Quantum chemical study and infrared spectroscopy of hydrogen-bonded CHCl3–NH3 in the gas phase

Abstract

Molecular association of chloroform with ammonia is studied by high-level quantum chemical calculations including correlated MP2 and CCSD(T) calculations with basis sets up to6-311++G(d,p) and counterpoise corrected energies, geometries, and frequencies. The calculations predict an eclipsed hydrogen-bonded complex of C(3v) symmetry (DeltaE(0)=-15.07 kJ mol(-1)) with 225.4 pm intermolecular CHcdots, three dots, centeredN distance. Intermolecular interactions are analysed by Kitaura-Morokuma [Int. J. Quantum Chem. 10, 325 (1976)] interaction energy decomposition. Compared to the monomer, the C-H bond is elongated, and the CH-stretching fundamental shifts to lower wave numbers and has a marked approximately 340-fold increase of its intensity. Based on these predictions, the complex is observed by infrared spectroscopy in the gas phase at room temperature. A subtraction procedure isolates its spectrum, and a dilution series confirms the presence of a 1:1 complex. The CHCl(3)cdots, three dots, centeredNH(3) complex has an experimental -17.5 cm(-1) shift of its CH-stretching vibration, and CDCl(3)cdots, three dots, centeredNH(3) a -12.5 cm(-1) shift of the CD-stretching vibration. After a deperturbation of the CH-stretching/bending mode Fermi resonance system, this indicates a "redshifting" or more appropriately, a "C-H elongating" hydrogen bond in agreement with the ab initio calculations. An estimate of the complex concentration gives the equilibrium constant K(p)=0.024 (p(theta)=10(5) Pa) at 295 K for the dimerization, providing one of the few examples where a hydrogen-bonded gas phase complex at room temperature could be quantitatively studied by infrared spectroscopy.

CH⋅⋅⋅N Hydrogen‐Bonding Interaction in 7‐Azaindole:CHX3 (X=F, Cl) Complexes

“…In contrast to the CÀH···O or CÀH···p interactions, the hydrogenbond donor CÀH group in these complexes always shows a redshift in its stretching frequency. [14,15] Studies in inert gas matrices show even larger redshifts, namely, 45 cm À1 in an Ar matrix and 94 cm À1 in an N 2 matrix. The 1:1 complexes of CHCl 3 with NH 3 have been studied by IR spectroscopic methods in the gas phase.…”

“…[13][14][15] Vibrational spectroscopy in conjunction with molecular beams is a very powerful technique for the investigation of weakly bound size-selected clusters. There are far fewer gas-phase experimental studies, and among these the CÀH···N interactions, which are no less abundant than their CÀH···O or CÀH···p counterparts, have received very little attention.…”

Structure and electronic configuration of tetracyanoquinodimethane layers on a Au(111) surface

“…1c allows us to also extract an intermolecular spacing (distance between the N and H atoms) of ∼3 Å. This is a large separation compared to the typical interatomic distance in hydrogen bonds in liquid and gas phase complexes [11]. It reflects the non-negligible role of the surface atomic corrugation, in spite of the physisorptive character of the interaction.…”

What are the spectroscopic properties of HFC-32? Answers from DFT

“…Thanks to the huge progresses made in computer hardware resources and the development of efficient algorithms, in the last years coupled cluster (CC) theory with singles, doubles excitations and a perturbative estimate of connected triples, CCSD(T), coupled to large basis sets or complete basis set extrapolation, has become the gold standard for the accurate prediction of thermochemical and spectroscopic properties of small molecules, containing up to a 10th of atoms (e.g., see Refs. [ and references therein). Nevertheless, due to the unfavorable scaling of CCSD(T) with system size ( N 6 – N 7 , N being the number of basis functions), the method cannot be routinely applied to medium and large systems which are of relevance in biochemistry, supramolecular chemistry, solid state chemistry, and material science.…”