1H MAS, 15N CPMAS, and DFT Investigation of Hydrogen-Bonded Supramolecular Adducts between the Diamine 1,4-Diazabicyclo-[2.2.2]octane and Dicarboxylic Acids of Variable Chain Len

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• 作者：Roberto Gobetto ; Carlo Nervi ; Enrico Valfrè ; Michele R. Chierotti ; Dario Braga ; Lucia Maini ; Fabrizia Grepioni ; Robin K. Harris ; and Phuong Y. Ghi
• 刊名：Chemistry of Materials
• 出版年：2005
• 出版时间：March 22, 2005
• 年：2005
• 卷：17
• 期：6
• 页码：1457 - 1466
• 全文大小：203K
• 年卷期：v.17,no.6(March 22, 2005)
• ISSN：1520-5002

文摘

Supramolecular adducts of formula [N(CH₂CH₂)₃N]-H-[OOC(CH₂)_nCOOH] (n = 1-7) havebeen obtained by mechanochemical reaction of solid dicarboxylic acids of variable chain lengthHOOC(CH₂)_nCOOH (n = 1-7) with solid 1,4-diazabicyclo[2.2.2]octane (dabco). ¹H MAS and ¹⁵NCPMAS spectra have been measured to investigate the presence of intermolecular hydrogen bonds betweenacid and base. Proton and nitrogen chemical shifts allow a distinction to be made between N⁺-H···O^-interactions (with proton transfer) and N···H-O interactions (without proton transfer) and between strongand weak hydrogen bonds. Correlations among isotropic ¹H, ¹⁵N chemical shift data and the N-O distancesof the atoms involved in the hydrogen bond interaction are found. Density functional theory, applied toexplore changes upon hydrogen bonding in the ¹H and ¹⁵N shielding parameters, is in agreement withthe experimental values found by solid-state NMR spectroscopy. Hydrogen/deuterium H/D isotope effectson the ¹⁵N NMR chemical shifts have been also investigated.