To prepare chiral metallo-mesogens with ferroelectric properties, new azobenzene compounds, HLN(n), bearing a chiral substituent have been synthesized. These ligands consist of two aliphatic chains of variable length, one of which contains a stereogenic center located in the para and para′ positions of an azobenzene core. The chiral groups (R*O) are as follows: N = 1, (R)-(-)-menthol; N = 2, (S)-(-)-β-citronellol, and N = 3, (R)-(-)-2-octanol; the aliphatic chains are linear n-alkoxy groups CnH2n+1O (n = 7, 10, 12, 14). Only the HL2(n) species display liquid-crystalline properties giving cholesteric or smectic A mesophases. The HLN(n) ligands react with [Pd(PhCN)2Cl2], to give the corresponding chloro-bridged dinuclear cyclopalladated products {Pd[LN(n)](μ-Cl)}2 as 1:1 mixtures of isomers arising from the nonselective attack of the palladium on the benzene ring bearing the chiral alkoxy group or on the benzene with the aliphatic alkoxy chain. The (Pd[L2(n)](μ-Cl)}2 compounds and the (Pd[L3(n)](μ-Cl)}2 (n = 10, 12, 14) exhibit smectic mesophases (Sc* in {Pd[L2(7)] (μ-Cl)}2, {Pd[L2(10)](μ-Cl)}2, {Pd[L3(10)](μ-Cl)}2, and {Pd[L3-(14)](μ-Cl)}2,SA in {Pd[L2(12)] (μ-Cl)}2, {Pd[L2(14)](μ-Cl)}2, {Pd[L3(12)]μ-Cl)}2). The Pd[LN(n)]-(μ-Cl)}2 compounds have been converted into the corresponding iodo analogues {Pd[LN(n)] (μ-I)}2. The chloro complexes display a richer mesomorphism than the respective iodo compounds.

Transition metals complexed to ordered mesophases. Synthesis, characterization, and mesomorphic properties of new potentially ferroelectric liquid crystals: chiral p,p'-dialkoxyazobenzenes and their cyclopalladated dinuclear complexes / E.Cesarotti, D.Pucci, M.Ghedini. - In: CHEMISTRY OF MATERIALS. - ISSN 0897-4756. - 1993:6(1993), pp. 883-890. [10.1021/cm00030a027]

Transition metals complexed to ordered mesophases. Synthesis, characterization, and mesomorphic properties of new potentially ferroelectric liquid crystals: chiral p,p'-dialkoxyazobenzenes and their cyclopalladated dinuclear complexes

E. Cesarotti
Primo
;
1993

Abstract

To prepare chiral metallo-mesogens with ferroelectric properties, new azobenzene compounds, HLN(n), bearing a chiral substituent have been synthesized. These ligands consist of two aliphatic chains of variable length, one of which contains a stereogenic center located in the para and para′ positions of an azobenzene core. The chiral groups (R*O) are as follows: N = 1, (R)-(-)-menthol; N = 2, (S)-(-)-β-citronellol, and N = 3, (R)-(-)-2-octanol; the aliphatic chains are linear n-alkoxy groups CnH2n+1O (n = 7, 10, 12, 14). Only the HL2(n) species display liquid-crystalline properties giving cholesteric or smectic A mesophases. The HLN(n) ligands react with [Pd(PhCN)2Cl2], to give the corresponding chloro-bridged dinuclear cyclopalladated products {Pd[LN(n)](μ-Cl)}2 as 1:1 mixtures of isomers arising from the nonselective attack of the palladium on the benzene ring bearing the chiral alkoxy group or on the benzene with the aliphatic alkoxy chain. The (Pd[L2(n)](μ-Cl)}2 compounds and the (Pd[L3(n)](μ-Cl)}2 (n = 10, 12, 14) exhibit smectic mesophases (Sc* in {Pd[L2(7)] (μ-Cl)}2, {Pd[L2(10)](μ-Cl)}2, {Pd[L3(10)](μ-Cl)}2, and {Pd[L3-(14)](μ-Cl)}2,SA in {Pd[L2(12)] (μ-Cl)}2, {Pd[L2(14)](μ-Cl)}2, {Pd[L3(12)]μ-Cl)}2). The Pd[LN(n)]-(μ-Cl)}2 compounds have been converted into the corresponding iodo analogues {Pd[LN(n)] (μ-I)}2. The chloro complexes display a richer mesomorphism than the respective iodo compounds.
Settore CHIM/03 - Chimica Generale e Inorganica
1993
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/2434/185969
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