CP-MAS C-13 NMR-SPECTRA OF POLY(N-VINYLCARBAZOLE) COMPLEXES WITH 2,4,7-TRINITRO-9-FLUORENONE AND 2,4,5,7-TETRANITRO-9-FLUORENONE

Charge-transfer complexes of poly(N-vinylcarbazole) (PNVC) with 2,4,7-trinitro-9-fluorenone (TNF) and 2,4,5,7-tetranitro-9-fluorenone (TENF) were prepared by slow evaporation of a common solvent and investigated by CP-MAS C-13 NMR spectroscopy. Parallel studies were performed on crystalline complexes of N-ethylcarbazole (NEC) with the same electron-acceptor molecules: TNF and TENF. Charge-transfer interaction is observed in the complexes by upfield shifts of various signals. In the PNVC complexes, only one signal can be assigned to the charge-transfer complex with TENF. All the other potential shifts are overlapped by the broad polymer signals. TNF and TENF are not proton-rich substances, and in their complexes almost all the magnetization arises from intermolecular interaction, transmitted from the electron-donor molecule, which is richer in protons. Charge-transfer interaction depresses the value of the spin-lattice relaxation time in the rotating frame (T1-rho-H) of PNVC to a higher extent in its complexes with TENF. This allows selective observation of "uncomplexed" electron-acceptor molecules at longer contact times. The number of T1-rho-H values found for a particular complex is indicative of the homogeneity of that charge-transfer complex. It appears that PNVC-TENF is homogeneous for any sample containing less than 50 mol % TENF and becomes a mixture of at least two components at higher TENF content. Mixtures of PNVC with TNF, however, are not homogeneous at any composition.