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Strong Near Infrared Absorbing Porphyrins: A DFT Study
摘要： A systematic density functional theory study of electronic properties and optical spectra of four potential fused porphyrins with extended π-conjugation has been reported employing the M06 functional along with 6-31G(d)+LanL2DZ basis set. Symmetrical tetra fusion of the benzene rings at the β-meso-β position of porphyrins, resulted in four quadruply-fused porphyrins. Such studies revealed the fact that the ring fusion with extended π-electrons causes remarkable red-shifts with narrowed band gaps. Thus, such systems can be used to extend the absorption deeper in to near-infrared (NIR) to even better utilize the photon rich region of solar spectrum. These fused porphyrins have emerged as promising NIR absorbing materials, having utility in molecular solar-conversion systems.
关键词： Porphyrins,DFT,TD-DFT,NIR absorptions
更新于2025-09-04 15:30:14
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Synthesis, Structural, Electrochemical and Energy Transfer Studies of π‐Extended Mono‐β‐Functionalized Porphyrin Dyads
摘要： A series of π-conjugated mono-β-functionalized donor-acceptor porphyrin dyads (1-4) with various (phenyl, naphthyl, anthracenyl and pyrenyl) donors and their metal complexes (M = Zn(1a-4a), Cu(1b-4b), Co(1c-4c) and Ni(1d-4d)) were synthesized and characterized by various spectroscopic and electrochemical techniques. Modified one-step Horner-Wadsworth-Emmons reaction was performed on monoformyl porphyrin to get ethenyl linked mono-β-porphyrin dyads in good to excellent yields (70-90%). Red shifted absorption and emission spectra were observed as compared to unsubstituted pristine tetraphenylporphyrins due to π-extended donors. Time resolved fluorescence studies confirmed the effective intramolecular F?rster energy transfer from donor moiety to porphyrin core in anthracene and pyrene appended porphyrin dyads. DFT and TD-DFT optimization signified the orientation of donor and acceptor plays a vital role in energy transfer as co-planarity of donor with porphyrin core increases the energy transfer efficiency. The distribution of electron density on HOMOs and LUMOs indicated the EET mechanism from donor moiety to porphyrin acceptor core. All porphyrin dyads exhibited cathodic shift in their oxidation potential suggesting facile oxidation of porphyrin core due to π-extension and the presence of electron donating moieties. Finally, femtosecond transient absorption spectral studies were performed to secure evidence of excitation transfer and kinetic information of the energy transfer event in the dyads.
关键词： DFT,energy transfer,mono-β-functionalized,porphyrin dyads,Horner-Wadsworth-Emmons reaction,π-Extended,femtosecond transient absorption,TD-DFT
更新于2025-09-04 15:30:14
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Raman Characterization of Phenyl-Derivatives: From Primary Amine to Diazonium Salts
摘要： The objective of the present work is to use Raman spectroscopy for characterizing, the fate of phenyl-derivatives, from phenyl-amines to aryl-diazonium derivatives (ADD). Four ADD were investigated: (i) benzene diazoniumtetrafluoroborate (DS), (ii) 4-decyl benzene diazoniumtetrafluoroborate (DS-C10H21), (iii) 4-carboxybenzene diazoniumtetrafluoroborate (DS-COOH) and (iv) 4-(aminoethyl) benzene diazoniumtetrafluoroborate (DS-(CH2)2NH2). Raman investigation of the above ADD confirmed the existence of an N≡N bond stretching in the range of 2285-2305 cm-1. Moreover, the strong band related to CH in plane-bending and C-N-stretching modes in the 1073-1080 cm-1 range, is a signature of phenyl derivatives stemming from ADD. Furthermore, we analyzed and discuss the H-N-(ring) symmetric stretching modes and the ring-N, as well as the benzene-ring vibrational modes, the C-H related vibrations and the functions in para-position carried by the aromatic ring. The effect of structural changes, the conformational rearrangements from amines to ADD and the influence of the substituent located in the para-position on Raman modes, were examined as well. Finally, Raman experiments supported by Density Functional Theory (DFT) modeling allowed us to determine the crystalline structure of DS-COOH.
关键词： Raman,Diazonium salts,Synthesis and characterization,DFT calculations,Phenyl-amines
更新于2025-09-04 15:30:14
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Experimental and density functional theory insights into the effect of withdrawing ligands on the fluorescence yield of Ru(II)-based complexes
摘要： The quality of emission spectra of metal complexes gives good insights into their performance in many optoelectronic applications. Herein, the effect of the number and position of various ligand structures on the emission spectra of Ru bipyridine complexes was studied. Specifically, the use of a different number of withdrawing groups (COOH) was investigated in detail. The complexes were first investigated using density functional theory (DFT) and time‐dependent DFT calculations and then confirmed experimentally. The bandgap energy, reactivity, emission spectra and Stokes shift were found to depend on the number and position of the withdrawing groups attached to the Ru(bpy)2 complexes. Upon increasing the number of withdrawing groups, the electrons were found to be withdrawn from the carbon orbitals and resonated to reach the metal, and accumulated around it, thus enhancing the metal‐to‐ligand charge transfer mechanism instead of the ligand‐to‐ligand charge transfer mechanism. The complexes with more withdrawing groups showed spectra with more intense emission peaks with shorter lifetime, indicating the enhancement in the photoactivity of the complexes. Ligands with ring nitrogens with two COOH groups showed the greatest effect on the enhancement of the emission spectra with a lifetime of 0.5359 ns. The resulting collective emission spectra covered a wide wavelength range, making the investigated complexes a good choice for many optoelectronic applications.
关键词： DFT,lifetime,Ru(II) complexes,fluorescence,withdrawing groups
更新于2025-09-04 15:30:14
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A Quantitative Analysis of Nutrient Requirements for Hydroponic Spinach (Spinacia oleracea L.) Production Under Artificial Light in a Plant Factory
摘要： Surplus absorption of elements that contribute little to crop productivity and quality can be avoided, and fertilizer consumption costs minimized, by applying elements quantitatively to the nutrient solution fed to the plants. The aim of this study was to determine the minimum macronutrient requirements of spinach (Spinacia oleracea L.) with a desired plant size, so that fertilizer management in plant factories can be maximized. Spinach plants were grown in a plant factory (20°C/17°C day/night temperature, photosynthetic photon flux (PPF) of 350 μmol·m-2·s-1 for 12 hours per day using cool-white fluorescent lamps, 1,000 μmol·mol-1 CO2). Spinach grew and developed rapidly, and reached its desired marketable size in only 12–15 days after being transplanted to the study conditions. At day 15 of cultivation under the treatment conditions, the required quantities of macronutrients per plant (90 grams in fresh weight) were determined as follows: 191 mg N, 31 mg P, 345 mg K, 34 mg Ca, 38 mg Mg, and 13 mg S. In conclusion, a quantitative nutrient managing method with low nutrient concentrations is feasible and resource-saving for hydroponic vegetable production in plant factories.
关键词： Quantitative fertilizer management,Macronutrients,Deep flow technique (DFT)
更新于2025-09-04 15:30:14
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Bis[1]benzothieno[1,4]thiazines - Planarity, Enhanced Redox Activity and Luminescence by Thieno-Expansion of Phenothiazine
摘要： Twofold Buchwald-Hartwig aminations selectively furnish all three regioisomers of bis[1]benzothieno[1,4]thiazines and X-ray structure analyses and DFT calculations were corroborated for correlation of their electronic properties. All regioisomers outscore the parent compound phenothiazine with respect to a low lying oxidation potential and reversible redox activity. The anti-anti bis[1]benzothieno[3,2-b:2',3'-e][1,4]thiazines possess lowest oxidation potentials in this series and display pronounced green luminescence in solution (?F ≈ 20%) and in the solid state. Syn-anti regioisomers are only weakly luminescent in solution, but show aggregation induced emission enhancement and solid state luminescence. Most interestingly, found by X-ray structure analyses anti-anti derivatives reveal an amazingly coplanar structure of the pentacyclic anellated 1,4-thiazine system, emphasizing a structural similarity to heteroacenes. The calculated theoretical nucleus-independent chemical shifts additionally suggest that the 8?-electron core systems can be considered as first electronically unbiased anellated 1,4-thiazines with antiaromatic character.
关键词： Heterocycles,1,4-Thiazines,Fluorescence,Buchwald-Hartwig coupling,Cyclic voltammetry,Absorption,Antiaromaticity,Aggregation induced emission enhancement,Polymorphism,DFT calculations
更新于2025-09-04 15:30:14
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[ACS Symposium Series] Raman Spectroscopy in the Undergraduate Curriculum Volume 1305 || Quantitative Analysis of Xylene Mixtures Using a Handheld Raman Spectrometer
摘要： Xylene isomers (meta-xylene, ortho-xylene, and para-xylene) have been extensively analyzed by different instrumental methods. In this chapter, xylene isomers and their mixtures were analyzed qualitatively and quantitatively by Raman spectroscopy. First, we identified peaks that discriminated each isomer along with peaks that remain unchanged regardless of isomeric form. We used theoretical calculations to aid in the peak assignments. Then, we tested the efficacy of the technique in qualitatively and quantitatively apportioning isomeric mixtures of xylenes.
关键词： Xylene isomers,DFT calculations,Raman spectroscopy,quantitative analysis,handheld Raman spectrometer
更新于2025-09-04 15:30:14
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Microcosmic sulfidization mechanism of S2 on the massicot (1?0?0) surface by DFT study
摘要： The sul?dization mechanism of S2 on the massicot surface was simulated by density function theory (DFT) calculation to illustrate the microscopic reaction mechanism during the surface sul?dization process of lead oxide minerals at high temperature. The calculated results showed that the massicot (1 0 0) surface was the most stable cleavage surface and the main active sites were the O atoms of the surface. The S atoms more easily absorbed on the O atoms of massicot surface in contrast with Pb atoms, leading to the formation of sulfur dioxide in the following reactions. The density of state (DOS) results revealed that O 2p orbital at surface layers of the massicot and S 3p orbital of S2 overlapped ranging from ?0.7 to 0.7 eV, implying that chemical adsorption could occur. The results of Mulliken population suggested that the oxidation and reduction reactions of S atoms from the sul?dization agent were simultaneously involved in the adsorption process. This paper revealed the mechanism of surface sul?dization at an atomic level. It was expected that the study could provide a theoretical reference to improve the sul?dization roasting performance of massicot.
关键词： Microcosmic mechanism,Surface sul?dization,DFT,Massicot,S2
更新于2025-09-04 15:30:14
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Activation of CO2 at chromia-nanocluster-modified rutile and anatase TiO2
摘要： Converting CO2 to fuels is required to enable the production of sustainable fuels and to contribute to alleviating CO2 emissions. In considering conversion of CO2, the initial step of adsorption and activation by the catalyst is crucial. In addressing this difficult problem, we have examined how nanoclusters of reducible metal oxides supported on TiO2 can promote CO2 activation. In this paper we present density functional theory (DFT) simulations of CO2 activation on heterostructures composed of clean or hydroxylated extended rutile and anatase TiO2 surfaces modified with chromia nanoclusters. The heterostructures show non-bulk Cr and O sites in the nanoclusters and an upshifted valence band edge that is dominated by Cr 3d- O 2p interactions. We show that the supported chromia nanoclusters can adsorb and activate CO2 and that activation of CO2 is promoted whether the TiO2 support is oxidised or hydroxylated. Reduced heterostructures, formed by removal of oxygen from the chromia nanocluster, also promote CO2 activation. In the strong CO2 adsorption modes, the molecule bends giving OeCeO angles of 127 - 132° and elongation of CeO distances up to 1.30 ?; no carbonates are formed. The electronic properties show a strong CO2eCreO interaction that drives the interaction of CO2 with the nanocluster and induces the structural distortions. These results highlight that a metal oxide support modified with reducible metal oxide nanoclusters can activate CO2, thus helping to overcome difficulties associated with the difficult first step in CO2 conversion.
关键词： DFT,CO2 Activation,Adsorption,Heterostructures
更新于2025-09-04 15:30:14
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Internal path investigation of the acting electrons during the photocatalysis of panchromatic ruthenium dyes in dye-sensitized solar cells
摘要： A series of heteroleptic Ru(II) complexes were theoretically investigated using time-dependent density functional theory. These dyes, including K8 and N3, are based on a common motif formed by Ru center, N]C]S, and polypyridyl ligands, but differ only by the nature of the added group in para position of each pyridyl. The presence of these ligands will enable the evaluation of the electronic effects ±I and ±M. This work focuses on the localization of the part, among the metal, the eN]C]S, the polypyridyl ligands, and the added group R, which is most actively involved in the photocatalysis process. We dealt with both ground and excited states as well as the electronic transitions between them. To illustrate the effect of each functional group R on its photophysical properties, the geometries of ?ve dyes were optimized in the molecular and univalent cationic states. All molecules are asymmetrical in shape with a distorted octahedral coordination of the RuN6 core. Atomic charge and spin density distributions show that a charge transfer process occurs from the NCS/Ru to polypyridyl ligand. Analysis of the electronic absorption spectra reveals that the band with the highest wavelength value is assigned to metal-to-ligand charge transfer transition. On the contrary, two other bands are assigned to multi-transitions Ru/NCS to polypyridylep*. These attributions have been con?rmed by the localization of all atoms intervening in them. We also introduced an adapted way to estimate the ionization probability values in each atomic center in the ground and ?rst excited states. Phenomenal properties such as mobility, redox potential, electronic spectrum, ionization potential, and optical gap of the most ef?cient dye, which is the N3, ?t well with experimental values.
关键词： DSSC,TD-DFT,Ru(II) complexes,Atomic ionization probability
更新于2025-09-04 15:30:14