title: Electronic Spectra of the Tetraphenylcyclobutadienecyclopentadienylnickel(II) Cation and Radical.
abstract: Properties of the tetraphenylcyclobutadienecyclopentadienylnickel(II) cation 1 and its tetra-o-fluoro derivative 1a have been measured and calculated. The B3LYP/TZP optimized geometry of the free cation 1 agrees with a single-crystal X-ray diffraction structure except that in the crystal one of the phenyl substituents is strongly twisted to permit a close-packing interaction of two of its hydrogens with a nearby BF4(-) anion. The low-energy parts of the solution electronic absorption and magnetic circular dichroism (MCD) spectra of 1 and 1a have been interpreted by comparison with TD-DFT (B3LYP/TZP) results. Reduction or pulse radiolysis lead to a neutral 19-electron radical, whose visible absorption and MCD spectra have been recorded and interpreted as well. The reduction is facilitated by ∼0.1 V upon going from 1 to 1a. Unsuccessful attempts to prepare several other aryl substituted derivatives of 1 by the classical synthetic route are described in the Supporting Information .
authors.affiliation: Department of Chemistry and Biochemistry, University of Colorado , Boulder, Colorado 80309-0215, United States.
authors.forename: Peter R
authors.initials: PR
authors.lastname: Craig
authors.affiliation: Institute of Organic Chemistry and Biochemistry, Academy of Science of the Czech Republic , 16610 Prague 6, Czech Republic.
authors.forename: Zdeněk
authors.initials: Z
authors.lastname: Havlas
authors.affiliation: Department of Chemistry and Biochemistry, University of Colorado , Boulder, Colorado 80309-0215, United States.
authors.forename: Marianela
authors.initials: M
authors.lastname: Trujillo
authors.affiliation: Department of Chemistry and Biochemistry, University of Colorado , Boulder, Colorado 80309-0215, United States.
authors.forename: Pawel
authors.initials: P
authors.lastname: Rempala
authors.affiliation: Chemistry Department, Brookhaven National Laboratory , Bldg. 555A, Upton, New York 11973, United States.
authors.forename: James P
authors.initials: JP
authors.lastname: Kirby
authors.affiliation: Chemistry Department, Brookhaven National Laboratory , Bldg. 555A, Upton, New York 11973, United States.
authors.forename: John R
authors.initials: JR
authors.lastname: Miller
authors.affiliation: Department of Chemistry and Biochemistry, University of Colorado , Boulder, Colorado 80309-0215, United States.
authors.forename: Bruce C
authors.initials: BC
authors.lastname: Noll
authors.affiliation: Department of Chemistry and Biochemistry, University of Colorado , Boulder, Colorado 80309-0215, United States.|Institute of Organic Chemistry and Biochemistry, Academy of Science of the Czech Republic , 16610 Prague 6, Czech Republic.
authors.forename: Josef
authors.initials: J
authors.lastname: Michl