Assembly of Heteroleptic Copper Complexes with Silver Salts: From Discrete Trinuclear Complexes to Infinite Networks

The use of heteroleptic copper complexes functionalized with two differentiated coordinating groups for the elaboration of heterometallic extended networks is presented. Two novel 5-phenyl-dipyrrin (dpm) ligands appended with an imidazole or a pyrazole function, dpm-imid and dpm-pz, have been prepared and used as ligands for the synthesis of a series of heteroleptic (acacR)Cu(dpm) complexes (acacH = acetylacetonate; acacCN = 3-cyanoacetylacetonate). The X-ray crystal structures of these complexes revealed that, albeit no particular association mode is observed for the acac capping ligand, one-dimensional networks are formed with the acacCN capping ligand. Whereas the imidazole peripheral ligand is coordinated to the copper center of a neighboring complex in the structure of (acacCN)Cu(dpm-imid), such an interaction is absent for the pyrazole appended derivative, (acacCN)Cu(dpm-pz), leading to an association mode involving the peripheral nitrile group of the acacCN ligand. Upon reaction of the imidazole functionalized complexes, (acac)Cu(dpm-imid) and (acacCN)Cu(dpm-imid), with silver salts, trinuclear species, {[(acacR)Cu(dpm-imid)]2Ag}+, are formed as a result of the coordination of the azole nitrogen atom of two copper complexes to the silver ion. As expected, in the case of (acac)Cu(dpm-imid), these species do not self-assemble into an extended network owing to the absence of a peripheral coordinating group. However, for the (acacCN)Cu(dpm-imid) complex, the trinuclear species are equipped with peripheral nitrile groups, thus allowing the binding of metal centers. Consequently, these species self-assemble into one-dimensional polymers with association modes varying with the nature of the anion present in the silver salt.

本工作报道了采用经两个差异化配位基团功能化的异配铜配合物（heteroleptic copper complexes）构建异金属延展网络（heterometallic extended networks）的相关研究。我们合成了两种分别带有咪唑（imidazole）或吡唑（pyrazole）官能团的新型5-苯基二吡咯甲烷（5-phenyl-dipyrrin, dpm）配体，即dpm-imid与dpm-pz，并将其作为配体用于合成一系列异配型(acacᴿ)Cu(dpm)配合物（其中acacH为乙酰丙酮（acetylacetonate），acacCN为3-氰基乙酰丙酮）。对上述配合物的X射线晶体结构（X-ray crystal structures）分析结果显示：尽管乙酰丙酮封端配体未呈现特殊的组装模式，但当采用3-氰基乙酰丙酮作为封端配体时，可形成一维网络（one-dimensional networks）结构。在(acacCN)Cu(dpm-imid)的晶体结构中，外围咪唑配体可与邻近配合物的铜中心配位；而对于带有吡唑官能团的衍生物(acacCN)Cu(dpm-pz)，则不存在此类配位作用，转而通过acacCN配体的外围腈基（peripheral nitrile group）实现组装。将咪唑功能化的配合物(acac)Cu(dpm-imid)与(acacCN)Cu(dpm-imid)分别与银盐（silver salts）反应后，两个铜配合物的唑类氮原子（azole nitrogen atom）与银离子配位，生成了三核物种（trinuclear species）{[(acacᴿ)Cu(dpm-imid)]₂Ag}⁺。如所预期，对于(acac)Cu(dpm-imid)，由于缺乏外围配位基团，此类三核物种无法自组装（self-assemble）形成延展网络；而对于(acacCN)Cu(dpm-imid)配合物，其三核物种带有外围腈基，可与金属中心结合。因此，这些三核物种会自组装形成一维聚合物，其组装模式随银盐中阴离子（anion）的种类而变化。