Homogeneous and Heterogeneous Noncovalent Dimers of Formaldehyde and Thioformaldehyde: Structures, Energetics, and Vibrational Frequencies

Abstract

This work provides the first characterization of five stationary points of the homogeneous thioformaldehyde dimer, (CH2S)2, and seven stationary points of the heterogeneous formaldehyde/thioformaldehyde dimer, CH2O/CH2S, with correlated ab initio electronic structure methods. Full geometry optimizations and corresponding harmonic vibrational frequencies were computed with second-order Møller-Plesset perturbation theory (MP2) and 13 different density functionals in conjunction with triple-ζ basis sets augmented with diffuse and multiple sets of polarization functions. The MP2 results indicate that the three stationary points of (CH2S)2 and four of CH2O/CH2S are minima, in contrast to two stationary points of the formaldehyde dimer, (CH2O)2. Single-point energies were also computed using the explicitly correlated MP2-F12 and CCSD(T)-F12 methods and basis sets as large as heavy-aug-cc-pVTZ. The (CH2O)2 and CH2O/CH2S MP2 and MP2-F12 binding energies deviated from the CCSD(T)-F12 binding energies by no more than 0.2 and 0.4 kcal mol(-1), respectively. The (CH2O)2 and CH2O/CH2S global minimum is the same at every level of theory. However, the MP2 methods overbind (CH2S)2 by as much as 1.1 kcal mol(-1), effectively altering the energetic ordering of the thioformaldehyde dimer minima relative to the CCSD(T)-F12 energies. The CCSD(T)-F12 binding energies of the (CH2O)2 and CH2O/CH2S stationary points are quite similar, with the former ranging from around -2.4 to -4.6 kcal mol(-1) and the latter from about -1.1 to -4.4 kcal mol(-1). Corresponding (CH2S)2 stationary points have appreciably smaller CCSD(T)-F12 binding energies ranging from ca. -1.1 to -3.4 kcal mol(-1). The vibrational frequency shifts upon dimerization are also reported for each minimum on the MP2 potential energy surfaces.

Roles of H2O to hydrogen bonds, structure and strength of complexes of CH3CHS and H2O

“…Therefore, we want to have an insight into this issue in the complexes of CH3CHS with nH2O (n=1-3) and explain the role of water in hydrogen bonding to help us understand more about stability and the nature of H-bond in these systems, the effect of water on cooperativity and strength of complexes. The results will help contribute to shed more light on the origin of the C-H blue shifting Hbond and classification of H-bonds, [11,12,13] helping further to synthesize drugs for life and improving human health. [14] 2.…”

Theoretical Characterization of Hydrogen Bonding Interactions between RCHO (R = H, CN, CF3, OCH3, NH2) and HOR′(R′ = H, Cl, CH3, NH2, C(O)H, C6H5)

“…37,[41][42][43] There are numerous reports on hydrogen bonded carbonyl complexes by theoreticians and experimentalists [44][45][46][47][48][49][50][51][52][53][54][55][56][57][58][59][60][61] in the past and even today. [62][63][64][65][66][67][68] For example, the earlier work by Bobadova-Parvanova and his co-worker investigated the hydrogen bonded complexes between open-chain substituted aliphatic carbonyl compounds and hydrogen fluoride at the HF/6-31G * * level. 50 They analyzed vibrational-frequency and infrared intensity for the isolated and hydrogen-bonded complexes and a linear correlation for the variation of HB strength ( E) with H-F stretching frequency shift, change in H-F bond length, molecular electrostatic potential was found.…”

A computational study on multiple formaldehyde complexes and their possible chemical reactions as well as the catalytic effect in the gas phase

“…The electronic structures and spectra of formaldehyde dimers were studied by several researchers experimentally and theoretically [1,2,17,[26][27][28] Dornshuld et al investigated the minima structures of formaldehyde and thioformaldehyde dimers such as Karpfen studied the minima structures of some dimers such as trans-glyoxal, trans-acrolein, and formaldehyde. He optimized all stationary points at the MP2/aug-cc-pVTZ level and the precise energies computed at the CCSD(T)/ aug-cc-pVTZ level.…”

“…Our result show this unstability is 2.6 kcal/mol at the CCSD/6-311++g (3df, 3pd) level of theory. The mentioned researchers also calculated the trimer structures of formaldehyde, which were termed by EQ0 [3-0]-EQ9 [3][4][5][6][7][8][9] (see Figure 2 and Table 4 in reference [1]). The obtained energies at the B3LYP-D3/aug-cc-pVTZ level show that the EQ1 and EQ8 [3][4][5][6][7][8] were 0.19 and 11.16 kJ/mol more unstable than the EQ0 [3-0] structure [1].…”

“…Understanding and controlling intermolecular interactions play a crucial role in molecular recognition [1,2], crystal engineering [3][4][5][6] and biological systems [7,8]. Describing the interactions in molecular systems usually involves interpreting their geometry [9,10] and overall energy [11].…”