High pressure, a protocol to identify the weak dihydrogen bonds: experimental evidence of C-H•••H-B interaction

Pressure, as a thermodynamic parameter, provides an appropriate method to detect weak intermolecular interactions. The C-H center dot center dot center dot H-B dihydrogen bond is so weak that the experimental evidence of this interaction is still limited. A combination of in situ high pressure Raman spectra and angle-dispersive X-ray diffraction (ADXRD) experiments was utilized to explore the dihydrogen bonds in dimethylamine borane (DMAB). Both Raman and ADXRD measurements suggested that the crystal structure of DMAB is stable in the pressure region from 1 atm (1 atm=1.01325x10(5) Pa) to 0.54 GPa. The red shift of CH stretching and CH3 distortion modes gave strong evidence for the existence of C-H center dot center dot center dot H-B dihydrogen bonds. Further analysis of Raman spectra and Hirshfeld surface confirmed our proposal. This work provided a deeper understanding of dihydrogen bonds. And we wish that high pressure could be applied to identify other unconfirmed hydrogen or dihydrogen bond.