A homodimeric compound of formula wherein: n is 1 or 2 m is an integer from 0 to 3 A is NR 1 R 2, or N + R 1 R 2 R 3 R 1, R 2 and R 3 are, each independently, - hydrogen; - C 1-8 alkyl or heteroalkyl; C 2-8 alkenyl or heteroalkenyl; C 2-8 alkynyl or heteroalkynyl; - optionally substituted aryl, alkylaryl, heteroaryl, alkylhetemaryl; or any two of R 1, R 2, and R 3 taken together with the nitrogen to which they are attached form a heterocyclic group, optionally substituted by one or more oxo, thioxo, and optionally comprising a heteroatom selected from O, S, and N, provided that the heteroatom is separated from the nitrogen atom by a least two carbon atoms; R 4 are each independently - hydrogen; - optionally substituted C 1-18 alkyl or heteroalkyl; C 2-18 alkenyl or heteroalkenyl; C 2-18 alkynyl or heteroalkynyl; - optionally substituted aryl, alkylaryl, heteroaryl, or alkylheteroaryl; B is - C 1-4 alkyl; C 2-4 alkenyl; C 2-4 alkynyl; - aryl, alkylaryl, heteroaryl or alkylheteroaryl; all optionally substituted by one or more halogen; Y is selected among OR 5, NHR 5, NR 5 R 6, NH-S 2 -R 5, N + (R 5) 3, SR 5, N 3, C OR 5, CN, C OR 5, C NHR 5, C NHR 5, NH NHR 5, NH NHR 5, NH NHR 5 or R 5 is - hydrogen; - optionally substituted C 1-8 alkyl; C 2-8 alkenyl; C 2-8 alkynyl; - optionally substituted aryl; alkylaryl; heteroaryl; R 6 is - optionally substituted C 1-8 alkyl; C 2-8 alkenyl; or C 2-8 alkynyl; - optionally substituted aryl; alkylaryl; or heteroaryl.; L is a "linker" selected among those listed as L1 to L56 in Table I of the present description. n is 1 or 2 m is an integer from 0 to 3 A is NR 1 R 2, or N + R 1 R 2 R 3 R 1, R 2 and R 3 are, each independently, - hydrogen; - C 1-8 alkyl or heteroalkyl; C 2-8 alkenyl or heteroalkenyl; C 2-8 alkynyl or heteroalkynyl; - optionally substituted aryl, alkylaryl, heteroaryl, alkylhetemaryl; or any two of R 1, R 2, and R 3 taken together with the nitrogen to which they are attached form a heterocyclic group, optionally substituted by one or more oxo, thioxo, and optionally comprising a heteroatom selected from O, S, and N, provided that the heteroatom is separated from the nitrogen atom by a least two carbon atoms; - hydrogen; - C 1-8 alkyl or heteroalkyl; C 2-8 alkenyl or heteroalkenyl; C 2-8 alkynyl or heteroalkynyl; - optionally substituted aryl, alkylaryl, heteroaryl, alkylhetemaryl; or R 4 are each independently - hydrogen; - optionally substituted C 1-18 alkyl or heteroalkyl; C 2-18 alkenyl or heteroalkenyl; C 2-18 alkynyl or heteroalkynyl; - optionally substituted aryl, alkylaryl, heteroaryl, or alkylheteroaryl; - hydrogen; - optionally substituted C 1-18 alkyl or heteroalkyl; C 2-18 alkenyl or heteroalkenyl; C 2-18 alkynyl or heteroalkynyl; - optionally substituted aryl, alkylaryl, heteroaryl, or alkylheteroaryl; B is - C 1-4 alkyl; C 2-4 alkenyl; C 2-4 alkynyl; - aryl, alkylaryl, heteroaryl or alkylheteroaryl; all optionally substituted by one or more halogen; - C 1-4 alkyl; C 2-4 alkenyl; C 2-4 alkynyl; - aryl, alkylaryl, heteroaryl or alkylheteroaryl; all optionally substituted by one or more halogen; Y is selected among OR 5, NHR 5, NR 5 R 6, NH-S 2 -R 5, N + (R 5) 3, SR 5, N 3, C OR 5, CN, C OR 5, C NHR 5, C NHR 5, NH NHR 5, NH NHR 5, NH NHR 5 or R 5 is - hydrogen; - optionally substituted C 1-8 alkyl; C 2-8 alkenyl; C 2-8 alkynyl; - optionally substituted aryl; alkylaryl; heteroaryl; - hydrogen; - optionally substituted C 1-8 alkyl; C 2-8 alkenyl; C 2-8 alkynyl; - optionally substituted aryl; alkylaryl; heteroaryl; R 6 is - optionally substituted C 1-8 alkyl; C 2-8 alkenyl; or C 2-8 alkynyl; - optionally substituted aryl; alkylaryl; or heteroaryl.; - optionally substituted C 1-8 alkyl; C 2-8 alkenyl; or C 2-8 alkynyl; - optionally substituted aryl; alkylaryl; or heteroaryl.; L is a "linker" selected among those listed as L1 to L56 in Table I of the present description.