Complexes Having the fac-{M(CO)3}+ Core (M = Tc, Re) Useful in Radiopharmaceuticals: X-ray and NMR Structural Characterization and Density Functional Calculations of Speci

详细信息    查看全文

• 作者：Malgorzata Lipowska ; Renzo Cini ; Gabriella Tamasi ; Xiaolong Xu ; Andrew T. Taylor ; and Luigi G. Marzilli
• 刊名：Inorganic Chemistry
• 出版年：2004
• 出版时间：November 29, 2004
• 年：2004
• 卷：43
• 期：24
• 页码：7774 - 7783
• 全文大小：183K
• 年卷期：v.43,no.24(November 29, 2004)
• ISSN：1520-510X

文摘

Radiopharmaceuticals containing the "fac-{M(CO)₃}⁺" core (M = ^99mTc, ¹⁸⁶Re, or ¹⁸⁸Re) have potential as diagnosticor therapeutic agents. Complexes with this core with sp³ amine donors have received little attention. We havestudied adducts formed by ENDACH₂ (HO₂CCH₂NHCH₂CH₂NHCH₂CO₂H) and ENACH (NH₂CH₂CH₂NHCH₂CO₂H).Re(CO)₃(ENDACH)-A (1A) and Re(CO)₃(ENDACH)-B (1B) isomers were obtained by the reaction of ENDACH₂with Re(CO)₅Cl. Re(CO)₃(ENAC) (2) was obtained by the reaction of ENACH with aqueous [Re(CO)₃(H₂O)₃]⁺.From single-crystal X-ray data, the three new neutral complexes, 1A, 1B, and 2, have a six-coordinate, pseudo-octahedral Re center with facially coordinated carbonyl ligands. ENDACH^- and ENAC^- bind facially to Re throughboth amine nitrogens and one carboxyl oxygen, forming two five-membered chelate rings. The Re(CO)₃(ENDACH)isomers have an uncoordinated, dangling -CH₂CO₂H group, which is an ideal coupling site for attachment tobiomolecules. The isomers differ by the configuration of the NH center bearing this dangling group. The H atomof the amine (N2) is endo (near the carbonyl ligands in the basal plane) in 1A and exo (away from carbonylligands) in isomer 1B. Isomers reach equilibrium (1A:1B, 70:30) after 3 days at high pH. Density functional structureoptimizations were performed for isolated molecules of the type Tc^I/Re^I(CO)₃(N₂O): [Re(CO)₃(NH₃)₂(H₂O)]⁺,[Tc(CO)₃(NH₃)₂(H₂O)]⁺, [Re(CO)₃(EN)(H₂O)]⁺ (EN, ethylenediamine), [Tc(CO)₃(EN)(H₂O)]⁺, and various models for1A, 1B, and 2. The computed structures are in good agreement with the X-ray structures. The theoretical andexperimental Re-N bond distances usually agree within 0.045 Å. The total electronic energy values for the computed1A and 1B models differ by 0.815 kcal mol^-1, giving an isomer ratio of 80:20, in good agreement with the 1A/1Bratio (70:30) found.