A series of alkaline earth metal-based bio-analogous metalâorganic frameworks (1â4) based on a cyclic dipeptide (2,5-piperazinedione-1,4-diacetic acid, H2PODC) were prepared under the same synthetic conditions and the effect of earth metal ion on the (geometrical and electronic) property of these MOFs was investigated. Crystal analysis demonstrates that the metal ion radii play an important role in coordination number, coordination modes of the ligand and bond length. The binding mode between metal ion and peptide can be divided into two groups: (1) Mg2+ and Sr2+; (2) Ca2+ and Ba2+ ions, where the difference is whether the carbonyl group participates in coordination. The result may be relevant to the different biophysical phenomena of protein between alkaline earth metal ions. UV-vis spectra show two adsorption peaks for compounds 1â4, while fluorescence spectra display one emission peak. Via first-principles density functional theory (DFT) calculation, we found that two adsorption peaks should be attributed to the transition of valence band (VB) â two empty bands and VB â conduction band (CB), while one emission peak may result from the transition of CB â VB.
在相同的合成条件下,基于环状二肽(2,5-
哌嗪二酮-1,4-二
乙酸,H2PODC)制备了一系列碱土
金属基
生物类
金属有机骨架(1-4),并研究了碱土
金属离子对这些MOF(几何和电子)性质的影响。晶体分析表明,
金属离子的半径在配位数、
配体的配位方式和键长中起着重要作用。
金属离子和肽之间的结合方式可分为两类:(1)Mg2+和Sr2+;(2)Ca2+和Ba2+离子,区别在于羰基是否参与配位。结果可能与碱土
金属离子之间蛋白质的不同
生物物理现象有关。紫外可见光谱显示化合物1-4有两个吸附峰,而荧光光谱显示一个发射峰。通过第一性原理密度泛函理论(DFT)计算,我们发现两个吸附峰应归因于价带(VB)→两个空带和VB→导带(CB)的跃迁,而一个发射峰可能是由CB→VB的跃迁引起的。