On the Crystal Structure of the Organic Charge-Transfer Salt Derived from Hexamethylenetetraselenafulvalene (HMTSF) and Tetrafluoro-7,7,8,8- Tetracyano-p-Quinodimethane (TCNQF4), HMTSF-TCNQF4

Abstract

The charge-transfer salt HMTSF-TCNQF4 crystallizes in the monoclinic system, space group C2/m, with the following crystal data: a = 21.906(5) Å, b = 12.918(3) Å, c = 4.018(1) Å, β = 91.66(1)°, V = 1136.5 ų Z = 2, D _cale, = 2.186 g cm⁻³ D_cale,= 2.17(2) g cm⁻³. A structural model was readily deduced from standard Patterson-Fourier methods and has been refined (based on 1175 counter-collected X-ray data) to an R value of 0.048. The crystalline motif is dominated by uniform, segregated stacks of donors and acceptors. Within each stack, the molecular overlap pattem is of the ring-over-bond type and the mean interplanar separations are 3.68 Å (donor column) and 3.24 Å (acceptor column). Principal intercolumn contacts are of two types: Se(donor) … F(acceptor) at 3.19 Å and Se(donor) … N(acceptor) at 3.36 Å. Comparisons are made between the crystal structure and physical properties of HMTSF-TCNQF4 and HMTSF-TCNQ (to which it is isostructural) and to those of HMTTF-TCNQ and HMTTF-TCNQF4 (to which it is closely related).