Direct Investigation of Covalently Bound Chlorine in Organic Compounds by Solid‐State 35Cl NMR Spectroscopy and Exact Spectral Line‐Shape Simulations

摘要: 35/37Cl NMR spectroscopy studies of organic systems are very rare, with only a few neat liquids having been studied.1 The lack chlorine data may be explained by the fact that 35Cl and 37Cl quadrupolar (spin I=3/2) low-frequency isotopes. quadrupole moments nuclei couple electric field gradient (EFG) tensor at nuclei; this phenomenon is known as interaction (QI). coupling constant, CQ, asymmetry parameter, ηQ, describe magnitude QI. In solution, one consequences QI fast relaxation, which means signals for covalently bound chlorines broad low intensity.1 For these reasons, chemically distinct sites difficult to distinguish solution spectroscopy. However, in solid state, nuclear spin relaxation typically slower, thus enabling higher quality 35Cl NMR spectra collected, least principle. Unfortunately, large because substantial, anisotropic EFG Cl atom, owing mainly its electronic configuration when it forms chlorine–carbon bond. Conventional wisdom such cannot studied powders solid-state central transition (CT; mI=1/2↔−1/2) can span tens megahertz typical commercially available magnetic fields. reason, ionic chlorides2 inorganic chlorides3 have studied, chlorides often an order smaller than atoms molecules. bonding environments types substantially different from those chloride-containing molecules previously.2, 3 A partial spectrum hexachlorophene has briefly mentioned literature.4 On other hand, most interesting chemistry occurs carbon where atom acts leaving group. Chlorine also important many pharmaceuticals well crystal design applications they form halogen bonds.5 Recent show biological where, example, tryptophan 7-halogenase was found selectively chlorinate moieties.6