Robert Pollice

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Pollice

First Name

Robert

ORCID

0000-0001-8836-6266

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Publications 1 - 9 of 9

Solvation Free Energies of Ion Dissociations in Dichloromethane: En Route to Accurate Computations
Savoy, Adélaïde; Paenurk, Eno; Pollice, Robert; et al. (2025)
The Journal of Physical Chemistry B
Calculating accurate free energies for solution-phase reactions is notoriously difficult. In our previous joint experimental and computational studies, we observed a striking failure of quantum mechanical calculations with popular implicit solvent models to even qualitatively reproduce the experimental trends of dissociation free energies of numerous proton-bound pyridine dimers in organic solvents [; [. In this article, we expand the computational study of the dissociation of proton-bound pyridine dimers in the gas phase and in dichloromethane (DCM). In an effort to determine the prerequisites for reproducing the experimental trends and magnitudes of the dissociation free energies (Delta G diss) in solvent, we investigated the impact of accounting for the ensemble free energy, umbrella sampling, thermodynamic integration, and explicit solvation using semiempirical quantum mechanics and molecular mechanics. We estimated the effect of conformational free energy contributions with semiempirical quantum mechanics (SE). Molecular dynamics (MD) with explicit solvation and classical molecular mechanics (MM) was used as a method to treat not only the solute but also the solvent configurational entropy. We found that explicit solvation with MM is indeed capable of reproducing Delta G diss in DCM for our test system within an acceptable error margin. We analyze and discuss the results and limitations of our approach for calculating the solvation free energy.
Compensation of London Dispersion in the Gas Phase and in Aprotic Solvents
Pollice, Robert; Fleckenstein, Felix; Shenderovich, Ilya; et al. (2019)
Angewandte Chemie. International Edition
Rhodium-catalyzed direct alkylation of benzylic amines using alkyl bromides
Anschuber, Martin; Pollice, Robert; Schnürch, Michael (2019)
Monatshefte für Chemie
Within this contribution, the development and substrate scope evaluation of a direct alkylation protocol of the C(sp3)–H bond of benzylic amines using alkyl bromides is reported. This pyridine-directed method is initiated by elimination of the alkyl bromide to a terminal olefin, which is then the true alkylating agent.
London Dispersion in Molecular Systems
Pollice, Robert (2019)
Origin of the Immiscibility of Alkanes and Perfluoroalkanes
Pollice, Robert; Chen, Peter (2019)
Journal of the American Chemical Society
A universal quantitative descriptor of the dispersion interaction potential
Pollice, Robert; Chen, Peter (2019)
Angewandte Chemie. International Edition
Ultrafast Computational Screening of Molecules with Inverted Singlet-Triplet Energy Gaps Using the Pariser-Parr-Pople Semiempirical Quantum Chemistry Method
Jorner, Kjell; Pollice, Robert; Lavigne, Cyrille; et al. (2024)
The Journal of Physical Chemistry A
Molecules with an inverted energy gap between their first singlet and triplet excited states have promising applications in the next generation of organic light-emitting diode (OLED) materials. Unfortunately, such molecules are rare, and only a handful of examples are currently known. High-throughput virtual screening could assist in finding novel classes of these molecules, but current efforts are hampered by the high computational cost of the required quantum chemical methods. We present a method based on the semiempirical Pariser-Parr-Pople theory augmented by perturbation theory and show that it reproduces inverted gaps at a fraction of the cost of currently employed excited-state calculations. Our study paves the way for ultrahigh-throughput virtual screening and inverse design to accelerate the discovery and development of this new generation of OLED materials.
Investigations of the generality of quaternary ammonium salts as alkylating agents in direct C-H alkylation reactions: solid alternatives for gaseous olefins
Schönbauer, David; Spettel, Manuel; Pollice, Robert; et al. (2019)
Organic & biomolecular chemistry
C–H alkylation reactions using short chain olefins as alkylating agents could be operationally simplified on the lab scale by using quaternary ammonium salts as precursors for these gaseous reagents: Hofmann elimination delivers in situ the desired alkenes with the advantage that the alkene concentration in the liquid phase is high. In case a catalytic system did not tolerate the conditions for Hofmann elimination, a very simple spatial separation of both reactions, Hofmann elimination and direct alkylation, was achieved to circumvent possible side reactions or catalyst deactivation. Additionally, the truly catalytically active species of a rhodium(I) mediated alkylation reaction could be identified by using this approach.
Probing London Dispersion in Proton-Bound Onium Ions: Are Alkyl-Alkyl Steric Interactions Reliably Modeled?
Gorbachev, Vladimir; Savoy, Adélaïde; Tsybizova, Alexandra; et al. (2025)
Journal of the American Chemical Society
We report spectroscopic and spectrometric experiments that probe the London dispersion interaction between tert-butyl substituents in three series of covalently linked, protonated bis-pyridines in the gas phase. Molecular ions in the three test series, along with several reference molecules for control, were electrosprayed from solution into the gas phase and then probed by infrared multiphoton dissociation spectroscopy and trapped ion mobility spectrometry. The observed N-H stretching frequencies provided an experimental readout diagnostic of the ground-state geometry of each ion, which could be furthermore compared to a second, independent structural readout via the collision cross section. In each of the three series, the strength of a London dispersion interaction could be modulated systematically by a progressive increase in the size of substituents from H to Me to tert-Bu. Parallel to the experimental study, extensive dispersion-corrected density functional theory (DFT-D3BJ) calculations were performed with a range of exchange correlation functionals. A full analysis of the conformational space for the flexible members of the series, and an analysis of the vibrational spectra in the context of a general double-well potential, finds that DFT-D3BJ appears to significantly overbind alkyl-alkyl interactions, specifically interactions between tert-Bu groups, even failing to predict the minimum energy structures reliably in the case of molecules in which London dispersion competes with other noncovalent interactions such as hydrogen bonding.

Publications 1 - 9 of 9

Robert Pollice

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