Last but not least : A simple molecular redox system is used to split water into hydrogen and oxygen photochemically. Two separate photolyses are combined to a cyclic process (see scheme). Osmocene ([Cp2OsII] with Cp?=C5H5?) serves as photocatalyst.
We report the synthesis of telechelic poly(norbornene) and poly(cyclooctene) homopolymers by ring‐opening metathesis polymerization (ROMP) and their subsequent functionalization and block copolymer formation based on noncovalent interactions. Whereas all the poly(norbornene)s contain either a metal complex or a hydrogen‐bonding moiety along the polymer side‐chains, together with a single hydrogen‐bonding‐based molecular recognition moiety at one terminal end of the polymer chain. These homopolymers allow for the formation of side‐chain‐functionalized AB and ABA block copolymers through self‐assembly. The orthogonal natures of all side‐ and main‐chain self‐assembly events were demonstrated by 1H NMR spectroscopy and isothermal titration calorimetry. The resulting fully functionalized block copolymers are the first copolymers combining both side‐ and main‐chain self‐assembly, thereby providing a high degree of control over copolymer functionalization and architecture and bringing synthetic materials one step closer to the dynamic self‐assembly structures found in nature. 相似文献
Tetranuclear manganese(II) phosphates [Mn(dipp)(bpy)]4?4 H2O ( 1 ) and [Mn4(dmpp)2(dmppH)4(bpy)4(H2O)2]?H2O ( 2 ) have been prepared from Mn(OAc)2?4 H2O and 2,6‐diisopropylphenyl phosphate (dippH2) or 2,6‐dimethylphenyl phosphate (dmppH2) in the presence of 2,2′‐bipyridine (bpy). In contrast, the reaction between [Mn(bpy)2(OAc)(ClO4)]?H2O and dippH2 affords [Mn(bpy)2(dippH)]2?2 ClO4?2 CH3OH ( 3 ). The reactions of Mn(OAc)2?4 H2O, dippH2, and pyridine (py) or 3,5‐dimethylpyrazole (dmpz) in CH3CN under reflux afford hexanuclear complexes [Mn6(dipp)6(py)8]?2CH3CN ( 4 ) and [Mn6(dipp)6(dmpz)6(AcOH)2]?2 H2O ( 5 ), respectively. Although compounds 1 and 2 are tetrameric, the former is a closed cubane‐like structure resembling the D4R secondary building unit of zeolites, whereas the latter exists in a staircase structure with fused Mn2O4P2 rings. The core structure of 3 contains a Mn2O4P2 eight‐membered ring that resembles the S4R building block of zeolites. Single‐crystal X‐ray diffraction studies reveal that compounds 4 and 5 have a similar core structure and differ from each other by the neutral ligands coordinated to manganese ions. All six phosphate ligands exist in a doubly deprotonated [(RO)PO32?] form and exhibit two types of binding modes [5.222] and [3.111]. An interesting feature of compounds 1 – 5 is that although they are oligonuclear complexes, there is an absence of oxido bridges. The magnetic properties of compounds 1 – 5 have been investigated in the temperature range 5–298 K, and it was found that all the compounds obey the Curie law. 相似文献
Leading light : A series of zinc(II) bis‐terpyridine complexes (see picture) is investigated by means of DFT calculations combined with Bader's quantum theory of atoms in molecules. Raman spectroscopy experiments and studies of the electro‐optical properties of the complexes in solution and the solid state are also performed to examine their potential as new emissive materials in light‐emitting devices.
Hexagonal tubes and rings with unusual shapes were generated through a unique self‐template‐directed growth mechanism. As described by M. Oh and co‐workers in the Communication on page 1459 ff., initially formed solid coordination polymer particles (CPPs) act as templates for the growth of the final hexagonal tubes and rings. Simple calcination of these unusually shaped CPPs results in the spontaneous formation of ZnO particles while the unique shape is maintained.
A sensitive cluster : The labile rhodathiaborane [(PPh3)2(H)‐nido‐RhSB9H9(NC5H5)] combines the redox and coordinative flexibility of the {(PPh3)2(H)Rh} fragment with the capability of the 11‐vertex rhodathiaborane cluster to undergo oxidative nido‐to‐closo transformations induced by coordination of alkynes to the metal centre, which leads to hydrogenation of the triple bond, dehydrogenation of the cluster and oxidative addition of sp C? H bonds.
The interaction in aqueous media of 4,6-dimethyl-1,2,3-triazolo[4,5-d]pyrimidin-5,7-dione (1,3-dimethyl-8-azaxanthine, Hdmax) with salts of divalent Mn, Co, Ni, Cu, Zn and Cd in the presence of an excess of pyridine (py) leads to the formation of crystalline solids, the structures of which have been solved by single crystal X-ray diffraction. The solids containing Mn, Co, Zn and Cd are isostructural, presenting a formulation trans-[M(H2O)4(py)2](dmax)2, with the heterocycle in the anionic form and not directly linked to the metal atom. The H-bond network of these complexes include a tape superstructure topologically identical to that present in the previously reported hexa-aqua salts of the dmax− anion, which may be regarded as a case of molecular recognition between dmax− and the square planar [M(H2O)4] subunit. On the other hand, for Ni and Cu the triazolopyrimidine ligand is directly coordinated to the metal through the external imidazole nitrogen atom (N2) generating the compounds [M(dmax)2(H2O)2(py)2] · 2H2O, which display a less tight H-bonding network. 相似文献
Six polymeric metal(II)-benzoate complexes of formula [Co2(O2CPh)4(4,4′-bpy)2]n (1-Co), [Ni(O2CPh)4(H2O)2(4,4′-bpy)]n (2-Ni), [Cu2(O2CPh)4(4,4′-bpy)]n (3-Cu), [Zn2(O2CPh)2(OH)2(4,4′-bpy)2]n (4-Zn), [Zn3(O2CPh)4(μ-OH)2(4,4′-bpy)2]n (5-Zn), and [Cd2(O2CPh)4(4,4′-bpy)2]n (6-Cd) have been synthesized and characterized (4,4′-bpy = 4,4′-bipyridine). 1-Co and 6-Cd show ladder-type double chains, 2-Ni does a helical structure, 3-Cu does a one-dimensional chain containing paddle-wheel units, 4-Zn does a zigzag chain, and 5-Zn does two-dimensional sheets. Since different structures provide different coordination geometry of each metal ion, it is clear that selection of appropriate metal ions can control the coordination geometry of each metal ion to form different crystal structures. Reactivity study of the compounds 1–7 for the transesterification of a variety of esters has shown that 4-Zn and 5-Zn are very efficient and the best among them. The catalyst 6-Cd containing Cd ion, well known as an inert metal ion for the ligand substitution, also catalyzed efficiently the transesterification of a variety of esters, and its reactivity is comparable to 4-Zn and 5-Zn. Moreover, the redox-active metal-containing polymers, 1-Co, 3-Cu, and 7-Mn, have shown efficient catalytic reactivities for the transesterification reactions, while 2-Ni has displayed a very slow conversion. The reactivities of the compounds used in this study are in the order of 5-Zn > 4-Zn > 6-Cd > 7-Mn ∼ 3-Cu > 1-Co > 2-Ni, indicating that the non-redox metal-containing compounds (5-Zn, 4-Zn, and 6-Cd) show better activity than the redox-active metal-containing compounds (7-Mn, 3-Cu, 1-Co, and 2-Ni). These results suggest that it is possible to tune the catalytic activities by changing from Zn to those metals such as Cd, a kinetically inert metal, or Cu, Mn, and Co, the redox-active metals. 相似文献
