1,3-Disubstituted Ferrocene-Containing Thermotropic Liquid Crystals: Synthesis, Mesomorphic Properties and the Crystal and Molecular Structure

Deschenaux, Robert; Kosztics, Isabelle; Marendaz, Jean-Luc; Stœckli-Evans, Helen

doi:10.2533/chimia.1993.206

Cited by 47 publications

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Synthesis of Soluble 1,3-Bridged Ferrocene-Acetylene Polymers and the Divergent-Convergent Synthesis of Defined Oligomers

Plenio

Hermann

Leukel

1998

Eur. J. Inorg. Chem.

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A –CH2NMe2 group attached to ferrocene can be used as an ortho/ortho‐directing group to selectively synthesize 1,2,3‐substituted ferrocenes, which are used as starting materials for novel 1,3‐linked ferrocene polymers and oligomers. The Sonogashira coupling reaction of 1‐(I),2‐(CH2NMe2)‐ferrocene with HC≡CSiEt3 results in 1‐(C≡CSiEt3),2‐(CH2NMe2)‐ferrocene (1b), which – following an ortho‐lithiation/iodination sequence – is converted into 1‐(I),2‐(CH2NMe2),3‐(C≡CSiEt3)‐ferrocene (1d). Removal of the –SiEt3 protective group yields 1‐(I),2‐(CH2NMe2),3‐(C≡CH)‐ferrocene, which can be polymerized under Sonogashira conditions to yield a soluble, bimodal ferrocene‐acetylene polymer of MW = 3700/7100 and Mn = 4272. To understand the properties of the polymer better and to evaluate the effect of 1,3‐substitution on the electronic communication between the metal centers, a divergent‐convergent approach was used to synthesize defined di‐, tri‐ and tetranuclear ferrocenes. Accordingly, 1d was cross‐coupled with 1‐(CH2NMe2),2‐(C≡CH)‐ferrocene to give [2‐(CH2NMe2)‐ferrocene‐1‐yl]‐C≡C‐[2‐(CH2NMe2),3‐(C≡CSiEt3)‐ferrocene‐1‐yl] (2a). Removal of the protective group in 2a led to [2‐(CH2NMe2)‐ferrocene‐1‐yl]‐C≡C‐[2‐(CH2NMe2),3‐(C≡CH)‐ferrocene‐1‐yl] (2b), which was treated with [1‐(I),2‐(CH2NMe2)ferrocene‐3‐yl]‐C≡C‐[2‐(CH2NMe2),3‐(C≡CSiEt3)‐ferrocene‐1‐yl] (2c) to result in the corresponding tetrameric ferrocene (4a).

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Synthesis of Soluble 1,3-Bridged Ferrocene-Acetylene Polymers and the Divergent-Convergent Synthesis of Defined Oligomers

Plenio

Hermann

Leukel

1998

Eur. J. Inorg. Chem.

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Thermotropic Liquid Crystals from Planar Chiral Compounds: [2.2]Paracyclophane as a Mesogen Core

Rozenberg

Popova

Hopf

2002

HCA

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New thermotropic mesomorphic compounds containing a [2.2]paracyclophane (PC) unit were synthesized and investigated (Scheme). Carboxylic acids were selected as the starting PC building blocks. The influence of structural features on the stability of the mesomorphic phases was studied (Figs. 1 and 2): for this purpose, the structures of the PC-carboxylate unit and the organic fragment of the aryl-ester moiety were varied systematically. Esters derived from PC-monocarboxylic acid did not exhibit liquid-crystalline (LC) properties, while diaryl PC-dicarboxylates favored mesomorphism. Dicarboxylate substituents arranged in the paraposition provided LC phases in a broad temperature range and considerably increased the mesomorphic interval in comparison with that of the structurally related pseudo-para PC derivatives.Introduction. ± Unique physical properties, providing wide application in electrooptic devices and particularly the recent discovery of new mesophases, such as antiferroelectric, ferrielectric, and twist-grain boundary phases, have put chiral liquidcrystalline (LC) materials in the centre of liquid-crystal research [1] [2]. Historically, up to now, most chiral LC compounds contain molecules incorporating a centre of chirality. More recently, compounds with planar and axial chirality are beginning to attract the growing interest of researchers dealing with LC materials. The unique geometry of this type of compounds provides a rigid interaction between the origin of the symmetry-breaking chirality and the mesogenic unit, thus resulting in a definite fixation of the source of chirality in a LC matrix.In principle, planar chirality could drastically change the physical properties of the resultant LC material: 1) In terms of molecular structure, a rigid steric coupling between the transverse dipole, chiral centre, and the mesogen rod should maximize the local ferroelectric polarization [3], allowing consideration of the above compounds as possible chiral dopants for ferroelectric compositions, which are able to confer a high value of spontaneous polarization (P s ) to the achiral host [4]. 2) Electro-optical effects exhibited by LC materials such as electroclinic effects or nonlinear optical (NLO) properties are expected to be larger for compounds with rigid interaction between the chiral and optical portions of the molecule [5].However, the bulkiness of the structural units necessary to realize an axis or a plane of chirality significantly disturbs the desired rigid rod-like shape of the molecule, thus creating a serious obstacle to achieving stable mesomorphic properties. So far, only a

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Low Molecular Weight Calamitic Metallomesogens

Serrano¹,

Sierra²

1995

Metallomesogens

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1,3-Disubstituted Ferrocene-Containing Thermotropic Liquid Crystals: Synthesis, Mesomorphic Properties and the Crystal and Molecular Structure

Cited by 47 publications

References 0 publications

Synthesis of Soluble 1,3-Bridged Ferrocene-Acetylene Polymers and the Divergent-Convergent Synthesis of Defined Oligomers

Synthesis of Soluble 1,3-Bridged Ferrocene-Acetylene Polymers and the Divergent-Convergent Synthesis of Defined Oligomers

Thermotropic Liquid Crystals from Planar Chiral Compounds: [2.2]Paracyclophane as a Mesogen Core

Low Molecular Weight Calamitic Metallomesogens

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