FG Theoretische Chemie

16 Items

Recent Submissions
Einfluß der Reaktionsenthalpie auf die Bildung von "Twisted Intramolecular Charge Transfer" (TICT) — Anregungszustände in unpolaren Lösungsmitteln: p-substituierte N,N-Dimethylaniline

Wermuth, Günter (1983)

In saturated hydrocarbons dual fluorescence appears both in p-N,N-Dimethylaminobenzonitrile (DMABN) and p-N,N-Dimethylaminoethylbenzoate (DMABEE). The temperaturedependence of the fluorescence quantum yield suggests that in DMABEE E(B*) ≈ E(TICT) and in DMABN E(B*) Smectic A1 — Smectic Ad Transition in Binary Mixtures of Compounds with Strongly Polar Terminal Groups

Bahr, Ch. ; Heppke, G. ; Shashidhar, R. (1985)

On the basis of high pressure studies we present here the evidence for the existence of a smectic A, — smectic Aj transition at high pressure in a binary liquid crystal mixture consisting of terminally polar compounds. A feature of this observation is that both the constituent compounds are three phenyl ring systems wherein the bridging dipoles are disposed additive with respect to the polar en...

Kerr Orientation Influence on Excited State Absorption Measurements

Menzel, Ralf ; Rapp, Werner (1986)

The possible influence of a strong nonresonant laser field on the orientation of dyes in solution is discussed as a potential source of measuring errors in excited state absorption analysis. The results of investigations on some typical samples suggest that, fortunately, the effect is very small.

Esters of (S)-1,2-propanediol and (R,R)-2,3-butanediol — Chiral Compounds Inducing Cholesteric Phases with a Helix Inversion ·

Heppke, G. ; Lötzsch, D. ; Oestreicher, F. (1987)

Mesogenic chiral esters of optically active (S)-1,2-propanediol and (R,R)-2,3-butanediol were synthesized. The compounds, added to a nematic phase induce cholesteric phases exhibiting a helix inversion with temperature variation. This effect is independent of the molecular structure of the nematic solvent. The inversion temperature varies only slightly with concentration but can be influenced b...

Fully relativistic calculations of EPR and paramagnetic NMR parameters for heavy atom compounds

Gohr, Sebastian (2018)

In the thesis at hand, a 4-component relativistic density functional theory (DFT) approach is applied within the ReSpect program package to calculations of magnetic resonance parameters for various open-shell systems containing heavy 4d and 5d transition metals. Such calculations represent a relatively uncharted territory. Therefore, the present work starts with a comprehensive benchmark study ...

Coarse-grained treatment of the self-assembly of colloids suspended in a nematic host phase

Püschel-Schlotthauer, Sergej ; Stieger, Tillmann ; Melle, Michael ; Mazza, Marco G. ; Schoen, Martin (2016)

The complex interplay of molecular scale effects, nonlinearities in the orientational field and long-range elastic forces makes liquid-crystal physics very challenging. A consistent way to extract information from the microscopic, molecular scale up to the meso- and macroscopic scale is still missing. Here, we develop a hybrid procedure that bridges this gap by combining extensive Monte Carlo (...

Synthesis, structure and bonding of hexaphenyl thorium(IV): observation of a non-octahedral structure

Pedrick, Elizabeth A. ; Hrobárik, Peter ; Seaman, Lani A. ; Wu, Guang ; Hayton, Trevor W. (2016)

We report herein the synthesis of the first structurally characterized homoleptic actinide aryl complexes, [Li(DME)(3)](2)[Th(C6H5)(6)] (1) and [Li(THF)(12-crown-4)](2)[Th(C6H5)(6)] (2), which feature an anion possessing a regular octahedral (1) or a severely distorted octahedral (2) geometry. The solid-state structure of 2 suggests the presence of pseudo-agostic ortho C-H center dot center dot...

Characterization of the [3Fe-4S](0/1+) cluster from the D14C variant of Pyrococcus furiosus ferredoxin via combined NRVS and DFT analyses

Lauterbach, Lars ; Gee, Leland B. ; Pelmenschikov, Vladimir ; Jenney, Francis E., Jr. ; Kamali, Saeed ; Yoda, Yoshitaka ; Adams, Michael W. W. ; Cramer, Stephen P. (2016)

The D14C variant of Pyrococcus furiosus ferredoxin provides an extraordinary framework to investigate a [3Fe-4S] cluster at two oxidation levels and compare the results to its physiologic [4Fe-4S] counterpart in the very same protein. Our spectroscopic and computational study reveals vibrational property changes related to the electronic and structural aspects of both Fe-S clusters.

Giant spin-orbit effects on H-1 and C-13 NMR shifts for uranium(VI) complexes revisited: role of the exchange-correlation response kernel, bonding analyses, and new predictions

Greif, Anja H. ; Hrobárik, Peter ; Autschbach, Jochen ; Kaupp, Martin (2016)

Previous relativistic quantum-chemical predictions of unusually large H-1 and C-13 NMR chemical shifts for ligand atoms directly bonded to a diamagnetic uranium(VI) center (P. Hrobarik, V. Hrobarikova, A. H. Greif and M. Kaupp, Angew. Chem., Int. Ed., 2012, 51, 10884) have been revisited by two- and four-component relativistic density functional methods. In particular, the effect of the exchang...

New approaches for the calibration of exchange-energy densities in local hybrid functionals

Maier, Toni M. ; Haasler, Matthias ; Arbuznikov, Alexey V. ; Kaupp, Martin (2016)

The ambiguity of exchange-energy densities is a fundamental challenge for the development of local hybrid functionals, or of other functionals based on a local mixing of exchange-energy densities. In this work, a systematic construction of semi-local calibration functions (CFs) for adjusting the exchange-energy densities in local hybrid functionals is provided, which directly links a given CF t...

The impact of substrate curvature on the self-assembly of liquid crystals

Püschel-Schlotthauer, Sergej (2017)

The interplay of anisotropic molecular interactions, nonlinearities of the orientational field, and long-range orientational correlations make the physics of liquid crystals both challenging and fascinating. Liquid crystals are known for their dual nature, i.e. a high degree of the orientational order combined with a certain degree of fluidity. The liquid-crystalline order can be enhanced, pert...

Quantum chemical studies of transition-metal complexes and aqueous solvent effects

Theilacker, Kolja (2016)

Thanks to the rapid development in the area of computer hardware, and appreciable advances in algorithms and theoretical chemistry methods, quantum chemical calculations have become a crucial tool over the last decades to gain deeper insights into the electronic structure of molecules. This is especially important for the development and improvement of new catalysts and in the assessment of sol...

Nonlinear nonequilibrium dynamics in a nematic liquid crystal

Stieger, Tillmann (2016)

Liquid crystals are elongated molecules with a rich and surprising phase behavior. Nonequilibrium conditions open a myriad possibilities of manipulating matter, and reach collective states not accessible under equilibrium conditions. We perform nonequilibrium molecular dynamics simulations of a nematic liquid crystal flowing around a colloidal particle. Because of a mismatch between the nematic...

Development of local hybrid functionals for time-dependent density functional theory

Maier, Toni Mike (2016)

The present work is concerned with the advancement of the relatively recent class of local hybrid functionals. The first part of the work addresses the conjunction of local hybrid functionals with linear-response time-dependent density functional theory (TDDFT), which is the most widely used quantum chemical method for excited-state calculations. Besides a detailed derivation of the required fo...

Computational and spectroscopic studies of organic mixed-valence compounds: where is the charge?

Kaupp, Martin ; Renz, Manuel ; Parthey, Matthias ; Stolte, Matthias ; Würthner, Frank ; Lambert, Christoph (2011)

This article discusses recent progress by a combination of spectroscopy and quantum-chemical calculations in classifying and characterizing organic mixed-valence systems in terms of their localized vs.delocalized character. A recently developed quantum-chemical protocol based on non-standard hybrid functionals and continuum solvent models is evaluated for an extended set of mixed-valence bis-tr...

Cluster or periodic, static or dynamic-the challenge of calculating the g tensor of the solid-state glycine radical

Pauwels, Ewald ; Asher, James ; Kaupp, Martin ; Waroquier, Michel (2011)

The calculation of the g tensor of the main +NH3–˙CH–COO− radiation-induced radical in solid-state α-glycine presents a real challenge to computational methods. Density functional calculations of this spectroscopic property struggle with its small anisotropy and the zwitterionic nature of the amino acids in the crystal of this seemingly simple system. Here, several factors influencing the calcu...