A compound of the following formula: or a pharmaceutically acceptable salt or solvate thereof, a stereoisomer or a mixture of stereoisomers in any ratio, in particular a mixture of enantiomers, and more particularly a racemic mixture, or a water-soluble derivative, in which: - M is Fe, Ru or Os, - n is an integer comprised between 1 and 8, notably between 2 and 6, - R1 and R2 are, independently from each other, H, CF 3, CN, OR 4 or NR 5 R 6, and - R3 is CO 2 R 7, OR 8 or NR 9 R 10, wherein: - R 4 is H, (C 1 -C 6)alkyl, -CO-(C 1 -C 6)alkyl or -(CH 2) m NR 11 R 12, - R 5, R 6, R 11 and R 12 are, independently from one another, H, (C 1 -C 6)alkyl or -CO-(C 1 -C 6)alkyl, - R 7 is H or (C 1 -C 6)alkyl, - R 8 is H, (C 1 -C 6)alkyl or -CO-(C 1 -C 6)alkyl, - R 9 and R 10 are, independently from one another, H, (C 1 -C 6)alkyl or -CO-(C 1 -C 6)alkyl, or R 9 and R 10 form together with the nitrogen atom bearing them a cycle of the following formula: in which: ∘ ----- represents a single or double bond, ∘ X1 and X2 are, independently from one another, C=O, SO 2 CH-OR 19, CH-SR 20, CH-NR 21 R 22 or CH-NHC R 23, ∘ R 13 and R 14 are, independently from one another, H or (C 1 -C 6)alkyl, or R 13 and R 14 form together with the carbon atoms bearing them a 5- or 6-membered hydrocarbon cycle, ∘ R 19, R 20, R 21 and R 22 are, independently from one another, H or (C 1 -C 6)alkyl, and ∘ R 23 is a (C 1 -C 6)alkyl group, and - m is an integer comprised between 1 and 8, wherein a water-soluble derivative of a compound of formula is a compound of formula in which at least one of R1, R2 and R3 represents an ester, a saccharidic moiety or a water-soluble polymer moiety bound to the rest of the molecule by means of an oxygen atom. - M is Fe, Ru or Os, - n is an integer comprised between 1 and 8, notably between 2 and 6, - R1 and R2 are, independently from each other, H, CF 3, CN, OR 4 or NR 5 R 6, and - R3 is CO 2 R 7, OR 8 or NR 9 R 10, - R 4 is H, (C 1 -C 6)alkyl, -CO-(C 1 -C 6)alkyl or -(CH 2) m NR 11 R 12, - R 5, R 6, R 11 and R 12 are, independently from one another, H, (C 1 -C 6)alkyl or -CO-(C 1 -C 6)alkyl, - R 7 is H or (C 1 -C 6)alkyl, - R 8 is H, (C 1 -C 6)alkyl or -CO-(C 1 -C 6)alkyl, - R 9 and R 10 are, independently from one another, H, (C 1 -C 6)alkyl or -CO-(C 1 -C 6)alkyl, or R 9 and R 10 form together with the nitrogen atom bearing them a cycle of the following formula: in which: ∘ ----- represents a single or double bond, ∘ X1 and X2 are, independently from one another, C=O, SO 2 CH-OR 19, CH-SR 20, CH-NR 21 R 22 or CH-NHC R 23, ∘ R 13 and R 14 are, independently from one another, H or (C 1 -C 6)alkyl, or R 13 and R 14 form together with the carbon atoms bearing them a 5- or 6-membered hydrocarbon cycle, ∘ R 19, R 20, R 21 and R 22 are, independently from one another, H or (C 1 -C 6)alkyl, and ∘ R 23 is a (C 1 -C 6)alkyl group, and ∘ ----- represents a single or double bond, ∘ X1 and X2 are, independently from one another, C=O, SO 2 CH-OR 19, CH-SR 20, CH-NR 21 R 22 or CH-NHC R 23, ∘ R 13 and R 14 are, independently from one another, H or (C 1 -C 6)alkyl, or R 13 and R 14 form together with the carbon atoms bearing them a 5- or 6-membered hydrocarbon cycle, ∘ R 19, R 20, R 21 and R 22 are, independently from one another, H or (C 1 -C 6)alkyl, and ∘ R 23 is a (C 1 -C 6)alkyl group, and - m is an integer comprised between 1 and 8,