A compound of formula I D 1 -Z D -(A 1 -Z 1) r -B 1 -(Z 2 -A 2) s -Sp-G in which D 1 denotes a diamondoid radical, A 1, A 2 on each occurrence, identically or differently, denote an aromatic, heteroaromatic, alicyclic or heteroaliphatic ring having 4 to 25 ring atoms, which may also contain condensed rings and which may be mono- or polysubstituted by Y, Y on each occurrence, identically or differently, denotes F, CI, CN, SCN, SF 5 or straight-chain or branched, in each case optionally fluorinated alkyl, alkoxy, alkylcarbonyl, alkoxycarbonyl, alkylcarbonyloxy or alkoxycarbonyloxy having 1 to 12 C atoms, B1 denotes where the groups may be oriented in both directions, L 1 to L 5, independently of one another, denote F, CI, Br, I, CN, SF 5, CF 3 or OCF 3, preferably CI or F, where L 3 may alternatively also denote H, Z 1, Z 2 on each occurrence, identically or differently, denote a single bond, -CF 2 O-, -OCF 2 -, -CF 2 S-, -SCF 2 -, -CH 2 O-, -OCH 2 -, -C O-, -OC -, -C S-, -SC -, -(CH 2) n1 -, -(CF 2) n2 -, -CF 2 -CH 2 -, -CH 2 -CF 2 -, -CH=CH-, -CF=CF-, -CF=CH-, -CH=CF-, -(CH 2) n3 O-, -O(CH 2) n4 -, -C≡C-, -O-, -S-, -CH=N-, -N=CH-, -N=N-, -N=N -, -N =N- or -N=C-C=N-, n1, n2, n3, n4 identically or differently, are 1, 2, 3, 4, 5, 6, 7, 8, 9 or 10, Sp denotes a spacer group or a single bond, Z D has one of the meanings of Z 1 and Z 2 or of Sp, G denotes -CH=CH 2, -OH, -CH(CH 2 OH) 2, -C(CH 2 OH) 3, -SH, -SO 2 OH, -OP 2, -PO 2, -C (PO 2) 2, -COOH, -B 2, -Si(OR x) 3 or -SiCl 3, -SO 2 OR V, -OP (OR V) 2, -PO(OR V) 2, -C (PO(OR V) 2) 2,-COOR V, -Si(OR V) 3, R V denotes straight-chain or branched alkyl having 1 to 20 C atoms, R x denotes straight-chain or branched alkyl having 1 to 6 C atoms, and r and s, independently of one another, denote 0, 1, 2 or 3, where r + s ≤ 4, with the proviso that if Sp denotes a single bond, Z 2 is not O, S, CH 2 or CF 2. D 1 denotes a diamondoid radical, A 1, A 2 on each occurrence, identically or differently, denote an aromatic, heteroaromatic, alicyclic or heteroaliphatic ring having 4 to 25 ring atoms, which may also contain condensed rings and which may be mono- or polysubstituted by Y, Y on each occurrence, identically or differently, denotes F, CI, CN, SCN, SF 5 or straight-chain or branched, in each case optionally fluorinated alkyl, alkoxy, alkylcarbonyl, alkoxycarbonyl, alkylcarbonyloxy or alkoxycarbonyloxy having 1 to 12 C atoms, B1 denotes where the groups may be oriented in both directions, L 1 to L 5, independently of one another, denote F, CI, Br, I, CN, SF 5, CF 3 or OCF 3, preferably CI or F, where L 3 may alternatively also denote H, Z 1, Z 2 on each occurrence, identically or differently, denote a single bond, -CF 2 O-, -OCF 2 -, -CF 2 S-, -SCF 2 -, -CH 2 O-, -OCH 2 -, -C O-, -OC -, -C S-, -SC -, -(CH 2) n1 -, -(CF 2) n2 -, -CF 2 -CH 2 -, -CH 2 -CF 2 -, -CH=CH-, -CF=CF-, -CF=CH-, -CH=CF-, -(CH 2) n3 O-, -O(CH 2) n4 -, -C≡C-, -O-, -S-, -CH=N-, -N=CH-, -N=N-, -N=N -, -N =N- or -N=C-C=N-, n1, n2, n3, n4 identically or differently, are 1, 2, 3, 4, 5, 6, 7, 8, 9 or 10, Sp denotes a spacer group or a single bond, Z D has one of the meanings of Z 1 and Z 2 or of Sp, G denotes -CH=CH 2, -OH, -CH(CH 2 OH) 2, -C(CH 2 OH) 3, -SH, -SO 2 OH, -OP 2, -PO 2, -C (PO 2) 2, -COOH, -B 2, -Si(OR x) 3 or -SiCl 3, -SO 2 OR V, -OP (OR V) 2, -PO(OR V) 2, -C (PO(OR V) 2) 2,-COOR V, -Si(OR V) 3, R V denotes straight-chain or branched alkyl having 1 to 20 C atoms, R x denotes straight-chain or branched alkyl having 1 to 6 C atoms, and r and s, independently of one another, denote 0, 1, 2 or 3, where r + s ≤ 4,