Measurement of interfluorine distances in solids

F-19 homonuclear dipolar recoupling methods were used to measure internucle ar distances ranging from 5 to 12 Angstrom in fluorinated organic compounds in the solid state. Magic-angle-spinning-based high-resolution techniques were utilized. Trifluoromethyl and aromatic fluorine groups were seperated by rigid aromatic spacers; these compounds were diluted into nonfluorinated host molecule matrices to give isolated homonuclear spin pairs with known internuclear distances. Radiofrequency-driven recoupling (RFDR) was used to elicit magnetization exchange between the spin pairs in 1D and 2D experime nts. Simulation of the exchange was accomplished using a Monte Carlo-type a lgorithm to search the parameter space. These methods allow the determinati on of distances with an accuracy of 1 Angstrom at shorter distances and 2 A ngstrom at longer distances, with the assumption of no prior knowledge of T -2(ZQ). (C) 2001 Academic Press.