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Crystal structure, vibrational spectra, optical properties and density functional theory approach of a picrate salt based on substituted triphenylphosphinium
摘要： A new organic crystal, [BzTPP][PIC](1) ([BzTPP]+ = benzyl triphenylphosphinium, [PIC]- = picrate), has been grown by slow evaporation solution growth technique. Single crystal XRD reveals that it belongs to monoclinic system with P21/c. The two neighboring [BzTPP]+ cations from a dimer through C-H···π interaction while anions stack into a columnar structure through N···O, O···O and π···π interaction. The anions and cations form a column structure alternately in ···AC-AC-AC-AC··· sequence through C-H···O hydrogen bonds. The experimental vibrational bands (IR and Raman) have been discussed and assigned based on DFT calculations. The HOMO-LUMO energy gap explains the charge transfer interactions in the molecule. The thermal stability of the hybrid crystal was analyzed by TG-TDA-MS technique and revealed that the title crystal was stable up to 290 °C. The fluorescence spectra reveal three main emission peaks at 295, 388 and 543 nm upon excitation at 250 nm in solid state at room temperature. The energy of weak interactions in the molecule and nonlinear optical properties were studies using DFT calculations.
关键词： Substituted benzyl triphenylphosphinium picrate,Optical properties,vibrational spectra,Crystal structure,DFT calculations
更新于2025-09-23 15:21:01
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Lawsone isomers, lawsone ether and bilawsone for dye-sensitized solar cells applications: DFT and UV–Vis studies
摘要： Structural and optoelectronic properties of lawsone (L), lawsone ether (LE) and bilawsone (BL) were studied theoretically using the DFT and time-dependent DFT methods with hybrid functional B3LYP5 and 6-311G (2d,p) basis set. For the monomer lawsone molecule, isomerization reaction between two rotational isomers was analyzed based on a thermodynamic approach. The electronic spectra of the dyes molecules in a vacuum and solvents (DMSO and CH2Cl2) were computed. The maximum wavelengths were found at 355e408 nm for the LE and 350e448 nm for BL that indicated bands shift to visible range compared to L (340 nm). The UVeVis spectra of the L and BL were measured experimentally in DMSO solution. For the BL, a broad and intensive band was observed in a visible region at 452 nm that apparently would favour sensitizing ability of the dye. The optoelectronic properties of the LE and BL showed them as more promising candidates for DSSCs applications compared to the individual lawsone dye.
关键词： Lawsone ether,Dye-sensitized solar cells,Lawsone isomers,DFT/TD-DFT,Bilawsone,UVeVis/vibrational spectra
更新于2025-09-19 17:13:59
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Structural, spectroscopic, physical properties and quantum chemical investigation on bromide salt of 4-dimethylaminopyridine NLO material for optoelectronic applications
摘要： In this paper, investigations on the crystal structure, vibrational, physical properties on charge transfer single crystals of 4-dimethylaminopyridinium bromide. Its structural parameters, vibrational, mechanical and optical properties have been studied by SCXRD, FT-IR, FT-Raman, Vickers microhardness test and Ultraviolet-Visible spectral analysis. The computational investigations were carried out to determine the molecular geometries, vibrational modes, HOMO-LUMO analysis, population analysis, MEP, thermodynamics and macroscopic NLO response of the compound. The theoretical and experimental molecular geometrical parameters and vibrational assignments have been in good agreement. Mulliken charge distribution of the present compound was studied systematically. The chemical hardness, electro-negativity and chemical potential of the molecule have been computed by HOMO - LUMO plot. FMO analysis indicates the electron delocalization on the title compound and also its low value of energy gap indicates electron transfer. NLO parameters were calculated by DFT. The calculated hyperpolarizability values showed that the compound is a good candidate for NLO applications.
关键词： Quantum chemical calculation,Single crystals,Nonlinear Optics,Mayer Index,Vibrational spectra
更新于2025-09-19 17:13:59
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Vibrational Spectra of Thiolate-Protected Gold Nanocluster with Infrared Reflection Absorption Spectroscopy: Size- and Temperature-Dependent Ordering Behavior of Organic Monolayer
摘要： Vibrational spectra of thiolate-protected gold nanoclusters, prepared in a monolayer manner using the Langmuir?Blodgett method, were measured by means of infrared re?ection absorption spectroscopy (IRAS). A transferred monolayer of gold nanoclusters ligated by dodecanethiolate or 2-phenylethane-1-thiolate onto a single-crystal gold (Au) surface of Au(111) exhibits worthy IRAS spectra that reveal temperature-dependent behaviors from 100 to 340 K as well as comprehensive peak assignments based on density functional theory calculations: the conformation change in ligands between all trans and gauche defect forms with temperature. In addition to the temperature dependence, the cluster size dependence of alkyl and phenyl moieties is discussed, compared with the IRAS spectra of the corresponding self-assembled monolayers (SAMs) on Au(111). Ligands spreading three-dimensionally from the Au core determine the coordination structure of the ligated Au nanoclusters.
关键词： self-assembled monolayers,density functional theory calculations,Langmuir?Blodgett method,thiolate-protected gold nanoclusters,Vibrational spectra,temperature-dependent behaviors,infrared re?ection absorption spectroscopy
更新于2025-09-12 10:27:22
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Electronic structures and spectroscopic signatures of silicon-vacancy containing nanodiamonds
摘要： The presence of midgap states introduced by localized defects in wide-band-gap-doped semiconductors can strongly affect the electronic structure and optical properties of materials, generating a wide range of applications. Silicon-divacancy defects in diamond have been recently proposed for probing high-resolution pressure changes and performing quantum cryptography, making them good candidates to substitute for the more common nitrogen-vacancy centers. Using group-theory and ab initio electronic structure methods, the molecular origin of midgap states, zero-phonon line splitting, and size dependence of the electronic transitions involving the silicon-vacancy center is investigated in this paper. The effects of localized defects on the Raman vibrational and carbon K-edge x-ray absorption spectra are also explored for nanodiamonds. This paper presents an important analysis of the electronic and vibrational structures of nanosized semiconductors in the presence of midgap states due to localized defects, providing insight into possible mechanisms for modulating their optical properties.
关键词： midgap states,electronic structure,optical properties,nanodiamonds,Raman vibrational spectra,quantum cryptography,x-ray absorption spectra,silicon-vacancy defects
更新于2025-09-10 09:29:36
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A Frequency Range Selection Method for Vibrational Spectra
摘要： Theoretical calculations of vibrational properties are widely used to explain and predict experimental spectra. However, with standard quantum chemical methods all molecular motions are considered, which is rather time-consuming for large molecules. As typically only a specific spectral region is of experimental interest, we propose here an efficient method that allows calculation of only a selected frequency interval. After a computationally cheap low-level estimate of the molecular motions, the computational time is proportional to the number of normal modes needed to describe this frequency range. Results for a medium-sized molecule show a reduction in computational time of up to one order of magnitude with negligible loss in accuracy. We also show that still larger computational savings are possible by using an additional intensity-selection procedure.
关键词： frequency range selection,IR absorption spectra,quantum chemical methods,vibrational spectra,computational efficiency
更新于2025-09-09 09:28:46