Search results for "delocalization"
showing 10 items of 10 documents
Electron delocalization in mixed-valence Keggin polyoxometalates. Ab initio calculation of the local effective transfer integrals and its consequence…
2002
We present a quantitative evaluation of the influence of the electron transfer on the magnetic properties of mixed-valence polyoxometalates reduced by two electrons. For that purpose, we extract from valence-spectroscopy ab initio calculations on embedded fragments the value of the transfer integrals between W nearest-neighbor atoms in a mixed-valence alphaPW(12)O(40) polyoxowolframate Keggin anion. In contradiction with what is usually assumed, we show that the electron transfer between edge-sharing and corner-sharing WO(6) octahedra have very close values. Considering fragments of various ranges, we analyze the accuracy of calculations on fragments based on only two WO(5) pyramids which s…
Investigations of Chl a aggregates cross-linked by dioxane in 3-methylpentane
1997
In this work, dioxane-bound aggregates of chlorophyll a are prepared in 3-methylpentane. The properties of the aggregates are studied by using steady-state and time-resolved spectroscopies. The Q -region absorption spectrum of the y chlorophyll a-dioxane aggregate shows four clearly resolvable narrow bands with comparable intensities. The band maxima are located at 683, 689, 698 and 702 nm. The emission spectrum consists of two emission bands centred at 699 and 702 nm suggesting the presence of two types of aggregates. High degree of fluorescence polarization is detected yielding the angles between the absorption transition moments with respect to the 702 nm emission transition moment. The …
Über Phosphor‐haltige Heterocyclen, II: Molekül‐ und Kristallstruktur von 1,2,3,4,5‐Pentaphenyl‐1λ 5 ‐phosphol‐1‐on
1976
Die Struktur der Titelsubstanz wurde rontgenographisch aus Diffraktometer-Einkristalldaten bestimmt und bis zu einem konventionellen R von 0.076 verfeinert. Der 5-ring besitzt „envelope”-Konformation. Fehlende Planaritat und Bindungslangenverteilung schliesen eine Elektronendelokalisation im λ5-Phospholsystem aus. Das Propellersystem der Phenylsubstituenten bildet eine Cs-symmetrische Doppelschneckenschraube. Die Struktur besteht aus 14-fach koordinierten Molekulen. On Heterocyclic Systems Containing Phosphorus, II: Molecular and Crystal Structure of 1,2,3,4,5-Pentaphenyl-1 λ5-phosphol-1-one The crystal structure of the title compound has been determined from single crystal X-ray data and r…
Building a State’s Global Competitive Advantage by Improving Its Finances: A System Dynamic Model Tailored for the Italian State
2014
The present study analyzes and tests a new way to recover economy and public finances in time of crisis. An exclusive focus on State financial short-term stability risks to undermine the economic growth and to erode the social environment, thus it depletes the sources of State finances on the long-term. While a sustainable strategizing focuses on performance drivers that generate these last. Such approach in public strategizing is based on the assumption that State could increase its budgets by improving the organizational and legal framework in which private firms operate, in order to reduce their overhead costs for compliance of rules, and public facilities’ inefficiencies. This improveme…
Comparative Structural Studies of 4-Diazopyrazole Derivatives by X-Ray Diffraction and Theoretical Investigation
2005
The X-Ray crystal and molecular structures of the 4-pyrazol derivatives 3-methyl-4-diazo-5-benzamido-1H-pyrazole (4) and 3-benzamido-5-methyl-1H-pyrazole (3) have been determined. A dimeric structure has been found for the first and polymeric for the second. A comparison of 4 with 1,3-dimethyl-4-diazo-5-benzamido-lH-pyrazole (2) shows differences in the geometrical parameters of the pyrazole ring due to electron delocalization in 2 consequent to the nitrogen negative charge in the latter. Theoretical investigation at the density functional theory (DFT) level shows difference in the molecular electronic distribution of 2 and 4, in agreement with the structural parameters and the IR stretchin…
Simultaneous field-free molecular orientation and planar delocalization by THz laser pulses
2022
This study shows the unexpected and counter-intuitive possibility of simultaneously orienting a molecule while delocalizing its molecular axis in a plane in field-free conditions. The corresponding quantum states are characterized and different control strategies using shaped THz laser pulses are proposed to reach such states at zero and nonzero temperatures. The robustness against temperature effects of a simple control procedure combining a laser and a THz pulse is shown. Such control strategies can be applied not only to linear molecules but also to symmetric top molecules.
Synthesis and structure of charge transfer salts of tetrathiafulvalene (TTF) and tetramethyl-TTF with 2,4,7-trinitro and 2,4,5,7-tetranitro-9-fluoren…
2009
Charge transfer salts of tetrathiafulvalene (TTF) and tetramethyltetrathiafulvalene (TMTTF) with the organic acceptors 2,4,7-trinitro-9-fluorenone and 2,4,5,7-tetranitro-9-fluorenone have been prepared and characterized. The compounds (TTF)(TENF) (1), (TTF)3(TRNF)2 (2) and (TMTTF)(TRNF) (3) contain mixed stacks of alternating TTF and nitrofluorenone units. Surprisingly, the degree of charge transfer that occurs in these salts is not controlled solely by the redox potentials of the building blocks, but apparently also by the most effective intermolecular interactions in the solid, as determined from the crystal struc- tures obtained. These three compounds exhibit poor electron delocalization…
Molecular Materials from Polyoxometalates
2006
The present article highlights recent results and provide a perspective of the interest of polyoxometalates as inorganic component of molecular materials with active physical properties. Three different aspects will be presented: i) The interest of the magnetic and mixed valence clusters provided by polyoxometalate chemistry in molecular magnetism; ii) The use of these inorganic anions as magnetic component of crystalline conducting materials based on organic donor molecules; iii) The construction of well-organized films of polyoxometalate monolayers by using the Langmuir-Blodgett technique.
MVPACK: a package to calculate energy levels and magnetic properties of high nuclearity mixed valence clusters.
2010
We present a FORTRAN code based on a new powerful and efficient computational approach to solve the double exchange problem for high-nuclearity MV clusters containing arbitrary number of localized spins and itinerant electrons. We also report some examples in order to show the possibilities of the program.
π-Electron delocalization in 2-benzoyl-5-phenylpyrazolidin-3-one
2018
Abstract The crystal and molecular structures of 2-benzoyl-5-phenylpyrazolidin-3-one have been characterized by X-ray diffraction along with density functional theory studies. Cinnamic acid chloride was reacted with benzhydrazide, yielding 2-benzoyl-5-phenylpyrazolidin-3-one. This product was formed in the transformation comprising the nucleophilic addition of benzhydrazide to the styryl fragment of the α,β-unsaturated arrangement and subsequent cyclization. The molecule contains two benzene rings and one five-membered heterocyclic ring with an N–N single bond. The five-membered ring is composed of three atoms of sp 3 hybridization and two atoms of sp 2 hybridization, which cause the flatte…