ZnO with Different Morphologies Sensitized by Metalloporphyrins as Catalysts for H2 Production by Water Splitting under Sunlight.

In this work, zinc oxide with different morphologies and textural properties were prepared and sensitized with metalloporphyrins (MPs) aiming to improve its solar energy harvesting capability for H2 production by water splitting under sunlight (a 300 W Xe/Hg lamp). An anionic iron(III)porphyrin and a cationic manganese(III)porphyrin were immobilized on different ZnO solids predominantly by electrostatic interactions. In general, the prepared MP-free ZnO solid yielded modest catalytic results which had apparently no direct correlation with their textural properties or morphology. On the other hand, when these ZnO solids had iron or manganese porphyrin sensitizing them, their catalytic performances changed and a superior yield towards H2 production was observed in comparison to the pure ZnO solids, making evident the synergy achieved between these two components (ZnO and metalloporphyrins) for the prepared solids. It was also observed that the metalloporphyrins and the respective free-base ligand suffered redox reactions when used as homogenous catalyst in this reaction, which could influence their performances as catalysts. The same was not observed in the solids containing immobilized MP, suggesting some protective effect of the ZnO solids on the MP complexes upon immobilization probably due to interaction of the complexes with the ZnO matrix.

Novel organically linked ZnII hydrogenselenite coordination polymers: synthesis, characterization, and efficient TiO2 photosensitization for enhanced photocatalytic hydrogen production.

This study focused on the solvothermal synthesis, characterization, and photocatalytic activities of two novel coordination polymers, namely [Zn(µ-HSeO3)2(bipy)]n (1) and [Zn(µ-HSeO3)2(phen)]n (2). These compounds represent the first organically linked ZnII hydrogenselenite coordination polymers. The synthesis of compounds 1 and 2 involved the addition of 2,2'-bipyridine and 1,10-phenanthroline, respectively, to SeO2 and ZnO in methanol as the solvent. The novel hydrogenselenite compounds were thoroughly characterized using spectroscopic and crystallographic methods. The photocatalytic solids (TiO2-1A and TiO2-2A) were prepared by immobilizing compounds 1-2 onto TiO2 through the sol-gel approach. These photocatalysts were then evaluated for hydrogen evolution via water splitting using a 300 W Hg/Xe lamp as the irradiation source. Among the newly synthesized photocatalytic materials, TiO2-1A demonstrated auspicious photocatalytic performance for hydrogen gas production. Its catalytic activity overcame the observed for the pure solid support TiO2 and Degussa P25 (commercial titania), making compound 1 a particularly attractive TiO2 photosensitizer. Additionally, TiO2-1A exhibited superior photocatalytic activity compared to TiO2-2A. The latter performed better than freshly prepared TiO2, approaching that of Degussa P25. These findings highlight the potential of compound 1 as an effective photosensitizer for TiO2-based photocatalysis, making it a promising candidate for applications in clean energy generation, specifically in hydrogen production by water splitting.

A three-dimensional metal-organic polymer: poly[bis(µ2-pyrimidine-2-thiolato-κ4N¹,S:S,N³)lead(II)].

The title compound, [Pb(C4H3N2S)2]n, was prepared by the reaction of [Pb(OAc)2]·3H2O (OAc is acetate) with pyrimidine-2-thione in the presence of triethylamine in methanol. In the crystal structure, the Pb(II) atom has an N4S4 coordination environment with four ligands coordinated by N- and S-donor atoms. This compound shows that the pyrimidine-2-thiolate anion can lead to a three-dimensional network when the coordination number of the metal ion can be higher than 6, as is the case with the Pb(II) ion. This compound presents only covalent bonds, showing that despite the possibility of the hemidirected geometries of Pb(II), the eight-coordinated ion does not allow the formation of an isolated molecular structure with pyrimidine-2-thiolate as the ligand.

Chelation of UO2(2+) and Th(IV) by N,N'-bis(pyridoxylideneiminato)R (R=n-propyl, diethylamine), new dianionic Schiff bases derived from vitamin B6: Synthesis and structural features of [Th(pyr2pen)2] (pen=1,3-propylendiamine), [UO2(pyr2pen)(CH3OH)] and [UO2(pyr2dien)].2H2O (dien=diethylenetriamine). Searching further modelings for heavy metals damage inhibition in living beings.

Th(NO(3))(4).5H(2)O reacts with H(2)pyr(2)pen {propylenediamine-bis(pyridoxylideneimine)}, UO(2)(NO(3))(2).6H(2)O reacts with H(2)pyr(2)pen and H(2)pyr(2)dien {diethylenetriamine-bis(pyridoxylideneimine)} under deprotonation of the endo hydroxyl groups of the Schiff bases rings to give the chelate complexes [Th(pyr(2)pen)(2)] (1), [UO(2)(pyr(2)pen)(CH(3)OH)] (2) and [UO(2)(pyr(2)dien)].2H(2)O (3). In 1 the thorium center is the common vertex of two square pyramids displaced on 45 degrees to each other. In 2 and 3 the uranium atoms are the centers of distorted pentagonal bipyramides. In 2 a methanol molecule achieves the coordination number 7 of the uranium(VI) ion, in 3 the central N atom of the dien section of the ligand accomplishes the coordination polyhedra, resulting a chelate complex with remarkable higher symmetry. Some radiological factors are also discussed, correlating the knowledges of new chemical properties of uranium and thorium with the understanding of its metabolism in living beings, what, in principle, should give support for clinical studies about prevention, diagnosis and treatment of uranium, thorium and/or heavy metals poisoning.

Chelation of ThIV, EuIII and NdIII by dianionic N,N'-bis(pyridoxylideneiminato)ethylene, (Pyr2en)2-. On the search of feasible modelings for heavy metals damage inhibition in living beings.

The neutral Schiff base N,N'-bis(pyridoxylideneiminato)ethylene {H(2)pyr(2)en} reacts with Th(NO(3))4.4H2O, NdCl3.6H2O and EuCl3.6H2O to give [Th(pyr(2)en)2(H2O)] (1), [Nd(pyr(2)en)(Hpyr(2)en)].12H2O (2) and [Eu(pyr(2)en)(Hpyr(2)en)] (3). In the three not yet reported bimolecular chelate systems the endo hydroxyl groups of the rings undergo deprotonation confirming the remarkable ability of the pyridoxal-containing ligand H(2)pyr(2)en to yield stable heavy metal chelates with unusual coordination polyhedra. Complexes 2 and 3 show a coordination number 8 for Nd and Eu, achieving a distorted quadratic antiprism. In complex 1 the additional water molecule increases the coordination number of Th to 9 producing a capped square antiprism. The synthesis and structural elucidation of the title complexes starting from a probably non-toxic metabolite like H(2)pyr(2)en should represent a useful contribution to the research on models of prevention and therapy of damage caused by radioactive and heavy elements.

Chelation of UO(2)(2+) by vitamin B6 complex derivatives: synthesis and characterization of [UO2(beta-pyracinide)2(H2O)] and [UO2(Pyr2en)DMSO]Cl2{Pyr2en=N,N'-ethylenebis(pyridoxylideneiminato)}. A useful modeling of assimilation of uranium by living beings.

The vitamin B(6) derivatives 4-pyridoxic acid (anionic) and the Schiff base N,N'-ethylenebis(pyridoxylideneiminato) react with UO(2)(NO(3))(2) * 6H(2)O to give [UO(2)(beta-pyracinide)(2)(H(2)O)] (beta-pyracin=4-pyridoxic acid) and [UO(2)(Pyr(2)en)DMSO]Cl(2)(Pyr(2)en=N,N'-ethylenebis(pyridoxylideneiminato); DMSO=dimethyl sulfoxide). In both compounds the two uranyl oxo ligands set the axis of distorted pentagonal bipyramides. The ability of vitamin B(6) derivatives to react with UO(2)(2+) allowing the chelation of one uranium atom represents a very specific model of assimilation of uranium by living beings. It could also explain the serious damages caused by heavy or radioactive metals like uranium since their complexation "in vivo" by enzymatic systems like pyridoxal phosphate-containing enzymes would lead to a modification of the prosthetic groups of the metalloenzymes with loss of their catalytic activities.

Bis(1-naphthyl) ditelluride.

The title compound, C(20)H(14)Te(2), shows a transoid conformation, with a C[bond]T[bond]-[bond]Te[bond]C torsion angle of 97.96 (9) degrees. The Te[bond]Te units show approximate eta(6) interactions with neighbouring naphthyl groups, forming chains along the c axis. The molecule lies about a crystallographic twofold axis.