title: Hydrogen bonding and multiphonon structure in copper pyrazine coordination polymers.
abstract: We report a systematic investigation of the temperature-dependent infrared vibrational spectra of a family of chemically related coordination polymer magnets based upon bridging bifluoride (HF(2)-) and terminal fluoride (F-) ligands in copper pyrazine complexes including Cu(HF(2))(pyz)(2)BF(4), Cu(HF(2))(pyz)(2)ClO(4), and CuF(2)(H(2)O)(2)(pyz). We compare our results with several one- and two-dimensional prototype materials including Cu(pyz)(NO(3))(2) and Cu(pyz)(2)(ClO(4))(2). Unusual low-temperature hydrogen bonding, local structural transitions associated with stronger low-temperature hydrogen bonding, and striking multiphonon effects that derive from coupling of an infrared-active fundamental with strong Raman-active modes of the pyrazine building-block molecule are observed. On the basis of the spectroscopic evidence, these interactions are ubiquitous to this family of coordination polymers and may work to stabilize long-range magnetic ordering at low temperature. Similar interactions are likely to be present in other molecule-based magnets.
authors.affiliation: Department of Chemistry, University of Tennessee, Knoxville, Tennessee 37996, USA.
authors.forename: S
authors.initials: S
authors.lastname: Brown
authors.forename: J
authors.initials: J
authors.lastname: Cao
authors.forename: J L
authors.initials: JL
authors.lastname: Musfeldt
authors.forename: M M
authors.initials: MM
authors.lastname: Conner
authors.forename: A C
authors.initials: AC
authors.lastname: McConnell
authors.forename: H I
authors.initials: HI
authors.lastname: Southerland
authors.forename: J L
authors.initials: JL
authors.lastname: Manson
authors.forename: J A
authors.initials: JA
authors.lastname: Schlueter
authors.forename: M D
authors.initials: MD
authors.lastname: Phillips
authors.forename: M M
authors.initials: MM
authors.lastname: Turnbull
authors.forename: C P
authors.initials: CP
authors.lastname: Landee