Department of Chemistry, University of Wisconsin, Madison, Wisconsin 53706, USA.
Inorg Chem. 2009 Jul 6;48(13):5704-14. doi: 10.1021/ic802361q.
The recently synthesized sterically constrained copper(I) complex Cu(dtbp)(2) (1), where dtbp is 2,9-di-tert-butyl-1,10-phenanthroline, exhibits unique photophysical and reactivity properties. Complex 1 (lambda(abs), 425 nm; epsilon, 3100 L M(-1) cm(-1); lambda(emission), 599 nm) has the longest metal-to-ligand charge-transfer (MLCT) emission lifetime (tau, 3260 ns) and largest quantum yield (varphi, 5.6%) of all Cu(R(2)phen)(2) complexes. Complex 1 also exhibits a large positive reduction potential for the [Cu(2+)(dtbp)(2)]|[Cu(+)(dtbp)(2)] couple (E(1/2) = 0.70 V vs Fc(+/0)) and a large negative excited-state reduction potential for the [Cu(2+)(dtbp)(dtbp(-*))]|[Cu(2+)(dtbp)(2)] couple (E(1/2) = -1.66 V vs Fc(+/0)), indicating that this complex is a potent photoreductant in the excited state. The steric constraint imposed by the t-butyl substituents in 1 enables unusual ligand replacement reactivity. Either CH(3)CN or CO replaces one of the dtbp ligands, a reaction that is readily followed by loss of the unique emission signature of 1. Monodentate CH(3)CN binds to the copper(I) center with an affinity 2 orders of magnitude greater than that of the displaced dtbp, despite the fact that the displaced ligand is bidentate. CO-induced displacement of dtbp from 1 is reversible, but only in the presence of 1 equiv of unbound dtbp. The exceptionally strong donor ligand CH(3)NC displaces both dtbp ligands from 1. In contrast to the facile ligand displacement reactivity with good donor ligands, 1 does not react readily with O(2), by either a ligand displacement or an oxidative pathway. Rather, O(2) induces partial quenching of emission via an outer-sphere interaction with 1.
最近合成的具有空间位阻的铜（I）配合物 Cu(dtbp)(2)（1），其中 dtbp 是 2,9-二-叔丁基-1,10-菲咯啉，表现出独特的光物理和反应性。配合物 1（lambda(abs)，425nm；epsilon，3100 L M(-1) cm(-1)；lambda(emission)，599nm）具有最长的金属-配体电荷转移（MLCT）发射寿命（tau，3260ns）和所有Cu(R(2)phen)(2)配合物中最大的量子产率（varphi，5.6%）。配合物 1 还表现出[Cu(2+)(dtbp)(2)]|[Cu(+)(dtbp)(2)]对的较大正还原电势（E(1/2) = 0.70V 相对于 Fc(+/0)）和[Cu(2+)(dtbp)(dtbp(-*))]|[Cu(2+)(dtbp)(2)]对的较大负激发态还原电势（E(1/2) = -1.66V 相对于 Fc(+/0)），表明该配合物在激发态是一种有效的光还原剂。1 中叔丁基取代基施加的空间位阻导致了不寻常的配体取代反应性。无论是 CH(3)CN 还是 CO 都可以取代一个 dtbp 配体，该反应很容易伴随着 1 的独特发射特征的丧失。尽管取代的配体是双齿配体，但单齿 CH(3)CN 与铜（I）中心的结合亲和力比取代的 dtbp 高两个数量级。CO 诱导的 dtbp 从 1 的置换是可逆的，但仅在存在 1 当量未结合的 dtbp 的情况下。异常强的供体配体 CH(3)NC 从 1 中取代了两个 dtbp 配体。与与良好供体配体的易发生配体取代反应形成对比，1 不易与 O(2)发生反应，无论是通过配体取代还是氧化途径。相反，O(2)通过与 1 的外球相互作用诱导部分发射猝灭。
