Search results for "Ground state"
showing 10 items of 928 documents
Toward device applicable second order NLO polymer materials: definition of the chromophore figure of merit
2007
Maximal achieved second order non linear optical (NLO) efficiency of the PMMA based host – guest systems containing eight dimethylaminobenzylidene -1, 3 - indandione (DMABI) related chromophores have been analysed. Two contradicting sets of NLO chromophore figure of merit (FOM) equations were tested. One of them predicts that NLO efficiency of the poled polymer host -guest film is proportional to ground state dipole d33 ~ 1/μg, another to d33 ~ 1/μg. The best correlations for the maximal achieved nonlinearity were obtained with second set of FOM, especially if high ground state dipole (μg > 7D) chromofores are included in analysis.
New Figure of Merit for Tailoring Optimal Structure of the Second Order NLO Chromophore for Guest-Host Polymers
2008
Reliability to forecast SHG efficiency using two sets of non linear optical (NLO) chromophore figures of merit (FOM) was tested. One of them predicts that SHG efficiency d 33 of the poled guest-host polymer is proportional to ground state dipole ∼ μg, another to ∼ 1/μg. Correlation of maximal achieved second order NLO efficiency of the PMMA based systems containing eight dimethylaminobenzylidene-1, 3-indandione (DMABI) related chromophores with proposed FOM have been analyzed. The best correlations were obtained with second set of FOM, especially if high dipole moment (μg > 7D) chromophores are included in analysis.
From Bowls to Capsules: Assembly of Hexanuclear Ni II Rings Tailored by Alkali Cations
2020
An anionic hexanuclear NiII metallamacrocycle with endo and exo linking sites has been employed as a building block to generate a series of capsules and bowls of nanometric size. The supramolecular arrangement of the {Ni6 } rings was tailored by the size of the alkali cations, showing the transition from {Ni6 -M2 -Ni6 } capsules (M=LiI and NaI ) to {Ni6 -M} bowls (M=KI and CsI ). The alkyl co-cations are determinant to stabilize the assemblies by means of CH⋅⋅⋅π interactions on the exo side of the metallamacrocycles. The effect on the topology of the supramolecular assemblies of the cation size, cation charge, Et3 NH+ or Me4 N+ counter cations has been analyzed. Magnetic measurements reveal…
Ground and excited state properties of polyamine chains bearing two terminal naphthalene units
2002
A series of compounds bearing two naphthalene units linked through methylene groups to both ends of different open-chain polyamines has been investigated. The fluorescence emission studies show the presence of an excimer species whose formation depends on the protonation state and length of the polyamine chains and implies the existence of a bending movement in the excited state allowing the two naphthalene units to approach and interact. This interpretation was clearly proven by time-resolved fluorescence with the appearance of double exponential decays with a rise time observed at the excimer emission wavelength. For comparison purposes one bis-chromophoric compound containing a rigid cha…
Theoretical Studies of the Electronic Spectra of Organic Molecules
1995
The complete active space (CAS) SCF method in conjunction with multiconfigurational second-order perturbation theory (CASPT2) has been used to study the electronic spectra of a large number of molecules. The wave functions and the transition properties are computed at the CASSCF level, while dynamic correlation contributions to the excitation energies are obtained through the perturbation treatment. The methods yield energies, which are accurate to at least 0.2 eV, except in a few cases, where the CASSCF reference function does not characterize the electronic state with sufficient accuracy. The applications comprise: the polyenes from ethene to octatetraene (cis- and trans-forms); a number …
An Understanding of the Electrophilic/Nucleophilic Behavior of Electro-Deficient 2,3-Disubstituted 1,3-Butadienes in Polar Diels−Alder Reactions. A D…
2008
The electrophilic/nucleophilic behavior of dimethyl 2,3-dimethylenesuccinate 1, an electron-deficient 2,3-disubstituted 1,3-butadiene, in polar Diels-Alder reactions has been studied using DFT methods at the B3LYP/6-31G(d) level of theory. The electronic nature of bonding of the transition structures involved in the cycloaddition reactions of the diene 1 toward the nucleophilically activated dienophile 6 and the strong electrophilically activated dienophile 7 has been carefully examined within the natural bond orbital (NBO) and the topological analysis of the electron localization function (ELF) frameworks. Additionally, a study of the global electrophilicity pattern of the reagents at the …
On the vertical excitation energy of cyclopentadiene
2004
The vertical excitation energy for the lowest valence pi--pi(*) transition of cyclopentadiene is investigated. Using a combination of high-level theoretical methods and spectroscopic simulations, the vertical separation at the ground state geometry is estimated to be 5.43+/-0.05 eV. This value is intermediate between those calculated with coupled-cluster and multireference perturbation theory methods and is about 0.13 eV higher than the observed maximum in the absorption profile.
X-ray crystal structure and electronic properties of chlorobis(mepirizole)copper(II) tetrafluoroborate (mepirizole = 4-methoxy-2-(5-methoxy-3-methyl-…
1997
Abstract The crystal structure of [Cu(mep)2Cl](BF4)[mep = 4-methoxy-2-(5-methoxy-3-methyl-1H-pyrazol-1-yl)-6-methylpyrimidine] has been determined by X-ray diffraction. The crystal structure is built up of [Cu(mep)2Cl]+ cations and BF4− anions. The structure of the cation involves a five-coordinated CuN4Cl chromophore, with a stereochemistry near to a compressed trigonal bypyramid (TBP) but with a significant degree of distortion towards the square pyramidal (SP) topology. The EPR spectrum is indicative of a mixed dz2/dx2 − y2 ground state for the copper(II) ions, in agreement with the structural data.
Exciton and multiexciton optical properties of single InAs/GaAs site-controlled quantum dots
2013
We have studied the optical properties of InAs site-controlled quantum dots (SCQDs) grown on pre-patterned GaAs substrates. Since InAs nucleates preferentially on the lithography motifs, the location of the resulting QDs is determined by the pattern, which is fabricated by local oxidation nanolithography. Optical characterization has been performed on such SCQDs to study the fundamental and excited states. At the ground state different exciton complex transitions of about 500 μeV linewidth have been identified and the fine structure splitting of the neutral exciton has been determined (≈65 μeV). The observed electronic structure covers the demands of future quantum information technologies.…
Synthesis, crystal structure, DFT calculations, Hirshfeld surface, vibrational and optical properties of a novel hybrid non-centrosymmetric material …
2019
This present work undertakes the study of a novel organic–inorganic hybrid material, which has been obtained successfully by an acid-base reaction at room temperature and structurally studied by the single crystal X-ray diffraction method. (C10H15N2)2H2P2O7 crystallizes in the triclinic system with the non-centrosymmetric space group P1 with the following lattice parameters: a = 5.9159(2) Å, b = 13.8451(6) Å, c = 14.5973(5) Å, ? = 74.507(2)°, ? = 89.980(2)°, ? = 89.231(2)° with V = 1152.06(8) Å3 and Z = 2. The X-ray structural analysis supported by a detailed Hirshfeld 2D fingerprint plots has been performed to elucidate the different inter-contacts in the crystal structure mainly associate…