Search

The phosphate‐coordination triple helicates A2L3 (A=anion) with azobenzene‐spaced bis‐bis(urea) ligands (L) have proven to undergo a rare in situ photoisomerization (without disassembly of the structure) rather than the typically known, stepwise "disassembly‐isomerization‐reassembly" process. This is enabled by the structural self‐adaptability of the "aniono" assembly arising from multiple relatively weak and flexible hydrogen bonds between the phosphate anion and bis(urea) units. Notably, the Z→E thermal relaxation rate of the isomerized azobenzene unit is significantly decreased (up to 20‐fold) for the triple helicates compared to the free ligands. Moreover, the binding of chiral guest cations inside the cavity of the Z‐isomerized triple helicate can induce optically pure diastereomers, thus demonstrating a new strategy for making light‐activated chiroptical materials. [ABSTRACT FROM AUTHOR]

The phosphate‐coordination triple helicates A2L3 (A=anion) with azobenzene‐spaced bis‐bis(urea) ligands (L) have proven to undergo a rare in situ photoisomerization (without disassembly of the structure) rather than the typically known, stepwise "disassembly‐isomerization‐reassembly" process. This is enabled by the structural self‐adaptability of the "aniono" assembly arising from multiple relatively weak and flexible hydrogen bonds between the phosphate anion and bis(urea) units. Notably, the Z→E thermal relaxation rate of the isomerized azobenzene unit is significantly decreased (up to 20‐fold) for the triple helicates compared to the free ligands. Moreover, the binding of chiral guest cations inside the cavity of the Z‐isomerized triple helicate can induce optically pure diastereomers, thus demonstrating a new strategy for making light‐activated chiroptical materials. [ABSTRACT FROM AUTHOR]

An azobenzene‐functionalized bis‐bis(urea) ligand (Lazo) and phosphate anion assemble to give the first photoactive "aniono" constructs, tetrahedron (A4L6) and helicate (A2L3), which readily undergo interconversion through cis‐trans isomerization of the azo group under irradiation/heating. Most strikingly, the tetrahedral cage can accommodate an [18]crown‐6 molecule, which can capture two tetramethylammonium (TMA+) ions with an unusually high affinity, even capable of replacing K+ in [K([18]crown‐6)]+ to form a {(TMA)2⊂ ([18]crown‐6)}⊂ cage "Russian doll" structure. Thus, the current work may provide a model for the light‐driven binding and exchange of the biologically important K+ and TMA+ ions. [ABSTRACT FROM AUTHOR]

An azobenzene‐functionalized bis‐bis(urea) ligand (Lazo) and phosphate anion assemble to give the first photoactive "aniono" constructs, tetrahedron (A4L6) and helicate (A2L3), which readily undergo interconversion through cis‐trans isomerization of the azo group under irradiation/heating. Most strikingly, the tetrahedral cage can accommodate an [18]crown‐6 molecule, which can capture two tetramethylammonium (TMA+) ions with an unusually high affinity, even capable of replacing K+ in [K([18]crown‐6)]+ to form a {(TMA)2⊂ ([18]crown‐6)}⊂ cage "Russian doll" structure. Thus, the current work may provide a model for the light‐driven binding and exchange of the biologically important K+ and TMA+ ions. [ABSTRACT FROM AUTHOR]