Magnetically induced CD

Fig. 7. The absorption (solid curves) and magnetically-induced CD spectrum (broken curves) of (Bu4N)2 [C0CI4] in CDCI3 solution containing a ten-fold excess of BU4NCI over the regions of the A2 -+ T](F) (spectra at the left), and the - Ti(P) transition (spectra at the right), at 295 K. ([AelT = (et - R)/Tesla)...

Further experimental examples of temperature-dependent and magnetically-induced quadrupole splittings are provided in the first volume of this book (Chap. 6, see CD-ROM, Part VI) and also in Sect. 9.4 in Chap. 9 of the present volume. 

When eda transitions occur in two non-identical achiral chromophores, as with the degenerate case, a linear motion of charge at a distance (in another chromo-phore) has a circular (magnetic) component locally. Thus if the two transitions couple, an induced CD signal (4) is found. The main differences between the non-degenerate and degenerate cases are that for the non-degenerate case ... 

Chiral-at-metal cations can themselves serve as chirality inducers. For example, optically pure Ru[(bipy)3] proved to be an excellent chiral auxihary for the stereoselective preparation of optically active 3D anionic networks [M(II)Cr(III)(oxalate)3]- n (with M = Mn, Ni), which display interesting magnetic properties. In these networks all of the metalhc centers have the same configuration, z or yl, as the template cation, as shown by CD spectroscopy and X-ray crystallography [43]. 

Referred to as the induced optical activity, the resultant CD spectrum has measurable peaks only when the transition is either electrically or magnetically allowed. Thus, this IC-D method is useful for discriminating the two types of transition 162). 

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