Synthesis and characterization of the pseudo-1-d mixed-valence (Et[sub 4[minus]n]Me[sub n]N)Cu[sub 2]X[sub 4] salts: Pinned charge density wave systems exhibiting intervalence charge transfer

Journal Article · Wed Jun 10 00:00:00 EDT 1992 · Inorganic Chemistry; (United States)

DOI:https://doi.org/10.1021/ic00038a034· OSTI ID:6975788

Scott, B; Willett, R ^[1]; Porter, L; Williams, J ^[2]

---

1. Washington State Univ., Pullman (United States)
2. Argonne National Lab., IL (United States)

A series of mixed-valence Cu(I)/Cu(II) linear chain compounds exhibiting pinned charge density waves have been synthesized. The compounds have stoichiometry ACu[sup I]Cu[sup II]X[sub 4] with X = Cl or Br and A = tetraethylammonium (TEA), triethylmethylammonium (TEM), or diethyldimethylammonium (DEM). The crystal structures of the bromide analogues have been determined. The (TEM)Cu[sub 2]Br[sub 4] salt is tetragonal. The (DEM)Cu[sub 2]Br[sub 4] salt is also tetragonal. The (TEA)Cu[sub 2]Br[sub 4] salt is orthorhombic. These structures reveal infinite chains of alternating Cu[sup I]X[sub 4][sup 3[minus]] and Cu[sup II]X[sub 4][sup 2[minus]] tetrahedra (distorted) sharing edges, the chains being effectively isolated by bulky tetraalkylammonium cations. Although the valence states appear to be localized, with a 0.1 [angstrom] difference in the Cu(I)-X and Cu(II)-X bond lengths, several characterization techniques indicate Robin and Day class II behavior. The data also support a Peierls 4k[sub f] distorted charge density wave state for these chains. All salts show an intervalence charge-transfer band in the visible region of the spectrum. Conductivity measurements indicate semiconductive behavior. Temperature-dependent magnetic susceptibility measurements on (TEA)Cu[sub 2]Br[sub 4] reveal weak antiferromagnetic coupling, which is attributed to short Br[center dot][center dot][center dot]Br contacts between Cu[sup II]X[sub 4][sup 2[minus]] species within the chains. The above physical properties are rationalized in light of previous EHMO band calculations.

• DOE Contract Number: W-31109-ENG-38
• OSTI ID: 6975788
• Journal Information: Inorganic Chemistry; (United States), Vol. 31:12; ISSN 0020-1669
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
36 MATERIALS SCIENCE
COPPER COMPLEXES
CHEMICAL PREPARATION
PHYSICAL PROPERTIES
ABSORPTION SPECTRA
AMMONIUM COMPOUNDS
ANTIFERROMAGNETIC MATERIALS
BOND ANGLE
BOND LENGTHS
CHARGE DENSITY
CHARGE TRANSPORT
COPPER HALIDES
CRYSTAL STRUCTURE
ELECTRIC CONDUCTIVITY
MAGNETIC SUSCEPTIBILITY
ORTHORHOMBIC LATTICES
SALTS
SEMICONDUCTOR MATERIALS
TEMPERATURE DEPENDENCE
TETRAGONAL LATTICES
X-RAY DIFFRACTION
COHERENT SCATTERING
COMPLEXES
COPPER COMPOUNDS
CRYSTAL LATTICES
DIFFRACTION
DIMENSIONS
ELECTRICAL PROPERTIES
HALIDES
HALOGEN COMPOUNDS
LENGTH
MAGNETIC MATERIALS
MAGNETIC PROPERTIES
MATERIALS
SCATTERING
SPECTRA
SYNTHESIS
TRANSITION ELEMENT COMPLEXES
TRANSITION ELEMENT COMPOUNDS
400201* - Chemical & Physicochemical Properties
360606 - Other Materials- Physical Properties- (1992-)