With the help of spectroscopic data, we have characterized several isolated entities resulting from the reaction of lanthanide ions with a hexadentate Schiff base ligand obtained by reacting o-vanillin and 1,2-diaminoethane. This H2L ligand possesses two coordination sites, an N2O2 inner site and an O2O2 outer site. In the first isolated complex, formulated as (H2L)Pr(NO3)3·H2O 1Pr, the NMR data confirm that the Pr3+ ion is only linked to the ligand by its deprotonated phenol functions while the ligand does exist in a neutral zwitterionic phenolato-iminium form (O−, NH+) in agreement with a migration of the protons from the phenolic functions to the imine groups. Deprotonation of the ligand in 1Pr yields a new and original product,
LPr(NO3)·H2O·CH3OH 2Pr for which spectroscopic results agree with a coordination of the Pr3+ ion at the N2O2 site. This result, which is surprising in view of the oxophilic character of the lanthanide ions, is also confirmed by comparison with the NMR data of the LZnPr(NO3)3 complex 3Pr that retains the Pr3+ ion in the O2O2 site. Another anionic complex 4Pr, L2PrCs, with two ligands linked to the lanthanide centre by their N2O2 sites is also isolated. Starting with the mononuclear cationic or anionic entities, 2Pr or 4Pr, we have not been able to isolate and characterize genuine homo- or hetero-dinuclear
lanthanide complexes.
在光谱数据的帮助下,我们对由
镧系离子与通过反应
香草醛和1,2-二
氨基
乙烷获得的六齿式施夫碱
配体反应所产生的几种孤立实体进行了表征。该H2L
配体具有两个配位位点,一个是
N2O2内位点,另一个是O2O2外位点。在第一个孤立的配合物中,命名为(H2L)Pr(
NO3)3·
H2O 1Pr,NMR数据确认Pr3+离子仅通过去质子化的
酚官能团与
配体相连,同时
配体确实以中性内盐
酚基-
亚胺形式存在(O−, NH+),这与质子从
酚官能团迁移到
亚胺基团的现象一致。在1Pr中,
配体的去质子化生成了一种新颖的产物 LPr( )· ·CH3OH 2Pr,光谱结果表明Pr3+离子在 位点配位。考虑到
镧系离子的亲氧性,这一结果令我们感到惊讶,同时通过与保留Pr3+离子在O2O2位点的LZnPr( )3复合物3Pr的NMR数据进行比较也得到了验证。另一个阴离子复合物4Pr,
L2PrCs,具有两个
配体通过其 位点与
镧系中心相连也被孤立。从单核阳离子或阴离子实体2Pr或4Pr出发,我们未能孤立和表征真正的同种或异种双核
镧系配合物。