P═O Moiety as an Ambidextrous Hydrogen Bond Acceptor

Abstract

Hydrogen bond patterns of crystals of phosphinic, phosphonic, and phosphoric acids and their cocrystals with phosphine oxides were studied using 31 P NMR and single-crystal X-ray diffraction. Two main factors govern these patterns and favor or prevent the formation of cocrystals. The first one is a high proton-accepting ability of the PO moiety in these acids. As a result, this moiety effectively competes with other proton acceptors for hydrogen bonding. For example, this moiety is a stronger proton acceptor than the CO moiety of carboxylic acids. The second factor is the inclination of the PO moiety of both the acids and the oxides to form two hydrogen bonds at once. The peculiarity of these bonds is that they weaken each other to a little degree only. In order to highlight this point, we are using the term "ambidextrous". These two features should govern the interactions of PO moiety with water and other proton donors and acceptors in molecular clusters, the active sites of enzymes, soft matter, and at surfaces.

Hydrophobic Deep Eutectic Solvents Incorporating Trioctylphosphine Oxide: Advanced Liquid Extractants

“…However ∆δ 31 P remains approximately constant suggesting that as additional phenol is added, over the range χ TOPO = 0.5-0.2, it contributes directly to changes to the local TOPO environment. In the solid state, trialkylphosphine oxides tend to form two hydrogen-bonds in co-crystals 53 and it is likely that the observed eutectic minimum around χ TOPO = 0.33 (2:1 phenol:TOPO stoicheometry) reflects this maximum number of hydrogen-bonding interactions in the liquid mixtures. however, unlike static hydrogen-bonding enabling solid-state co-crystal formation, the dynamic nature of hydrogen-bonds here probably lead to disruptively competition with lattice packing forces to induce the liquid formation.…”

Phosphine Oxides as Spectroscopic Halogen Bond Descriptors: IR and NMR Correlations with Interatomic Distances and Complexation Energy

“…Phosphine oxides in general are perspective probes for the diagnostics of non-covalent interactions. Intermolecular hydrogen-bonded complexes of phosphine oxides and their related compounds are discussed in several publications [48][49][50][51]. Moreover, there are several publications where the participation of phosphine oxides in halogen bonds is considered.…”

Inter- vs. Intramolecular Hydrogen Bond Patterns and Proton Dynamics in Nitrophthalic Acid Associates

“…The former is critically important in solids [ 5 , 6 , 7 , 8 , 9 ], at confined geometries [ 10 , 11 , 12 ], and in aqueous solutions [ 13 , 14 , 15 , 16 ]. The latter is characteristic for P=O moiety [ 17 , 18 ], specially designed organic molecules [ 19 , 20 ], but most of all for biomolecules [ 21 , 22 ]. The adjustments of bridging proton positions in H-bonds act as one of the mechanisms governing the chemical properties of macromolecules [ 23 , 24 , 25 ] and biosystems [ 26 , 27 ].…”