The magnetic circular dichroism (MCD) spectrum of ferrocene in cyclohexane solution is measured using a Cary 60 spectropolarimeter with a CD attachment and superconducting solenoid, with computer analysis of the data in the uv and visible regions. It is compared with solution and vapor phase data for ordinary absorption in the same regions. MCD reveals five more transitions than does the absorption data for a ferrocene solution, and also reveals three more transitions than does vapor phase absorption data. The MCD spectrum of acetylferrocene is also discussed and used as support for the interpretation of the ferrocene data. Possible assignments are discussed.

Supplementary Material Available: Listings of additional bond lengths and angles, hydrogen atom parameters, and anisotropic thermal parameters for 5-7 (9 pages); tables of the observed and calculated structure factors (82 pages). Ordering information is given on any current masthead page.

The rotational strengths of the four longer wavelength transitions, BsU, Bju, and the two El , of adenosine derivatives constrained in the syn form have been investigated theoretically and experimentally. The theory combines a complete neglect of differential overlap version S (CNDO/S) description of the base with a generalized bond exciton metho by means of a matrix method. Rotational strength wheels for these transitions showing the rotational strength as a function of the glycosidic rotational angles are presented and sector rules discussed. Similar sector rules are predicted for purine nucleoside derivatives containing the 6-amino substituent, regardless of heteroatom content at positions 1 or 3 of the base. The sector rules for the Bs" rotational strength of purine nucleosides lacking the 6-amino substituent are strongly influenced by aza substitution. The circular dichroism spectra of 3-deazaadenosine, 8-a-hydroxyisopropyl)adenosine, and other purine nucleosides having a strong preference for the syn conformation are presented and compared with the theoretical results.Circular dichroism (CD) has been used extensively to study the conformation of nucleosides and nucleotides in solution. These studies have yielded some useful rules and diagrams (1-10) relating the sign of the first CD band to anomeric configuration and to sugar-base torsion angle. Several excellent reviews in this area are now available (11)(12)(13)(14)(15) We report here a theoretical CD study of some purine nucleosides closely related to adenosine which are conformationally restricted more or less to the syn conformation. The complete neglect of differential overlap version S (CNDO/S) procedure of Del Bene and Jaffe (27, 28) is used to calculate the optical parameters of the purine bases instead of our PariserParr-Pople method used in previous calculations (17,18). This and other modifications of the theoretical procedure have improved agreement between experimental data and theoretical results.COMPUTATIONAL METHODS The self-consistent field method has been widely used for the study of the electronic structure of molecules. The molecular orbitals 0t are expressed as linear combination of atomic orbitals 4u according to the equationThe coefficients Ct of the molecular orbital matrix are the solutions of the Hartree-Fock-Roothaan equations 3398The publication costs of this article were defrayed in part by page charge payment. This article must therefore be hereby marked "advertisement" in accordance with 18 U. S. C. §1734 solely to indicate this fact.