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Neoisostegane, the first naturally occurring steganin without a functional group at C-5, was isolated from two different collections of Steganotaenia araliacea. The structure of neoisostegane, which contained five aromatic methoxyl groups rather than the more usual three methoxyls and one methylenedioxy moiety, was elucidated by comparison of the pmr coupling constants with those of synthetic steganes and by selective decoupling experiments. The structure was confirmed by cmr data, by preparation of a derivative having five aromatic methoxyl moieties from stegane, which was compared spectroscopically to neoisostegane, and by thermal isomerization experiments.

The mid- and far-infrared spectra of Ho(III) and Gd(III) chloride hexahydrate, anhydrous Gd(III) formate, Ho(III) and Gd(III) acetate hemihydrate and trihydrate, and Gd(III) benzoate monohydrate have been computed by the ROHF/SBKJC method in GAMESS. The calculated spectra successfully simulated the experimental spectra down to 50 cm(-1). Absorptions due to coordinated water were distinguished from those due to O-C-O bending in chelate rings. The number of water molecules bound to Ln(III) in a complex was successfully predicted from the match of the experimental spectra to the simulated Ln-O vibrations in the far IR.

Unpolarized emission spectra and magnetic field induced circularly polarized emission spectra are reported for EuC13 and for five different tris(|8-diketonate) Eu(III) complexes in methanol and in yV./V-dimethylformamide solutions. Analysis of the EuCl3 spectra suggests the predominance of axially symmetric coordination species with C3v point-group symmetry.Analysis of the tris(/3-diketonate) Eu(III) spectra show the predominance of nonaxially symmetric structures with very strong orthorhombic crystal field components. The observed 7F2 *-5D0 and 7F, *-5D0 emission intensity ratios exhibit a strong sensitivity to the structural details and chemical nature of the ligand environment, with the magnitude of /(7F2 «-5D0):/(7F! *-5D0) correlating closely with ligand or ligand substituent polarizabilities. The latter is explained in terms of the ligand dipolar polarization model for 4f -4f electric dipole intensities. The 7F0 *-5D0 transition intensity (relative to that of 7F, •*-5D0) is also observed to be very sensitive to the ligand environment, and this is attributed to its "stealing" intensity from the 7F2 «-5D0 transition via a mechanism involving crystal field induced mixings between the 7F0 and 7F2 (and 5D0 and 5D2) multiplet states. to F.S.R.) and the National Institutes of Health (Grant R01-CA-30148 to L.M.V.).