Metallomesogens as Biaxial Dopants in a Calamitic Nematic Liquid Crystal H. Ayeb, F. Ciuchi, G. Lombardo, and R. Barberi CNR-INFM LiCryL, Cemif.Cal MiUR Excellence center, Physics Departments, University of Calabria, Rende, Italy The electric field induced nematic order reconstruction is a way to achieve controlled transitions between uniaxial nematic textures with different topologies, hence allow- ing intrinsic textural bistability. The order reconstruction connects perpendicular nematic director orientations by exchanging two eigenvalues of the nematic order tensor Q, implying intermediate transient biaxial order. This phenomenon avoids the full nematic melting; in fact the nematic scalar order parameter does not vanish. The Biaxial Order Reconstruction in a calamitic Nematic (BORN) is mainly gov- erned by the biaxial coherence length n b . Therefore, by varying n b , one can favour or inhibit the transient biaxial order. Recently, it has been demonstrated that n b can be controlled by suitable dopants and in this work we study the BORN tran- sition threshold for liquid crystal mixtures made of the commercial nematic liquid crystal E7 and three different metallomesogens with board-like shape. Recently, the high electric field induced Biaxial Order Reconstructions in Nematics (BORN) has been proposed as a new tool to achieve nematic textural changes with variable topology [1,2]. This fast transition has a threshold depending on the order and on the biaxial coherence length n b of the nematic material, which can be controlled by suitable dopants [3]. In this work, we study the electric BORN transition threshold for liquid crystal mixtures [4] of the commercial nematic liquid crystal E7 doped with three different complexes whose molecules have board-like shape, synthesized in the Chemistry Department of the University of Calabria. The BORN behaviour has been investigated by means of dynamical electro-optical observations [1,2]. The authors thank Mauro Ghedini and Daniela Pucci for materials synthesis and helpful discussion and Alfredo Pane for technical assistance. Address correspondence to R. Barberi, CNR-INFM LiCryL Cemif.Cal MiUR Excellence center, Physics Departments, University of Calabria, Rende, Italy. E-mail: barberi@fis.unical.it Mol. Cryst. Liq. Cryst., Vol. 481, pp. 73–79, 2008 Copyright # Taylor & Francis Group, LLC ISSN: 1542-1406 print=1563-5287 online DOI: 10.1080/15421400701834096 73