By using solubility control to crystallize the prenucleation clusters of hydrosol, a family of titanium-oxo clusters possessing the {Ti18O27} core in which the 18 Ti(IV)-ions are uniquely connected with μ-oxo ligands into a triple-decked pentagonal prism was obtained. The cluster cores are wrapped by external sulfate and aqua ligands, showing good solubilities and stabilities in a variety of solvents including acetonitrile and water and allowing their solution chemistry being studied by means of electrospray ionization mass spectroscopy, (17)O NMR, and vibrational spectroscopy. Furthermore, this study provides new titanium oxide candidates for surface modifications and homogeneous photocatalysis.
A novel family of water-soluble, polyoxocationic titanium-oxide host-guest clusters are reported herein. They exhibit an unprecedented hexagonal prismatic core structure for hosting univalent cationic guests like K, Rb, Cs and HO. Guest exchange has been studied using Cs NMR, showing the flexible pore of a host permits passage of a comparatively larger cation and giving an equilibrium constant of ca. 13 for displacing Rb by Cs. Attractive ion-dipole interaction, depending on host-guest size complementarity, plays a dominant role for the preferential encapsulation of larger alkali-metal cationic guests.
In this paper, using a simple method, 17 isostructural polyoxotitanates (POTs) were synthesized, including the pristine [Ti12O16(O(i)Pr)16], the monodefected [Ti11O13(O(i)Pr)18], and the heterometal-doped [Ti11O14(O(i)Pr)17(ML)] (M = Mg, Ca, Zn, Cd, Co, or Ni; L = Cl, Br, I, or NO3). The electronic structures of these POTs were determined by UV-vis spectroscopy and DFT calculations. Upon UV irradiation of the POTs, electron spin resonance showed the formation of Ti(III) under anaerobic conditions and superoxide (O2(•-)) in the presence of O2. The photoactivities of the POTs were then probed with Ti(III) production and short-circuit photocurrent experiments. The photophysical processes were studied using steady-state and transient photoluminescence. The results show that within the very similar structures, the deexcitation processes of the photoexcited POTs can be greatly affected by the dopants, which result in enhanced or decreased photoactivities. Co and Ni doping enhances the absorption of the visible light accompanied by serious loss of UV photoactivities. On the other hand, a Ti vacancy (in [Ti11O13(O(i)Pr)18]) does not reduce the band gap of a POT but improves the UV photoactivities by serving as surface reaction site. The POTs were then used as molecular models of titanium oxide nanoparticles to understand some important issues relevant to doped titanate, i.e., coordination environment of the dopant metal, electronic structure, photoactivities, and photophysical processes. Our present findings suggest that for solar energy harvesting applications of titanium oxides like photocatalysis and solar cells substitution of titanium atoms by transition metal ions (like Co and Ni) to extend the absorption edges may not be an efficient way, while loading of Ti vacancies is very effective.
Significance CDK5 and GSK3β are recognized as interrelated kinases; they share a strong structural resemblance, and both are known tau kinases that contribute to the etiology of Alzheimer’s disease. We report here that p25 but not p35, the normal cyclin-like activator of CDK5, unexpectedly binds to GSK3β in the AXIN-binding region. The binding of p25 increases GSK3β activity and alters its substrate specificity. Results, both in vivo and in vitro, suggest that many of the effects of p25 previously assumed to be due to hyperactivation of CDK5 must now be reexamined for the potential role of altered GSK3β activity. This result carries important implications for how we approach disease-modifying strategies for the treatment of Alzheimer’s and other neurodegenerative diseases.
During solvothermal alcoholysis of a mixture of TiI4 and Ti(O(i)Pr)4, a {I@Ti22} cage cluster encapsulating an OH and iodide guests is crystallized. The {I@Ti22} host-guest cluster surface is postfunctionalizable with catecholate and carboxylate ligands. The synthetic details, structural characterization, spectroscopic properties of the obtained cages clusters are provided. The present study provides candidates for modeling ligand exchange and electron-hole transfer at the titanate nanoparticle surface, and meanwhile offers new opportunities for understanding the TiO2 nanocrystalline formation in solvothermal processes.
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