TY - JOUR
T1 - 1,2-Di(phenylethynyl)ethenes with axially chiral, 2,2′-bridged 1,1′-binaphthyl substituents
T2 - Potent cholesteric liquid-crystal inducers
AU - Wu, Yi Lin
AU - Ferroni, Fiammetta
AU - Pieraccini, Silvia
AU - Schweizer, W. Bernd
AU - Frank, Brian B.
AU - Spada, Gian Piero
AU - Diederich, François
PY - 2012/10/21
Y1 - 2012/10/21
N2 - Axially chiral, 3,5-dihydro-4H-dinaphtho[2,1-c:1′,2′-e]azepine (dinaphthazepine) and 1,1′-binaphthyl-2,2′-disulfonimide (dinaphthosulfonimide) moieties were rigidly connected via N-p-phenylene linkers to photochemically (E)/(Z)-isomerisable 1,2-diethynylethene scaffolds. The chemical stability of the resulting systems was found to be critically related to the other substituents on the central π-conjugated scaffold. High helical twisting power (HTP), up to 315 μm-1, for the induction of a cholesteric liquid-crystalline phase through doping of a nematic phase was measured, resulting from the introduction of the chiral, mesogenic 1,1′-binaphthyl motifs. Single crystal X-ray analysis revealed that the phenylene spacer is in π-conjugation with the N-atom of the dinaphthazepine but not with the N-atom of the dinaphthosulfonimide moiety. This difference in orientation results in visible-transparency in the electronic absorption spectrum and higher (E)/(Z)-photoisomerisation quantum yields of the dinaphthosulfonimide-derived chiral dopants, as compared to the dinaphthazepine systems, which feature intramolecular charge-transfer absorption in the visible region.
AB - Axially chiral, 3,5-dihydro-4H-dinaphtho[2,1-c:1′,2′-e]azepine (dinaphthazepine) and 1,1′-binaphthyl-2,2′-disulfonimide (dinaphthosulfonimide) moieties were rigidly connected via N-p-phenylene linkers to photochemically (E)/(Z)-isomerisable 1,2-diethynylethene scaffolds. The chemical stability of the resulting systems was found to be critically related to the other substituents on the central π-conjugated scaffold. High helical twisting power (HTP), up to 315 μm-1, for the induction of a cholesteric liquid-crystalline phase through doping of a nematic phase was measured, resulting from the introduction of the chiral, mesogenic 1,1′-binaphthyl motifs. Single crystal X-ray analysis revealed that the phenylene spacer is in π-conjugation with the N-atom of the dinaphthazepine but not with the N-atom of the dinaphthosulfonimide moiety. This difference in orientation results in visible-transparency in the electronic absorption spectrum and higher (E)/(Z)-photoisomerisation quantum yields of the dinaphthosulfonimide-derived chiral dopants, as compared to the dinaphthazepine systems, which feature intramolecular charge-transfer absorption in the visible region.
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U2 - 10.1039/c2ob25983d
DO - 10.1039/c2ob25983d
M3 - Article
C2 - 22955910
AN - SCOPUS:84874964894
VL - 10
SP - 8016
EP - 8026
JO - Organic and Biomolecular Chemistry
JF - Organic and Biomolecular Chemistry
SN - 1477-0520
IS - 39
ER -