Trianionic Carbocyclic NCN Pincer Ligand: Coordination Chemistry and Reactivity Studies.

(BCHT-NCN)H3 (1) [1,6-bis(methylene(bis-2,6-diisopropylaniline)(benzo)cycloheptatriene)] was synthesized by nucleophilic substitution treating 1,6-bis(methylenebromide)(benzo)cycloheptatriene with 2 equiv of Li[2,6-iPr2C6H3NH], Li[Dipp-NH]. Triple deprotonation of (BCHT-NCN)H3 (1) using n-BuLi yields the deprotonation product [(BCHT-NCN)Li3] (2), which crystallizes as a dimer [{[BCHT-NCN]Li3(Et2O)2}2] (2)2. Coordination compounds of the trianionic pincer ligand were obtained with SnCl2, YCl3(THF)3.5, and HfCl4(THF)2: [(BCHT-NCN)SnLi] (3), [(BCHT-NCN)Y(THF)2] (4), [(BCHT-NCN)HfCl2][Li(THF)4] (5), respectively. A hafnium hydride complex [(BCHT-NCN)HfH(HBEt3)][K(Et2O)2] (6) was isolated after reaction of 5 with K[HBEt3]. A MeNHC substitution product [(BCHT-NCN)HfCl(MeNHC)] (7) was synthesized treating compound 5 with MeNHC at rt. Following an n-BuLi reaction of 7 gives an alkyl complex [(BCHT-NCN)Hf(n-Bu)(MeNHC)] (8). Thermolysis of 7 yields the isomerization product [(BCHT-NCN#)HfCl(MeNHC)] (9), which was transferred into a methyl complex [(BCHT-NCN#)HfMe(MeNHC)] (10) upon treatment with MeMgBr. Hydride abstraction from complex 9 leads to a cationic complex [(BCHT-NCN+)HfCl(MeNHC)][Al(OtBuF)4] (11).

Tailoring the Morphology of Monodisperse Mesoporous Silica Particles Using Different Alkoxysilanes as Silica Precursors.

The hard template method for the preparation of monodisperse mesoporous silica microspheres (MPSMs) has been established in recent years. In this process, in situ-generated silica nanoparticles (SNPs) enter the porous organic template and control the size and pore parameters of the final MPSMs. Here, the sizes of the deposited SNPs are determined by the hydrolysis and condensation rates of different alkoxysilanes in a base catalyzed sol-gel process. Thus, tetramethyl orthosilicate (TMOS), tetraethyl orthosilicate (TEOS), tetrapropyl orthosilicate (TPOS) and tetrabutyl orthosilicate (TBOS) were sol-gel processed in the presence of amino-functionalized poly (glycidyl methacrylate-co-ethylene glycol dimethacrylate) (p(GMA-co-EDMA)) templates. The size of the final MPSMs covers a broad range of 0.5-7.3 µm and a median pore size distribution from 4.0 to 24.9 nm. Moreover, the specific surface area can be adjusted between 271 and 637 m2 g-1. Also, the properties and morphology of the MPSMs differ according to the SNPs. Furthermore, the combination of different alkoxysilanes allows the individual design of the morphology and pore parameters of the silica particles. Selected MPSMs were packed into columns and successfully applied as stationary phases in high-performance liquid chromatography (HPLC) in the separation of various water-soluble vitamins.

Monodisperse Porous Silica/Polymer Nanocomposite Microspheres with Tunable Silica Loading, Morphology and Porosity.

Hybrid organic/inorganic nanocomposites combine the distinct properties of the organic polymer and the inorganic filler, resulting in overall improved system properties. Monodisperse porous hybrid beads consisting of tetraethylene pentamine functionalized poly(glycidyl methacrylate-co-ethylene glycol dimethacrylate) particles and silica nanoparticles (SNPs) were synthesized under Stoeber sol-gel process conditions. A wide range of hybrid organic/silica nanocomposite materials with different material properties was generated. The effects of n(H2O)/n(TEOS) and c(NH3) on the hybrid bead properties particle size, SiO2 content, median pore size, specific surface area, pore volume and size of the SNPs were studied. Quantitative models with a high robustness and predictive power were established using a statistical and systematic approach based on response surface methodology. It was shown that the material properties depend in a complex way on the process factor settings and exhibit non-linear behaviors as well as partly synergistic interactions between the process factors. Thus, the silica content, median pore size, specific surface area, pore volume and size of the SNPs are non-linearly dependent on the water-to-precursor ratio. This is attributed to the effect of the water-to-precursor ratio on the hydrolysis and condensation rates of TEOS. A possible mechanism of SNP incorporation into the porous polymer network is discussed.

Anisotropic and Amphiphilic Mesoporous Core-Shell Silica Microparticles Provide Chemically Selective Environments for Simultaneous Delivery of Curcumin and Quercetin.

Porous silica materials are often used for drug delivery. However, systems for simultaneous delivery of multiple drugs are scarce. Here we show that anisotropic and amphiphilic dumbbell core-shell silica microparticles with chemically selective environments can entrap and release two drugs simultaneously. The dumbbells consist of a large dense lobe and a smaller hollow hemisphere. Electron microscopy images show that the shells of both parts have mesoporous channels. In a simple etching process, the properly adjusted stirring speed and the application of ammonium fluoride as etching agent determine the shape and the surface anisotropy of the particles. The surface of the dense lobe and the small hemisphere differ in their zeta potentials consistent with differences in dye and drug entrapment. Confocal Raman microscopy and spectroscopy show that the two polyphenols curcumin (Cur) and quercetin (QT) accumulate in different compartments of the particles. The overall drug entrapment efficiency of Cur plus QT is high for the amphiphilic particles but differs widely between Cur and QT compared to controls of core-shell silica microspheres and uniformly charged dumbbell microparticles. Furthermore, Cur and QT loaded microparticles show different cancer cell inhibitory activities. The highest activity is detected for the dual drug loaded amphiphilic microparticles in comparison to the controls. In the long term, amphiphilic particles may open up new strategies for drug delivery.

Multifunctional silica nanoparticles for optical and magnetic resonance imaging.

The surface of spherical, nonporous silica nanoparticles (SiO2-NPs) was modified with gadolinium (Gd) complexes, fluorophores, and cell-penetrating peptides to achieve multifunctionality on a single particle. The Gd surface concentrations were 9-16 µmol/g resulting in nanomaterials with high local longitudinal and transversal relaxivities (~1×10(5) and ~5×10(5) /mm/s/NP, respectively). Rapid cellular uptake was observed in vitro; however, larger extracellular agglomerates were also formed. In vivo administration revealed a fast distribution throughout the body followed by a nearly complete disappearance of fluorescence in all organs except the lungs, liver, and spleen after 24 h. Such NPs have the potential to serve as efficient multimodal probes in molecular imaging.

Brightly blue and green emitting Cu(I) dimers for singlet harvesting in OLEDs.

With the chelating aminophosphane ligands Ph2P-(o-C6H4)-N(CH3)2 (PNMe2) and Ph2P-(o-C6H4)-NC4H8 (PNpy), the four halide (Cl, Br, I)-bridged copper coordination compounds [Cu(µ-Cl)(PNMe2)]2 (1), [Cu(µ-Br)(PNMe2)]2 (2), [Cu(µ-I)(PNMe2)]2 (3), and [Cu(µ-I)(PNpy)]2 (4) were synthesized and structurally characterized. Their photophysical properties were studied in detail. The complexes exhibit strong blue (λmax = 464 (3) and 465 nm (4)) and green (λmax = 506 (1) and 490 nm (2)) luminescence as powders with quantum yields of up to 65% at decay times as short as 4.1 µs. An investigation of the emission decay behavior between 1.3 and 300 K gives insight into the nature of the emitting states. At temperatures below T ≈ 60 K, the decay times of the studied compounds are several hundred microseconds long, which indicates that the emission originates from a triplet state (T1 state). DFT calculations show that this state is of (metal+halide)-to-ligand charge transfer (3)(M+X)LCT character. Investigations at 1.3 K allow us to gain insight into the three triplet substates, in particular, to determine the individual substate decay times being as long as a few milliseconds. The zero-field splittings are smaller than 1 or 2 cm(-1). With an analysis of these data, conclusions about the effectiveness of spin-orbit coupling (SOC) can be drawn. Interestingly, the large differences of SOC constants of the halides are not obviously displayed in the triplet state properties. With a temperature increase from T ≈ 60 to 300 K, a significant decrease of the emission decay time by almost 2 orders of magnitude is observed, and at ambient temperature, the decay times amount only to ∼4-7 µs without a significant reduction of the emission quantum yields. This drastic decrease of the (radiative) decay time is a result of the thermal population of a short-lived singlet state (S1 state) that lies energetically only a few hundred wavenumbers (460-630 cm(-1)) higher than the T1 state. Such an emission mechanism corresponds to a thermally activated delayed fluorescence (TADF). At ambient temperature, almost only a delayed fluorescence (∼98%) is observed. Compounds showing this mechanism are highly attractive for applications in OLEDs or LEECs as, in principle, it is possible to harvest all singlet and triplet excitons for the generation of light in the lowest excited singlet state. This effect represents the singlet harvesting mechanism.

Incorporation of silica nanoparticles into porous templates to fabricate mesoporous silica microspheres for high performance liquid chromatography applications.

High-performance liquid chromatography is one of the most important analytical tools for the identification and separation of substances. The efficiency of this method is largely determined by the stationary phase of the columns. Although monodisperse mesoporous silica microspheres (MPSM) represent a commonly used material as stationary phase their tailored preparation remains challenging. Here we report on the synthesis of four MPSMs via the hard template method. Silica nanoparticles (SNPs) which form the silica network of the final MPSMs were generated in situ from tetraethyl orthosilicate (TEOS) in the presence of (3-aminopropyl) triethoxysilane (APTES) functionalized p(GMA-co-EDMA) as hard template. Methanol, ethanol, 2-propanol, and 1-butanol were applied as solvents to control the size of the SNPs in the hybrid beads (HB). After calcination, MPSMs with different sizes, morphology and pore properties were obtained and characterized by scanning electron microscopy, nitrogen adsorption and desorption measurements, thermogravimetric analysis, solid state NMR and DRIFT IR spectroscopy. Interestingly, the 29Si NMR spectra of the HBs show T and Q group species which suggests that there is no covalent linkage between the SNPs and the template. The MPSMs were functionalized with trimethoxy (octadecyl) silane and used as stationary phases in reversed-phase chromatography to separate a mixture of eleven different amino acids. The separation characteristics of the MPSMs strongly depend on their morphology and pore properties which are controlled by the solvent during the preparation of the MPSMs. Overall, the separation behavior of the best phases is comparable with those of commercially available columns. The phases even achieve faster separation of the amino acids without loss of quality.

Sol-Gel-Controlled Size and Morphology of Mesoporous Silica Microspheres Using Hard Templates.

Mesoporous silica microspheres (MPSMs) represent a promising material as a stationary phase for HPLC separations. The use of hard templates provides a preparation strategy for producing such monodisperse silica microspheres. Here, 15 MPSMs were systematically synthesized by varying the sol-gel reaction parameters of water-to-precursor ratio and ammonia concentration in the presence of a porous p(GMA-co-EDMA) polymeric hard template. Changing the sol-gel process factors resulted in a wide range of MPSMs with varying particle sizes from smaller than one to several micrometers. The application of response surface methodology allowed to derive quantitative predictive models based on the process factor effects on particle size, pore size, pore volume, and specific surface area of the MPSMs. A narrow size distribution of the silica particles was maintained over the entire experimental space. Two larger-scale batches of MPSMs were prepared, and the particles were functionalized with trimethoxy(octadecyl) silane for the application as stationary phase in reversed-phases liquid chromatography. The separation of proteins and amino acids was successfully accomplished, and the effect of the pore properties of the silica particles on separation was demonstrated.

Synthesis and characterization of N-[2-P(i-Pr)2-4-methylphenyl]2- (PNP) pincer tin(IV) and tin(II) complexes.

N-[2-P(i-Pr)(2)-4-methylphenyl](2)(-) (PNP) pincer complexes of tin(IV) and tin(II), [(PNP)SnCl(3)] (2) and [(PNP)SnN(SiMe(3))(2)] (3), respectively, were prepared and characterized by X-ray diffraction, solution and solid state NMR spectroscopy, and (119)Sn Mössbauer spectroscopy. Furthermore, (119)Sn cross polarization magic angle spinning NMR spectroscopic data of [Sn(NMe(2))(2)](2) are reported. Compound 2 is surprisingly stable toward air, but attempts to substitute chloride ligands caused decomposition.

Rational Design of Pore Parameters in Monodisperse Porous Poly(glycidyl methacrylate-co-ethylene glycol dimethacrylate) Particles Based on Response Surface Methodology.

Monodisperse porous poly(glycidyl methacrylate-co-ethylene glycol dimethacrylate) particles are widely applied in different fields, as their pore properties can be influenced and functionalization of the epoxy group is versatile. However, the adjustment of parameters which control morphology and pore properties such as pore volume, pore size and specific surface area is scarcely available. In this work, the effects of the process factors monomer:porogen ratio, GMA:EDMA ratio and composition of the porogen mixture on the response variables pore volume, pore size and specific surface area are investigated using a face centered central composite design. Non-linear effects of the process factors and second order interaction effects between them were identified. Despite the complex interplay of the process factors, targeted control of the pore properties was possible. For each response a response surface model was derived with high predictive power (all R2predicted > 0.85). All models were tested by four external validation experiments and their validity and predictive power was demonstrated.

Influence of calcium-induced aggregation on the sensitivity of aminobis(methylenephosphonate)-containing potential MRI contrast agents.

A novel class of 1,4,7,10-tetraazacyclododecane-1,4,7-tris(methylenecarboxylic) acid (DO3A)-based lanthanide complexes with relaxometric response to Ca(2+) was synthesized, and their physicochemical properties were investigated. Four macrocyclic ligands containing an alkyl-aminobis(methylenephosphonate) side chain for Ca(2+)-chelation have been studied (alkyl is propyl, butyl, pentyl, and hexyl for L(1), L(2), L(3), and L(4), respectively). Upon addition of Ca(2+), the r(1) relaxivity of their Gd(3+) complexes decreased up to 61% of the initial value for the best compounds GdL(3) and GdL(4). The relaxivity of the complexes was concentration dependent (it decreases with increasing concentration). Diffusion NMR studies on the Y(3+) analogues evidenced the formation of agglomerates at higher concentrations; the aggregation becomes even more important in the presence of Ca(2+). (31)P NMR experiments on EuL(1) and EuL(4) indicated the coordination of a phosphonate to the Ln(3+) for the ligand with a propyl chain, while phosphonate coordination was not observed for the analogue bearing a hexyl linker. Potentiometric titrations yielded protonation constants of the Gd(3+) complexes. log K(H1) values for all complexes lie between 6.12 and 7.11 whereas log K(H2) values are between 4.61 and 5.87. Luminescence emission spectra recorded on the Eu(3+) complexes confirmed the coordination of a phosphonate group to the Ln(3+) center in EuL(1). Luminescence lifetime measurements showed that Ca-induced agglomeration reduces the hydration number which is the main cause for the change in r(1). Variable temperature (17)O NMR experiments evidenced high water exchange rates on GdL(1), GdL(2), and GdL(3) comparable to that of the aqua ion.

Carbocyclic pincer carbene complexes of ruthenium: syntheses and reversible hydrogenation.

The ruthenium carbene pincer complex 2 was synthesized treating the benzo annulated cycloheptatriene bisphosphine 1 with RuCl3. Addition of three equivalents of hydrogen to the carbocyclic carbene complex 2 was achieved in reaction of 2 with hydrogen at elevated temperatures. Hydrogenated complex 4, exhibiting a rigid chair conformation in solution, was dehydrogenated by heating a toluene solution of complex 4 to reflux for 5-7 d. In reaction with ethylene, complex 4 transfers one equivalent of hydrogen, forming ethane and alkyl complex 5.

Chemical Imaging of Single Anisotropic Polystyrene/Poly (Methacrylate) Microspheres with Complex Hierarchical Architecture.

Monodisperse polystyrene spheres are functional materials with interesting properties, such as high cohesion strength, strong adsorptivity, and surface reactivity. They have shown a high application value in biomedicine, information engineering, chromatographic fillers, supercapacitor electrode materials, and other fields. To fully understand and tailor particle synthesis, the methods for characterization of their complex 3D morphological features need to be further explored. Here we present a chemical imaging study based on three-dimensional confocal Raman microscopy (3D-CRM), scanning electron microscopy (SEM), focused ion beam (FIB), diffuse reflectance infrared Fourier transform (DRIFT), and nuclear magnetic resonance (NMR) spectroscopy for individual porous swollen polystyrene/poly (glycidyl methacrylate-co-ethylene di-methacrylate) particles. Polystyrene particles were synthesized with different co-existing chemical entities, which could be identified and assigned to distinct regions of the same particle. The porosity was studied by a combination of SEM and FIB. Images of milled particles indicated a comparable porosity on the surface and in the bulk. The combination of standard analytical techniques such as DRIFT and NMR spectroscopies yielded new insights into the inner structure and chemical composition of these particles. This knowledge supports the further development of particle synthesis and the design of new strategies to prepare particles with complex hierarchical architectures.

Macrocyclic Gd3+ chelates attached to a silsesquioxane core as potential magnetic resonance imaging contrast agents: synthesis, physicochemical characterization, and stability studies.

Two macrocyclic ligands, 1,4,7,10-tetraazacyclododecane-1-glutaric-4,7,10-triacetic acid (H(5)DOTAGA) and the novel 1,4,7,10-tetraazacyclododecane-1-(4-(carboxymethyl)benzoic)-4,7,10-triacetic acid (H(5)DOTABA), were prepared and their lanthanide complexes (Ln = Gd(3+), Y(3+)) attached to an amino-functionalized T(8)-silsesquioxane. The novel compounds Gadoxane G (GG) and Gadoxane B (GB) possess eight monohydrated lanthanide complexes each, as evidenced by multinuclear ((1)H, (13)C, (29)Si) NMR spectroscopy and high resolution mass spectrometry (HR-MS). Pulsed-field gradient spin echo (PGSE) diffusion (1)H NMR measurements revealed hydrodynamic radii of 1.44 nm and global rotational correlation times of about 3.35 ns for both compounds. With regard to potential MRI contrast agent applications, a variable-temperature (17)O NMR and (1)H nuclear magnetic relaxation dispersion (NMRD) study was carried out on aqueous solutions of the gadolinium(III) complexes of the Gadoxanes and the corresponding monomeric ligands to yield relevant physicochemical properties. The water exchange rates of the inner-sphere water molecules are all very similar (k(ex)(298) between (5.3 +/- 0.5) x 10(6) s(-1) and (5.9 +/- 0.3) x 10(6) s(-1)) and only slightly higher than that reported for the gadolinium(III) complex of 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid (H(4)DOTA) (k(ex)(298) = 4.1 x 10(6) s(-1)). Despite their almost identical size and their similar water exchange rates, GB shows a significantly higher longitudinal relaxivity than GG over nearly the whole range of magnetic fields (e.g., 17.1 mM(-1) s(-1) for GB and 12.1 mM(-1) s(-1) for GG at 20 MHz and 25 degrees C). This difference arises from their different local rotational correlation times (tau(lR)(298) = 240 +/- 10 ps and 380 +/- 20 ps, respectively), because of the higher rigidity of the phenyl ring of GB as compared to the ethylene spacer of GG. A crucial feature of these novel compounds is the lability of the silsesquioxane core in aqueous media. The hydrolysis of the Si-O-Si moieties was investigated by (29)Si NMR and PGSE diffusion (1)H NMR spectroscopy, electrospray ionization mass spectrometry (ESI-MS), as well as by relaxivity measurements. Although frozen aqueous solutions (pH 7.0) of GG and GB can be stored at -28 degrees C for at least 10 months without any decomposition, with increasing temperature and pH the hydrolysis of the silsesquioxane core was observed (e.g., t(1/2) = 15 h at pH 7.4 and 55 min at pH 8.1 for GG at 37 degrees C). No change in relaxivity was detected within the first 3 h, since the hydrolysis of the initial Si-O-Si moieties has no influence on the rotational correlation time. However, the further hydrolysis of the silsesquioxane core leads to smaller fragments and therefore to a decrease in relaxivity.

Conformation controlled stepwise hydride shuffling from the metal to the ligand backbone.

The benzo annulated cycloheptatriene PCP pincer ruthenium hydrido dicarbonyl complex syn-2 was prepared in one step by treatment of the ligand 1 with Ru3(CO)12. Protonation of syn-2 with the superacid [H(Et2O)2][BArF24] {[BArF24]- = tetrakis[bis(trifluoromethyl)phenyl]borate} initiates the highly stereoselective hydrogenation of one of the double bonds in the cycloheptatriene backbone. This results in the formation of the pentacoordinate cationic 16-electron dicarbonyl ruthenium complex 3. Hydrogenation of 3 with LiAlH4 generates the hydride complexes syn-4 and anti-4 which after protonation allow isolation of the symmetric 5. In 5 a second double bond of the cycloheptatriene backbone was hydrogenated. Complex 5 was also obtained directly by the reaction of 3 with hydrogen (1 bar). Storage of 5 under a hydrogen atmosphere yields two pairs of η2-H2 complexes (syn-7, anti-7) which are in a tautomeric equilibrium with their corresponding dihydrides (syn-8, anti-8). A stepwise transfer of the hydrides to the ligand backbone can be deduced from the distribution of deuterium along the seven membered ring after applying the deuterated reagents (D+, D2). The observed stereochemistry suggests that the hydride transfer is controlled by conformational constraints.

High-temperature chlorination-reduction sequence for the preparation of silicon hydride modified silica surfaces.

A general method for the functionalization of silica surfaces with silicon hydride (Si-H) groups is described for four different preparations of silica. The silica surface is reduced in a two-step chlorination-reduction procedure within a simple gas-flow system at high temperatures. After initial dehydroxylation of the silica surface, silicon chloride groups are formed by the reaction with thionyl chloride. The chlorination activates otherwise inaccessible surface siloxane moieties. A high silicon-hydride surface concentration results from the subsequent reduction of the chlorinated surface with hydrogen. The physical properties of the resulting silica are analyzed using scanning electron microscopy, as well as dynamic light scattering and Brunauer-Emmet-Teller measurements. The chlorination-reduction sequence has no significant impact on the structure, surface area and mesopore size of the silica materials used. The surface of the materials is characterized by diffuse reflectance infrared Fourier transform (DRIFT) and (29)Si CP/MAS NMR spectroscopy. The silicon-hydride groups are mostly of the ${{\rm T}{{3\hfill \atop {\rm H}\hfill}}}$-type. The use of high temperatures (>800 degrees C) results in the condensation of internal and surface silanol groups. Therefore, materials with both a fully condensed silica matrix as well as a surface free of silanol groups are obtained. The materials are ideal precursors for further molecular silica surface modification, as demonstrated with a ferrocene derivative.

A simple approach to a new T8-POSS based MRI contrast agent.

A fast and simple route was developed to synthesize a new T8-silsesquioxane based contrast agent for potential application in Magnetic Resonance Imaging. For this purpose the novel C2-thiol-functionalized T8-silsesquioxane (3) was constructed as a carrier molecule as well as the DOTA based gadolinium(iii) complex (11) equipped with allyl terminated linkers was prepared. The linkage of the complexes to the T8-silsesquioxane was performed via an UV-light catalyzed thiol-ene click reaction within one hour which affords the desired product 13 in a yield of 80%. The successful transformation as well as the intactness of the cube was confirmed by spectroscopic methods and mass spectrometry. This new and simple approach offers a highly effective access to T8-silsesquioxanes functionalized with eight metal complexes. Longitudinal relaxivity measurements of compound 13 (9.5 ± 0.9 mM-1 s-1) at 3 T in HEPES buffered cell culture medium (physiological conditions) show a significant enhancement of r1 per 1 mM gadolinium in comparison to the clinically applied contrast agent Dotarem™ (3.4 mM-1 s-1). In relation to the former reported T8-silsesquioxane based contrast agent Gadoxane G (10.6 mM-1 s-1) a similar relaxivity is found. As the T8-core of polyhedral oligosilsesquioxanes (POSS) based contrast agents undergoes a hydrolysis process depending on the pH, long-term r1 measurements in different solutions (water, cell culture medium and HEPES buffered medium) as well as 1H, 1H/29Si HSQC and PGSE diffusion 1H NMR spectroscopic investigations on aqueous solutions were performed. In solutions featuring an approximately neutral pH (D2O, pD = 7.0; water and HEPES buffered medium, pH = 7.4-7.5) contrast agent 13 (t1/2 = 2.4 d, HEPES/medium) shows a slower decomposition of the T8-cage in comparison to the previously synthesized Gadoxane G (t1/2 = 15 ± 3 h, HEPES/medium). However, under more basic conditions (medium, pH = 8.4-8.5) the decomposition process of 13 is considerably accelerated (t1/2 ∼ 55-60 min), indicating a higher sensitivity of the T8-cage to pH shifts into the basic range similar to Gadoxane G.

One-pot synthesis of micron partly hollow anisotropic dumbbell shaped silica core-shell particles.

A facile method is described to prepare micron partly hollow dumbbell silica particles in a single step. The obtained particles consist of a large dense part and a small hollow lobe. The spherical dense core as well as the hollow lobe are covered by mesoporous channels. In the case of the smaller lobe these channels are responsible for the permeability of the shell which was demonstrated by confocal imaging and spectroscopy.

Synthesis of Polysiloxane-Bound (Ether-phosphine)palladium Complexes. Stoichiometric and Catalytic Reactions in Interphases(1).

The reaction of two equiv of the monomeric ether-phosphine O,P ligand (MeO)(3)Si(CH(2))(3)(Ph)PCH(2)-Do [1a(T(0)()), 1b(T(0)())] {Do = CH(2)OCH(3) [1a(T(0)())], CHCH(2)CH(2)CH(2)O [1b(T(0)())]} with PdCl(2)(COD) yields the monomeric palladium(II) complexes Cl(2)Pd(P approximately O)(2) [2a(T(0)())(2)(), 2b(T(0)())(2)()]. The compounds 2a(T(0)())(2)() and 2b(T(0)())(2)() are sol-gel processed with variable amounts (y) of Si(OEt)(4) (Q(0)()) to give the polysiloxane-bound complexes 2a(T(n)())(2)()(Q(k)())(y)(), 2b(T(n)())(2)()(Q(k)())(y)() (Table 1) {P approximately O = eta(1)-P-coordinated ether-phosphine ligand; for T(n)() and Q(k)(), y = number of condensed T type (three oxygen neighbors), Q type (four oxygen neighbors) silicon atoms; n and k = number of Si-O-Si bonds; n = 0-3; k = 0-4; 2a(T(n)())(2)()(Q(k)())(y)(), 2b(T(n)())(2)()(Q(k)())(y)() = {[M]-SiO(n)()(/2)(OX)(3)(-)(n)()}(2)[SiO(k)()(/2)(OX)(4)(-)(k)()](y)(), [M] = (Cl(2)Pd)(1/2)(Ph)P(CH(2)Do)(CH(2))(3)-, X = H, Me, Et}. The complexes 2b(T(n)())(2)()(Q(k)())(y)() (y = 4, 12, 36) show high activity and selectivity in the hydrogenation of 1-hexyne and tolan. The dicationic complexes [Pd(P&arcraise;O)(2)][SbF(6)](2) [3a(T(0)())(2)(), 3b(T(0)())(2)()] are formed by reacting Cl(2)Pd(P approximately O)(2) with 2 equiv of a silver salt {P&arcraise;O = eta(2)-O&arcraise;P-coordinated ether-phosphine ligand; 3a(T(0)())(2)(), 3b(T(0)())(2)() = [M]-SiOMe(3); [M] = {[Pd(2+)](1/)(2)P(Ph)(CH(2)CH(2)OCH(3))(CH(2))(3)-}{SbF(6)} (a), {[Pd(2+)](1/)(2)P(Ph)(CH(2)CHCH(2)CH(2)CH(2)O)(CH(2))(3)-}{SbF(6)} (b)}. Their polysiloxane-bound congeners 3a(T(n)())(2)(), 3b(T(n)())(2)() {[M]-SiO(n)()(/2)(OX)(3)(-)(n)} are obtained if a volatile, reversible bound ligand like acetonitrile is employed during the sol-gel process. The bis(chelate)palladium(II) complexes 3a(T(n)())(2)(), 3b(T(n)())(2)() are catalytic active in the solvent-free CO-ethene copolymerization, producing polyketones with chain lengths comparable to those obtained with chelating diphosphine ligands. The polysiloxane-bound palladium(0) complexes 5a(T(n)())(2)()(Q(k)())(4)(), 5b(T(n)())(2)()(Q(k)())(4)() {[M]-SiO(n)()(/)(2)(OX)(3)(-)(n)}(2)[SiO(k)()(/2)(OX)(4)(-)(k)](4), [M] = [(dba)Pd](1/)(2)P(Ph)(CH(2)Do)(CH(2))(3)-} undergo an oxidative addition reaction with iodobenzene in an interphase with formation of the complexes PhPd(I)(P approximately O)(2).4SiO(2) [6a(T(n)())(2)()(Q(k)())(4)(), 6b(T(n)())(2)()(Q(k)())(4)()] {[M]-SiO(n)()(/)(2)(OX)(3)(-)(n)](2)[SiO(k)()(/2)(OX)(4)(-)(k)](4), [M] = [PhPd(I)](1/2)P(Ph)(CH(2)Do)(CH(2))(3)-}, which insert carbon monoxide into the palladium-aryl bond even in the solid state.

Benzo annulated cycloheptatriene PCP pincer iridium complexes.

The benzo annulated cycloheptatriene PCP pincer ligand was prepared in five steps. Treatment of with Ir(CO)3Cl gave the meridional cyclometalated chlorohydrido carbonyl iridium complexes which differ in their arrangement of the H, Cl, and CO ligands around iridium. Storing in THF led to isomerization processes. Hydrogen shifts from the sp(3)-CH carbon bound to iridium into the ligand backbone produced the three isomers . Reductive elimination of HCl from these complexes resulted in the square planar Ir(i) carbonyl complexes . Abstraction of the hydrogen from the sp(3)-CH-Ir fragment could be achieved either by treatment of with Ph3CBF4 or by the elimination of H2 which is initiated by CF3SO3H. The mass spectrometric characterisation of using fast atom bombardment reveals a complex fragmentation pattern. These different "fragment" ions were further investigated by electro-spray ionisation (tandem) mass spectrometry in high and low resolution. The identified compounds were attributed to structures by DFT calculations.