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Photolysis of PCl <sub/>3</sub> /POCl <sub/>3</sub> with Oxygen Dopant Using 193?nm ArF Excimer at Low Temperatures: Oxygen Insertion through ‘Phosphadioxirane’ Pathway
摘要： Photolysis was performed on PCl3 and POCl3 in the presence of oxygen dopant in Ar matrix at low temperatures using 193 nm ArF excimer laser. The photo irradiation initially facilitated the formation of ozone in situ in the low temperature matrix. For PCl3 + O2 photolysis with 193 nm ArF excimer, initially POCl3 was produced and subsequent oxygen atom insertion on POCl3 generated PO2Cl3. Furthermore, secondary reaction channel opens up in PCl3 + O2 photolysis to form a variety of photoproducts such as POCl, PIIIO2Cl, PVO2Cl and PO3Cl. The insertion of oxygen atom on POCl through phosphadioxirane intermediate generated PIIIO2Cl and the direct oxygen atom addition resulted in PVO2Cl. A successive oxygen insertion on PVO2Cl triggered the PO3Cl generation. The identification of all the photoproducts was confirmed through 18O2 isotopic experiments and quantum chemical computations performed using density functional theory (DFT). Computations carried out at B3LYP level of theory with 6–311 + + G(d,p) basis set were used to correlate the structure of photo products obtained experimentally. Interestingly, photo irradiation of POCl3 with oxygen dopant in Ar matrix @193 nm ArF excimer resulted in the generation of PO2Cl3, PO3Cl3 and PO4Cl3 photo products by a sequential insertion of oxygen atoms through phosphadioxirane intermediate. A compelling evidence for the passage of the reaction through phosphadioxirane intermediate is established through 18O2 isotopic substitution experiments.
关键词： DFT computations,matrix isolation,infrared spectroscopy,photolysis,phosphadioxirane intermediate
更新于2025-09-23 15:23:52
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Novel A2-D-A1-D-A2 type NIR absorbing symmetrical squaraines based on 2, 3, 3, 8-tetramethyl-3H-pyrrolo [3, 2-h] quinoline: Synthesis, photophysical, electrochemical, thermal properties and photostability study
摘要： Two novel acceptor–donor-acceptor-donor-acceptor type pi-conjugated symmetrical squaraine dyes, denoted by PQSQ 1 and PQSQ 2 based on 2, 3, 3, 8-tetramethyl -3H-pyrrolo [3,2-h] quinoline were successfully synthesized for the first time to arrive absorption and emission at NIR region. These dyes comprise indolenines as electron donor units, squaryl ring as a central electron acceptor and pyridines as terminal electron acceptor units. The relationship between molecular structures and photophysical properties of these dyes was studied in comparison with their parent compounds (ISQ and N-Et ISQ). These novel squaraine dyes displayed an intense absorption within the range 671 to 692 nm in polar to non- polar solvents respectively with good molar extinction coefficients (? 105 Lmol-1cm-1). Compared to their parent squaraines, both dyes showed red-shifted absorption (33 - 44 nm) as well as emission (38 - 59 nm) due to the electron-accepting ability of the ancillary pyridine acceptors and extended pi-conjugation. These dyes exhibited negative solvatochromism and Reichardt's ET (30) scale was applied to propose a quantitative relationship of the relative stability of ground and excited-state of these squaraines with solvent polarity. The electrochemical and computational properties of these symmetrical squaraines were investigated with the help of cyclic voltammetry and density functional theory (DFT). Moreover, PQSQ 1-2 exhibited high thermal and photo-stability. These A2-D-A1-D-A2 type dyes showed improved photostabilities compared to their parent D-A-D type dyes.
关键词： 2, 3, 3, 8-tetramethyl -3H-pyrrolo [3, 2-h] quinoline,NIR absorbing dyes,acceptor-donor-acceptor-donor-acceptor,squaraines,DFT computations,red shift
更新于2025-09-23 15:21:21
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Synthesis, spectroscopic studies and DFT/TD-DFT/PCM calculations of molecular structure, spectroscopic characterization and NBO of charge transfer complex between 5-amino-1,3-dimethylpyrazole (5-ADMP) with chloranilic acid (CLA) in different solvents
摘要： New charge transfer complex between the n- and π-donor 5-amino-1,3-dimethyl pyrazole (5-ADMP) with the π-acceptor chloranilic acid was synthesized and characterized experimentally and theoretically. The experimental work was carried out in solution and solid state. The selected solvents were chloroform (CHL), methanol (MeOH), ethanol (EtOH) and acetonitrile (AN). upon mixing the donor with acceptor a change in color takes place immediately to pink one with absorption maxima at λmax 530, 531, 530 and 522 nm in CHL, EtOH, MeOH, and AN, respectively. The complex was stable for more than 2 h. The stability constant was calculated using Bensie-Hildebrand equation where it recorded the highest value in chloroform and the least one in methanol. Thermodynamic parameters were calculated where the enthalpy of formation recorded high value in chloroform. The solid complex was prepared where elemental analysis con?rmed its composition at 1:1 in concordant with that in solution. The infrared spectra of the formed complex con?rmed the existence of proton transfer hydrogen bond beside charge transfer interaction. A theoretical computations using DFT at the basis set B3LYP/6-31 G(d,p) was applied to support the experimental results. Optimization energy and geometrical parameters con?rmed the high stability of the complex due to the presence of CT beside PT in its chemical structure. Reactivity parameters strongly recommended that 5-ADMP is good electron donor and CLA is good electron acceptor. MEP maps con?rmed the presence of proton transfer hydrogen bond where OH of CLA is the electrophile and the pyridinic-like ring nitrogen of 5-ADMP is the nucleophile. The origin of electronic spectra was computed by TD-DFT using PCM as solvation model. Two absorption maxima were recorded in the calculated spectra attributing to π-π? and n-π? transitions in all media. Natural population analysis was applied to estimate the natural atomic charges and natural bond orbital (NBO). Both con?rmed the existence of strong proton transfer hydrogen bonding beside charge transfer in the produced complex.
关键词： DFT computations,Hydrogen bond,Pyrazole,Charge transfer,Spectroscopy
更新于2025-09-19 17:15:36
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Physicochemical and Ion-Sensing Properties of Benzofurazan-Appended Calix[4]arene in Solution and on Gold Nanoparticles: Spectroscopy, Microscopy, and DFT Computations in Support of the Species of Recognition
摘要： A calix[4]arene conjugate (L) functionalized at the lower rim with a benzofurazan fluorophore (NBD) and at the upper rim with a thioether moiety has been synthesized and characterized by 1H NMR, 13C NMR, and mass spectrometry techniques. Both the absorption and emission spectral data for L in different solvents exhibited progressive changes with an increase in polarity. Ion recognition studies were performed by absorption and fluorescence spectroscopy using 10 different metal ions. Among these, Hg2+ exhibited greater changes in these spectra, whereas Cu2+ showed only significant changes and all other ions showed no change in the spectral features. Although the Hg2+ has dominant influence on the spectral features and provides a detection limit of 56.0 ± 0.6 ppb, the selectivity was hampered because of the presence of the derivatizations present on both the rims of L for ion interaction in solution. Therefore, L was immobilized onto gold nanoparticles (AuNPL) so that the upper rim derivatizations anchor onto the gold surface through Au?S interactions, and this leaves out only the lower rim NBD derivatization for interaction with ions selectively. The AuNPL’s were characterized by transmission electron microscopy, scanning electron microscopy, energy-dispersive X-ray spectroscopy, and X-ray photoelectron spectroscopy (XPS) analyses. The surface characteristics were analyzed by contact angle measurements. The AuNPL’s exhibit greater selectivity and enhanced sensitivity for Hg2+ ions with a lowest detection limit of 48.0 ± 0.8 ppb. The immobilization of L onto AuNPs was reflected in the corresponding fluorescence lifetime values, and the addition of Hg2+ to either L or AuNPL showed fluorescence quenching. The reversible recognition of Hg2+ by L was demonstrated by titrating L or AuNPL with Hg2+ followed by tetra-butyl ammonium iodide for several cycles. The structural features of Hg2+-bound species were demonstrated by density functional theory computations and were supported by the XPS data. The Hg2+ induces aggregated fibrillar morphology into supramolecular L, as demonstrated by microscopy when Hg2+ was added either to L or to AuNPL, supporting aggregation-caused quenching.
关键词： calix[4]arene,benzofurazan,Hg2+ detection,DFT computations,fluorescence quenching,gold nanoparticles
更新于2025-09-04 15:30:14