So much scientific interest has been dedicated during the last years to the Weak Hydrogen Bond (WHB), a non covalent interaction which manifests itself in myriad ways in Structural Chemistry and Biology, that this topic deserved recently the publication of a book [1]. Only a few rotationally resolved spectroscopic investigations, which detail specific or local interactions, are available, however, on WHB. The three C-H×××F-C WHB interactions of the difluoromethane dimer [2] and the three C-H···O interactions of dimethylether dimer [3] have been characterized from their pure rotational spectra. Each of these interactions has been estimated to have an energy of about 2 kJ/mol and a little blue shift of the C-H stretching. Here we report the results of the investigations of the rotational spectra of some heterodimers held together through WHB’s. 1) Oxirane-trifluoromethane. The investigation of the parent and of its two 13C species has been used to establish a Cs geometry, with the two moieties bound by one C-H×××O and two C-H×××F-C hydrogen bonds. 2) 1,4-dioxane-trifluoromethane. The FT-MW spectrum of the Cs conformation with CHF3 axial with respect to 1,3-dioxane has been assigned. It is stabilized by one C-H×××O and two C-H×××F weak hydrogen bonds. 3) Cyclobutanone-trifluoromethane. This is the first rotationally resolved investigation of a complex with a C-H×××O interaction involving one carbonylic oxygen. This bridge, together with two C-H×××F weak hydrogen bonds, stabilizes the configuration shown aside. [1] “The weak hydrogen bond in structural chemistry and biology” IUCr Monographs on crystallography, Vol. IX (G.R.Desiraju and T.Steiner Ed.s) Oxford University Press, (2001). [2] Caminati, W.; Melandri, S.; Moreschini, P.; Favero, P.G.; Angew. Chem. Int. Ed., 1999, 38, 2924. [3] Y. Tatamitani, B. Liu, J. Shimada, T. Ogata, P. Ottaviani, A. Maris, W. Caminati and J. L. Alonso, J. Am. Chem. Soc., 124 (2002) 2739.
W.Caminati, P.Ottaviani, B.M. Giuliano, L. B. Favero, J.L.Alonso, S. Antolínez, et al. (2004). Chemical Information from Rotationally resolved Spectroscopy: Features of C-H···O and C-H···F intermolecular hydrogen bonds by Fourier transform microwave spectroscopy. NAPOLI : s.n.
Chemical Information from Rotationally resolved Spectroscopy: Features of C-H···O and C-H···F intermolecular hydrogen bonds by Fourier transform microwave spectroscopy
CAMINATI, WALTHER;OTTAVIANI, PAOLO;GIULIANO, BARBARA MICHELA;
2004
Abstract
So much scientific interest has been dedicated during the last years to the Weak Hydrogen Bond (WHB), a non covalent interaction which manifests itself in myriad ways in Structural Chemistry and Biology, that this topic deserved recently the publication of a book [1]. Only a few rotationally resolved spectroscopic investigations, which detail specific or local interactions, are available, however, on WHB. The three C-H×××F-C WHB interactions of the difluoromethane dimer [2] and the three C-H···O interactions of dimethylether dimer [3] have been characterized from their pure rotational spectra. Each of these interactions has been estimated to have an energy of about 2 kJ/mol and a little blue shift of the C-H stretching. Here we report the results of the investigations of the rotational spectra of some heterodimers held together through WHB’s. 1) Oxirane-trifluoromethane. The investigation of the parent and of its two 13C species has been used to establish a Cs geometry, with the two moieties bound by one C-H×××O and two C-H×××F-C hydrogen bonds. 2) 1,4-dioxane-trifluoromethane. The FT-MW spectrum of the Cs conformation with CHF3 axial with respect to 1,3-dioxane has been assigned. It is stabilized by one C-H×××O and two C-H×××F weak hydrogen bonds. 3) Cyclobutanone-trifluoromethane. This is the first rotationally resolved investigation of a complex with a C-H×××O interaction involving one carbonylic oxygen. This bridge, together with two C-H×××F weak hydrogen bonds, stabilizes the configuration shown aside. [1] “The weak hydrogen bond in structural chemistry and biology” IUCr Monographs on crystallography, Vol. IX (G.R.Desiraju and T.Steiner Ed.s) Oxford University Press, (2001). [2] Caminati, W.; Melandri, S.; Moreschini, P.; Favero, P.G.; Angew. Chem. Int. Ed., 1999, 38, 2924. [3] Y. Tatamitani, B. Liu, J. Shimada, T. Ogata, P. Ottaviani, A. Maris, W. Caminati and J. L. Alonso, J. Am. Chem. Soc., 124 (2002) 2739.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
