Enhanced Visible-Light Photocatalytic Activity of Bismuth Ferrite Hollow Spheres Synthesized via Evaporation-Induced Self-Assembly.

Semiconductor hollow spheres have garnered significant attention in recent years due to their unique structural properties and enhanced surface area, which are advantageous for various applications in catalysis, energy storage, and sensing. The present study explores the surfactant-assisted synthesis of bismuth ferrite (BiFeO3) hollow spheres, emphasizing their enhanced visible-light photocatalytic activity. Utilizing a novel, facile, two-step evaporation-induced self-assembly (EISA) approach, monodisperse BiFeO3 hollow spheres were synthesized with a narrow particle size distribution. The synthesis involved Bi/Fe citrate complexes as precursors and the triblock copolymer Pluronic P123 as a soft template. The BiFeO3 hollow spheres demonstrated outstanding photocatalytic performance in degrading the emerging pollutants Rhodamine B and metronidazole under visible-light irradiation (100% degradation of Rhodamine B in <140 min and of metronidazole in 240 min). The active species in the photocatalytic process were identified through trapping experiments, providing crucial insights into the mechanisms and efficiency of semiconductor hollow spheres. The findings suggest that the unique structural features of BiFeO3 hollow spheres, combined with their excellent optical properties, make them promising candidates for photocatalytic applications.

Hydrothermal Synthesis of Bismuth Ferrite Hollow Spheres with Enhanced Visible-Light Photocatalytic Activity.

In recent years, semiconductor hollow spheres have gained much attention due to their unique combination of morphological, chemical, and physico-chemical properties. In this work, we report for the first time the synthesis of BiFeO3 hollow spheres by a facile hydrothermal treatment method. The mechanism of formation of pure phase BiFeO3 hollow spheres is investigated systematically by variation of synthetic parameters such as temperature and time, ratio and amount of precursors, pressure, and calcination procedures. The samples were characterized by X-ray powder diffraction, scanning electron microscopy, energy dispersive X-ray spectroscopy, and UV-vis diffuse reflectance spectroscopy. We observe that the purity and morphology of the synthesized materials are very sensitive to synthesis parameters. In general, the chemically and morphologically very robust hollow spheres have diameters in the range of 200 nm to 2 µm and a wall thickness of 50-200 nm. The synthesized BiFeO3 hollow spheres were applied as catalysts in the photodegradation of the model pollutant Rhodamine B under visible-light irradiation. Notably, the photocatalyst demonstrated exceptionally high removal efficiencies leading to complete degradation of the dye in less than 150 min at neutral pH. The superior efficiencies of the synthesized material are attributed to the unique features of hollow spheres. The active species in the photocatalytic process have been identified by trapping experiments.

Structural and Magnetic Diversity in Alkali-Metal Manganate Chemistry: Evaluating Donor and Alkali-Metal Effects in Co-complexation Processes.

By exploring co-complexation reactions between the manganese alkyl Mn(CH2SiMe3)2 and the heavier alkali-metal alkyls M(CH2SiMe3) (M=Na, K) in a benzene/hexane solvent mixture and in some cases adding Lewis donors (bidentate TMEDA, 1,4-dioxane, and 1,4-diazabicyclo[2,2,2] octane (DABCO)) has produced a new family of alkali-metal tris(alkyl) manganates. The influences that the alkali metal and the donor solvent impose on the structures and magnetic properties of these ates have been assessed by a combination of X-ray, SQUID magnetization measurements, and EPR spectroscopy. These studies uncover a diverse structural chemistry ranging from discrete monomers [(TMEDA)2 MMn(CH2SiMe3)3] (M=Na, 3; M=K, 4) to dimers [{KMn(CH2SiMe3)3 ⋅C6 H6}2] (2) and [{NaMn(CH2SiMe3)3}2 (dioxane)7] (5); and to more complex supramolecular networks [{NaMn(CH2SiMe3)3}∞] (1) and [{Na2Mn2 (CH2SiMe3)6 (DABCO)2}∞] (7)). Interestingly, the identity of the alkali metal exerts a significant effect in the reactions of 1 and 2 with 1,4-dioxane, as 1 produces coordination adduct 5, while 2 forms heteroleptic [{(dioxane)6K2Mn2 (CH2SiMe3)4(O(CH2)2OCH=CH2)2}∞] (6) containing two alkoxide-vinyl anions resulting from α-metalation and ring opening of dioxane. Compounds 6 and 7, containing two spin carriers, exhibit antiferromagnetic coupling of their S=5/2 moments with varying intensity depending on the nature of the exchange pathways.

Accessing sodium ferrate complexes containing neutral and anionic N-heterocyclic carbene ligands: structural, synthetic, and magnetic insights.

This study reports the synthesis and single-crystal X-ray crystallographic, NMR spectroscopic, and magnetic characterization of a series of sodium ferrates using bis(amide) Fe(HMDS)2 as a precursor (HMDS = 1,1,1,3,3,3-hexamethyldisilazide). Reaction with sodium reagents NaHMDS and NaCH2SiMe3 in hexane afforded donor-solvent-free sodium ferrates [{NaFe(HMDS)3}∞] (1) and [{NaFe(HMDS)2(CH2SiMe3)}∞] (2), respectively, which exhibit contacted ion pair structures, giving rise to new polymeric chain arrangements made up of a combination of inter- and intramolecular Na···Me(HMDS) electrostatic interactions. Addition of the unsaturated NHC IPr (IPr = 1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene) to 1 and 2 caused deaggregation of their polymeric structures to form discrete NHC-stabilized solvent-separated ion pairs [Na(IPr)2](+)[Fe(HMDS)3](-) (3) and [(THF)3·NaIPr](+)[Fe(HMDS)2CH2SiMe3](-) (4), where in both cases, the NHC ligand coordinates preferentially to Na. In contrast, when IPr is sequentially reacted with the single-metal reagents NaCH2SiMe3 and Fe(HMDS)2, the novel heteroleptic ferrate (THF)3Na[:C{[N(2,6-(i)Pr2C6H3)]2CHCFe(HMDS)2}] (5) is obtained. This contains an anionic NHC ligand acting as an unsymmetrical bridge between the two metals, coordinating through its abnormal C4 position to Fe and its normal C2 position to Na. The formation of 5 can be described as an indirect ferration process where IPr is first metalated at the C4 position by the polar sodium alkyl reagent, which in turn undergoes transmetalation to the more electronegative Fe(HMDS)2 fragment. Treatment of 5 with 1 molar equiv of methyl triflate (MeOTf) led to the isolation and structural elucidation of the neutral abnormal NHC (aNHC) tricoordinate iron complex [CH3C{[N(2,6-iPr2C6H3)]2CHCFe(HMDS)2}] (6) with the subsequent elimination of NaOTf, disclosing the selectivity of complex 5 to react with this electrophile via its C2 position, leaving its Fe-C4 and Fe-N bonds intact. The magnetic susceptibility properties of compounds 1-6 have been examined. This study revealed a drastic change of magnetic susceptibility in replacing a pure σ donor from an idealized trigonal coordination environment by an NHC π donating character.

Homoleptic hexa and penta gallylene coordinated complexes of molybdenum and rhodium.

The reactions of molybdenum(0) and rhodium(I) olefin containing starting materials with the carbenoid group 13 metal ligator ligand GaR (R = Cp*, DDP; Cp* = pentamethylcyclopentadienyl, DDP = HC(CMeNC(6)H(3)-2,6-(i)Pr(2))(2)) were investigated and compared. Treatment of [Mo(η(4)-butadiene)(3)] with GaCp* under hydrogen atmosphere at 100 °C yields the homoleptic, hexa coordinated, and sterically crowded complex [Mo(GaCp*)(6)] (1) in good yields ≥50%. Compound 1 exhibits an unusual and high coordinated octahedral [MoGa(6)] core. Similarly, [Rh(GaCp*)(5)][CF(3)SO(3)] (2) and [Rh(GaCp*)(5)][BAr(F)] (3) (BAr(F) = B{C(6)H(3)(CF(3))(2)}(4)) are prepared by the reaction of GaCp* with the rhodium(I) compound [Rh(coe)(2)(CF(3)SO(3))](2) (coe = cyclooctene) and subsequent anion exchange in case of 3. Compound 2 features a trigonal bipyramidal [RhGa(5)] unit. In contrast, reaction of excess Ga(DDP) with [Rh(coe)(2)(CF(3)SO(3))](2) does not result in a high coordinated homoleptic complex but instead yields [(coe)(toluene)Rh{Ga(DDP)}(CF(3)SO(3))] (4). The common feature of 2 and 4 in the solid state structure is the presence of short CF(3)SO(2)O···Ga contacts involving the GaCp* or rather the Ga(DDP) ligand. Compounds 1, 2, and 4 have been fully characterized by single crystal X-ray diffraction, variable temperature (1)H and (13)C NMR spectroscopy, IR spectroscopy, mass spectrometry, as well as elemental analysis.

Molecular alloys: experimental and theoretical investigations on the substitution of zinc by cadmium and mercury in the homologous series [Mo(M'R)12] and [M(M'R)8] (M=Pd, Pt; M'=Zn, Cd, Hg).

The synthesis and structural characterization of novel, metal-rich, highly coordinated compounds [Mo(M'R)(12)] and [M(M'R)(8)] (M: Pd, Pt, Mo; M': Zn, Cd; R: Me=CH(3), Cp*=pentamethylcyclopentadienyl) are reported. Additionally, a description of the bonding situation of the new compounds by means of quantum-chemical calculations is presented including the Hg analogues. Reaction of [Pt(GaCp*)(4)] with CdMe(2) results in the formation of the unprecedented all-Cd coordinated [Pt(CdMe)(4)(CdCp*)(4)] (1). Similarly, the treatment of the all-Zn coordinated [Pd(ZnMe)(4)(ZnCp*)(4)] with CdMe(2) affords the novel Zn/Cd mixed compound [Pd(CdMe)(4)(ZnCp*)(4)] (2). The related Zn/Cd mixed compound [Mo(ZnCp*)(3)(CdMe)(9)] (3) is prepared by reaction of [Mo(ZnCp*)(4)(GaMe)(4)] with an excess amount of CdMe(2). All compounds were analyzed by (1)H and (13)C NMR spectroscopy, elemental analysis, and single-crystal X-ray diffraction. The bonding situation of these highly coordinated, metal-rich molecules 1-3 were studied by quantum-chemical calculations using density functional theory (DFT) at the BP86/TZ2P+ level, atoms-in-molecules (AIM) analysis, and energy-decomposition analysis (EDA), as well as the its natural orbitals for chemical valence variation (EDA-NOCV) and including the hypothetically all-Hg-coordinated analogues. The results point out that the radial interactions M-M' in the icosahedral compounds that have twelve ligands are best described as classical electron-pair-sharing covalent bonds, whereas the dodecahedral species, which have eight ligands, exhibit metal-ligand donor-acceptor bonds. The attractive interactions between the metal-ligand fragments M'R by means of M'-M' bonds are weaker but not insignificant. All complexes fulfill the 18-electron rule. The analysis clarifies the electronic structures as being distinctly different from typical endohedral clusters M@(M''R)(n) that exhibit strong peripheral M''-M'' interactions: The M'-M' bonds are not strong enough to yield stable (M'R)(n) cages.

Nanocasting synthesis of BiFeO3 nanoparticles with enhanced visible-light photocatalytic activity.

In this work, monodisperse BiFeO3 nanoparticles with a particle diameter of 5.5 nm were synthesized by a nanocasting technique using mesoporous silica SBA-15 as a hard template and pre-fabricated metal carboxylates as metal precursors. To the best of our knowledge, the synthesized particles are the smallest BiFeO3 particles ever prepared by any method. The samples were characterized by X-ray powder diffraction, transmission electron microscopy and UV-vis diffuse reflectance spectroscopy. The phase purity of the product depends on the type of carboxylic acid used in the synthesis of the metal precursors, the type of solvent in the wet impregnation process, and the calcination procedure. By using tartaric acid in the synthesis of the metal precursors, acidified 2-methoxyethanol in the wet impregnation process and a calcination procedure with intermediate plateaus, monodisperse 5.5 nm BiFeO3 nanoparticles were successfully obtained. Furthermore, the nanoparticles were applied in photodegradation reactions of rhodamine B in aqueous solution under visible-light irradiation. Notably, the cast BiFeO3 nanoparticles demonstrated very high efficiencies and stability under visible-light irradiation, much higher than those of BiFeO3 nanoparticles synthesized by other synthetic methods. The possible mechanism in the photodegradation process has been deeply discussed on the basis of radical trapping experiments.

Molecular alloys, linking organometallics with intermetallic Hume-Rothery phases: the highly coordinated transition metal compounds [M(ZnR)(n)] (n >or= 8) containing organo-zinc ligands.

This paper presents the preparation, characterization and bonding analyses of the closed shell 18 electron compounds [M(ZnR)(n)] (M = Mo, Ru, Rh, Ni, Pd, Pt, n = 8-12), which feature covalent bonds between n one-electron organo-zinc ligands ZnR (R = Me, Et, eta(5)-C(5)(CH(3))(5) = Cp*) and the central metal M. The compounds were obtained in high isolated yields (>80%) by treatment of appropriate GaCp* containing transition metal precursors 13-18, namely [Mo(GaCp*)(6)], [Ru(2)(Ga)(GaCp*)(7)(H)(3)] or [Ru(GaCp*)(6)(Cl)(2)], [(Cp*Ga)(4)RhGa(eta(1)-Cp*)Me] and [M(GaCp*)(4)] (M = Ni, Pd, Pt) with ZnMe(2) or ZnEt(2) in toluene solution at elevated temperatures of 80-110 degrees C within a few hours of reaction time. Analytical characterization was done by elemental analyses (C, H, Zn, Ga), (1)H and (13)C NMR spectroscopy. The molecular structures were determined by single crystal X-ray diffraction. The coordination environment of the central metal M and the M-Zn and Zn-Zn distances mimic the situation in known solid state M/Zn Hume-Rothery phases. DFT calculations at the RI-BP86/def2-TZVPP and BP86/TZ2P+ levels of theory, AIM and EDA analyses were done with [M(ZnH)(n)] (M = Mo, Ru, Rh, Pd; n = 12, 10, 9, 8) as models of the homologous series. The results reveal that the molecules can be compared to 18 electron gold clusters of the type M@Au(n), that is, W@Au(12), but are neither genuine coordination compounds nor interstitial cage clusters. The molecules are held together by strong radial M-Zn bonds. The tangential Zn-Zn interactions are generally very weak and the (ZnH)(n) cages are not stable without the central metal M.

Syntheses and crystal structures of ruthenium and rhodium olefin complexes containing GaCp.

The reactivity of olefin containing complexes of the d(8) metals Ru(0) and Rh(I) toward GaCp* and AlCp* is presented. [Ru(eta(4)-butadiene)(PPh(3))(3)] reacts with GaCp* to give the substitution product [Ru(eta(4)-butadiene)(PPh(3))(2)(GaCp*)] (1), which proved to be stable in the presence of GaCp* even under hydrogenolytic conditions. In contrast, the bis-styrene complex [Ru(PPh(3))(2)(styrene)(2)] undergoes full substitution of the olefin ligands to give [Ru(PPh(3))(2)(GaCp*)(3)] (2), whereas reaction of [Ru(eta(2),eta(2)-COD)(eta(6)-COT)] (COD = 1,5-cyclooctadiene, C(8)H(12), COT = 1,3,5-cyclooctatriene, C(8)H(10)) and GaCp* leads to [Ru(eta(2),eta(2)-COD)(GaCp*)(3)] (3) under mild hydrogenolytic conditions. Analogously, the Rh(I) compounds [{Rh(eta(2),eta(2)-NBD)(PCy(3))(2)}{BAr(F)}] (NBD = norbornadiene) and [{Rh(eta(2),eta(2)-COD)(2)}{BAr(F)}] ({BAr(F)}= B{[C(6)H(3)(CF(3))(2)](4)) yield the complexes [{Rh(eta(2),eta(2)-NBD)(PCy(3))(GaCp*)(2)}{BAr(F)}] (4), [{Rh(eta(2),eta(2)-COD)(GaCp*)(3)}{BAr(F)}] (5), and [{Rh(eta(2),eta(2)-COD)(AlCp*)(3)}{BAr(F)]}] (6) upon reaction with the appropriate ECp* ligand (E = Al, Ga). All new complexes have been characterized by means of (1)H and (13)C NMR spectroscopy and elemental analysis, as well as X-ray single crystal structure analysis in the case of 1-5.

Substituent-free gallium by hydrogenolysis of coordinated GaCp*: synthesis and structure of highly fluxional [Ru2(Ga)(GaCp*)7(H)3].

All change: Complete ligand exchange through the hydrogenation of [Ru(eta(4)-cod)(eta(6)-cot)] in the presence of GaCp* under mild conditions leads to the title complex featuring a "naked" gallium atom bridging two ruthenium centers (see structure: C white, Ga blue, Ru red). This cluster can be considered as a trapped intermediate on the way to mixed-metal nanoparticles; cot = 1,3,5-cyclooctatriene; cod = 1,5-cyclooctadiene, Cp* = C(5)Me(5).

Organometallic chemistry of Ga(+): formation of an unusual gallium dimer in the coordination sphere of ruthenium.

New insights into the distinct organometallic chemistry of the Ga(+) ion are presented. Ga(+) reacts as a strong electrophile with the electron rich ligand trismethylene-methane (C(CH(2))(3) (2-)) attached at Ru by insertion into a Ru--C bond. The resulting "gallamethylallyl" ligand behaves like strong nucleophile similar to known monovalent GaR species. This donor property leads to the dimeric structure of the product [{Ru(GaCp*)(3)[eta(3)-(CH(2))(2)C{CH(2)(mu-Ga)}]}(2)][(BAr(F))(2)] (4) (Cp*=C(5)Me(5), [BAr(F)]=[B{C(6)H(3)(CF(3))(2)}(4)]). Very unexpectedly, the two gallium ligands in this dimer are found in close vicinity to each other with a distance in the range of Ga--Ga bonds. Indeed, AIM calculations confirm a weak attractive closed shell Ga--Ga interaction. Finally, a novel example of a complex with substituent-free Ga(+) as a ligand was found in the compound [Ru(PCy(3))(2)(GaCp*)(2)(Ga)][BAr(F)] (6) (Cy=C(6)H(11), cyclohexyl), the very short Ru--Ga bond length confirming the assumption that Ga(+) represents a pure sigma/pi-accepting ligand in this case.

Towards dipyrrins: oxidation and metalation of acyclic and macrocyclic Schiff-base dipyrromethanes.

Oxidation of acyclic Schiff-base dipyrromethanes cleanly results in dipyrrins, whereas the macrocyclic 'Pacman' analogues either decompose or form new dinuclear copper(ii) complexes that are inert to ligand oxidation; the unhindered hydrogen substituent at the meso-carbon allows new structural motifs to form.

Homo- and heteroleptic alkoxycarbene f-element complexes and their reactivity towards acidic N-H and C-H bonds.

The reactivity of a series of organometallic rare earth and actinide complexes with hemilabile NHC-ligands towards substrates with acidic C-H and N-H bonds is described. The synthesis, characterisation and X-ray structures of the new heteroleptic mono- and bis(NHC) cyclopentadienyl complexes LnCp2(L) 1 (Ln = Sc, Y, Ce; L = alkoxy-tethered carbene [OCMe2CH2(1-C{NCHCHN(i)Pr})]), LnCp(L)2 (Ln = Y) , and the homoleptic tetrakis(NHC) complex Th(L)4 4 are described. The reactivity of these complexes, and of the homoleptic complexes Ln(L)3 (Ln = Sc 3, Ce), with E-H substrates is described, where EH = pyrrole C4H4NH, indole C8H6NH, diphenylacetone Ph2CC(O)Me, terminal alkynes RC≡CH (R = Me3Si, Ph), and cyclopentadiene C5H6. Complex 1-Y heterolytically cleaves and adds pyrrole and indole N-H across the metal carbene bond, whereas 1-Ce does not, although 3 and 4 form H-bonded adducts. Complexes 1-Y and 1-Sc form adducts with CpH without cleaving the acidic C-H bond, 1-Ce cleaves the Cp-H bond, but 2 reacts to form the very rare H(+)-[C5H5](-)-H(+) motif. Complex 1-Ce cleaves alkyne C-H bonds but the products rearrange upon formation, while complex 1-Y cleaves the C-H bond in diphenylacetone forming a product which rearranges to the Y-O bonded enolate product.

Accessing low denticity coordination modes of a high denticity tripodal ligand to complete its coordinative repertoire.

New coordination complexes of the neutral tripodal tetra-amine Me(6)TREN with tBu(3)Ga or tBu(2)Zn have been synthesised and studied with their molecular structures revealing, for the first time, coordination to metal centres via an η(1) or η(2) mode, adding to previously reported η(3) and η(4) ligated examples.

One electron organozinc ligands in metal rich molecules by Ga/Zn exchange: from Cp*Rh(GaCp*)2 to Cp*Rh(ZnR)4 units.

Two unusual compounds, [{Cp*Rh(ZnCp*)(2)(ZnMe)(ZnCl)}(2)] (1) and [Cp*(2)Rh][(Cp*Rh)(6)Zn(18)Cl(12)(mu(6)-Cl)] (2), both bearing closed shell 18-electron square pyramidal Cp*RhZn(4) building units were obtained by combined Ga/Zn, Me/Cp* and Me/Cl exchange upon treatment of [Cp*Rh(GaCp*)(2)(GaCl(2)Cp*)] with ZnMe(2) (Cp* = pentamethylcyclopentadienyl).