Xia Bin, Gao Qian, Hu Zhen-Peng, Wang Qing-Lun, Cao Xue-Wei, Li Wei, Song You, Bu Xian-He
College of Chemistry, State Key Lab of Elemento-Organic Chemistry, Nankai University, Tianjin 300071, China.
School of Physics, Nankai University, Tianjin 300071, China.
Research (Wash D C). 2021 Feb 10;2021:5490482. doi: 10.34133/2021/5490482. eCollection 2021.
Stimulus-responsive metal-organic frameworks (MOFs) can be used for designing smart materials. Herein, we report a family of rationally designed MOFs which exhibit photoresponsive chiroptical and magnetic properties at room temperature. In this design, two specific nonphotochromic ligands are selected to construct enantiomeric MOFs, {Cu(L-mal)(bpy)(HO)·3HO} (1) and {Cu(D-mal)(bpy)(HO)·3HO} (2) (mal = malate, bpy = 4, 4' - bipyridine), which can alter their color, magnetism, and chiroptics concurrently in response to light. Upon UV or visible light irradiation, long-lived bpy radicals are generated via photoinduced electron transfer (PET) from oxygen atoms of carboxylates and hydroxyl of malates to bpy ligands, giving rise to a 23.7% increase of magnetic susceptibility at room temperature. The participation of the chromophores (-OH and -COO) bound with the chiral carbon during the electron transfer process results in a small dipolar transition; thus, the Cotton effects of the enantiomers are weakened along with a photoinduced color change. This work demonstrates that the simultaneous responses of chirality, optics, and magnetism can be achieved in a single compound at room temperature and may open up a new pathway for designing chiral stimuli-responsive materials.
刺激响应性金属有机框架（MOF）可用于设计智能材料。在此，我们报道了一类经过合理设计的MOF，它们在室温下表现出光响应性手性光学和磁性。在这种设计中，选择了两种特定的非光致变色配体来构建对映体MOF，{Cu（L-苹果酸）（联吡啶）（H₂O）·3H₂O}（1）和{Cu（D-苹果酸）（联吡啶）（H₂O）·3H₂O}（2）（苹果酸 = 苹果酸盐，联吡啶 = 4,4'-联吡啶），它们可以响应光同时改变其颜色、磁性和手性光学性质。在紫外或可见光照射下，通过光诱导电子转移（PET）从羧酸盐的氧原子和苹果酸盐中的羟基向联吡啶配体产生长寿命的联吡啶自由基，导致室温下磁化率增加23.7%。在手性碳结合的发色团（-OH和-COO）在电子转移过程中的参与导致了一个小的偶极跃迁；因此，对映体的科顿效应随着光诱导的颜色变化而减弱。这项工作表明，在室温下，单一化合物可以实现手性、光学和磁性的同时响应，并可能为设计手性刺激响应材料开辟一条新途径。
