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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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Modeling core-level excitations with variationally optimized reduced-density matrices and the extended random phase approximation
摘要： The information contained within ground-state one- and two-electron reduced-density matrices (RDMs) can be used to compute wave functions and energies for electronically excited states through the extended random phase approximation (ERPA). The ERPA is an appealing framework for describing excitations out of states obtained via the variational optimization of the two-electron RDM (2-RDM), as the variational 2-RDM (v2RDM) approach itself can only be used to describe the lowest-energy state of a given spin symmetry. The utility of the ERPA for predicting near-edge features relevant to x-ray absorption spectroscopy is assessed for the case that the 2-RDM is obtained from a ground-state v2RDM-driven complete active space self-consistent field (CASSCF) computation. A class of killer conditions for the CASSCF-speci?c ERPA excitation operator is derived, and it is demonstrated that a reliable description of core-level excitations requires an excitation operator that ful?lls these conditions; the core-valence separation (CVS) scheme yields such an operator. Absolute excitation energies evaluated within the CASSCF/CVS-ERPA framework are slightly more accurate than those obtained from the usual random phase approximation (RPA), but the CVS-ERPA is not more accurate than RPA for predicting the relative positions of near-edge features. Nonetheless, CVS-ERPA is established as a reasonable starting point for the treatment of core-level excitations using variationally optimized 2-RDMs.
关键词： reduced-density matrices,extended random phase approximation,v2RDM,CASSCF,core-level excitations,x-ray absorption spectroscopy
更新于2025-09-04 15:30:14
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Ferromagnetic Behavior and Electronic Characterization of ZnO Nanoparticles
摘要： In this work, Al-doped ZnO nanoparticles encapsulated with amorphous SiO2 were prepared by the wet chemical method. The obtained precursor was annealed and the nanoparticle sizes were controlled by adjusting the annealing temperature. These nanomaterials showed ferromagnetic behavior, even though the ZnO bulk crystal was diamagnetic. The results of electrical conductivity and XANES suggested that ferromagnetism of the Al-doped nanoparticles was results of carrier transport and oxygen vacancies. The Al-doped ZnO nanoparticles are extremely interesting from the perspective of solid state physics. [DOI: 10.1380/ejssnt.2018.406]
关键词： Nano-particles, quantum dots, and supra-molecules,Magnetic, structural, and other properties of nanostructures,Zinc oxide,Luminescence,Near edge extended X-ray absorption fine structure (NEXAFS)
更新于2025-09-04 15:30:14
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PH SENSITIVITY DEPENDENCY ON THE ANNEALING TEMPERATURE OF SPIN-COATED TITANIUM DIOXIDE THIN FILMS
摘要： Titanium dioxide (TiO2) thin films were fabricated on indium tin oxide (ITO) glass substrates using the spin coating technique and further were implemented as sensing membranes of the extended gate field effect transistor (EGFET) based pH sensor. The as-deposited thin films were annealed at different temperatures from 200 - 600 °C in room ambient for 20 min. The effects of different annealing temperatures on electrical and crystalline properties were analyzed by I-V two point probes measurement and X-ray diffraction respectively. Meanwhile, the surface morphology of thin films was observed by field emission scanning electron microscope (FESEM). We then measured the transfer characteristics (ID-VG) of the TiO2/ITO sensing membrane using a semiconductor parametric device analyzer for sensor characterization. It was found that, TiO2/ITO sensing membrane annealed at 300 °C achieved higher sensitivity and good linearity of 51.48 mV/pH and 0.99415, respectively in the pH buffer solutions of 4, 7, 10, and 12. Thin film annealed at 300 °C gives higher conductivity thin film of 384.62 S/m. We found that the conductivity of TiO2/ITO thin films was proportional with the sensitivity of sensing membrane.
关键词： titanium dioxide,Annealing temperature,sol-gel spin coating,extended gate field effect transistor
更新于2025-09-04 15:30:14
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Extended π-Conjugated Structures via Dehydrative C–C Coupling
摘要： We describe a methodology for the synthesis of extended aromatic structures through dehydrative C?C coupling from readily accessible diols. Treatment of the diols with a Br?nsted acid (para-toluenesulfonic acid) induces the nucleophilic addition of an arene or heteroarene, yielding fully aromatic products in high to quantitative yields with thiophenes, furan, indole, and N,N-dimethylaniline as coupling partners. The C?C coupling reactions proceed under mild, open flask conditions and offer high atom economy, while providing an attractive alternative approach to metal-catalyzed cross-coupling.
关键词： metal-catalyzed cross-coupling,extended aromatic structures,atom economy,para-toluenesulfonic acid,dehydrative C?C coupling,Br?nsted acid
更新于2025-09-04 15:30:14