A compound of formula, wherein: L is a nitrogen containing macrocyclic metal ligand of the formula: X is -(CH 2) 3 -; Y is a molecular recognition moiety; R 4 is selected from the group consisting of H, OH, halogen, NO 2, NH 2, optionally substituted C 1 -C 12 alkyl, optionally substituted C 6 -C 18 aryl, cyano, CO 2 R 5, NHR 5, N(R 5) 2 and a group of the formula: wherein X 1 is a linking moiety; Y 1 is selected from the group consisting of OR 6, SR 7, N(R 8) 2 and a molecular recognition moiety; wherein R 5 is H or C 1 -C 12 alkyl; R 6 is selected from the group consisting of H, halogen, an oxygen protecting group, optionally substituted C 1 -C 12 alkyl, optionally substituted C 2 -C 12 alkenyl, optionally substituted C 2 -C 12 alkynyl and optionally substituted C 2 -C 12 heteroalkyl; R 7 is selected from the group consisting of H, halogen, a sulfur protecting group, optionally substituted C 1 -C 12 alkyl, optionally substituted C 2 -C 12 alkenyl, optionally substituted C 2 -C 12 alkynyl and optionally substituted C 2 -C 12 heteroalkyl; each R 8 is independently selected from the group consisting of H, a nitrogen protecting group, optionally substituted C 1 -C 12 alkyl, optionally substituted C 2 -C 12 alkenyl, optionally substituted C 2 -C 12 alkynyl and optionally substituted C 2 -C 12 heteroalkyl. or a pharmaceutically acceptable salt or complex thereof. X is -(CH 2) 3 -; Y is a molecular recognition moiety; R 4 is selected from the group consisting of H, OH, halogen, NO 2, NH 2, optionally substituted C 1 -C 12 alkyl, optionally substituted C 6 -C 18 aryl, cyano, CO 2 R 5, NHR 5, N(R 5) 2 and a group of the formula: wherein X 1 is a linking moiety; Y 1 is selected from the group consisting of OR 6, SR 7, N(R 8) 2 and a molecular recognition moiety; wherein R 5 is H or C 1 -C 12 alkyl; R 6 is selected from the group consisting of H, halogen, an oxygen protecting group, optionally substituted C 1 -C 12 alkyl, optionally substituted C 2 -C 12 alkenyl, optionally substituted C 2 -C 12 alkynyl and optionally substituted C 2 -C 12 heteroalkyl; R 7 is selected from the group consisting of H, halogen, a sulfur protecting group, optionally substituted C 1 -C 12 alkyl, optionally substituted C 2 -C 12 alkenyl, optionally substituted C 2 -C 12 alkynyl and optionally substituted C 2 -C 12 heteroalkyl; each R 8 is independently selected from the group consisting of H, a nitrogen protecting group, optionally substituted C 1 -C 12 alkyl, optionally substituted C 2 -C 12 alkenyl, optionally substituted C 2 -C 12 alkynyl and optionally substituted C 2 -C 12 heteroalkyl. or a pharmaceutically acceptable salt or complex thereof. X 1 is a linking moiety; Y 1 is selected from the group consisting of OR 6, SR 7, N(R 8) 2 and a molecular recognition moiety; wherein R 5 is H or C 1 -C 12 alkyl; R 6 is selected from the group consisting of H, halogen, an oxygen protecting group, optionally substituted C 1 -C 12 alkyl, optionally substituted C 2 -C 12 alkenyl, optionally substituted C 2 -C 12 alkynyl and optionally substituted C 2 -C 12 heteroalkyl; R 7 is selected from the group consisting of H, halogen, a sulfur protecting group, optionally substituted C 1 -C 12 alkyl, optionally substituted C 2 -C 12 alkenyl, optionally substituted C 2 -C 12 alkynyl and optionally substituted C 2 -C 12 heteroalkyl; each R 8 is independently selected from the group consisting of H, a nitrogen protecting group, optionally substituted C 1 -C 12 alkyl, optionally substituted C 2 -C 12 alkenyl, optionally substituted C 2 -C 12 alkynyl and optionally substituted C 2 -C 12 heteroalkyl.