Bimesogenic compounds and mesogenic media

Bimesogenic compounds of formula I

• wherein
• R11 and R12 are each independently H, F, Cl, CN, NCS or a straight-chain or branched alkyl group with 1 to 25 C atoms which may be unsubstituted, mono- or polysubstituted by halogen or CN, it being also possible for one or more non-adjacent CH2 groups to be replaced, in each occurrence independently from one another, by —O—, —S—, —NH—, —N(CH3)—, —CO—, —COO—, —OCO—, —O—CO—O—, —S—CO—, —CO—S—, —CH═CH—, —CH═CF—, —CF═CF— or —C≡C— in such a manner that oxygen atoms are not linked directly to one another, preferably a polar group, more preferably F, Cl, CN, OCF3, CF3,
• MG11 and MG12 are each independently a mesogenic group and
• at least one of
• MG11 and MG12 each comprises one, two or more 6-atomic rings, and
• Sp1 is a spacer group comprising 1, 3 or 5 to 40 C atoms, wherein one or more non-adjacent groups may also be replaced by —O—, —S—, —NH—, —N(CH3)—, —CO—, —O—CO—, —S—CO—, —O—COO—, —CO—S—, —CO—O—, —CH(halogen)-, —CH(CN)—, —CH═CH— or —C≡C—, however in such a way that no two O-atoms are adjacent to one another, now two —CH═CH— groups are adjacent to each other and no two groups selected from —O—CO—, —S—CO—, —O—COO—, —CO—S—, —CO—O— and —CH═CH— are adjacent to each other,
• X11 is a group selected from —CO—S—, —S—CO—, —CS—S—, —S—CS—, —CS—O—, —O—CS—, —S—CO—S—, —S—CS—S— and —S—,
• X12 independently from X11 has one of the meanings given for X11 or is a group selected from —CO—O—, —O—CO—, —CH═CH—, —C≡C— and —O— or a single bond,
• however under the condition that in —X11—Sp1-X12— no two O atoms are adjacent to one another, no two —CH═CH— groups are adjacent to each other and no two groups selected from —O—CO—, —S—CO—, —O—COO—, —CO—S—, —CO—O— and —CH═CH— are adjacent to each other.