Cover Feature: Hydrogen Bonding vs Dihydrogen Bonding in the Air Stable Primary Phosphine ortho-Phosphinophenol (Eur. J. Inorg. Chem. 25/2024)

The Cover Feature depicts two of four lowest energy conformational isomers of ortho-phosphinophenol predicted by theory. Interestingly, these two particular isomers reflect intramolecular forms of attractive P⋅⋅⋅HO hydrogen bonding (HB) or PH₂⋅⋅⋅HO dihydrogen bonding (DHB) withing the same molecule. In the gas phase, the isomer possessing bifurcated DHB is predicted to be lower in energy than the isomer with HB. Experimental evidence supports the existence of a) multiple isomers in solution (solution-phase IR spectral data), b) the presence of intermolecular P⋅⋅⋅HO HB in the solid state (single-crystal X-ray structure), and c) the presence of substantial intermolecular OH⋅⋅⋅S HB (S=solvent lone pair or π-system) interactions in solution (³¹P NMR spectral data). More information can be found in the Research Article by J. D. Protasiewicz and co-workers.