Electrical, magnetic, and structural characterisation of [1,2-Bis(1-ethyl-4-pyridinium)ethane]2+ (7,7,8,8-tetracyano-p-quinodimethanide)42−

Abstract

The 1:4 complex salt, [1,2‐bis(1‐ethyl–4‐pyridinium)ethane]2+(7,7,8,8‐tetracyano‐pquinodime‐thanide) 42−, (DEPA) (TCNQ)4, is monoclinic, space group P2J/c, with a = 15.21(1), b = 25.97(2), c = 7.77(1) Å, β = 116.3(1)°, U = 2751 Å3, Dm = 1.30 Mg m−3, Z = 2, Dc = 1.28 Mg m−3. The structure is solved by direct methods and refined to a final R of 0.065 for 2036 observed reflections. The mean lengths of the chemically similar bonds of the TCNQ moieties indicate partial electron localisation with 0.3e on TCNQ(A) and 0.6e on TCNQ(B). (DEPA) (TCNQ)4 is a small band gap semiconductor. Along b, the electrical conductivity varies as σ = σ0 exp (−Ea/kT) where σ300K = 1 × 10−3 S cm−1 end Ea = 0.29(4) eV above 300 K and 0.20(2) eV below. The magnetic susceptibility shows singlet‐triplet behaviour with a singlet‐triplet separation of 0.017 eV.

Semiconductive 2D arrays of pancake-bonded oligomers of partially charged TCNQ radicals

“…There are also tetramers, usually composed of TCNQ À moieties with a formal charge of À1/2 [therefore, a tetramer has a charge of À2, implying paired spins (Ashwell & Nowell, 1984;Ashwell & Wallwork, 1985;Rindorf et al, 1988;Takagi et al, 1994;Malatesta et al, 1995)]. These tetramers can stack, forming 1D (Ashwell et al, 1977c,d;Filhol et al, 1980;Filhol & Thomas, 1984;U ¨ngo ¨r et al, 2021b) or 2D arrays (Kubota et al, 2014).…”

Structural and Physical Properties of a Series of 7,7,8,8-Tetracyanoquinodimethane Salts with Dications Bearing Two Terminal Pyridinium Rings

“…In the 1970s and 1980s, Ashwell investigated similar (dication)­(TCNQ) x series using dipyridinium salts, as indicated in Scheme . − The most remarkable salt among those studied is (DEPE)­(TCNQ) 4 (DEPE = 1,2-di­( N -ethyl-4-pyridinium)­ethylene). The conductivity of (DEPE)­(TCNQ) 4 is 150–2200 S cm –1 at room temperature, and it shows metallic behavior down to 30 mK .…”