以氨基酸配子自組裝合成仿生材料

Abstract

本篇論文之研究重點乃以天然氨基酸為有機配子，並遵循軟硬酸鹼理論，利用室溫自組裝的方式合成仿生結構的配位聚合物。化合物 [Cu(L-argininato)(H2O)3]n (1) 由左旋精氨酸與硝酸銅依 1：1 的比例組裝而得，為一維螺旋結構，水分子的三聚團簇以氫鍵作用力吸附於聚合物孔洞內，並穩定主架構。化合物 [Cu0.5(L-methioninato)]n (2) 由左旋甲硫氨酸與硝酸銅以 1：1 的比例組裝而得，為一維鋸齒狀結構，並以AAA形式堆疊，整體結構並無孔洞產生，所以沒有任何客分子存在。化合物[{Ag3Cu3(L-methioninato)6(NO3)3(H2O)3}7H2O]n (3) 則由甲硫氨酸同時與硝酸銅和硝酸銀組裝而得。由銅金屬中心所形成的一維左旋螺旋結構與蛋白質中的 α-螺旋結構相似，並由甲硫氨酸側鏈的硫原子與銀金屬配位鍵結，共同形成一個具有異雙金屬的三維結構，存在一條貫穿主架構的螺旋通道，通道內有三個配位水與七個客分子水以氫鍵作用力結合在一起，形成一維鋸齒狀的水分子鏈。變溫粉末繞射實驗顯示水分子鏈的存在與否，可以調整化合物作晶形–非晶形之可逆交替變化。

The biomimetic coordination polymers have been sythesized at ambient temperature by using amino acids as ligands on the basis of soft-hard principle. The 1D helix compound [Cu(L-argininato)(H2O)3]n (1) was assembled from L-arginine and copper nitrate in a matel-to-ligand ratio of 1：1. The trimeric water clusters are located inside the pore of 1. Hydrogen-bonding interactions between the host and the water clusters stablize the whole structure. Compound [Cu0.5(L-methioninato)]n (2), assembled from L-methionine and copper nitrate in a matel-to-ligand ratio of 1：1, adopts a 1D zigzag structure, which packs in an AAA order. Compound [{Ag3Cu3(L-methioninato)6(NO3)3(H2O)3}7H2O]n (3) was assembled from L-methionine, copper nitrate, and silver nitrate at room temperature. An infinite left-handed Cu∞-helix chain is analogous to the α-helix structure of a protein. The sulfur atoms on the side chain of the ligand are all bound to AgΙ centers and formed a 3D homochiral hetero-bimetallic helix network with a 1D right-handed helical channels. Three coordinated water molecules and seven free water molecules arranged in a zigzag conformation inside the channels through numerous hydrogen-bonds. PXRD studies reveal that the crystal-to-amorphous transformation of 3 is reversible by the desorption-sorption of water molecules.