The Polarized Crystal Spectra of Tris(octamethylpyrophosphoramide)cobalt(II), -nickel(II), and -copper(II) Perchlorates
Polarized single-crystal electronic spectra of the tris-octamethylpyrophosphoramide complexes of cobalt(II), nickel(II), and copper(II) in the isomorphous crystals Mi(OMPA)3(ClO4)2 have been measured at temperatures down to 5°K. The high energy of charge transfer and the low value of Dq combine to permit observation of all predicted spin-allowed and most spin-forbidden transitions. Trigonal electric dipole selection rules are clearly obeyed in the spin-allowed bands with only slight vibronic breakdown. The Co(OMPA)32+ and Ni(OMPA)32+ spectra at 5°K have been fitted to electrostatic ligand field calculations with the following results: for Ni(OMPA)32+, Dq = 0.731 kK, B = 0.950 kK, C = 3.74 kK; for Co(OMPA)32+, Dq = 0.765 kK, B = 0.855 kK, C = 3.68 kK; for Cu(OMPA)32+, Dq = 1.0 kK. Trigonal splittings are apparently insignificant in the Co(OMPA)32+ and Ni(OMPA)32+ spectra. The spectrum of Cu(OMPA)32+ yields an apparent v of 1.0 kK, although analysis in terms of lower symmetry is suggested. © 1971, American Chemical Society. All rights reserved.
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