A computational investigation of the red and blue shifts in hydrogen bonded systems

Abstract

The present work reports results of computational investigations of hydrogen bonding, with regard to the most common red shift in the vibrational frequency, as well as the less common blue shift in several hydrogen bonded systems. A few new correlations of the frequency shifts with the calculated electrostatic parameters are proposed, thereby generating new insight into both types of the frequency shifts. Thus, the frequency shifts in X-H--Y hydrogen bonded systems at different H-Y distances are shown to correlate well with the Mulliken charges on H and Y, with the positive and negative charges on Y correlating with the blue and red shift of the frequency of X-H vibration, respectively. The role played by charge transfers at other parts of the interacting system is also discussed.

Single-Photon Ionization Induced New Covalent Bond Formation in Acrylonitrile(AN)–Pyrrole(Py) Clusters

“…The broad and intense band from 2600 to 3200 cm –1 observed in the experimental spectrum corresponds to the intense band centered at 2828 cm –1 of (AN-Py) + -VI, which is assigned to the strong H-bonded (proton-shared) NH stretching vibrations of Py of (AN-Py) + -VI. In the experimental IR spectra of cationic clusters, the band corresponding to the proton-shared structure is frequently observed as a very broad and intense component due to the hot bands and anharmonic couplings. , Similar broad and intense bands have also been observed in many previous studies on strong H-bonded XH (X = N, O) bands. ,− The weak band at 3335 cm –1 observed in the experimental spectrum corresponds to the H-bonded NH stretching vibration of (AN-Py) + -II, III, and V. The slight red shift of the NH stretching vibration at 3335 cm –1 indicates that a weak H-bond is involved. The weak band at 3420 cm –1 observed in the experimental spectrum corresponds to the free NH stretching vibration of (AN-Py) + -I and IV.…”

“…In the experimental IR spectra of cationic clusters, the band corresponding to the proton-shared structure is frequently observed as a very broad and intense component due to the hot bands and anharmonic couplings. 52,53 Similar broad and intense bands have also been observed in many previous studies on strong H-bonded XH (X = N, O) bands. 51,54−58 The weak band at 3335 cm −1 observed in the experimental spectrum corresponds to the Hbonded NH stretching vibration of (AN-Py) + -II, III, and V. The slight red shift of the NH stretching vibration at 3335 cm −1 indicates that a weak H-bond is involved.…”

Extractive Adsorption of Lactic Acid from Fermentation Broth on a Novel Ion Exchange Resin Impregnated by the [Bmim]PF6 Ionic Liquid

“…The stretching vibrations of –O–H in the hydroxyl group and –CO in the carboxyl group of LA were a hypochromatic shift from 3397 to 3439 cm –1 and from 1720 to 1747 cm –1 , respectively. The formation of hydrogen bonds between LA and [Bmim]­PF 6 may cause a shift in the band position. , …”

“…29 In the LA-[Bmim]PF 6 extraction systems, the hydroxyl and carboxyl groups in LA can serve as hydrogen bond donor groups. The highly electronegative element fluorine in 40,41 Quantum Chemical Calculations. Quantum chemistry calculations can help to further clarify specific extraction processes and visualize the representation of intermolecular interactions.…”

Comparison of the Molecular Properties of Euglobals Differing by the Mutual Positions of the Two R–C=O Groups (R = H and CH2CH(CH3)2): A Computational Study

“…The formation of an H-bond most often causes an elongation of the bond length of the donor, which results in a decrease in its IR vibrational frequency [60][61][62][63]; the decrease is called redshift. Redshifts are mostly frequent for highly polar donors like O-H.…”