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Geometrically Constrained Cationic Low-Coordinate Tetrylenes: Highly Lewis Acidic σ-Donor Ligands in Catalytic Systems.

ABSTRACT: A novel non-innocent ligand class, namely cationic single-centre ambiphiles, is reported in the phosphine-functionalised cationic tetrylene Ni⁰ complexes, [^PhR DippENi(PPh₃ )₃ ]⁺ (4 a/b (Ge) and 5 (Sn); ^PhR Dipp={[Ph₂ PCH₂ SiR₂ ](Dipp)N}^- ; R=Ph, ⁱ Pr; Dipp=2,6-ⁱ Pr₂ C₆ H₃ ). The inherent electronic nature of low-coordinate tetryliumylidenes, combined with the geometrically constrained [N-E-Ni] bending angle enforced by the chelating phosphine arm in these complexes, leads to strongly electrophilic E^II centres which readily bind nucleophiles, reversibly in the case of NH₃ . Further, the Ge^II centre in 4 a/b readily abstracts the fluoride ion from [SbF₆ ]^- to form the fluoro-germylene complex ^PhR DippGe(F)Ni(PPh₃ )₃ 9, despite this Ge^II centre simultaneously being a σ-donating ligand towards Ni⁰ . Alongside the observed catalytic ability of 4 and 5 in the hydrosilylation of alkynes and alkenes, this forms an exciting introduction to a multi-talented ligand class in cationic single-centre ambiphiles.

SUBMITTER: Keil PM

PROVIDER: S-EPMC9302135 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:BackgroundWe suggest a new type of modeling approach for the coarse grained, particle-based spatial simulation of combinatorially complex chemical reaction systems. In our approach molecules possess a location in the reactor as well as an orientation and geometry, while the reactions are carried out according to a list of implicitly specified reaction rules. Because the reaction rules can contain patterns for molecules, a combinatorially complex or even infinitely sized reaction network can be defined. For our implementation (based on LAMMPS), we have chosen an already existing formalism (BioNetGen) for the implicit specification of the reaction network. This compatibility allows to import existing models easily, i.e., only additional geometry data files have to be provided.ResultsOur simulations show that the obtained dynamics can be fundamentally different from those simulations that use classical reaction-diffusion approaches like Partial Differential Equations or Gillespie-type spatial stochastic simulation. We show, for example, that the combination of combinatorial complexity and geometric effects leads to the emergence of complex self-assemblies and transportation phenomena happening faster than diffusion (using a model of molecular walkers on microtubules). When the mentioned classical simulation approaches are applied, these aspects of modeled systems cannot be observed without very special treatment. Further more, we show that the geometric information can even change the organizational structure of the reaction system. That is, a set of chemical species that can in principle form a stationary state in a Differential Equation formalism, is potentially unstable when geometry is considered, and vice versa.ConclusionsWe conclude that our approach provides a new general framework filling a gap in between approaches with no or rigid spatial representation like Partial Differential Equations and specialized coarse-grained spatial simulation systems like those for DNA or virus capsid self-assembly.

Project description:The sigma 1 receptor (?1R) and the mu-opioid receptor (MOR) regulate the transient receptor potential (TRP) V1 calcium channel. A series of proteins are involved in the cross-regulation between MORs and calcium channels like the glutamate N-methyl-D-aspartate receptor (NMDAR), including the histidine triad nucleotide-binding protein 1 (HINT1), calmodulin (CaM), and the ?1R. Thus, we assessed whether similar mechanisms also apply to the neural TRP ankyrin member 1 (TRPA1), TRP vanilloid member 1 (TRPV1), and TRP melastatin member 8 (TRPM8). Our results indicate that ?1R and CaM bound directly to cytosolic regions of these TRPs, and this binding increased in the presence of calcium. By contrast, the association of HINT1 with these TRPs was moderately dependent on calcium. The ?1R always competed with CaM for binding to the TRPs, except for its binding to the TRPA1 C-terminal where ?1R binding cooperated with that of CaM. However, ?1R dampened HINT1 binding to the TRPA1 N-terminal. When the effect of ?1R ligands was addressed, the ?1R agonists PRE084 and pregnenolone sulfate enhanced the association of the ?1R with the TRPM8 N-terminal and TRPV1 C-terminal in the presence of physiological calcium, as seen for the ?1R-NMDAR interactions. However, these agonists dampened ?1R binding to the TRPA1 and TRPV1 N-terminal domains, and also to the TRPA1 C-terminal, as seen for ?1R-binding immunoglobulin protein (BiP) interactions in the endoplasmic reticulum (ER). By contrast, the ?1R antagonists progesterone and S1RA reduced the association of ?1R with TRPA1 and TRPV1 C-terminal regions, as seen for the ?1R-NMDAR interactions. Conversely, they enhanced the ?1R interaction with the TRPA1 N-terminal, as seen for ?1R-BiP interactions, whereas they barely affected the association of ?1R with the TRPV1 N-terminal. Thus, depending on the calcium channel and the cytosolic region examined, the ?1R agonists pregnenolone sulfate and PRE084 opposed or collaborated with the ?1R antagonists progesterone and S1RA to disrupt or promote such interactions. Through the use of cloned cytosolic regions of selected TRP calcium channels, we were able to demonstrate that ?1R ligands exhibit biased activity to regulate particular ?1R interactions with other proteins. Since ?1Rs are implicated in essential physiological processes, exploiting such ligand biases may represent a means to develop more selective and efficacious pharmacological interventions.

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Geometrically Constrained Cationic Low-Coordinate Tetrylenes: Highly Lewis Acidic σ-Donor Ligands in Catalytic Systems.

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