Title
Formation of a metal-to-nitrogen bond of normal length by a neutral sufonamide group within a tridentate ligand. A new approach to radiopharmaceutical bioconjugation
Document Type
Article
Publication Date
3-4-2013
Abstract
We demonstrate that a tertiary sulfonamide group, N(SO2R)R'2, can rehybridize to form a M-N bond of normal length even when the group is in a linear tridentate ligand, such as in the new tridentate N(SO2R)dpa ligands derived from di-(2-picolyl)amine (N(H)dpa). N(SO2R)dpa ligands were used to prepare fac-[Re(CO)3(N(SO2R)dpa)](PF6 or BF4) complexes. Structural characterization of the new complexes established that the tertiary sulfonamide nitrogen atom binds to Re with concomitant sp(2)-to-sp(3) rehybridization, facilitating facial coordination. The new fac-[Re(CO)3(N(SO2R)dpa)]X structures provide the only examples for any metal with the sulfonamide as part of a noncyclic linear tridentate ligand and with a normal metal-to-nitrogen(tertiary sulfonamide) bond length. Rare previous examples of such normal M-N bonds have been found only in more constrained situations, such as with tripodal tetradentate ligands. Our long-term objectives for the new tridentate N(SO2R)dpa ligands are to develop the fundamental chemistry relevant to the eventual use of the fac-[M(I)(CO)3](+) core (M = (99m)Tc, (186/188)Re) in imaging and therapy. The sulfonamide group uniquely contributes to two of our goals: expanding ways to conjugate the fac-[M(I)(CO)3](+) core to biological molecules and also developing new symmetrical tridentate ligands that can coordinate facially to this core. Tests of our conjugation method, conducted by linking the fac-[Re(I)(CO)3](+) core to a new tetraarylporphyrin (T(N(SO2C6H4)dpa)P) as well as to a dansyl (5-(dimethylamino)naphthalene-1-sulfonyl) group, demonstrate that large molecular fragments can be tethered via a coordinated tertiary sulfonamide linkage to this core.
Publication Source (Journal or Book title)
Inorganic chemistry
First Page
2412
Last Page
21
Recommended Citation
Perera, T., Abhayawardhana, P., Marzilli, P. A., Fronczek, F. R., & Marzilli, L. G. (2013). Formation of a metal-to-nitrogen bond of normal length by a neutral sufonamide group within a tridentate ligand. A new approach to radiopharmaceutical bioconjugation. Inorganic chemistry, 52 (5), 2412-21. https://doi.org/10.1021/ic302180t