Fluorine-19 NMR from retrosynthesis to NMR crystallography

Recently, the need for more accurate structure description that will allow to analyze possible retrosynthesis of microporous compounds has led us to u se and develop new structural strategies to access structure determination by solid state NMR techniques. At first, an example, AlPO4-CJ2, between cry stallogenesis and crystal structure is explored. AlPO4-CJ2 has been studied by hydrothermal in-situ NMR. A soluble species exists in supersaturated li quid as well as the product of redissolution of AlPO4-CJ2. This species, th e prenucleation building units (PNBU) is different from structural building s units (SBU) the sub-ensembles of the crystal. How this PNBU gets into the structure and becomes therefore a structural building unit (SBU) is our ma in question. To answer it, an HETCOR experiment between fluorine and alumin um has been performed. This experiment shows that when the PNBU enters the solid, it forms at the same time than growing the solid, a fluorinated brid ge. On ULM-18 after structure elucidation positioning hydrogen, a dynamic c harge compensation mechanism is proposed for the solid formation. On TMPGaP O, a set of 2D experiments using radio frequency driven dipolar recoupling (RFDR) on F-19, Double Quanta on P-31 and HETCOR between F-19 and P-31 allo wed analyzing the topology of the network. (C) 2000 Elsevier Science S.A. A ll rights reserved.