锝化学研究 Ⅸ.脑显像剂Tc^(Ⅴ)ON_2S_2类配合物结构稳定性和价态的研究

STUDY OF TECHNETIUM CHEMISTRY Ⅸ STABILITY OF THE STRUCTURE AND VALENCE OF THE BRAIN IMAGINGS BELONGING TO THE ANALOGUES OF 99 Tc m(Ⅴ) O BAT

采用改进的ＣＮＤＯ／２法模拟了ＢＡＴ类脑显像剂Ｔｃ（Ⅴ）Ｏ配合物价态的转换过程，发现Ｎ２Ｓ２类配体与Ｔｃ（Ⅴ）Ｏ核配位时，可能存在配位平衡离子Ｘ。在溶液中由于Ｘ离子的优先解络，瞬间存在＋１价对称性９９Ｔｃｍ配合物，并且，它又自动向相对稳定的０价不对称性９９Ｔｃｍ配合物转换，在动态转换过程中，将导致仅有一个配位Ｎ原子保留一个质子，这与实验结果一致。采用键级削弱百分数概念，表征配位过程的二个配位Ｎ原子上保留程度，解释了Ｔｃ（Ⅴ）Ｏ核、Ｔｃ（Ⅴ）≡Ｎ核Ｎ２Ｓ２类配合物两个Ｎ－Ｈ键上质子保留程度不同的原因，为今后设计不同价态锝配合物结构提供理论依据。

The transformation process of valence of the brain imagings belonging to the analogues of Tc (Ⅴ) O BAT is studied with the improved CNDO/2 method. It has been proposed that ion X for coordination balance probably exists after the complexation of N 2S 2 derivatives with the TcO 3+ core. Then symmetrical 99 Tc m complex with one positive charge may be formed due to the prior decomplexation of X in solution. Immediately,it will automatically transform to the unsymmetrical and relatively more stable neutral 99 Tc m complex.Therefore,the process of transformation results,in the fact that only one coordinating nitrogen atom retains a proton.The concept of decreasing percent of bond order is suggested as an indicator of retention property of the proton linked to the coordinating nitrogen atom in the process of coordination.The essential factor of different retention propery of the protons between two coordinating nitrogen atoms of 99 Tc m(Ⅴ) O N 2S 2 complexes and that of 99 Tc m(Ⅴ) complexes is well explained.The results may give some theoretical informations for designing the structure of 99 Tc m complex with different valences.