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In order to investigate the relationships between crystal structures and electronic properties of -type BEDT-TTF organic conductors, electrical properties of -(BEDT-TTF) 2 Ag(CN) 2 and -(BEDT-TTF) 2 CsZn(SCN) 4 and crystal structures of -(BEDT-TTF) 2 CsZn(SCN) 4 under uniaxial strain are investigated. The resistivity measurements for both salts under uniaxial strain show that the intercolumnar uniaxial strain preserves the metallic nature while the intra-columnar one induces an insulating behavior, which are reminiscent of the charge-ordered state of -(BEDT-TTF) 2 RbZn(SCN) 4 . Structure analyses of -(BEDT-TTF) 2 CsZn(SCN) 4 under uniaxial strain indicate that the inter-columnar strain slightly increases the diagonal transfer integral but does not vary the vertical one, and the intra-columnar uniaxial strain largely increases the vertical transfer integral but does not change the diagonal one. Based on these experimental results, the key parameters to determine the electrical properties of -type BEDT-TTF salts are discussed. It is suggested that the transfer integral along the intra-columnar direction dominates the occurence of the charge-ordered state.

Single-crystal X-ray structure analyses and the measurements of static magnetic susceptibility and ESR have been performed for the title compounds. Crystal data:  for Cu[C(CN)3]2, space group Pmna, a = 7.212(5) Å, b = 5.452(7) Å, c = 10.696(7) Å, and Z = 2; for Mn[C(CN)3]2, space group Pmna, a = 7.742(5) Å, b = 5.411(6) Å, c = 10.561(6) Å, and Z = 2. Both salts are essentially isostructural. The Cu atoms are bridged by two [C(CN)3]- anions to form an infinite double chain structure, in which Cu has a square planar coordination (d Cu - N = 1.986(6) Å). The third CN end of the anion is weakly coordinated to the adjacent Cu chain (d Cu - N = 2.47(1) Å), making a three-dimensional network. The crystal is composed of two such interwoven networks. In the Mn complex, the third Mn−N distance (2.256(6) Å) is as short as the equatorial coordinations (2.236(4) Å), so that Mn is coordinated octahedrally. These compounds exhibit paramagnetic behavior following the Curie−Weiss law with Weiss temperatures −1.4 and −9 K, respectively, and the Mn complex undergoes an antiferromagnetic transition at T N = 5 K.

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