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Heteroleptic copper(I) complexes, with a diimine as a chromophoric unit and a bulky diphosphine as an ancillary ligand, have the advantage of a reduced pseudo Jahn–Teller effect in their excited state over the corresponding homoleptic bis(diimine) complexes. Nevertheless, their lowest absorption lies generally between 350 to 500 nm. Aiming at a strong absorption in the visible by stable heteroleptic Cu(I) complexes, we designed a novel diimine based on 4-(benzo[g]quinoxal-2′-yl)-1,2,3-triazole derivatives. The large π-conjugation of the benzoquinoxaline moiety shifted bathochromically the absorption with regard to other diimine-based Cu(I) complexes. Adding another Cu(I) core broadened the absorption and extended it to considerably longer wavelengths. Moreover, by fine-tuning the structure of the dichelating ligand, we achieved a panchromatic absorption up to 700 nm with a high molar extinction coefficient of 8000 M$^{-1}$ cm$^{-1}$ at maximum (λ = 570 nm), making this compound attractive for light-harvesting antennae.

Dinuclear gold(I) compounds are of great interest due to their aurophilic interactions that influence their photophysical properties. Herein, we showcase that gold–gold interactions can be influenced by tuning the electronic properties of the ligands. Therefore, various para substituted (R) N,N′-bis(2,6-dimethylphenyl)formamidinate ligands (pRXylForm; Xyl = 2,6-dimethylphenyl and Form = formamidinate) were treated with Au(tht)Cl (tht = tetrahydrothiophene) to give via salt metathesis the corresponding gold(I) compounds [pRXylForm$_2$Au$_2$] (R = –OMe, –Me, –Ph, –H, –SMe, and –CO$_2$Me). All complexes showed intense luminescence properties at low temperatures. Alignment with the Hammett parameter σ$_p$ revealed the trends in the $^1$H and $^{13}$C NMR spectra. These results showed the influence of the donor–acceptor abilities of different substituents on the ligand system which were confirmed with calculated orbital energies. Photophysical investigations showed their lifetimes in the millisecond range indicating phosphorescence processes and revealed a redshift with the decreasing donor ability of the substituents in the solid state.

The coordination chemistry of a ferrocene ligand with one bulky amidinate function attached to each ring toward two different coinage metal precursors was investigated. In dependence of the metal and the co-ligands, “ansa” type structures and non-bridged structures were obtained. Six different compounds are reported. In the “ansa” type structures, short Fe–M (M = Cu, Ag) distances were observed in the molecular structures in the solid state. However, theoretical calculations (DFT) did not reveal a stabilizing metal–metal interaction. Instead, dispersion interactions within the ligand and between the ligand and metal seem to represent the main stabilization forces.

The GW approximation and the Bethe���Salpeter equation have been implemented into the Turbomole program package for computations of molecular systems in a strong, finite magnetic field. Complex-valued London orbitals are used as basis functions to ensure gauge-invariant computational results. The implementation has been benchmarked against triplet excitation energies of 36 small to medium-sized molecules against reference values obtained at the approximate coupled-cluster level (CC2 approximation). Finally, a spectacular change of colour from orange to green of the tetracene molecule is induced by applying magnetic fields between 0 and 9,000 T perpendicular to the molecular plane.

Four new heteroleptic Cu(I) complexes based on 1, 2, 3-triazolyl-quinoline or quinoxaline and a chelating diphosphine were prepared and fully characterised. The mononuclear derivatives absorb in the visible region, up to 600 nm, while the dinuclear complex has a long-tail absorption up to 800 nm, showing an additional electronic state corroborated by theoretical calculations. Although a methylene group between the triazole and the quino(xa)line moiety increases the bite angle and decreases the luminescence in solution, all complexes emit brightly in the solid-state. Their redox properties in the excited state were determined, proving their ability in serving as photoredox catalysts in atom transfer radical addition successfully.

Dalton is a powerful general-purpose program system for the study of molecular electronic structure at the Hartree–Fock, Kohn–Sham, multiconfigurational self-consistent-field, Møller–Plesset, configuration-interaction, and coupled-cluster levels of theory. Apart from the total energy, a wide variety of molecular properties may be calculated using these electronic-structure models. Molecular gradients and Hessians are available for geometry optimizations, molecular dynamics, and vibrational studies, whereas magnetic resonance and optical activity can be studied in a gauge-origin-invariant manner. Frequency-dependent molecular properties can be calculated using linear, quadratic, and cubic response theory. A large number of singlet and triplet perturbation operators are available for the study of one-, two-, and three-photon processes. Environmental effects may be included using various dielectric-medium and quantum-mechanics/molecular-mechanics models. Large molecules may be studied using linear-scaling and massively parallel algorithms. Dalton is distributed at no cost from http://www.daltonprogram.org for a number of UNIX platforms. © 2013 John Wiley & Sons, Ltd. This is an open access article under the terms of the Creative Commons Attribution-NonCommercial-NoDerivs License, (CC BY-NC-ND 3.0)

Using explicitly-correlated coupled-cluster theory with single and double excitations, the intermolecular distances and interaction energies of the T-shaped imidazole⋯⋯benzene and pyrrole⋯⋯benzene complexes have been computed in a large augmented correlation-consistent quadruple-zeta basis set, adding also corrections for connected triple excitations and remaining basis-set-superposition errors. The results of these computations are used to assess other methods such as Møller–Plesset perturbation theory (MP2), spin-component-scaled MP2 theory, dispersion-weighted MP2 theory, interference-corrected explicitly-correlated MP2 theory, dispersion-corrected double-hybrid density-functional theory (DFT), DFT-based symmetry-adapted perturbation theory, the random-phase approximation, explicitly-correlated ring-coupled-cluster-doubles theory, and double-hybrid DFT with a correlation energy computed in the random-phase approximation.

Molekülspektroskopie ist ein wichtiges Werkzeug für die Charakterisierung chemischer Substanzen. Verschiedene Arten von Spektroskopie verwenden die Effekte, die durch Magnetfelder hervorgerufen werden, wie etwa Kernspinresonanz, Elektronenspinresonanz oder Magnetocirculardichroismus. Ihre theoretische Beschreibung erfolgt typischerweise durch quantenchemische Methoden in Kombination mit linearer Störungstheorie, da die Magnetfelder in solchen Experimenten klein sind, verglichen mit den für die chemische Bindung verantwortlichen, elektromagnetischen Kräften. Jenseits der linearen Effekte, die durch einen solchen Ansatz beschrieben werden, liegt eine vielfältige, faszinierende Chemie, die darauf wartet erforscht zu werden. Neue Arten chemischer Bindung, Spinphasenübergänge und Farbveränderungen aromatischer Verbindungen sind nur einige der nicht-linearen Effekte, die durch Magnetfelder hervorgerufen werden. Ihre theoretische Beschreibung erfordert einen Ansatz, in dem ein finites Feld explizit im Hamiltonoperator auftaucht. Solch ein Ansatz kann für eine korrekte Beschreibung von beliebig starken Magnetfeldern verwendet werden. Dadurch wird die Vorhersage spektroskopischer Eigenschaften von Molekülen in der Nähe interstellarer Objekte mit extrem starken Magnetfeldern ermöglicht, wie etwa magnetische Weiße Zwerge oder Neutronensterne. In solchen Fällen kann Molekülspektroskopie verwendet werden, um die Existenz kleiner Moleküle nachzuweisen. Die theoretische Beschreibung eines finiten Feldes erfordert hocheffiziente, rechnergestützte Methoden, deren Entwicklung und Anwendung Thema dieser Arbeit sind. Zunächst werden hierfür die theoretischen Grundlagen für die quantenchemische Beschreibung von Molekülspektroskopie eingeführt. Einige verbreitete Methoden der Quantenchemie werden adaptiert, inklusive der Dichtefunktionaltheorie (DFT), genähertem Coupled-Cluster (CC2), sowie der GW/BSE-Methode. Eine effiziente Implementierung wird entwickelt und getestet. Ausgewählte Anwendungen werden vorgestellt, inklusive Rechnungen an Magnetocirculardichroismusspektren eines organometallischen Komplexes, die Vorhersage der Farbveränderung von Tetracen im Magnetfeld mithilfe der UV/Vis-Spektroskopie, sowie die Untersuchung von Schwingungsrotationsspektren zweiatomiger Moleküle in starken Magnetfeldern.

We report a critical analysis and comparison of a variety of random-phase-approximation (RPA) based approaches to determine the electronic ground-state energy. Interrelations between RPA variants are examined by numerical example with particular attention paid to the role of spin-flipped excitations and the behaviour of the adiabatic-connection integrands where appropriate. In general, it is found that RPA variants that include Hartree–Fock exchange contributions are unsuitable as generally applicable methods for the determination of correlation energies. Of the remaining methods only the direct RPA and RPA with second-order screened exchange are recommended for general use.

This thesis studies the intermolecular interactions in (i) boron-nitrogen based systems for hydrogen splitting and storage, (ii) endohedral complexes, A@C60, and (iii) aurophilic dimers. We first present an introduction of intermolecular interactions. The theoretical background is then described. The research results are summarized in the following sections. In the boron-nitrogen systems, the electrostatic interaction is found to be the leading contribution, as 'Coulomb Pays for Heitler and London' (CHL). For the endohedral complex, the intermolecular interaction is formulated by a one-center expansion of the Coulomb operator 1/rab. For the aurophilic attraction between two C2v monomers, a London-type formula was derived by fully accounting for the anisotropy and point-group symmetry of the monomers. Ei saatavilla

Valence and all-electron correlation energies of Ne, N2, and H2O at fixed experimental geometries are computed at the levels of second-order perturbation theory (MP2) and coupled cluster theory with singles and doubles excitations (CCSD), and singles and doubles excitations with a perturbative triples correction (CCSD(T)). Correlation-consistent polarized valence and core-valence basis sets up to sextuple zeta quality are employed. Guided by basis-set limits established by rij-dependent methods, a number of extrapolation schemes for use with the correlation-consistent basis sets are investigated. Among the schemes considered here, a linear least-squares procedure applied to the quintuple and sextuple zeta results yields the most accurate extrapolations.

Multiple basis sets are used in calculations of perturbational corrections for triples replacements in the framework of single-reference coupled-cluster theory. We investigate a computational procedure, where the triples correction is calculated from a reduced space of virtual orbitals, while the full space is employed for the coupled-cluster singles-and-doubles model. The reduced space is either constructed from a prescribed unitary transformation of the virtual orbitals (for example into natural orbitals) with subsequent truncation, or from a reduced set of atomic basis functions. After the selection of a reduced space of virtual orbitals, the singles and doubles amplitudes obtained from a calculation in the full space are projected onto the reduced space, the remaining set of virtual orbitals is brought into canonical form by diagonalizing the representation of the Fock operator in the reduced space, and the triples corrections are evaluated as usual. The case studies include the determination of the spectroscopic constants of N2, F2, and CO, the geometry of O3, the electric dipole moment of CO, the static dipole polarizability of F−, and the Ne⋯Ne interatomic potential.

The basis-set convergence of the electronic correlation energy in the water molecule is investigated at the second-order Møller-Plesset level and at the coupled-cluster singles-and-doubles level with and without perturbative triples corrections applied. The basis-set limits of the correlation energy are established to within 2 mEhby means of (1) extrapolations from sequences of calculations using correlation-consistent basis sets and (2) from explicitly correlated calculations employing terms linear in the interelectronic distances rij. For the extrapolations to the basis-set limit of the correlation energies, fits of the form a + bX-3(where X is two for double-zeta sets, three for triple-zeta sets, etc.) are found to be useful. CCSD(T) calculations involving as many as 492 atomic orbitals are reported. © 1997 American Institute of Physics.