title: Pulsed ENDOR and ESEEM Study of [Bis(maleonitriledithiolato)nickel](-): An Investigation into the Ligand Electronic Structure.
abstract: By a combination of Q-band pulsed ENDOR (electron nuclear double resonance) and X-band ESEEM (electron stimulated echo envelope modulation) techniques, we have determined the hyperfine tensors for ethylene (C1) and cyano (C2) carbons and N, of [Ni(mnt)(2)](-), along with the quadrupole tensor for nitrogen. These measurements give pi electron spin densities of rho(C1) approximately 0.03 in the C1 2p(z)() orbital, rho(C2) < 0.003, rho(N) approximately 0.01, such that in total, approximately 0.15 of the spin resides on the ligand atoms C and N, while the rest resides in the NiS(4) core, giving rho(NiS(4)(-)) = 0.85. These results are compared with extended Hückel and density functional (BLYP) MO calculations, as well as with Xalpha calculations reported earlier.
authors.affiliation: Departments of Chemistry, Northwestern University, Evanston, Illinois 60208-3113, and University of Massachusetts, Amherst, Massachusetts 01003-4510.
authors.forename: Jennifer E.
authors.initials: JE
authors.lastname: Huyett
authors.forename: Suranjan B.
authors.initials: SB
authors.lastname: Choudhury
authors.forename: David M.
authors.initials: DM
authors.lastname: Eichhorn
authors.forename: Peter A.
authors.initials: PA
authors.lastname: Bryngelson
authors.forename: Michael J.
authors.initials: MJ
authors.lastname: Maroney
authors.forename: Brian M.
authors.initials: BM
authors.lastname: Hoffman