A Series of Homochiral Helical Metal–Organic Frameworks Based on Proline Derivatives

Eight novel three-dimensional homochiral helical metal–organic frameworks (HHMOFs), namely, [Cd3((S)-PIA)2­(PPA)­(H2O)2]n (1-L), [Cd3((R)-PIA)2­(PPA)­(H2O)2]n (1-D), [Cd4((R)-PIA)3­(DPP)4­(H2O)4]n (2-D), [Cd1.5((S)-PIA)­(4,4′-DIB)2]n (3-L), [Cd1.5((S)-PIA)­(DPEE)1.5]n (4-L), [Cd1.5((R)-PIA)­(DPEE)1.5]n (4-D), [Cd1.5((S)-PIA)­(DPEA)1.5]n (5-L), and [Cd1.5((S)-PIA)­(DPEA)1.5]n (5-D) (H3PIA = 5-(2-carboxypyrrolidine-1-carbonyl) isophthalic acid) have been synthesized using proline-derived ligands ((S)-H3PIA and (R)-H3PIA). Crystallographic analysis indicates that all the complexes contain homochiral left- and/or right-handed helical chains, which are constructed by PIA fragments and Cd­(II) ions. Meanwhile, in these complexes nitrogen heterocycle auxiliary ligands play an important role in structural diversity. Some physical characteristics, such as thermal stabilities, solid-state circular dichroism, and photoluminescent properties, are also investigated. Our results highlight an effective method to apply proline ligands to construct interesting HHMOFs.

本研究以脯氨酸衍生配体((S)-H3PIA与(R)-H3PIA)为构筑单元，成功合成了8种新型三维同手性螺旋金属有机框架（homochiral helical metal–organic frameworks, HHMOFs），其化学式依次为[Cd3((S)-PIA)2(PPA)(H2O)2]n(1-L)、[Cd3((R)-PIA)2(PPA)(H2O)2]n(1-D)、[Cd4((R)-PIA)3(DPP)4(H2O)4]n(2-D)、[Cd1.5((S)-PIA)(4,4′-DIB)2]n(3-L)、[Cd1.5((S)-PIA)(DPEE)1.5]n(4-L)、[Cd1.5((R)-PIA)(DPEE)1.5]n(4-D)、[Cd1.5((S)-PIA)(DPEA)1.5]n(5-L)及[Cd1.5((S)-PIA)(DPEA)1.5]n(5-D)（其中H3PIA指5-(2-羧基吡咯烷-1-羰基)间苯二甲酸）。晶体结构解析结果表明，所有配合物均含有由PIA片段与镉(II)离子构筑的同手性左手及/或右手螺旋链。与此同时，氮杂环辅助配体对这类配合物的结构多样性具有重要调控作用。本研究还对部分配合物的热稳定性、固态圆二色谱及光致发光性能等物理特性进行了表征分析。本研究结果为利用脯氨酸类配体构建新型同手性螺旋金属有机框架提供了一种有效的策略。