Integrated intensity of continuous absorption in infrared spectra of complexes with medium-strong and strong hydrogen bonds |
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| Affiliation: | 1. Energy Storage and Distributed Resources Division, Lawrence Berkeley National Laboratory, Berkeley, CA, 94720, USA;2. Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, Menlo Park, CA, 94025, USA;3. European X-Ray Free-Electron Laser Facility, Holzkoppel 4, D-22869, Schenefeld, Germany;4. Department of Chemistry, University of Illinois at Chicago, Chicago, IL, 60607, USA;1. Karlsruher Institute of Technology (KIT), Institute for Applied Materials-Energy Storage Systems (IAM-ESS), 76344 Eggenstein-Leopoldshafen, Germany;2. BMW Group, 80788 Munich, Germany;3. Forschungszentrum Juelich, Institute of Energy and Climate Research, 52425 Juelich, Germany;4. Helmholtz Institute Ulm (HIU) Electrochemical Energy Storage, P.O. Box 3640, D-76021 Karlsruhe, Germany;5. Physikalische und Theoretische Chemie, Freie Universitaet Berlin, Takustr. 3, D-14195 Berlin, Germany;1. Clean Nano Energy Center, State Key Laboratory of Metastable Materials Science and Technology, Yanshan University, Qinhuangdao 066004, China;2. Key Laboratory of Low Dimensional Materials and Application Technology of Ministry of Education, School of Materials Science and Engineering, Xiangtan University, Xiangtan 411105, China;3. Hebei Key Laboratory of Applied Chemistry, School of Environmental and Chemical Engineering, Yanshan University, Qinhuangdao 066004, China;4. State Key Laboratory for Mechanical Behavior of Materials, Xi’an Jiaotong University, Xi’an 710049, China;5. Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, GA 30332, USA |
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| Abstract: | A simple, nongraphical and reproducible method of separation of the complex absorption due to strong hydrogen bonds from that due to the skeleton is proposed. The method has been tested on 17 complexes of pyridine N-oxide, triphenylphosphine oxide and DMSO-d6 with dichloroacetic acid in dry dichloromethane and acetonitrile. The integrated intensity (ACPA) and the centre of gravity (mathtype1) of complex absorption due to protonic vibration were measured and correlated with pKa values of bases and chemical shifts of the hydrogen-bonded protons (δ), and discussed with respect to hydrogen bond strength variations. TheACPA values vary from 17.5 to 46 x 104 cm mmol-1 and were reproducible to within ± 1 x 104 cm mmol−1 (5-15 %). A nonlinear correlation between ACPA and (mathtype2) has been found in wide region of data; (mathtype3) varies from 500 to 2300 cm−1. A gradual proton transfer has been considered from the acid to pyridine N-oxides via strengthening intermolecular H-bonds, AH⋯ON, and further via weakening interionic H-bonds, A−⋯ HON+. The obtained correlations suggest that variations of hydrogen bond strength caused similar changes of ACPA and (mathtype4) both in molecular (A–H⋯B) and ionic (A−⋯H–B+) species. |
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