Thermotropic Mesomorphism in Salen-like Zinc Complexes

Abstract

The reaction between a series of non mesogenic tetradentate salen-like Schiff bases and Zn(II) acetate gives rise to the formation of liquid cristalline complexes showing nematic and smectic phases stable over a quite large temperature range. A dimeric structural arrangement could favour the appearance of such type of mesophase in the case of 1,3-diaminopropane and 1,3-diamino-2,2-dimethylpropane bridges containing ligands while for the salen derivatives a monomeric solvent-induced pentacoordinated arrengement observed in solution and in the crystalline molecular structure, probably prevent the liquid crystalline behaviour.

Keywords:

• metallomesogens
• salen-like Schiff bases
• zinc complexes

Acknowledgments

This research was supported by the Italian Ministero dell'Istruzione, dell'Università e della Ricerca (MIUR) through the Centro di Eccellenza CEMIF.CAL. We wish to thank Dr. Giovanna Callipari (Università della Calabria) for ¹H NMR spectra.

Notes

^a C: crystal; Sm: smectic; N: nematic; I: isotropic liquid; dec; decomposition.

^b From optical microscopy.