Disclosed are compounds of formula (V), wherein R2 and R7, independently of each other, are H, C1-C4 alkyl, C1-C4 alkoxy, C7-C12 aralkyl, C6-C16 aryl or halogen; R3 and R6, independently of each other, are H, C1-C4 alkyl, C7-C12 aralkyl or C6-C16 aryl; R4 is H, C1-C20 alkyl, C5-C8 cycloalkyl, C6-C12 aryl or C7-C12 aralkyl, the alkyl, cycloalkyl, aralkyl and aryl radicals being unsubstituted or substituted with C1-C4 alkoxy, F, Cl, Br, -CN, C1-C4 alkyl or -NO2; Me is a lanthanide metal or yttrium; Y is an anion of an acid; n stands for 2 or 3 and m is 1, 2 or 3; R9 is a radical of formula (VI) -Xp-A-X'q-A'r-Oligo, and R8 is H, C1-C4 alkyl, C1-C4 alkoxy, C7-C12 aralkyl, C6-C16 aryl, or R9 is H, C1-C4 alkyl, C1-C4 alkoxy, C7-C12 aralkyl, C6-C16 aryl and R8 is a radical of formula (VI); p, q and r, independently of one another, are 0 or 1; X and X', independently of each other, are a radical unsubstituted or substituted by C1-C4 alkoxy, F, Cl, Br, -CN, C1-C4 alkyl or -NO2 substituted radical selected from the group consisting of C1-C20 alkylene, C2-C12 alkenylene, C2-C12 alkinylene, -(CxH2xO)y-, wherein x equals a number from 2 to 6 and y equals a number from 1 to 20, C5-C8 cycloalkylene, C6-C12 arylene and C7-C12 aralkylene; A and A', independently of each other, are -O-, -S-, -S-S-, -NR12-CO-NR12-CO-NR12-, -NR12-CS-NR12-, -NR12-, -NR12-C(O)-O-, -C(O)O-, -C(O)S-, -C(O)NR12-, -C(S)S-, -C(S)O-, -C(S)NR12-, -SO2NR12-, -SO2-, -P(O)(OH)O-, P(S)(SH)S-, -P(S)(SH)O-, -P(S)(OH)O-, -P(O)(SH)S-, -P(O)(OH)S-, -P(O)(SH)O-, -P(O)(OH)-NR12-, -P(S)(SH)-NR12-, -P(S)(OH)-NR12-, -P(O)(SH)-NR12-, -HP(O)O-, -HP(S)S-, -HP(O)NR12- or -HP(S)NR12-, R12 being H or C1-C6 alkyl; and oligo is a natural, modified or synthetic sequence of natural, modified or synthetic deoxynucleosides or peptide nucleic acid units which are bonded via a nucleic base, an internucleotide bridge or a sugar and whose inner region is complementary to a target RNA.