catalyzed Tandem Cyclization Approach toN,O‐Chelated Boron Difluoride Complexes

AbstractA strategy for synthesizingN,O‐chelated boron difluoride complexes via copper‐catalyzed tandem cyclization of readily available 2‐aryl pyridines has been developed. This reaction tolerates a wide range of functional groups, providing the corresponding products in 43–91% yield. Furthermore, the photophysical properties were investigated by measuring the UV/Vis absorption and fluorescence spectra of several product derivatives.

Effect of cyclodextrins inclusion complexes into absorption and emission spectra of P-methylaminobenzoate derivatives: A DFT and TD-DFT investigation.

In this study, density functional theory (DFT) and time-dependent DFT (TD-DFT) studies of methyl 4-aminobenzoate and methyl 4- amino-2-hydroxybenzoate and their inclusions complexes with α and γ-cyclodextrins were applied to control the effect of cyclodextrins on the absorption and emission properties of P-methylaminobenzoate derivatives. Absorption and emission spectra of free and encapsulated P-methylaminobenzoate derivatives were successfully analysed and compared with experimental results. Interestingly, conformational changes between ground and excited states of both fluorophores were also studied.

Derivative Absorption Spectrophotometry for the determination of Bambermycin and Paracetamol in Pharmaceutical Drugs

Derivative spectrophotometric techniques were used for the determination of bambermycin with paracetol binary mixture. Simultaneous determination of these compounds was accomplished by derivative (1D,2D, and 3D) spectrophotometric technique and applying zero-crossing technique used for determination of bambermycin and paracetol in capsules (samera, India). The second order derivative absorption spectra at vally λ=235 nm were used for bambermycin and also the second order derivative absorption spectra at λ=268nm were used for paracetol . No interference were found between both constituents and those of matrix. A good accuracy and precision of simultaneous determination of these compounds were confirmed by statistical analysis. The recovery of individual constituent under established conditions is very high and ranges for synthetic standard mixture and capsules for 98.8- 96.85- 99- 96.5 respectively.

Growth and temperature tuned band gap characteristics of NaBi(MoO4)2 single crystal

Structural and optical properties of double sodium–bismuth molybdate NaBi(MoO4)2 semiconductor compound was investigated by x-ray diffraction, Raman and transmission experiments. From the x-ray diffraction experiments, the crystal that has tetragonal structure was obtained. Vibrational modes of the crystal were found from the Raman experiments. Transmission experiments were performed in the temperature range of 10–300 K. Derivative spectroscopy analysis and absorption spectrum analysis were performed to get information about the change in band gap energy of the crystal with temperature. It was observed that the band gap energies of the crystal at different temperatures obtained from these techniques are well consisted with each other. By the help of absorption spectrum which was obtained from transmission measurements performed at varying temperatures, absolute zero value of the band gap and average phonon energy as 3.03 ± 0.02 eV and = 24 ± 0.2 meV, respectively. Moreover, based on absorption spectrum analysis the Urbach energy of the crystal was obtained as 0.10 eV.

Absorption spectrum fitting method (ASF), DASF method and structural studies of Li2O–SrO–B2O3–MnO quaternary glass system

In this paper the quaternary glass system Li2O–SrO–B2O3–MnO was prepared by traditional melt-quenching technique. Alternative methods like Absorption Spectrum Fitting method (ASF) and Derivative Absorption Spectrum Fitting method (DASF) were put forward for the determination of optical energy band gap and Urbach energy values for the manganese doped lithium strontium borate glasses. These methods require only the measurement of the glass sample absorbance instead of thickness of the glass sample. The values of the optical band gap obtained using ASF and DASF methods were compared, and a good agreement between the values and similar trend was observed. In addition to the above two methods the FT-IR and Raman techniques are also employed to scrutinize the structural details of manganese doped lithium strontium borate glasses. The fraction of N4 and N3 values are also projected to investigate the structural changes of the obtained glass system.

One‐Pot Synthesis of Quinazolines via Elemental Sulfur‐Mediated Oxidative Condensation of Nitriles and 2‐(Aminomethyl)anilines

AbstractA strategy for the synthesis of quinazolines via elemental sulfur‐mediated oxidative condensation of nitriles and 2‐(aminomethyl)anilines was developed. The reaction was carried out under metal‐/solvent‐free conditions, tolerates a wide range of functional groups to provide the corresponding products in 56%‐91% yield, and can be performed on a gram‐scale. The UV/Vis absorption and fluorescence spectra of several product derivatives were measured to study their photophysical properties.magnified image

Stable Diarylamine-Substituted Tris(2,4,6-trichlorophenyl)methyl Radicals: One-Step Synthesis, Near-Infrared Emission, and Redox Chemistry

Stable Diarylamine-Substituted Tris(2,4,6-trichlorophenyl)methyl Radicals: One-Step Synthesis, Near-Infrared Emission, and Redox Chemistry

Development of Ecofriendly Derivative Spectrophotometric Methods for the Simultaneous Quantitative Analysis of Remogliflozin and Vildagliptin from Formulation.

Three rapid, accurate, and ecofriendly processed spectrophotometric methods were validated for the concurrent quantification of remogliflozin (RGE) and vildagliptin (VGN) from formulations using water as dilution solvent. The three methods developed were based on the calculation of the peak height of the first derivative absorption spectra at zero-crossing points, the peak amplitude difference at selected wavelengths of the peak and valley of the ratio spectra, and the peak height of the ratio first derivative spectra. All three methods were validated adapting the ICH regulations. Both the analytes showed a worthy linearity in the concentration of 1 to 60 µg/mL and 2 to 90 µg/mL for VGN and RGE, respectively, with an exceptional regression coefficient (r2 ≥ 0.999). The developed methods demonstrated an excellent recovery (98.00% to 102%), a lower percent relative standard deviation, and a relative error (less than ±2%), confirming the specificity, precision, and accuracy of the proposed methods. In addition, validated spectrophotometric methods were commendably employed for the simultaneous determination of VGN and RGE from solutions prepared in the laboratory and the formulation. Hence, these methods can be utilized for the routine quality control study of the pharmaceutical preparations of VGN and RGE in pharmaceutical industries and laboratories. The ecofriendly nature of the anticipated spectrophotometric procedures was confirmed by the evaluation of the greenness profile by a semi-quantitative method and the quantitative and qualitative green analytical procedure index (GAPI) method.

Ex Vivo Determination of Broadband Absorption and Effective Scattering Coefficients of Porcine Tissue

A novel approach for precise determination of the optical scattering and absorption properties of porcine tissue using an optimized integrating sphere setup was applied. Measurements on several sample types (skin, muscle, adipose tissue, bone, cartilage, brain) in the spectral range between 400 nm and 1400 nm were performed. Due to the heterogeneity of biological samples, measurements on different individual animals as well as on different sections for each sample type were carried out. For all samples, we used an index matching method to reduce surface roughness effects and to prevent dehydration. The derived absorption spectra were used to estimate the concentration of important tissue chromophores such as water, oxy- and deoxyhemoglobin, collagen and fat.

A Comprehensive Spectroscopic Analysis of the Ibuprofen Binding with Human Serum Albumin, Part II

Human serum albumin (HSA) is the most abundant human plasma protein. HSA plays a crucial role in many binding endos- and exogenous substances, which affects their pharmacological effect. The innovative aspect of the study is not only the interaction of fatted (HSA) and defatted (dHSA) human serum albumin with ibuprofen (IBU), but the analysis of the influence of temperature on the structural modifications of albumin and the interaction between the drug and proteins from the temperature characteristic of near hypothermia (308 K) to the temperature reflecting inflammation in the body (312 K and 314 K). Ibuprofen is a non-steroidal anti-inflammatory drug. IBU is used to relieve acute pain, inflammation, and fever. To determine ibuprofen’s binding site in the tertiary structure of HSA and dHSA, fluorescence spectroscopy was used. On its basis, the fluorescent emissive spectra of albumin (5 × 10−6 mol/dm3) without and with the presence of ibuprofen (1 × 10−5–1 × 10−4 mol/dm3) was recorded. The IBU-HSA complex’s fluorescence was excited by radiation of wavelengths of λex 275 nm and λex 295 nm. Spectrophotometric spectroscopy allowed for recording the absorbance spectra (zero-order and second derivative absorption spectra) of HSA and dHSA under the influence of ibuprofen (1 × 10−4 mol/dm3). To characterize the changes of albumin structure the presence of IBU, circular dichroism was used. The data obtained show that the presence of fatty acids and human serum albumin temperature influences the strength and type of interaction between serum albumin and drug. Ibuprofen binds more strongly to defatted human serum albumin than to albumin in the presence of fatty acids. Additionally, stronger complexes are formed with increasing temperatures. The competitive binding of ibuprofen and fatty acids to albumin may influence the concentration of free drug fraction and thus its therapeutic effect.