Christopher J. Stein

• Ph.D.
• Faculty Member at Technical University of Munich

Although organometallic complexes of the late 3d elements are known to undergo both one‐and two‐electron reactions, their relative propensities to do so remain poorly understood. To gain direct insight into the competition between these different pathways, we have analyzed the unimolecular gas‐phase reactivity of a series of well‐defined model comp...

Dieser Trendbericht erläutert Erkenntnisse der letzten beiden Jahre aus der Sicht von Wissenschaftlerinnen und Wissenschaftlern des interdisziplinären, durch die DFG geförderten Konsortiums Transregio 325. Die Autorinnen und Autoren forschen vor allem zu chemischer Photokatalyse und beleuchten besonders Themen mit molekülchemischer Komponente.

Kurzzusammenfassung Obwohl metallorganische Komplexe der späten 3d‐Elemente dafür bekannt sind, sowohl Ein‐ als auch Zwei‐Elektron‐Reaktionen einzugehen, bleiben die relativen Neigungen dazu noch unzureichend verstanden. Um direkte Einblicke in die Konkurrenz zwischen den unterschiedlichen Reaktionspfaden zu gewinnen, haben wir die unimolekulare Ga...

The induction of chirality on pristine fullerenes through non‐covalent embedding in an asymmetric nano‐confinement has only been rarely reported. Bringing molecules with such a unique electronic structure and broad application range into a chiral environment is particularly appealing for the development of chiroptical materials, enantioselective ph...

The induction of chirality on pristine fullerenes through non‐covalent embedding in an asymmetric nano‐confinement has only been rarely reported. Bringing molecules with such a unique electronic structure and broad application range into a chiral environment is particularly appealing for the development of chiroptical materials, enantioselective ph...

Large self-assembled systems (such as metallosupramolecular rings and cages) can be difficult to structurally characterize, in particular when they show a highly dynamic behavior. In the gas-phase, Ion Mobility Spectrometry (IMS), in tandem with Electrospray Ionization Mass Spectrometry (ESI MS), can yield valuable insights into the size, shape and...

We present an optimization strategy for atom‐specific spin‐polarization constants within the spin‐polarized GFN2‐xTB framework, aiming to enhance the accuracy of molecular simulations. We compare a sequential and global optimization of spin parameters for hydrogen, carbon, nitrogen, oxygen, and fluorine. Sensitivity analysis using Sobol indices gui...

Intermolecular charge-transfer is a highly important process in biology and energy-conversion applications where generated charges need to be transported over several moieties. However, its theoretical description is challenging since the...

2‐Acetonaphthones, which bear an alkenyl group tethered to its C1 carbon atom via an oxygen atom, were found to undergo an enantioselective intramolecular ortho photocycloaddition reaction. A chiral oxazaborolidine Lewis acid leads to a bathochromic absorption shift of the substrate and enables an efficient enantioface differentiation. Visible ligh...

2‐Acetonaphthones, which bear an alkenyl group tethered to its C1 carbon atom via an oxygen atom, were found to undergo an enantioselective, intramolecular ortho photocycloaddition reaction. A chiral oxazaborolidine Lewis acid leads to a bathochromic absorption shift of the substrate and enables an efficient enantioface differen­tiation. Visible li...

A widely used strategy to reduce the computational cost of quantum-chemical calculations is to partition the system into an active subsystem, which is the focus of the computational efforts, and an environment that is treated at a lower computational level. The system partitioning is mostly based on localized molecular orbitals. When reaction paths...

A widely used strategy to reduce the computational cost in quantum-chemical calculations is to partition the system into an active subsystem, which is the focus of the computational efforts and an environment that is treated at a lower computational level. The system partitioning is mostly based on localized molecular orbitals. When reaction paths...

The lack of a procedure to determine equilibrium thermodynamic properties of a small system interacting with a bath is frequently seen as a weakness of conventional statistical mechanics. A typical example for such a small system is a solute surrounded by an explicit solvation shell. One way to approach this problem is to enclose the small system o...

Quantum chemical calculations on atomistic systems have evolved into a standard approach to study molecular matter. These calculations often involve a significant amount of manual input and expertise although most of this effort could be automated, which would alleviate the need for expertise in software and hardware accessibility. Here, we present...

The lack of a procedure to determine equilibrium thermodynamic properties of a small system interacting with a bath is frequently seen as a weakness of conventional statistical mechanics. A typical example for such a small system is a solute surrounded by an explicit solvation shell. One way to approach this problem is to enclose the small system o...

Quantum chemical calculations on atomistic systems have evolved into a standard approach to study molecular matter. These calculations often involve a significant amount of manual input and expertise although most of this effort could be automated, which would alleviate the need for expertise in software and hardware accessibility. Here, we present...

The generation of reference data for deep learning models is challenging for reactive systems, and more so for combustion reactions due to the extreme conditions that create radical species and alternative spin states during the combustion process. Here, we extend intrinsic reaction coordinate (IRC) calculations with ab initio MD simulations and no...

We report a new deep learning message passing network that takes inspiration from Newton's equations of motion to learn interatomic potentials and forces. With the advantage of directional information from trainable force vectors, and physics-infused operators that are inspired by Newtonian physics, the entire model remains rotationally equivariant...

High‐valent tetraalkylcuprates(iii) and ‐argentates(iii) are key intermediates of copper‐ and silver‐mediated C−C coupling reactions. Here, we investigate the previously reported contrasting reactivity of [RMⁱⁱⁱMe3]⁻ complexes (M=Cu, Ag and R=allyl) with energy‐dependent collision‐induced dissociation experiments, advanced quantum‐chemical calculat...

Significance For centuries the double layer at the solid/electrolyte interface has been a central concept in electrochemistry. Today, it is still crucial for virtually all renewable energy storage and conversion technologies. Here, the double-layer formation is probed by THz spectroscopy with ultrabright synchrotron light as a source. Our results c...

High-valent tetraalkylcuprates(III) and -argentates(III) are key intermediates of copper and silver-mediated C−C coupling reactions. Here, we investigate the previously reported contrasting reactivity of [RM III Me 3 ] − complexes (M = Cu, Ag and R =allyl) with energy-dependent collision-induced dissociation experiments, advanced quantum-chemical c...

This article summarizes technical advances contained in the fifth major release of the Q-Chem quantum chemistry program package, covering developments since 2015. A comprehensive library of exchange–correlation functionals, along with a suite of correlated many-body methods, continues to be a hallmark of the Q-Chem software. The many-body methods i...

We report a new deep learning message passing network that takes inspiration from Newton's equations of motion to learn interatomic potentials and forces. With the advantage of directional information from trainable latent force vectors, and physics-infused operators that are inspired by the Newtonian physics, the entire model remains rotationally...

div> The double layer at the solid/electrolyte interface is a key concept in electrochemistry. Here, we present an experimental study combined with simulations, which provides a molecular picture of the double-layer formation in operando processes. By THz spectroscopy we are able to follow the stripping off of the cation/anion hydration shells for...

MOLCAS/OpenMolcas is an ab initio electronic structure program providing a large set of computational methods from Hartree–Fock and density functional theory to various implementations of multiconfigurational theory. This article provides a comprehensive overview of the main features of the code, specifically reviewing the use of the code in previo...

Multi-configurational wave functions are known to describe electronic structure across a Born-Oppenheimer surface qualitatively correct. However, for quantitative reaction energies, dynamical correlation originating from the many configurations involving excitations out of the restricted orbital space, the active space, must be considered. Standard...

We present the theory and implementation of a Poisson-Boltzmann implicit solvation model for electrolyte solutions. This model can be combined with arbitrary electronic structure methods that provide an accurate charge density of the solute. A hierarchy of approximations for this model includes a linear approximation for weak electrostatic potentia...

A new tool for the interpretation of multiconfigurational wavefunctions representing the spin states of exchange-coupled transition metal complexes is introduced. Based on orbital entanglement measures, herein derived from multi-configurational density matrix renormalization group calculations, the complexity of the wavefunction is reduced thus fac...

We present the theory and implementation of a Poisson-Boltzmann implicit solvation model for electrolyte solutions. This model can be combined with arbitrary electronic structure methods that provide an accurate charge density of the solute. A hierarchy of approximations for this model includes a linear approximation for weak electrostatic potentia...

In this article we describe the OpenMolcas environment and invite the computational chemistry community to collaborate. The open-source project already includes a large number of new developments realized during the transition from the commercial MOLCAS product to the open-source platform. The paper initially describes the technical details of the...

In this article we describe the OpenMolcas environment and invite the computational chemistry community to collaborate. The open-source project already includes a large number of new developments realized during the transition from the commercial MOLCAS product to the open-source platform. The paper initially describes the technical details of the...

Multi-configurational wave functions are known to describe electronic structure across a Born-Oppenheimer surface qualitatively correct. However, for quantitative reaction energies, dynamical correlation originating from the many configurations involving excitations out of the restricted orbital space, the active space, must be considered. Standard...

We present our implementation autoCAS for fully automated multiconfigurational calculations, which we also make available free of charge on our webpages. The graphical user interface of autoCAS connects a general electronic structure program with a density‐matrix renormalization group program to carry out our recently introduced automated active sp...

We present our implementation autoCAS for fully automated multi-configurational calculations, which we also make available free of charge on our webpages. The graphical user interface of autoCAS connects a general electronic structure program with a density matrix renormalization group program to carry out our recently introduced automated active s...

An efficient approximation to the full configuration interaction solution can be obtained with the density matrix renormalization group (DMRG) algorithm without a restriction to a predefined excitation level. In a standard DMRG implementation, however, excited states are calculated with a ground-state optimization in the space orthogonal to all low...

Configuration-interaction-type calculations on electronic and vibrational structure are often the method of choice for the reliable approximation of many-particle wave functions and energies. The exponential scaling, however, limits their application range. In vibrational spectroscopy, for example, molecules with more than 15 to 20 vibrational mode...

Configuration-interaction-type calculations on electronic and vibrational structure are often the method of choice for the reliable approximation of many-particle wave functions and energies. The exponential scaling, however, limits their application range. An efficient approximation to the full configuration interaction solution can be obtained wi...

An advanced protocol for the intramoleclar C-H amination of alkyl groups via amidyl radicals (Hofmann-Löffler reaction) under homogeneous iodine catalysis is reported. This protocol employs common mCPBA as terminal oxidant. It proceeds under mild conditions, with complete chemoselectivity, is compatible with radical intermediates and allows for the...

The pulsed-field-ionization zero-kinetic-energy photoelectron spectrum of C2H6 has been recorded in the region of the adiabatic ionization threshold. The partially rotationally resolved spectrum indicates the existence of several vibronic states of C2H6⁺ with less than 600 cm⁻¹ of internal excitation. The analysis of the rotational structures assis...

Supplementary

Chemical and electrochemical oxidation or reduction of our recently reported Ir(IV,IV) mono-µ-oxo dimers results in the formation of fully characterized Ir(IV,V) and Ir(III,III) complexes. The Ir(IV,V) dimers are unprecedented and exhibit remarkable stability under ambient conditions. This stability and modest reduction potential of 0.99 V vs. NHE...

The spin densities of radical cations of magnesium porphyrin, magnesium chlorine and a truncated chlorophyll a model are calculated with density-functional theory and multiconfigurational quantum chemical methods. The latter serve as a reference for approximate density-functional theory which yields spin densities that may suffer from the self-inte...

An unprecedented protocol for the cooperative interplay between molecular iodine and photoredox catalysis under dual light-activation for the intramolecular benzylic C-H amination is presented. Iodine serves as a catalyst for the formation of a new C-N bond by the activation of a remote Csp3-H bond (1,5-HAT process) under visible light irradiation,...

An unprecedented protocol for the cooperative interplay between molecular iodine and photoredox catalysis under dual light-activation for the intramolecular benzylic C-H amination is presented. Iodine serves as a catalyst for the formation of a new C-N bond by the activation of a remote Csp3-H bond (1,5-HAT process) under visible light irradiation,...

Variational approaches for the calculation of vibrational wave functions and energies are a natural route to obtain highly accurate results with controllable errors. However, the unfavorable scaling and the resulting high computational cost of standard variational approaches limit their application to small molecules with only few vibrational modes...

Variational approaches for the calculation of vibrational wave functions and energies are a natural route to obtain highly accurate results with controllable errors. However, the unfavorable scaling and the resulting high computational cost of standard variational approaches limit their application to small molecules with only few vibrational modes...

Quantum-chemical multi-configurational methods are required for a proper description of static electron correlation, a phenomenon inherent to the electronic structure of molecules with multiple (near-)degenerate frontier orbitals. Here, we review how a property of these frontier orbitals, namely the entanglement entropy is related to static electro...

Quantum-chemical multi-configurational methods are required for a proper description of static electron correlation, a phenomenon inherent to the electronic structure of molecules with multiple (near-)degenerate frontier orbitals. Here, we review how a property of these frontier orbitals, namely the entanglement entropy is related to static electro...

One of the most critical tasks at the very beginning of a quantum chemical investigation is the choice of either a multi- or single-configurational method. Naturally, many proposals exist to define a suitable diagnostic of the multi-configurational character for various types of wave functions in order to assist this crucial decision. Here, we pres...

One of the most critical tasks at the very beginning of a quantum chemical investigation is the choice of either a multi- or single-configurational method. Naturally, many proposals exist to define a suitable diagnostic of the multi-configurational character for various types of wave functions in order to assist this crucial decision. Here, we pres...

In this thesis accurate predictions for the spectroscopic parameters of l-C3H+ and C4 are made from state-of-the-art electronic structure calculations. Both molecules are of interest to interstellar cloud chemistry and only scarce experimental information about their rovibrational properties is available. Christopher J. Stein recapitulates the basi...

Multi-configurational approaches yield universal wave function parameterizations that can qualitatively well describe electronic structures along reaction pathways. For quantitative results, multi-reference perturbation theory is required to capture dynamic electron correlation from the otherwise neglected virtual orbitals. Still, the overall accur...

Multi-configurational approaches yield universal wave function parameterizations that can qualitatively well describe electronic structures along reaction pathways. For quantitative results, multi-reference perturbation theory is required to capture dynamic electron correlation from the otherwise neglected virtual orbitals. Still, the overall accur...

One of the key challenges of quantum-chemical multi-configuration methods is the necessity to manually select orbitals for the active space. This selection requires both expertise and experience and can therefore impose severe limitations on the applicability of this most general class of ab initio methods. A poor choice of the active orbital space...

One of the key challenges of quantum-chemical multi-configuration methods is the necessity to manually select orbitals for the active space. This selection requires both expertise and experience and can therefore impose severe limitations on the applicability of this most general class of ab initio methods. A poor choice of the active orbital space...

One of the key challenges of quantum-chemical multi-configuration methods is the necessity to manually select orbitals for the active space. This selection requires both expertise and experience and can therefore impose severe limitations on the applicability of this most general class of ab initio methods. A poor choice of the active orbital space...

Reliable quantum chemical methods for the description of molecules with dense-lying frontier orbitals are needed in the context of many chemical compounds and reactions. Here, we review developments that led to our newcomputational toolbo x which implements the quantum chemical density matrix renormalization group in a second-generation algorithm....

The equilibrium structure and rovibrational energies of nitrous oxide (N2O) in its electronic ground state (X1Σ+) are derived from a high-level ab initio potential energy function (PEF). This PEF is based on a composite approach with the basic contribution given by explicitly correlated coupled-cluster (CC) calculations. Smaller contributions inclu...

The equilibrium geometry and rovibrational spectroscopic parameters of the three astrochemical ions l-C3H+, l-SiC2H+, and C3N− and some of their isotopologues are obtained from high-level quantum chemical calculations. A composite approach based on the explicitly correlated coupled-cluster method CCSD(T)-F12b, that further includes core correlation...

Accurate near-equilibrium potential energy functions (PEFs) have been constructed for the nitronium ion (NO2+) by composite methods using either CCSD(T)-F12b or explicitly correlated multi-reference methods (MRCI-F12+Q or MRACPF-F12) as dominant contributions. Up to pentuple substitutions are required in the coupled-cluster based approach to reach...

Accurate bond dissociation energies ($D_0$) are reported for different isotopologues of the highly anharmonic systems \ce{ClHCl-}. The mass-independent equilibrium dissociation energy $D_\mathrm{e}$ was obtained by a composite method with frozen-core (fc) CCSD(T) as the basic contribution. Basis sets as large as aug-cc-pV(+d)8Z were employed and ex...

Highly accurate quantum chemical calculations beyond CCSD(T) have been used to study the molecular cation l-C3H+ which is the carrier of harmonically related radio lines observed in the Horsehead photodissociation region and toward Sgr B2(N). Excellent agreement with spectroscopic and radioastronomical measurements is obtained for the rotational co...

An accurate near-equilibrium potential energy surface (PES) has been constructed for the azide ion (N3(-)) on the basis of coupled cluster calculations up to CCSDTQ (M. Kállay and P. R. Surján, J. Chem. Phys. 2001, 115, 2945.), with contributions from inner-shell correlation and special relativity being taken into account as well. A larger number o...

Accurate bond dissociation energies (D 0) are determined for three isotopologues of the bifluoride ion (FHF−). While the zero-point vibrational contributions are taken from our previous work (P. Sebald, A. Bargholz, R. Oswald, C. Stein, P. Botschwina, J. Phys. Chem. A, DOI: 10.1021/jp3123677), the equilibrium dissociation energy (D e ) of the react...

Explicitly correlated coupled cluster theory at the CCSD(T*)-F12b level in conjunction with the aug-cc-pV5Z basis set has been used in the calculation of three-dimensional potential energy and dipole moment surfaces for the bifluoride ion (FHF-). An empirically corrected analytical potential energy function (PEF) was obtained by fit to four pieces...