A series of bifunctional cyclopentadienes of the type 1,3-EtOCO-HCp-linker-NH₂ were synthesized. In this series, the linker length (distance between the amine functionalities and the cyclopentadiene) has been systematically varied (CH₂)_n (n = 1–3). The corresponding Re complexes [(η⁵-C₅H₃RR′)Re(CO)₃] (R = −COOEt, R′ = −linker–NH₂) were synthesized and structurally characterized. They exhibit extraordinary stability toward water and air. All bifunctional cyclopentadienes have been labeled with the [^99mTc(CO)₃]⁺ moiety. Whereas the reactions with ethylene and propylene linked cyclopentadiene under mild reaction conditions led to the products in high radiochemical purity (>96%) without applying further purification protocols, harsher reaction conditions were required for the synthesis of the methylene-linked cyclopentadiene compound. Masking the amine in the methylene-linked cyclopentadiene by an amide bond bypasses this problem. The very hydrophilic characters of these complexes were assessed by K_OW analysis. The reported cyclopentadienes and their complexes offer a robust and versatile platform for (radio)metal incorporation into biologically active lead structures.

中文翻译：

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扩展环戊二烯基框架：具有正交功能的 99mTc/Re 复合物用于生物偶联

合成了一系列 1,3-EtOCO-HCp-接头-NH ₂型双功能环戊二烯。在该系列中，接头长度（胺官能团与环戊二烯之间的距离）已系统地变化 (CH ₂ ) _n ( n = 1–3)。合成并表征了相应的 Re 复合物 [(η ⁵ -C ₅ H ₃ RR')Re(CO) ₃ ] (R = -COOEt, R' = -linker-NH ₂ )。它们对水和空气表现出非凡的稳定性。所有双功能环戊二烯都用 [ ^99m Tc(CO) ₃ ] ⁺标记部分。虽然在温和的反应条件下与乙烯和丙烯连接的环戊二烯反应导致产物具有高放射化学纯度 (>96%)，而无需进一步纯化方案，但合成亚甲基连接的环戊二烯化合物需要更苛刻的反应条件。用酰胺键掩蔽亚甲基连接的环戊二烯中的胺绕过了这个问题。这些复合物的亲水特性通过K _OW分析进行评估。报道的环戊二烯及其配合物为（放射性）金属掺入具有生物活性的铅结构提供了一个强大而通用的平台。