Synthesis, Characterization, Photophysical Properties, and Biological Labeling Studies of a Series of Luminescent Rhenium(I) Polypyridine Maleimide Complexes

We report the synthesis, characterization, and photophysical properties of a series of rhenium(I) polypyridine maleimide
complexes [Re(N−N)(CO)3(py-3-mal)](CF3SO3) [N−N = 1,10-phenanthroline, phen (1), 2,9-dimethyl-1,10-phenanthroline, 2,9-Me2-phen (2), 3,4,7,8-tetramethyl-1,10-phenanthroline, 3,4,7,8-Me4-phen (3), 4,7-diphenyl-1,10-phenanthroline, 4,7-Ph2-phen (4), 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline, 2,9-Me2-4,7-Ph2-phen (5), 2,2‘-biquinonine, biq (6); py-3-mal = N-(3-pyridyl)maleimide]. The X-ray crystal structure of complex 2 has been
investigated. Upon excitation, the complexes exhibit intense and long-lived photoluminescence in fluid solutions at
298 K. The emission wavelengths range from 514 to 654 nm, and the emission lifetimes fall in the microsecond
time scale. The luminescence is assigned to originate from a metal-to-ligand charge-transfer MLCT [dπ(Re) →
π*(diimine)] triplet excited state. As the maleimide group can react with the sulfhydryl group to form a stable
thioether moiety, these complexes have been used as thiol-specific luminescent labels for a thiolated oligonucleotide,
glutathione, and bovine serum albumin and human serum albumin. The photoluminescence properties of the labeled
biological species have also been investigated.

本研究报道了一系列铼(I)多吡啶马来酰亚胺配合物的合成、表征及光物理性质，该系列配合物的通式为[Re(N−N)(CO)₃(py-3-mal)](CF₃SO₃)，其中各配体N−N分别为：1,10-邻菲啰啉（1,10-phenanthroline, phen，1）、2,9-二甲基-1,10-邻菲啰啉（2,9-Me₂-phen，2）、3,4,7,8-四甲基-1,10-邻菲啰啉（3,4,7,8-Me₄-phen，3）、4,7-二苯基-1,10-邻菲啰啉（4,7-Ph₂-phen，4）、2,9-二甲基-4,7-二苯基-1,10-邻菲啰啉（2,9-Me₂-4,7-Ph₂-phen，5）、2,2'-联喹啉（2,2'-biquinonine, biq，6）；py-3-mal指代N-(3-吡啶基)马来酰亚胺。已对配合物2的X射线晶体结构进行了表征。在激发条件下，该系列配合物于298 K的流体溶液中展现出强且长寿命的光致发光。其发射波长范围为514 nm至654 nm，发射寿命处于微秒级时间尺度。该发光被归因为源自金属到配体电荷转移（metal-to-ligand charge transfer, MLCT）三重激发态[dπ(Re) → π*(二亚胺)]。由于马来酰亚胺基团可与巯基（sulfhydryl group）反应生成稳定的硫醚基团，此类配合物已被用作巯基特异性发光标记物，用于巯基化寡核苷酸、谷胱甘肽、牛血清白蛋白（bovine serum albumin）以及人血清白蛋白（human serum albumin）的标记。本研究同时对标记后的生物样品的光致发光性质展开了探究。