Publications [#233760] of Richard A. Palmer

Journal Articles

  1. Yang, MC-L; Palmer, RA, "Natural Solid State Optical Activity of Tris(ethylenediamine)metal(II) Nitrates. II. Single Crystal Circular and Linear Dichroism of Tris(ethylenediamine)cobalt(II) Nitrate", J. Amer. Chem. Soc., 1975, 97(19), 5390, American Chemical Society (ACS) [Gateway.cgi], [doi].
    (last updated on 2024/07/16)

    Abstract:
    The electronic structure of tris(ethylenediamine)cobalt(II) nitrate has been investigated by measurement of the linear dichroism (LD) and circular dichroism (CD) spectra of cobalt-doped Zn(en)3(NO3)2 and of pure Co(en)3(NO3)2 single crystals. Spectra have been measured at ambient and cryogenic temperatures in the region from 7 to 35 kK. Cotton effects associated with all ligand field transitions are observed to have the same sign in the axial CD of a given crystal. Polarizations in the orthoaxial LD indicate that the ground state is 4A2 in the trigonal field. The main source of absorption spectral band intensity is a vibronic mechanism, whereas the CD intensity is primarily static in origin. The crystals of both the cobalt and zinc compounds appear to be completely isomorphous with Ni(en)3(NO3)2. The CD results show clearly that all three compounds represent unusual instances of spontaneous resolution of tris(bidentate) chelates by crystallization. The absolute configuration of the host crystal is deduced by reference to that of the kinetically inert Ru(en)32+ion and from this the chirality and signs of rotational strength of Co(en)32+ as well as of Cu(en)32+, Ni(en)32+, and Mn(en)32+ in the crystal have been correlated. © 1975, American Chemical Society. All rights reserved.