Trends in the stability of covalent dative bonds with variable solvent polarity depend on the charge transfer in the Lewis electron-pair system

In general, the stability of neutral complexes with dative bonds increases as the polarity of the solvent increases. This is based on the fact that the dipole moment of the complex increases as the charge transferred from the donor to the acceptor increases. As a result, the solvation energy of the complex becomes greater than that of subsystems, causing an increase in the stabilization energy with increasing solvent polarity. Our research confirms this assumption, but only when the charge transfer is sufficiently large. If it is below a certain threshold, the increase in the complex's dipole moment is insufficient to result in a higher solvation energy than subsystems. Thus, the magnitude of the charge transfer in the Lewis electron-pair system determines the stability trends of dative bonds with varying solvent polarity. We used molecular dynamics (MD) simulations based on an explicit solvent model, which is considered more reliable, to verify the results obtained with a continuous solvent model.Web of Science2538259642596

Unexpected strengthening of the H-bond complexes in a polar solvent due to a more efficient solvation of the complex compared to isolated monomers

It is generally assumed that hydrogen-bonded complexes are less stable in solvents than in the gas phase and that their stability decreases with increasing solvent polarity. This assumption is based on the size of the area available to the solvent, which is always smaller in the complex compared to the subsystems, thereby reducing the solvation energy. This reduction prevails over the amplification of the electrostatic hydrogen bond by the polar solvent. In this work, we show, using experimental IR spectroscopy and DFT calculations, that there are hydrogen-bonded complexes whose stability becomes greater with increasing solvent polarity. The explanation for this surprising stabilization is based on the analysis of the charge redistribution in the complex leading to increase of its dipole moment and solvation energy. Constrained DFT calculations have shown a dominant role of charge transfer over polarization effects for dipole moment and solvation energy.Web of Science126437943793

A new selective 'turn-on' small fluorescent cationic probe for recognition of RNA in cells

Fluorescent imaging probes have revolutionised cell biology by monitoring cellular objects. However, the lack of fluorescent probes with high selectivity for RNA has been a drawback. Thus, selective RNA binding for fluorescent sensors is essential. Here, we report the selective fluorescence enhancement upon addition of RNA. By exploiting a selective recognition of small tetra-cationic probe 1 for RNA, we also explain the possible binding mode for RNA. As a membranepermeant fluorescence probe, 1 provides selective imaging of RNA not only in human neuroblastoma tumour SH-SY5Y cell line used for Parkinson’s disease but also in the unicellular green alga cells. Further exploitation could open new opportunities in neurotoxin and cancer biology.1651sciescopu

A new selective 'turn-on' small fluorescent cationic probe for recognition of RNA in cells

Fluorescent imaging probes have revolutionised cell biology by monitoring cellular objects. However, the lack of fluorescent probes with high selectivity for RNA has been a drawback. Thus, selective RNA binding for fluorescent sensors is essential. Here, we report the selective fluorescence enhancement upon addition of RNA. By exploiting a selective recognition of small tetra-cationic probe 1 for RNA, we also explain the possible binding mode for RNA. As a membrane-permeant fluorescence probe, 1 provides selective imaging of RNA not only in human neuroblastoma tumour SH-SY5Y cell line used for Parkinson's disease but also in the unicellular green alga cells. Further exploitation could open new opportunities in neurotoxin and cancer biology

Precise Tuning of Cationic Cyclophanes toward Highly Selective Fluorogenic Recognition of Specific Biophosphate Anions

Cationic cyclophanes with bridging and spacer groups possess well-organized semirigid cavities and are able to encapsulate and stabilize anionic species through diverse molecular interactions. We highlight the precise tuning of functionalized cyclophanes toward selective recognition of AMP, GTP, and pyrophosphate (PPi) using fluorescence, NMR spectroscopy, and density functional theory (DFT)

The stability of covalent dative bond significantly increases with increasing solvent polarity

Non covalent complexes are often considerably destabilized in the solvent. Here the authors combine vibrational Raman and NMR spectroscopy with a coupled-cluster computational investigation to show that the solvent polarity enhance the complex stability of a Me3NBH3 complex. It is generally expected that a solvent has only marginal effect on the stability of a covalent bond. In this work, we present a combined computational and experimental study showing a surprising stabilization of the covalent/dative bond in Me3NBH3 complex with increasing solvent polarity. The results show that for a given complex, its stability correlates with the strength of the bond. Notably, the trends in calculated changes of binding (free) energies, observed with increasing solvent polarity, match the differences in the solvation energies (Delta E-solv) of the complex and isolated fragments. Furthermore, the studies performed on the set of the dative complexes, with different atoms involved in the bond, show a linear correlation between the changes of binding free energies and Delta E-solv. The observed data indicate that the ionic part of the combined ionic-covalent character of the bond is responsible for the stabilizing effects of solvents.Web of Science131art. no. 210

Precise tuning of cationic cyclophanes toward highly selective fluorogenic recognition of specific biophosphate anions

Cationic cyclophanes with bridging and spacer groups possess well-organized semirigid cavities and are able to encapsulate and stabilize anionic species through diverse molecular interactions. We highlight the precise tuning of functionalized cyclophanes toward selective recognition of AMP, GTP, and pyrophosphate (PPi) using fluorescence, NMR spectroscopy, and density functional theory (DFT).close0