STRONG ORTHO/PARA EFFECTS IN THE VIBRATIONAL SPECTRA OF Cl-H2 and CN-H2

Vibrational spectroscopy of Cu+(H2)4: about anharmonicity and fluxionality

“…Note, the nuclear spin isomers resulting from ortho-and para-dihydrogen were recently reported to play an important role in the formation and the far-IR spectroscopy of Cl À -(H 2 ) and CN À -(H 2 ) anion complexes. 21,22,57 However, the present study focuses on the near-IR spectral region and the positions of rovibrational lines from corresponding nuclear spin isomers are expected to differ by only 0.5 cm À1 , i.e., much smaller than the bandwidth of the IR laser pulses of B3.5 cm À1 .…”

“…19,20 The rotationally-resolved IRPD spectra indicate that all these cationic complexes adopt a C 2v T-shaped M + -(H 2 ) geometry rather than the linear M + -H-H structure that is preferred in the corresponding anion complexes. [20][21][22][23] The H-H stretching frequencies are redshifted by 67 cm À1 (Na + -H 2 ) to 406 cm À1 (Ag + -H 2 ) relative to the frequency of a free H 2 molecule (4161 cm À1 ). 24 The extent of the redshift depends on the charge and orbital interactions, which determine the balance between s donation and p backdonation.…”