To verify whether attractive metallophilic interactions exist in the dimer-of-dimers [Cu(2)(ophen)(2)](2) (Hophen=1H-[1,10]phenanthrolin-2-one) (1), we designed and synthesized a series of such [M(2)L(2)](2) structures by varying the d(10) metal and/or the ligand (M=Cu(I) or Ag(I), L=ophen or obpy; Hobpy=1H-[2,2']bipyridinyl-6-one), and have successfully obtained three dimers-of-dimers: [Ag(2)(ophen)(2)](2).6 H(2)O (2), [Cu(2)(obpy)(2)](2) (3), and [Ag(2)(obpy)(2)](2).4.5 H(2)O.0.5 DMF (4). X-ray analyses of these structures show that interdimer M-M separations in [Ag(2)-(ophen)(2)](2) (3.199 A) are remarkably shorter than those in [Cu(2)(ophen)(2)](2) (3.595 A). Shorter interdimer M-M separations are found in the structures of [M(2)(obpy)(2)](2) (2.986 and 2.993 A in [Cu(2)(obpy)(2)](2), 3.037 to 3.093 A in [Ag(2)(obpy)(2)](2)), in which the pi systems are smaller than in the complexes with the ophen ligand. Detailed structural comparison of these dimers-of-dimers indicates that the interdimer, face-to-face pi-pi interactions repulse rather than support the interdimer metal-metal attractive interactions. This study also yields qualitative comparison of the strengths between argentophilic, cuprophilic, and face-to-face pi-pi interactions. DFT calculations on the four dimers-of-dimers further support the above deduction. The structure of a trimer-of-dimers [Ag(2)(obpy)(2)](3) (Ag-Ag 3.171 to 3.274 A) is further evidence that the oligomerization of the [M(2)L(2)] molecules is favored by stronger metallophilic and weaker face-to-face pi-pi interactions. 相似文献
Aggregation and breakage of aggregates of fully destabilized polystyrene latex particles in turbulent flow was studied experimentally in both batch and continuous stirred tanks using small‐angle static light scattering. It was found that the steady‐state values of the root‐mean‐square radius of gyration are fully reversible upon changes of stirring speed as well as solid volume fraction. Steady‐state values of the root‐mean‐square radius of gyration were decreasing with decreasing solid volume fraction as well as with increasing stirring speed. Moreover, it was found that the steady‐state structure and shape of the aggregates is not influenced by the applied stirring speed. 相似文献
Humidity detection, and the quest for low‐cost facile humidity‐sensitive indicator materials is of great interest for many fields, including semi‐conductor processing, food transport and storage, and pharmaceuticals. Ideal humidity‐detection materials for a these applications might be based on simple clear optical readout with no power supply, i.e.: a clear color change observed by the naked eye of any untrained observer, since it doesn't require any extra instrumentation or interpretation. Here, the introduction of a synthesis‐free one‐step procedure, based on physical mixing of easily available commercial materials, for producing a humidity memory material which can be easily painted onto a wide variety of surfaces and undergoes a remarkable color change (approximately 100 nm blue‐shift of λMAX) upon exposure to various thresholds of levels of ambient humidity is reported. This strong color change, easily visible to as a red‐to‐orange color switch, is locked in until inspection, but can then be restored reversibly if desired, after moderate heating. By taking advantage of spontaneously‐forming reversible ‘soft’ supramolecular bonds between a red‐colored azo dye and a host polymer matrix, a reversible dye ‘migration’ aggregation appearing orange, and dis‐aggregation back to red can be achieved, to function as the sensor.
By using environmentally friendly [Ni(CN)4]2? as a cyanide source, three new heterometallic cyano‐bridged mixed‐valence CuI/CuII coordination polymers with three different electronic configurations (d8–d10), that is, [Cu2Ni(CN)5(H2O)3] ( 1 ), [Cu2Ni(CN)5(pn)H2O] ( 2 ), and [Cu3Ni(CN)6(pn)2] ( 3 , pn=1,2‐propane diamine) have been synthesized by gradually increasing the amount of pn. Compound 1 , which was hydrothermally synthesized in the absence of pn ligand, exhibits the famous 2D Cairo pentagonal tiling, in which the CuI, CuII, and NiII atoms act as trigonal, T‐shaped, and square‐planar nodes, respectively. Notably, there are three water molecules located at the meridianal positions of the octahedrally coordinated CuII atom in compound 1 . A similar reaction, except for the addition of a small amount of pn, generated a similar Cairo pentagonal tiling layer in which two of the water molecules that were located at the meridianal positions of the octahedrally coordinated CuII atom were replaced by a chelating pn group. Another similar hydrothermal reaction, with the addition of a larger amount of pn, yielded compound 3 , which showed a related two‐fold‐interpenetrated (3,4)‐connected 3D framework with an unprecedented {83}2{86} topology in which the CuII atom was chelated by two pn groups. These structural changes between compounds 1 , 2 , 3 can be explained by the chelating effect of the pn group. The replacement of two meridianally coordinated water molecules on the octahedral CuII atom in compound 1 by a pn group gives compound 2 , which shows similar Cairo tiling, and a further increase in the amount of pn results in the formation of the [Cu(NC)2(pn)2] unit and the two‐fold‐interpenetrated 3D framework of compound 3 . The mixed‐valence properties of compounds 1 , 2 , and 3 were confirmed by variable‐temperature magnetic‐susceptibility measurements. 相似文献
