Tuning the polarization along linear polyaromatic strands for rationally inducing mesomorphism in lanthanide nitrate complexes

Terazzi, Emmanuel; Guenee, Laure; Morgantini, Pierre-Yves; Bernardinelli, Gérald Hugues; Donnio, Bertrand; Guillon, Daniel; Piguet, Claude

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Title		Tuning the polarization along linear polyaromatic strands for rationally inducing mesomorphism in lanthanide nitrate complexes
Authors		Terazzi, Emmanuel Guenee, Laure Morgantini, Pierre-Yves Bernardinelli, Gérald Hugues Donnio, Bertrand Guillon, Daniel Piguet, Claude
Published in		Chemistry - A European Journal. 2007, vol. 13, no. 6, p. 1674-1691
Abstract		The opposite orientation of the ester spacers in the rodlike ligands L 4C12 (benzimidazole-OOC-phenyl) and L 5C12 (benzimidazole-COO-phenyl) drastically changes the electronic structure of the aromatic systems, without affecting their meridional tricoordination to trivalent lanthanides, Ln(III), and their thermotropic liquid crystalline (i.e., mesomorphic) behaviors. However, the rich mesomorphism exhibited by the complexes [Ln(L 4C12)(NO3)3] (Ln=La-Lu) vanishes in [Ln(L 5C12)(NO3)3], despite superimposable molecular structures and comparable photophysical properties. Density functional theory (DFT) and time-dependant DFT calculations performed in the gas phase show that the inversion of the ester spacers has considerable effects on the electronic structure and polarization of the aromatic groups along the strands, which control residual intermolecular interactions responsible for the formation of thermotropic liquid-crystalline phases. As a rule of thumb, an alternation of electron-poor and electron-rich aromatic rings favors intermolecular interactions between the rigid cores and consequently mesomorphism, a situation encountered for L 4C12, L 5C12, [Ln(L 4C12)(NO3)3], but not for [Ln(L 5C12)(NO3)3]. The intercalation of an additional electron-rich diphenol ring on going from [Ln(L 5C12)(NO3)3] to [Ln(L 6C12)(NO3)3] restores mesomorphism despite an unfavorable orientation of the ester spacers, in agreement with our simple predictive model.
Keywords		Electrostatic potentials — Intermolecular interactions — Lanthanides — Liquid crystals — Metallomesogens
Identifiers		DOI: 10.1002/chem.200601389 PMID: 17225230
Full text		Article (Published version) - Free access Other version: http://www3.interscience.wiley.com/cgi-bin/fulltext/114066314/PDFSTART
Structures		Faculté des sciences / Section de chimie et biochimie / Département de chimie minérale, analytique et appliquée Faculté des sciences / Section de chimie et biochimie / Département de chimie physique
Citation (ISO format)		TERAZZI, Emmanuel et al. Tuning the polarization along linear polyaromatic strands for rationally inducing mesomorphism in lanthanide nitrate complexes. In: Chemistry - A European Journal, 2007, vol. 13, n° 6, p. 1674-1691. https://archive-ouverte.unige.ch/unige:3599