IODINE CHARGE-TRANSFER SALTS OF BENZENE-BRIDGED BIS(1,2,3,5-DISELENADIAZOLYL) DIRADICALS - ELECTROCRYSTALLIZATION AND SOLID-STATE CHARACTERIZATION OF 1,3-[(SE2N2C)C6H4(CN2SE2)][I] AND 1,4-[(SE2N2C)C6H4(CN2SE2)][I]
Cd. Bryan et al., IODINE CHARGE-TRANSFER SALTS OF BENZENE-BRIDGED BIS(1,2,3,5-DISELENADIAZOLYL) DIRADICALS - ELECTROCRYSTALLIZATION AND SOLID-STATE CHARACTERIZATION OF 1,3-[(SE2N2C)C6H4(CN2SE2)][I] AND 1,4-[(SE2N2C)C6H4(CN2SE2)][I], Chemistry of materials, 8(3), 1996, pp. 762-768
Electroreduction of 1,3- and 1,4-benzene-bridged bis(diselenadiazolium
) salts [1,4-Se][SbF6](2) and [1,4-Se][SbF6](2) in acetonitrile, at a
Pt wire and in the presence of iodine affords the 1:1 charge-transfer
salts [1,4-Se][I] and [1,3-Se][I]. Crystals of [1,4-Se][I] belong to t
he monoclinic space group C2/m, with FW = 598.9, a = 10.586(2), b = 16
.713(2), c = 3.5006(14) Angstrom, beta = 104.26(2)degrees, V = 600.2(3
) Angstrom(3), Z = 2. Crystals of [1,3-Se][I] belong to the orthorhomb
ic space group Ima2, with FW = 598.9, a = 28.489(7), b = 3.543(2), c =
12.283(2) Angstrom, V = 1239.8(8) Angstrom(3), Z = 4. In the presence
of an excess of iodine, electrocrystallization of [1,4-Se](2+) afford
s the mixed iodide/triiodide salt [1,4-Se][I][I-3], space group C2/c,
FW = 979.59, a = 12.862(3), b = 15.063(2), c = 9.028(3) Angstrom, beta
= 100.62(2)degrees, V = 1719.1(7) Angstrom(3), Z = 4. The structures
of the two 1:1 compounds consist of perfectly superimposed stacks of m
olecular units interspersed by columns of disordered iodines. Intersta
ck contacts in both structures are limited, indicative of 1-dimensiona
l electronic structures. Variable-temperature single-crystal conductiv
ity measurements on [1,4-Se][I] reveal weakly metallic behavior at roo
m temperature, with a phase transition to a semiconducting state occur
ring at about 240 K. Magnetic susceptibility measurements on [1,4-Se][
I] are consistent with the conductivity data; the magnetic susceptibil
ity of [1,3-Se][I] behaves similarly. The crystal structures and trans
port properties are discussed in light of extended Huckel band structu
re calculations.