Trinuclear Oxo-Titanium Clusters: Synthesis, Structure, and Photocatalytic Activity

The interest in titanium (IV) oxo-complexes is due to their potential application in photodegradation processes and environmental pollutants reduction. Titanium (IV) oxo-complexes (TOCs) of the general formula [Ti3O(OiPr)8(OOCR’)2] (R’ = -C13H9 (1), -p-PhCl (2), -m-PhNO2 (3), -C4H7 (4)) were synthesized and structurally characterized. The use of the different carboxylate ligands allowed modulating the optical band gaps of the produced microcrystals, which were measured via diffuse reflectance ultraviolet and visible spectroscopy (UV-Vis-DRS) and calculated using the density functional theory (DFT) method. The dispersion of TOCs (1–3) in the poly (methyl methacrylate) matrix (PMMA) led to the formation of polymer/TOCs composites, which in the next stage of our works have been applied in the photocatalytic activity estimation of synthesized trinuclear Ti(IV) oxo-complexes. Studies of the photocatalytic degradation of methylene blue (MB) induced by UV irradiation exhibit that the PMMA-TOCs composite containing (1) oxo-clusters is the most active, followed by the system containing the complex (3)

Titanium(IV) Oxo-Complex with Acetylsalicylic Acid Ligand and Its Polymer Composites: Synthesis, Structure, Spectroscopic Characterization, and Photocatalytic Activity

The titanium oxo complexes are widely studied, due to their potential applications in photocatalytic processes, environmental protection, and also in the biomedical field. The presented results concern the oxo complex synthesized in the reaction of titanium(IV) isobutoxide and acetylsalicylic acid (Hasp), in a 4:1 molar ratio. The structure of isolated crystals was solved using the single-crystal X-ray diffraction method. The analysis of these data proves that [Ti4O2(OiBu)10(asp)2]·H2O (1) complex is formed. Moreover, the molecular structure of (1) was characterized using vibrational spectroscopic techniques (IR and Raman), 13C NMR, and UV–Vis diffuse reflectance spectroscopy (UV–Vis DRS). The photocatalytic activity of the synthesized complex was determined with the use of composite foils produced by the dispersion of (1) micrograins, as the inorganic blocks, in a polycaprolactone (PCL) matrix (PCL + (1)). The introduction of (1) micrograins to the PCL matrix caused the absorption maximum shift up to 425–450 nm. The studied PCL + (1) composite samples reveal good activity toward photodecolorization of methylene blue after visible light irradiation

Complex of rat transthyretin with tetraiodothyroacetic acid refined at 2.1 and 1.8 Å resolution.

The crystal structure of rat transthyretin (rTTR) complex with 3,5,3' ,5' -tetraiodothyroacetic acid (T4Ac) was determined at 1.8 Å resolution with low temperature synchrotron data collected at CHESS. The structure was refined to R = 0.207 and Rfree= 0.24 with the use of 8-1.8 Å data. The additional 8000 reflections from the incomplete 2.1-1.8 data shell, included in the refinement, reduced the Rfree index by 1.3%. Structure comparison with the model refined against the complete 8-2.1 Å data revealed no differences in the ligand orientation and the conformation of the polypeptide chain in the core regions. However, the high-resolution data included in the refinement improved the model in the flexible regions poorly defined with the lower resolution data. Also additional sixteen water molecules were found in the difference map calculated with the extended data. The structure revealed both forward and reverse binding of tetraiodothyroacetic acid in one binding site and two modes of forward ligand binding in the second site, with the phenolic iodine atoms occupying different sets of the halogen binding pockets

3D structure enhancers based on functionalized MIL-53(Al) for improved dimethyl carbonate/methanol pervaporative separation

International audienceDimethyl carbonate (DMC) is considered an alternative, green solvent. This paper focused on enhancement in membrane performance in DMC removal by pervaporation (PV) from azeotropic mixture of DMC/methanol as a consequence of the incorporation of nanofiller into a PDMS matrix. Engineering a hydrophobized analogue of MIL-53(Al) (NHOCOCF3-MIL-53(Al)) as nanoenhancers for improved membrane materials is presented. XRD analysis confirmed the successful synthesis of MOFs and proved that modification does not influence crystalline structure of MOF, which is well retained. Properties of the membranes in PV were assessed employing separation factor (β) and thickness-normalized Pervaporation Separation Index (PSIN). Modified PDMS membranes possess better separation properties compared with pristine one. Results revealed that the incorporation of 5 wt% of NHOCOCF3-MIL-53(Al) caused an increase of β from 3.1 to 3.7, a significant value for organic-organic PV. Essential part of the work was to analyze impact of the presence of water in the feed on overall membrane effectiveness. It was observed that in the case of traces amount of water in the feed solution, water was preferentially transported from the feed to the permeate side. However, the transport of water through membranes was partially suppressed when water content in the feed was over 0.7 wt%

Topology switch between AIE and ACQ: a balance of substituents

Intermolecular interactions appearing in solution, aggregates and solid state are known to affect the photophysical properties of fluorophores, leading either to emission quenching or to emission enhancement upon aggregation. The novel strategy for the aggregation-induced fluorescence change based upon the subtle balance of the intermolecular and intramolecular charge transfer in the benzothiazole derivatives is presented here, leading to the extremely bright aggregates of the compounds dark in solution or vice versa. The introduction of the two different mild substituents into the fluorophore core results in two regioisomers exhibiting the same crystal packing, but extremely different behavior upon aggregation. Such an approach opens a simple way of controlling the AIE/ACQ behavior of small molecules in the wide range of FQY values

Sorption and magnetic properties of oxalato-basedt trimetallic open framework stabilized by charge-assisted hydrogen bonds

We report a new structure of {[Co(bpy)(2)(ox)][{Cu(2)(bpy)(2)(ox)}Fe(ox)(3)]}(n)·8.5nH(2)O NCU-1 presenting a rare ladder topology among oxalate-based coordination polymers with anionic chains composed of alternately arranged [Cu(2)(bpy)(2)(ox)](2+) and [Fe(ox)(3)](3−) moieties. Along the a axis, they are separated by Co(III) units to give porous material with voids of 963.7 Å(3) (16.9% of cell volume). The stability of this structure is assured by a network of stacking interactions and charge-assisted C-H…O hydrogen bonds formed between adjacent chains, adjacent cobalt(III) units, and alternately arranged cobalt(III) and chain motifs. The soaking experiment with acetonitrile and bromobenzene showed that water molecules (8.5 water molecules dispersed over 15 positions) are bonded tightly, despite partial occupancy. Water adsorption experiments are described by a D’arcy and Watt model being the sum of Langmuir and Dubinin–Serpinski isotherms. The amount of primary adsorption sites calculated from this model is equal 8.2 mol H(2)O/mol, being very close to the value obtained from the XRD experiments and indicates that water was adsorbed mainly on the primary sites. The antiferromagnetic properties could be only approximately described with the simple Cu(II)-ox-Cu(II) dimer using H = −J·S(1)·S(2), thus, considering non-trivial topology of the whole Cu-Fe chain, we developed our own general approach, based on the semiclassical model (SC) and molecular field (MF) model, to describe precisely the magnetic superexchange interactions in NCU-1. We established that Cu(II)-Cu(II) coupling dominates over multiple Cu(II)-Fe(III) interactions, with J(CuCu) = −275(29) and J(CuFe) = −3.8(1.6) cm(−1) and discussed the obtained values against the literature data