H. Allouchi et al., CRYSTAL-STRUCTURE OF A TETRACATENAR MESOGEN DERIVED FROM 3,4-DIALKOXYCINNAMIC ACID, Molecular crystals and liquid crystals science and technology. Section A, Molecular crystals and liquid crystals, 239, 1994, pp. 153-164
The crystal structure of a biforked mesogen, exhibiting nematic and sm
ectic phases, derived from 3,4-dialkyloxyphenyl cinnamic acid has been
determined by direct methods. The crystal belongs to the P-21/c space
group (Z = 4): a = 42.380(7), b = 9.605(2), c = 18.12(1) Angstrom, be
ta = 97.93(2)degrees. Least squares refinement leads to R = 0.091. The
molecules adopt a zig-zag form and the non-aliphatic central core is
almost linear, and 35 Angstrom long. The four alkyloxy chains are stre
tched (ttt). The mean axis of the alkyloxy chains makes an angle close
to 130 degrees with the central core. The molecules make sheets of ab
our 43 Angstrom thick and are arranged as in a smectic C mesophase. Th
e polyaromatic central core makes an angle close to 70 degrees (tilt a
ngle) with the normal to the sheet and is quasi-parallel to the (xz) p
lane. The interactions between the sheets are very weak. The structure
is compared to those of similar compounds whose structure has recentl
y been published.