School of Chemistry and Chemical Engineering, Queen's University Belfast, UK.
Chemistry. 2012 Oct 22;18(43):13733-42. doi: 10.1002/chem.201201302. Epub 2012 Sep 20.
The composition of a dynamic mixture of similar 2,2'-bipyridine complexes of iron(II) bearing either an amide (5-benzylamido-2,2'-bipyridine and 5-(2-methoxyethane)amido-2,2'-bipyridine) or an ester (2,2'-bipyridine-5-carboxylic acid benzylester and 2,2'-bipyridine-5-carboxylic acid 2-methoxyethane ester) side chain have been evaluated by electrospray mass spectroscopy in acetonitrile. The time taken for the complexes to come to equilibrium appears to be dependent on the counteranion, with chloride causing a rapid redistribution of two preformed heteroleptic complexes (of the order of 1 hour), whereas the time it takes in the presence of tetrafluoroborate salts is in excess of 24 h. Similarly the final distribution of products is dependent on the anion present, with the presence of chloride, and to a lesser extent bromide, preferring three amide-functionalized ligands, and a slight preference for an appended benzyl over a methoxyethyl group. Furthermore, for the first time, this study shows that the distribution of a dynamic library of metal complexes monitored by ESI-MS can adapt following the introduction of a different anion, in this case tetrabutylammonium chloride to give the most favoured heteroleptic complex despite the increasing ionic strength of the solution.
在乙腈中，通过电喷雾质谱法评估了由铁(II)的类似 2,2'-联吡啶配合物组成的动态混合物的组成，这些配合物带有酰胺（5-苄酰胺基-2,2'-联吡啶和 5-(2-甲氧基乙烷)酰胺基-2,2'-联吡啶）或酯（2,2'-联吡啶-5-苯甲酸酯和 2,2'-联吡啶-5-羧酸 2-甲氧基乙酯）侧链。配合物达到平衡所需的时间似乎取决于抗衡阴离子，其中氯离子导致两种预先形成的杂配位配合物迅速重新分布（约 1 小时），而在存在四氟硼酸盐的情况下，所需时间超过 24 小时。同样，最终产物的分布取决于存在的阴离子，氯离子和溴离子在一定程度上更喜欢三种酰胺功能化配体，并且略微偏爱附加的苄基而不是甲氧基乙基。此外，这项研究首次表明，通过 ESI-MS 监测的动态金属配合物文库的分布可以在引入不同阴离子（在这种情况下为四丁基氯化铵）后进行适应，尽管溶液的离子强度增加，但仍能得到最有利的杂配位配合物。
