A conformational study of aromatic imide compounds. Part 2. Compounds containing diphenyl sulfide, diphenyl sulfone, and diphenylmethane moieties

An attempt was made to estimate the dihedral angles, phi, psi, omega(1), and omega(2), of bis(4-hydroxyphthalimide)s (BHPI) and bis(phenylphthalimide)s (BPI) having diphenyl sulfide, diphenyl sulfone, or diphenylmethane linkages at the center of molecules using solid-state C-13 CP/MAS NMR and ab initio nuclear shielding calculations. The TOSS and TOSS & DD pulse sequences were performed in the NMR measurements to obtain exact chemical shifts of each carbon. Total energies were calculated using the B3LYP/6-31G(d) level of theory, and shielding constants were calculated using the RHF/6-31G(d) level of theory for diphenyl sulfide, diphenyl sulfone, diphenylmethane with varying angles of phi, psi from 0 to 180degrees at intervals of 10degrees. It was clarified that the -S- and -SO2- linkages lead asymmetrical conformations with different omega(1) and omega(2) or with different phi and psi for BHPIs and BPIs. In contrast, the compounds having -CH2- linkages have symmetrical conformations. The dihedral angle of imide ring and phenylene ring (omega) are in the range of 40-90degrees, and the dihedral angles (phi, psi) distribute in the stable regions of the energy surfaces ranging from 40 to 90degrees. (C) 2002 Elsevier Science B.V. All rights reserved.