1,1′‐Disubstituted Ferrocene‐Containing Thermotropic Liquid Crystals of structure [Fe{(η⁵‐C₅H₄)COOC₆H₄XC₆H₄OC_nH_2n+1}₂] (X  OOC or COO). Influence of the orientation of the central ester function on the mesogenic properties

Abstract

The two series I and 11 of 1,l'-disubstituted ferrocenes which differ by the direction of the ester function included in the rigid organic part were synthesized and their liquid crystal properties examined. These latter were found to be strongly dependent on the orientation of the connecting ester group and on the alkyl chain length.Introduction. -Much interest is currently devoted to metallomesogens [ 11. First, these compounds, which combine the properties of liquid crystals and the characteristics of metals, have allowed fundamental studies at the interface of chemistry, physics, molecular electronics, and material science. New technologies could emerge from this interdisciplinary field of research. Secondly, a specific arrangement of organic frameworks around a metallic core opens the way to new geometries and new topologies, in comparison with purely organic liquid crystals, thus allowing to explore more deeply the relationship between structure and mesogenic properties.Most of the metallomesogens studied so far are coordination complexes built up from one or two transition-metal centers coordinated to monodentate or chelating ligands. Mononuclear Ni, Cu [7] complexes containing liquid crystals were reported and generated much enthusiasm. Much less attention was devoted to organotransition metallomesogens. Monosubstituted [S] and 1, 1'-disubstituted [9] ferrocene-containing liquid crystals were reported, and the first family of mesogenic (butadiene)iron-tricarbonyl derivatives was recently described [lo].Ferrocene-containing liquid crystals are interesting for three major reasons: i) they have a high thermal stability, giving rise to reversible transitions without decomposition, ii) they are soluble in common organic solvents, making their characterization straightforward, and iii) their three-dimensional structure offers multiple possibilities for the design of substituted derivatives. These properties prompted us to undertake a systematic study to exploit the ferrocene as a valuable organometallic unit to be incorporated into mesogenic materials.Recently, we reported the first 1,3-disubstituted ferrocene-containing metallomesogens and showed, by comparison of their mesomorphic properties with those of the

The effect of fluorinated terminal chains on the mesomorphic properties of 4,4′‐disubstituted phenyl benzoates

“…As we found for the corresponding alkynyl chain esters [5], a better approach is first to prepare a protected phenol ester 23, then remove the protecting group to obtain the phenol and esterify this with the fluorinated acid chloride to obtain the esters 25 (scheme 5). We found that the final products were easier to purify and yields were higher, despite the addition of two steps, confirming the reports of others [20]. With the fluorinated esters 25, the yields appeared to be higher when the phenol 24 was added to the acid chloride rather than the reverse sequence.…”

Non-symmetrical bent-shaped liquid crystals based on a laterally substituted naphthalene central core with four ester groups

“…Syntheses of the central cores, their O-benzyl protected acid 1, 2, and tert-butyldimethylsilyl protected acid 3, and the lengthening arms of the alkoxyphenyl 4-hydroxybenzoates (4a,b,d,e) (a octyl, b decyl, d dodecyl and e tetradecyl), and 4-[(4-alkoxybenzoyl)oxy]benzoic acids (7a-e) (a octyl, b decyl, c undec-10-enyl, d dodecyl and e tetradecyl) were published recently [17,[25][26][27]. The target bent-shaped LCs (series I-III) were obtained in a three-step sequence (Scheme 1): the acids 1-3 were esterified with the corresponding phenol 4 in the presence of N,N -dicyclohexylcarbodiimide (DCC) and dimethylaminopyridine (DMAP) to form esters of general formula 5.…”

The effect on mesomorphic properties of a triple bond in a terminal chain of 4,4′‐disubstituted phenyl benzoates and phenyl thiobenzoates

“…The synthesis for the esters 6 is presented in scheme 3 Obviously, the easiest approach to the desired phenol 36 would be a simple acylation of hydroquinone with one equivalent of the alkynyl acid chloride which was widely used earlier [16][17][18] More recent results indicate that acylation of a monoprotected hydroquinone is more effective [19]. In our experience, using only one equivalent of a reactant to obtain reaction on only one of two equally (or nearly so) reactive functional groups produces primarily the mono-product, but it is contaminated with small amounts of byproduct, starting material and some unknown higher molecular mass (polymer?)…”