N-ALKYL FLUORENYL PHASES IN CHROMATOGRAPHY - I - SYNTHESIS AND CHARACTERIZATION

A new class of silica gel-bound fluorene phases is described. The comp ounds are synthesized via reaction of fluorenyl lithium with omega-alk enyl bromides leading to 9-(5'-hexenyl)-9H- and 9-(9'-decenyl)-9H-fluo rene (1 and 2), followed by hydrosilation reactions with different hyd rosilanes. The resulting omega-functionalized silylalkyl fluorenes 3a( T-0), 3b(T-0), 4a(T-0), 4b(T-0) and 4c(M-0) (Scheme 1) react with surf ace silanol groups of silica gel to generate the new fluorene phases 3 a(T-n)(Q(m))(y), 3b(T-n)(Q(m))(y), 4a(T-n)(Q(m))(y), 4b(T-n)(Q(m)), an d 4c(M-1)(Q(m))(y). The phases are characterized by employing H-1, C-1 3 and Si-29 solid-state nuclear magnetic resonance spectroscopy. Their applicability in high-performance liquid chromatography is proved by the Sander and Wise test (SRM 869). In contrast to conventional n-alky l phases, pi-pi interactions are additionally involved in the separati on process and, therefore, the retention times of the polycyclic aroma tic hydrocarbons sample molecules depend on the ligand densities of th e applied fluorene phases. (C) 1998 Elsevier Science B.V.