Use of chiral, uncharged metal compounds as dopants for...

Details Use of chiral, uncharged metal compounds as dopants for... Use of chiral, uncharged metal compounds as dopants for...

2001-12-11

2004-02-24

Wu, Shean C. (Department: 1756)

Compositions

Liquid crystal compositions

Containing nonchiral additive having no specified mesophase

C252S299200, C556S042000, C556S054000

Reexamination Certificate

active

06695977

ABSTRACT:

Use of chiral, uncharged metal compounds as dopants for liquid-crystalline materials
The present invention relates to the use of chiral, uncharged compounds of the general formula Ia
[(P
1
—Y
1
—A
1
—Y
2
—M
1
—Y
3
—)
n
L]
2
Me  (Ia)
or Ib
[(P
1
—Y
1
—A
1
—Y
2
—M
1
—Y
3
—)
n
L]Me(L′(—Y
6
—M
2
—Y
5
—A
2
—Y
4
—P
2
)
n′
)
m
  (Ib),
in which, independently of one another,
P
1
and P
2
are hydrogen, C
1
-C
12
-alkyl, a group which is polymerizable or suitable for polymerization, or a radical which carries a group which is polymerizable or suitable for polymerization,
Y
1
to Y
6
are a single chemical bond, —O—, —S—, —CO—, —CO—O—, —O—CO—, —CO—N(R)—, —(R)N—CO—, —O—CO—O—, —O—CO—N(R)—, —(R)N—CO—O— or —(R)N—CO—N(R)—,
R is hydrogen or C
1
-C
4
-alkyl,
A
1
and A
2
are spacers having from one to 30 carbon atoms,
M
1
and M
2
are mesogenic groups,
n′ and n are values of 0 or 1,
m is a value of 1, 2 or 3,
where the m L′(—Y
6
—M
2
—Y
5
—A
2
—Y
4
—P
2
)
n′
groups in the formula Ib may be different,
Me is a transition metal from the fourth, fifth or sixth period, with the exception of technetium, silver, cadmium, gold, mercury and the lanthanoids, or a main-group element from group 14 (in the IUPAC system), with the exception of carbon and lead,
L is a tridentate ligand of the formula II
in which
U, V and W are nitrogen-, oxygen-, phosphorus- or sulfur-containing groups which contain a nitrogen, oxygen, phosphorus or sulfur atom respectively having at least one free electron pair via which the coordination to the center Me takes place,
b
1
and b
2
are alkylene or alkenylene bridges having two or three carbon atoms which are bonded to the nitrogen, oxygen, phosphorus or sulfur atom of the groups U and V (for b
1
) or of the groups V and W (for b
2
) and which, in the case of a C
2
-alkenylene bridge, may be substituted by up to two, in the other cases by up to four organic radicals having up to 12 carbon atoms, and in which two adjacent carbon atoms in the alkylene or alkenylene bridge may be part of an unsubstituted or substituted, simple or benzo-fused benzene ring, and
L′ is an organic radical having up to 12 carbon atoms,
as dopants for liquid-crystalline materials.
The invention furthermore relates to compounds of the general formula IIIa
[(P
1
—Y
1
—A
1
—Y
2
—M
1
—Y
3
—)L]
2
Me  (IIIa)
and IIIb
[(P
1
—Y
1
—A
1
—Y
2
—M
1
—Y
3
—)L]Me(L′(—Y
6
—M
2
—Y
5
—A
2
—Y
4
—P
2
)
n′
)
m
  (IIIb),
where the variables P
1
, P
2
, Y
1
to Y
6
, A
1
, A
2
, M
1
, M
2
, n′, m, Me, L and L′ are as already defined above.
Cholesteric liquid-crystal mixtures are usually prepared using a liquid-crystalline (nematic) base material and one or more optically active dopants. This enables the optical properties of the mixture to be varied by simply changing the ratio of liquid-crystalline base material to dopant.
Although chiral dopants for liquid-crystalline phases are known in large number from the scientific and patent literature, relatively little is known on the use of chiral, uncharged metal compounds as dopants for liquid-crystalline materials.
The phase behavior of chiral copper (II), nickel (II), oxovanadium (IV) and palladium (II) complexes of 4-(4-heptyloxybenzoyloxy)-N-(S)-2-methylbutylsalicylaldehyde, in which the central ion is tetracoordinated, has been investigated by W. Pyzuk and Yu. Galyametdinov in Liquid Crystals, 1993, Vol. 15, No. 2, pp. 265-268. The salicylaldehyde derivative here functions as bidentate ligand, via which the oxygen atom of the deprotonated hydroxyl group and the nitrogen atom of the Schiff's base of the aldehyde group are coordinated.
J. Buey et al. in Chem. Commun., 1999, pp. 441-442, have described the phase behavior of a monocyclic and of a bicyclic chiral palladium (II) complex and of mixtures of these complexes with a nematic host material. The palladium atoms are in each case tetracoordinated; in the monocyclic complex, the coordination of the two different bidentate ligands takes place via a carbon atom and a nitrogen atom or via an oxygen atom and a nitrogen atom. In the bicyclic complex, the palladium centers are linked to one another via a sulfur bridge and a carboxyl bridge, with the other coordinations to the palladium centers in each case being formed via a carbon atom and a nitrogen atom of two identical ligands.
G. Piao et al. in Synthetic Metals, 101, 1999, pp. 92-93, have described the polymerization of acetylene in the presence of a catalyst comprising a chiral titanium compound and triethylaluminum. One of the titanium compounds investigated is a titanium complex in which the metal center is tetracoordinated to two axial-chiral, bidentate (R)- or (S)-6,6′-di(4-(trans-4-n-pentylcyclohexyl)phenoxy-1-hexyl)-2,2′-dihydroxy-1,1′-binaphthyl ligands via the oxygen atoms of the deprotonated hydroxyl groups. The (R)- or (S)-titanium tetrakis(2-octanolate) was investigated as a further titanium compound. In addition, the preparation of chiral nematic phases by mixing the titanium compounds with liquid-crystalline materials is also mentioned.
Investigations by A. F. Drake et al. On the helical twisting power of trisacetylacetonate (“pentane-2,4-dionato”) complexes of trivalent cobalt, chromium, ruthenium, iridium and rhodium in liquid-crystalline materials are described in Chem. Phys. Letters, Vol. 110 (6), 1984, pp. 630-633. The central ions of the complex are hexacoordinated via the oxygen atoms of the three bidentate acetylacetonate ligands in each case. Only the type of coordination of the achiral ligands to the central atom provides the metal acetylacetonates described with chirality, which differentiates these compounds from those mentioned previously in which the ligands are themselves already chiral.
It is an object of the present invention to provide further chiral metal compounds which are suitable as dopants for liquid-crystalline materials.
We have found that this object is achieved by the compounds of the formulae IIIa and IIIb described at the outset and by the use of the compounds of the formulae Ia and Ib described at the outset.
The invention covers chiral metal compounds whose chirality is caused by chiral ligands L/L′ and by the spatial arrangement of achiral ligands L/L′ around the Me center.
The following comments regarding the meanings of the variables P
1
, Y
1
to Y
3
, A
1
and M
1
in the compound Ia, the variants P
1
, P
2
, Y
1
to Y
6
, A
1
, A
2
, M
1
and M
2
in the compound Ib and the variables P
2
, Y
4
to Y
6
, A
2
and M
2
in the compound IIIb are of course only of relevance if the variables n or n and n′ or n′ respectively in the corresponding formulae adopt the value 1.
Possible spacers A
1
or A
1
and A
2
in the compounds Ia, Ib, IIIa and IIIb are all groups known to the person skilled in the art for this purpose. In general, the spacers contain from one to 30, preferably from one to 12, particularly preferably from one to six, carbon atoms and consist predominantly of linear aliphatic groups. They may be interrupted in the chain, for example by non-adjacent oxygen or sulfur atoms or imino or alkylimino groups, for example methylimino groups. Possible substituents for the spacer chain are also fluorine, chlorine, bromine, cyano, methyl and ethyl.
Examples of representative spacers are the following:
where u is from 1 to 30, preferably from 1 to 12, v is from 1 to 14, preferably from 1 to 5, and w is from 1 to 9, preferably from 1 to 3.
Preferred spacers are ethylene, propylene, n-butylene, n-pentylene and n-hexylene.
The mesogenic groups M
1
or M
1
and M
2
used in the compounds Ia, Ib, IIIa and IIIb can be all groups which are suitable as such to the person skilled in the art.
Particularly suitable are mesogenic groups having the general structure IV
(—T—Y
7
)
r
—T—  (IV)
where the variables have the following meanings:
T is a divalent, saturated or unsaturated carbocyclic or heterocyclic radical,
Y
7
is a chemical b

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