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Very small and soft scorpionates: Water stable technetium tricarbonyl complexes combining a bis-agostic (k(3)-H, H, S) binding motif with pendant and integrated bioactive molecules


Maria, Leonor; Paulo, Antonio; Santos, Isabel C; Santos, Isabel; Kurz, Philipp; Spingler, Bernhard; Alberto, Roger (2006). Very small and soft scorpionates: Water stable technetium tricarbonyl complexes combining a bis-agostic (k(3)-H, H, S) binding motif with pendant and integrated bioactive molecules. Journal of the American Chemical Society, 128(45):14590-14598.

Abstract

The novel trihydro(mercaptoazolyl)borates NaH3B(tim(Me))] (L-1) (tim(Me) = 2-mercapto-1-methylimidazolyl), NaH3B(tim(Bupip))](L-2)(tim(Bupip))1-4-((2-methoxyphenyl)-1-pipera zinyl)butyl]-2-mercaptoimidazolyl), and NaH3B(bzt)](L-3)(bzt = 2-mercaptobenzothiazolyl) were synthesized by reaction of NaBH4 with the corresponding azole. Ligands L-1-L-3 represent a new class of light and soft scorpionates that stabilizes the M(CO)(3)](+) core (M = Tc-99, Re) by formation of the complexes fac-M{kappa(3)-H(mu-H)(2)B(tim(Me))}(CO)(3)] (M = Tc-99 (1), Re (2)), fac-Re{kappa(3)-H(mu-H)(2)B(tim(Bupip))}(CO)(3)] (3), and fac-Re{kappa(3)-H(mu-H)(2)B(bzt)}(CO)(3)] (4), respectively. The soft scorpionates are coordinated to the metal in unique (kappa(3)-H, H', S) fashion, as confirmed by X-ray crystallography of 1, 2, and 4. These complexes with bis-agostic hydride coordination are formed in aqueous solution with the two hydrides replacing two coordinating aquo ligands. The agostic hydrogen atoms were located directly, confirming an unprecedented donor atom set combining one sulfur and two hydrogen atoms. Preliminary studies have shown the possibility of preparing some of these complexes at the no carrier added level (Tc-99m), under conditions as required in radiopharmaceutical preparation. Due to their lipophilicity, small-size, and easy functionalization with adequate biomolecules, the trihydro (mercaptoazolyl) borate technetium tricarbonyl complexes are suitable for the design of CNS receptor ligand radiopharmaceuticals as exemplified with 3, comprising a pendant serotonergic 5-HT1A ligand. The integrated design of radiopharmaceuticals involving a bis-agostic scorpionate ligand is demonstrated by the synthesis of 4, with an integrated benzothiazolyl fragment for the recognition of beta-amyloid plaques.

Abstract

The novel trihydro(mercaptoazolyl)borates NaH3B(tim(Me))] (L-1) (tim(Me) = 2-mercapto-1-methylimidazolyl), NaH3B(tim(Bupip))](L-2)(tim(Bupip))1-4-((2-methoxyphenyl)-1-pipera zinyl)butyl]-2-mercaptoimidazolyl), and NaH3B(bzt)](L-3)(bzt = 2-mercaptobenzothiazolyl) were synthesized by reaction of NaBH4 with the corresponding azole. Ligands L-1-L-3 represent a new class of light and soft scorpionates that stabilizes the M(CO)(3)](+) core (M = Tc-99, Re) by formation of the complexes fac-M{kappa(3)-H(mu-H)(2)B(tim(Me))}(CO)(3)] (M = Tc-99 (1), Re (2)), fac-Re{kappa(3)-H(mu-H)(2)B(tim(Bupip))}(CO)(3)] (3), and fac-Re{kappa(3)-H(mu-H)(2)B(bzt)}(CO)(3)] (4), respectively. The soft scorpionates are coordinated to the metal in unique (kappa(3)-H, H', S) fashion, as confirmed by X-ray crystallography of 1, 2, and 4. These complexes with bis-agostic hydride coordination are formed in aqueous solution with the two hydrides replacing two coordinating aquo ligands. The agostic hydrogen atoms were located directly, confirming an unprecedented donor atom set combining one sulfur and two hydrogen atoms. Preliminary studies have shown the possibility of preparing some of these complexes at the no carrier added level (Tc-99m), under conditions as required in radiopharmaceutical preparation. Due to their lipophilicity, small-size, and easy functionalization with adequate biomolecules, the trihydro (mercaptoazolyl) borate technetium tricarbonyl complexes are suitable for the design of CNS receptor ligand radiopharmaceuticals as exemplified with 3, comprising a pendant serotonergic 5-HT1A ligand. The integrated design of radiopharmaceuticals involving a bis-agostic scorpionate ligand is demonstrated by the synthesis of 4, with an integrated benzothiazolyl fragment for the recognition of beta-amyloid plaques.

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Additional indexing

Item Type:Journal Article, refereed, original work
Communities & Collections:07 Faculty of Science > Department of Chemistry
Dewey Decimal Classification:540 Chemistry
Language:English
Date:November 2006
Deposited On:23 Oct 2012 13:36
Last Modified:05 Apr 2016 16:01
Publisher:American Chemical Society
ISSN:0002-7863
Publisher DOI:https://doi.org/10.1021/ja0644226
Other Identification Number:ISI:000241857200045

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