Bouziotis P, Pirmettis I, Pelecanou M, Raptopoulou C P, Terzis A, Papadopoulos M, Chiotellis E
Institute of Radioisotopes-Radiodiagnostic Products, National Center for Scientific Research Demokritos, Athens, Greece.
Chemistry. 2001 Sep 3;7(17):3671-80. doi: 10.1002/1521-3765(20010903)7:17<3671::aid-chem3671>3.0.co;2-l.
The simultaneous action of a bidentate aminothiol ligand, LnH, (n = 1: (CH3CH2)2NCH2CH2SH and n = 2: C5H10NCH2CH2SH) and a monodentate thiol ligand, LH (LH: p-methoxythiophenol) on a suitable MO (M = Re, 99gTc) precursor results in the formation of complexes of the general formula [MO(Ln)(L)3] (1, 2 for Re and 5. 6 for 99gTc). In solution these complexes gradually transform to [MO(Ln)(L)2] complexes (3, 4 for Re and 7, 8 for 99gTc). The transformation is much faster for oxotechnetium than for oxorhenium complexes. Complexes 1-4, 7, and 8 have been isolated and fully characterized by elemental analysis and spectroscopic methods. Detailed NMR assignments were made for complexes 3, 4, 7, and 8. X-ray studies have demonstrated that the coordination geometry around rhenium in complex 1 is square pyramidal (tau = 0.06), with four sulfur atoms (one from the L1H ligand and three from three molecules of p-methoxythiophenol) in the basal plane and the oxo group in the apical position. The L1H ligand acts as a monodentate ligand with the nitrogen atom being protonated and hydrogen bonded to the oxo group. The four thiols are deprotonated during complexation resulting in a complex with an overall charge of zero. The coordination geometry around rhenium in complex 4 is trigonally distorted square pyramidal (tau = 0.41), while in the oxotechnetium complex 7 it is square pyramidal (tau = 0.16). In both complexes LnH acts as a bidentate ligand. The NS donor atom set of the bidentate ligand and the two sulfur atoms of the two monodentate thiols define the basal plane, while the oxygen atom occupies the apical position. At the technetium tracer level (99mTc), both types of complexes, [99mTcO(Ln)(L)3] and [99mTcO(Ln)(L)2], are formed as indicated by HPLC. At high ligand concentrations the major complex is [99mTcO(Ln)(L)3], while at low concentrations the predominant complex is [99mTcO(Ln)(L)2]. The complexes [99mTcO(Ln)(L)3] transform to the stable complexes [99mTcO(Ln)(L)2]. This transformation is much faster in the absence of ligands. The complexes [99mTcO(Ln)(L)2] are stable, neutral, and also the predominant product of the reaction when low concentrations of ligands are used, a fact that is very important from the radiopharmaceutical point of view.
双齿氨基硫醇配体LnH（n = 1：(CH3CH2)2NCH2CH2SH，n = 2：C5H10NCH2CH2SH）与单齿硫醇配体LH（LH：对甲氧基苯硫酚）同时作用于合适的金属氧化物（M = Re、99gTc）前体，会形成通式为[MO(Ln)(L)3]的配合物（Re的配合物为1、2，99gTc的配合物为5、6）。在溶液中，这些配合物会逐渐转化为[MO(Ln)(L)2]配合物（Re的配合物为3、4，99gTc的配合物为7、8）。锝氧配合物的转化速度比铼氧配合物快得多。配合物1 - 4、7和8已通过元素分析和光谱方法分离并完全表征。对配合物3、4、7和8进行了详细的核磁共振归属。X射线研究表明，配合物1中铼周围的配位几何构型为四方锥（τ = 0.06），基面有四个硫原子（一个来自L1H配体，三个来自三个对甲氧基苯硫酚分子），氧原子位于顶端位置。L1H配体作为单齿配体，氮原子质子化并与氧原子形成氢键。四个硫醇在络合过程中去质子化，形成一个总电荷为零的配合物。配合物4中铼周围的配位几何构型为三角扭曲四方锥（τ = 0.41），而在锝氧配合物7中为四方锥（τ = 0.16）。在这两种配合物中，LnH均作为双齿配体。双齿配体的NS供体原子集和两个单齿硫醇的两个硫原子确定了基面，而氧原子占据顶端位置。在锝示踪剂水平（99mTc），如高效液相色谱所示，会形成两种类型的配合物，即[99mTcO(Ln)(L)3]和[99mTcO(Ln)(L)2]。在高配体浓度下，主要配合物为[99mTcO(Ln)(L)3]，而在低浓度下，主要配合物为[99mTcO(Ln)(L)2]。配合物[99mTcO(Ln)(L)3]会转化为稳定的配合物[99mTcO(Ln)(L)2]。在没有配体的情况下，这种转化要快得多。配合物[99mTcO(Ln)(L)2]是稳定的、中性的，并且在使用低浓度配体时也是反应的主要产物，从放射性药物的角度来看，这一事实非常重要。
