Sophya Garashchuk

We present a theoretical framework for a “trajectory”-driven nonadiabatic dynamics, that generalizes the variational Gaussian wavepacket approach to dynamics on multiple diabatic states. By applying the time-dependent variational principle to a single Gaussian wavepacket per state, we obtain a set of coupled equations for the Gaussian center and width parameters that include terms arising from the coupling potential. We investigate the role of these terms as they change the Gaussian time-evolution, and of the initial conditions on the wavefunction for several standard benchmarks of nonadiabatic dynamics, including a three-state and a two-dimensional model. The state populations obtained with the fully variational Gaussian dynamics is found in close agreement with exact quantum results. Finally, we demonstrate that the use of Gaussian wavefunction in nonadiabatic dynamics preserves the symplecticity of the variational space, which ensures the energy conservation and minimization of error when solving the time-dependent Schrödinger equation.

This manuscript reports a mixed‐spacer architecture for resolving the conductivity–swelling–stability tradeoff in ether‐free anion‐exchange membranes (AEMs). Unlike conventional spacer engineering, which usually relies on a single spacer length, the mixed‐spacer approach provides an additional degree of freedom for regulating membrane properties. Using mixed‐spacer engineering in polycarbazoles with mixed short and long spacer side chains, we show that hydroxide transport and membrane durability can be jointly optimized through control of hydration, ionic connectivity, and local cation solvation, rather than through ion exchange capacity alone. A series of membranes with varied ratios of short ( C4 ) and long ( C6 ) alkyl spacers were synthesized via acid‐catalyzed Friedel–Crafts polymerization followed by quaternization. The optimized membrane achieves a hydroxide conductivity of 184 mS cm ⁻¹ at 80°C, outperforming both short‐spacer and long‐spacer counterparts. Membranes rich in C4 spacers exhibit weaker alkaline stability, whereas those containing dominant C6 spacers show excellent stability. In a fuel cell device, the membrane delivers a peak power density of 2.51 W cm ⁻² , among the highest reported for polycarbazole AEMs. Mechanistic understanding was achieved through both experimental and computational investigations. These results demonstrate that mixed‐spacer molecular engineering is a promising and effective strategy for designing high‐performance AEMs.

This manuscript reports a mixed‐spacer architecture for resolving the conductivity–swelling–stability tradeoff in ether‐free anion‐exchange membranes (AEMs). Unlike conventional spacer engineering, which usually relies on a single spacer length, the mixed‐spacer approach provides an additional degree of freedom for regulating membrane properties. Using mixed‐spacer engineering in polycarbazoles with mixed short and long spacer side chains, we show that hydroxide transport and membrane durability can be jointly optimized through control of hydration, ionic connectivity, and local cation solvation, rather than through ion exchange capacity alone. A series of membranes with varied ratios of short ( C4 ) and long ( C6 ) alkyl spacers were synthesized via acid‐catalyzed Friedel–Crafts polymerization followed by quaternization. The optimized membrane achieves a hydroxide conductivity of 184 mS cm ⁻¹ at 80°C, outperforming both short‐spacer and long‐spacer counterparts. Membranes rich in C4 spacers exhibit weaker alkaline stability, whereas those containing dominant C6 spacers show excellent stability. In a fuel cell device, the membrane delivers a peak power density of 2.51 W cm ⁻² , among the highest reported for polycarbazole AEMs. Mechanistic understanding was achieved through both experimental and computational investigations. These results demonstrate that mixed‐spacer molecular engineering is a promising and effective strategy for designing high‐performance AEMs.

One of the most fascinating and key aspects in simulating vibrational spectra is accounting for the anharmonicity of the vibrational motions. The quasi-classical trajectory (QCT) method allows for the computation of fully anharmonic vibrational spectra, using a single trajectory initialized with quantized energy. Unfortunately, the everyday use of QCT requires constant juggling between the different input and output formats of the various quantum chemistry software and the use of different computational and visualization tools among these steps. In this paper, we showcase Dragonball, a modular Python suite that guides the user in each step of the QCT simulation, from guess geometry to final spectrum.

Stimuli-responsive heterogeneous catalysis is a powerful concept that unites the possibility for in situ regulation of the reaction parameter space with the enhanced recyclability of solid-state platforms. The presented work reports the first example of a light-responsive heterogeneous catalyst for a three-component coupling reaction that relies on photochromic-molecule-directed modulation of the copper oxidation states in metal-organic frameworks (MOFs) via a stimuli-responsive spiropyran derivative covalently integrated within a host scaffold. Comprehensive spectroscopic analysis, supported by theoretical modeling, establishes the first correlations among isomerization of a photochromic moiety, modulation of metal oxidation states in MOF metal nodes, and the material's overall chemical reactivity in a three-component coupling reaction. Moreover, this work provides the first confirmation that the photophysical performance of integrated spiropyran derivatives is maintained after exposure to selected reaction conditions, leading to material recyclability while preserving its catalytic activity. The developed photochromic MOF-based catalyst promoted the synthesis of 12 different compounds, including commodity chemicals and pharmaceuticals, with near-quantitative yields under mild reaction conditions while maintaining crystallinity and catalytic performance over multiple reaction cycles. Overall, these findings unlock a novel avenue toward noninvasive control of chemical reactivity via on-demand metal oxidation state modulation, establishing a new design principle for adaptive catalytic systems and offering a transformative pathway toward controllable chemical synthesis.

The quantum effects of nuclear and electronic motion play an important role in the structure, dynamics, and function of soft materials, yet they are difficult to capture with conventional classical simulations or static electronic–structure methods.

Light-induced and spontaneously occurring (in the dark) spectral shifts can be observed in a wide variety of systems where pigments are embedded in a somewhat amorphous environment, for instance, organic glasses, polymers, and proteins. They are observed directly in single-molecule spectroscopy experiments and serve as the basis for nonphotochemical spectral hole burning (NPHB). These shifts reflect small rearrangements of the local environment of the pigment that can be represented as transitions between the minima of the respective energy landscape. While methodology for determining the parameters of the energy landscapes from the results of optical spectroscopy experiments has been developed over the years, rigor has been sometimes sacrificed for the sake of clarity, and this may be the reason for the discrepancies between theories and experiments. Here, we demonstrate an application of rigorous quantum-mechanical (QM) approaches to modeling the results of single molecule (or single pigment-protein complex) spectroscopy and nonphotochemical hole burning. We employ rectangular and parabolic energy landscapes, with a linear or an angular generalized coordinate, and include phonon-assisted tunneling. Under these assumptions, the same transition rates are obtained for lower barriers and/or md² or moment of inertia compared with those predicted by the semiclassical model generally utilized in the analysis of NPHB data.

Adaptive (2D) materials with on-demand, tailored properties are a powerful concept that can be applied in next-generation optoelectronic devices, switchable heterogeneous catalysts, or multilevel data encryption systems. This work addresses current challenges associated with restricted/irreversible isomerization of photochromic moieties integrated within 2D materials via a novel strategy that leverages the tailoring of scaffold flexibility of two model material classes: metal-organic frameworks (MOFs) and perovskite-based materials. In particular, we demonstrate that flexible aliphatic groups, acting as "molecular grease", can reduce interactions between neighboring stimuli-responsive moieties within 2D layers, resulting in novel well-defined 2D crystalline materials with configurational freedom necessary for photoisomerization of confined "switches". To the best of our knowledge, this work unlocks a previously inaccessible class of photochromic materials containing high-energy Z isomers stabilized through "switch"-(2D) material cooperativity. Our synthetic strategy also allows for pressure-driven azobenzene isomerization without use of additional excitation sources, thereby broadening the applicability of azobenzene-based materials for device development. Moreover, the first analysis of photoswitch kinetics in perovskite-based materials is presented, showcasing the developed synthetic strategy's ability to provide sufficient material flexibility to promote "solution-like" photoisomerization rates of azobenzene derivatives. Overall, the design strategies herein allow for the preparation of 2D adaptive materials whose properties could be reversibly controlled via light and demonstrate how 2D confinement can shift the thermodynamic landscape of photochromic materials, favoring the stabilization of high-energy isomers that have not been reported to be stable in solution or existing materials to date.

Conventional theoretical and computational approaches to fully coupled quantum molecular dynamics, i.e. when both the electrons and nuclei are treated as quantum-mechanical particles, are impractical for all but the smallest chemical systems. In this paper we describe the formalism and implementation of the Factorized Electron Nuclear Dynamics (FENDy) with effective complex potential [J. Chem. Theory Comput. 19 (2023), pp 1393-1408], which goes beyond the established framework of the Born-Oppenheimer approximation or Born-Huang expansion of the molecular wavefunction. This method is based on the exact factorization of the molecular wavefunction, with the nuclei evolving under a complex time-dependent potential which captures the key features of dynamics in the nuclear subspace. The complementary electronic component of the molecular wavefunction is normalized to one for all nuclear configurations. We implement and employ FENDy to model the dynamics of H$_2^+$ molecular ion under a femtosecond laser pulse. The electronic wavefunction is represented within the standard electronic structure bases without referencing the electronic eigenstates. The nuclear wavefunction is represented as a quantum-trajectory ensemble, which in principle circumvents the exponential scaling of the numerical cost with the system size. The challenging evaluation of the gradients on unstructured grids is performed by projection on auxiliary bases.