Importance of Cu and Ag regium-π bonds in supramolecular chemistry and biology: a combined crystallographic and ab initio study.

Identifying and characterizing new binding events between electron donor and acceptor counterparts represents a crucial step to complete the molecular recognition and aggregation picture, which is key to chemistry and biology. In this study we interrogated both the PDB (Protein Data Bank) and CSD (Cambridge Structural Database) for the presence of Cu and Ag regium-π (Rg-π) bonds (an attractive noncovalent force between elements from group 11 and π-systems). Concretely, we found evidence of the plausible biological role of the interaction in protein-DNA systems, bacterial Ag extrusion processes and Heme group redox functionality. Furthermore, we also highlighted the implications of Rg-π bonds in the crystal packing of two host-guest systems, where this interaction is key for the binding and recognition of small organic molecules as well as for the encapsulation of organometallic complexes. Theoretical models were used to analyse the strength of the interaction (RI-MP2/def2-TZVP level of theory) together with QTAIM (Quantum Theory of Atoms in Molecules), NBO (Natural Bonding Orbital) and NCIplot (Non Covalent Interactions plot) analyses, which further assisted in the characterization of the regium-π interactions described herein. We expect the results from this study will be useful to attract the attention of chemical biologists as well as to expand the potential of the interaction to the supramolecular chemistry and crystal engineering communities.

Substituent Effects in π-Hole Regium Bonding Interactions Between Au(p-X-Py)2 Complexes and Lewis Bases: An ab initio Study.

Long range substituent effects in regium bonding interactions involving Au(I) linear complexes are investigated for the first time. The Au(I) atom is coordinated to two para-substituted pyridine ligands. The interaction energy (RI-MP2/def2-TZVP level of theory) of the π-hole regium bonding assemblies is affected by the pyridine substitution. The Hammett's plot representations for several sets of Lewis bases have been carried out and, in all cases, good regression plots have been obtained (interaction energies vs. Hammett's σ parameter). The Bader's theory of "atoms-in-molecules" has been used to evidence that the electron density computed at the bond critical point that connects the Au-atom to the electron donor can be used as a measure of bond order in regium bonding. Several X-ray structures retrieved from the Cambridge Structural Database (CSD) provide experimental support to the existence of π-hole regium bonding in [Au(Py)2 ]+ derivatives.

Frustrated Lewis Pairs Based on Carbon⋠⋠⋠Carbon+ Tetrel Bonds: A DFT Study.

The ability of Triangulenium (TA+ ) compounds to form Frustrated Lewis Pairs (FLPs) with N-HeteroCycle Carbenes (NHCs) is analysed in this manuscript at the PBE0-D3/def2-TZVP level of theory. We have used six TA+ -based moieties, three presenting similar bridging groups (O (trioxo), -CH2 (triaryl) and -NH (triaza)) and another three mixing, O, -CH2 and NH moieties. In addition, several aryl-substituted NHCs have been used as electron donor moieties to undergo carbon⋅⋅⋅carbon+ tetrel bonds with the TA+ derivatives. More precisely, -Me,-iPr, -tBu and -Ph groups were used. Finally, we have used Bader's quantum theory of "atoms in molecules" (QTAIM) and Natural Bonding Analysis (NBO) to characterize the carbon⋅⋅⋅carbon+ tetrel bonds described herein. We expect the results gathered herein will be useful for further exploitation of carbon⋅⋅⋅carbon+ bonds in the formation of FLPs as well as to expand the current knowledge of tetrel bonds to the fields of synthetic chemistry and catalysis.

Adsorption and Quantification of Volatile Organic Compounds (VOCs) by using Hybrid Magnetic Nanoparticles.

The ability of Fe3 O4 magnetic nanoparticles decorated with perylene bisimides to adsorb aromatic volatile organic compounds (VOCs) is reported. We have used DFT-D3 calculations to anticipate the strong ability of the electron-poor perylene bisimide to form noncovalent complexes with electron-rich aromatic rings belonging to the VOC family. Subsequently, we synthesized a hybrid magnetic nanomaterial based on bisimide perylene dopamine and iron oxide nanoparticles. This material was used to fill a sorbent tube to study its ability to adsorb aromatic VOCs. We connected two tubes in series filled with the hybrid nanoparticles. The analysis of the front and back tubes was performed by thermal desorption (TD) coupled with capillary gas chromatography (GC)/flame ionization detector (FID). Adsorption values (defined as %VOCs found in the back tube) were determined for a series of aromatic VOCs and compared with the DFT binding energies. The tubes can be desorbed and reutilized more than 200 times without losing their properties.