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.
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.
