Homochiral Helical Metal鈥揙rganic Frameworks of Group 1 Metals

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• 作者：Daniel L. Reger ; Andrew Leitner ; Mark D. Smith ; T. Thao Tran ; P. Shiv Halasyamani
• 刊名：Inorganic Chemistry
• 出版年：2013
• 出版时间：September 3, 2013
• 年：2013
• 卷：52
• 期：17
• 页码：10041-10051
• 全文大小：702K
• 年卷期：v.52,no.17(September 3, 2013)
• ISSN：1520-510X

文摘

The reactions of (S)-2-(1,8-naphthalimido)propanoic acid (HL_ala) and (S)-2-(1,8-naphthalimido)-3-hydroxypropanoic acid (HL_ser), protonated forms of ligands that contain a carboxylate donor group, an enantiopure chiral center, and a 1,8-naphthalimide 蟺路路路蟺 stacking supramolecular tecton and in the case of HL_ser an alcohol functional group, with the appropriate alkali metal hydroxide followed by a variety of crystallization methods leads to the formation of crystalline K(L_ala)(MeOH) (1), K(L_ala)(H₂O) (2), Na(L_ala)(H₂O) (3), KL_ser (4), CsL_ser (5), and CsL_ala (6). Each of these new complexes has a solid state structure based on six-coordinate metals linked into homochiral helical rod secondary building unit (SBU) central cores. In addition to the bonding of the carboxylate and solvent (in the case of L_ser the ligand alcohol) to the metals, both oxygens on the 1,8-naphthalimide act as donor groups. One naphthalimide oxygen bonds to the same helical rod SBU as the carboxylate group of that ligand forming a chelate ring. The other naphthalimide oxygen bonds to adjacent SBUs. In complexes 1鈥?b>3, this inter-rod link has a square arrangement bonding four other rods forming a three-dimensional enantiopure metal鈥搊rganic framework (MOF) structure, whereas in 4鈥?b>6 this link has a linear arrangement bonding two other rods forming a two-dimensional, sheet structure. In the latter case, the third dimension is supported exclusively by interdigitated 蟺路路路蟺 stacking interactions of the naphthalimide supramolecular tecton, forming enantiopure supramolecular MOF solids. Compounds 1鈥?b>3 lose the coordinated solvent when heating above 100 掳C. For 1, the polycrystalline powder reverts to 1 only by recrystallization from methanol, whereas compounds 2 and 3 undergo gas/solid, single-crystal to single-crystal transformations to form dehydrated compounds 2* and 3*, and rehydration occurs when crystals of these new complexes are left out in air. The reversible single-crystal to single-crystal transformation of 2 involves the dissociation/coordination of a terminal water ligand, but the case of 3 is remarkable considering that the water that is lost is the only bridging ligand between the metals in the helical rod SBU and a carboxylate oxygen that is a terminal ligand in 3 moves into a bridging position in 3* to maintain the homochiral helical rods. Both 2* and 3* contain five-coordinate metals. There are no coordinated solvents in compounds 4鈥?b>6, in two cases by designed ligand modification, which allows them to have high thermal stability. Compounds 1鈥?b>3 did not exhibit observable Second Harmonic Generation (SHG) efficiency at an incident wavelength of 1064 nm, but compounds 4鈥?b>6 did exhibit modest SHG efficiency for MOF-like compounds in the range of 30 脳 伪-SiO₂.