Optimum operating conditions for manufacturing ibuprofen tablets coated with polyethylene glycol by melt crystallization process

Journal of Thermal Analysis and Calorimetry - The aim of this work is to apply the melt crystallization technology to manufacture ibuprofen tablets coated with polyethylene glycol in a single step....     

Photophysical and structural impact of phosphorylated anions associated to lanthanide complexes in water

A new ligand, LC, bis-[(6'-carboxy-2,2'-bipyridine-6-yl)]phenylphosphine oxide, in which the tridentate 6-carboxy-2,2'-bipyridyl arms are directly linked to a phenylphosphine oxide fragment, has been synthesized. The corresponding [Ln.LC]Cl.xH2O complexes (Ln = Eu, x = 4, and Tb, x = 3) were isolated from solutions containing equimolar amounts of LC and hydrated LnCl3 salts and characterized by elemental analysis, mass spectrometry, and infrared spectroscopy. The interactions of the Eu complex with various anions (AMP(2-), ADP3-, ATP,4- HPO4(2-), and NO3-) were studied by titration experiments, using UV-vis, luminescence spectroscopy, and excited-state lifetime measurements. The results are in keeping with strong interactions with the ADP3-, ATP4-, and phosphate anions in TRIS/HCl buffer (0.01 M, pH = 7.0), as revealed by the determination of the conditional stepwise association constants. These values are higher than the one determined for ligand LB, bis[(6'-carboxy-2,2'-bipyridine-6-methyl-yl)]-n-butylamine (Delta log K approximately 1-2). The interaction of complexes [Ln.LB]+ and [Ln.LC]+ with nitrate, monohydrogenophosphate, methyl phosphate (MeP2-), methyldiphosphate (MeDP3-), and methyltriphosphate (MeTP4-) anions was investigated by means of quantum mechanical (QM) calculations. The results, combined with data on the photophysical impact of the sequential competitive binding of anions to the Eu complexes in water, suggest that LB is too flexible to ensure a good coordination pocket, while the molecular structure of ligand LC stabilizes both the formation of the lanthanide complexes and its adducts with ATP.     

Tuning the coordination sphere around highly luminescent lanthanide complexes

A series of three ligands designed for the formation of water-soluble luminescent lanthanide complexes is described. All ligands are based on a 6'-carboxy-2,2':6',2'-terpyridine framework linked via a methylene bridge to n-butylamine. The second negatively charged arm consists of a 6-carboxy-2-methylenepyridine for L1, a 6'-carboxy-6-methylene-2,2'-bipyridine for L2, and a 6'-carboxy-6-methylene-2,2':6',2'-terpyridine for L3. The photophysical properties of the Eu and Tb complexes were studied in aqueous solutions by means of absorption spectroscopy and steady-state and time-resolved luminescence spectroscopy. Luminescence excited-state lifetimes were recorded and led to the determination of two water molecules in the first coordination sphere. The europium complexes were characterized by means of (1)H NMR spectroscopy in D 2O and DFT calculations performed at the B3LYP level both in vacuo and in aqueous solution. Finally, the influence of different phosphorylated anions such as HPO 4 (2-), ATP (4-), ADP (3-), and AMP (2-) on the luminescence properties of the [Eu L X (H 2O) 2] (+) complexes ( X = 1-3) was investigated in buffered aqueous solutions (0.01 M TRIS, pH 7.0), showing a significant interaction of ATP (4-) with [Eu( L2)(H 2O) 2] (+). The coordination of anions was understood in terms of partial decomplexation of one arm of the ligands and water displacement, with formation of ternary species, and it was rationalized on the basis of the structural models of the complexes obtained from DFT calculations.     

A disymmetric terpyridine based ligand for the formation of luminescent di-aquo lanthanide complexes

The synthesis of ligand H3 based on a disymmetrically substituted terpyridine core functionalised by a carboxylic acid in the 6-position and a bis(carboxymethyl)aminomethyl function in the 6'-position is described. The coordination behaviour of this heptadentate (4N/3O) ligand with lanthanide cations (Ln=Eu, Gd and Tb) was studied in solution showing the formation of complexes with [Ln] stoichiometry. Complexes with general formula [Ln(H2O)2] were isolated from neutral water solutions containing equimolar amounts of cations and ligands, and the complexes were characterized in the solid state (elemental analysis, IR) and in solution (mass spectrometry). The photo-physical properties of the luminescent complexes of Eu and Tb were studied in water solution by means of absorption, steady state and time-resolved emission spectroscopies. Evolution of the luminescence lifetimes of the Eu and Tb complexes in H2O and D2O reveals the presence of two water molecules coordinated in the first coordination sphere of the cations. Despite this important hydration number, the overall luminescence quantum yields of the complexes remained elevated, especially in the case of Tb (Phi=22.0 and 6.5% respectively for Tb and Eu). Upon crystallisation the Gd complex formed dimeric species in which two gadolinium atoms are each heptacoordinated by one ligand, the coordination sphere being completed by a single water molecule and a bridging carboxylate function, pointing to different behaviours in the solid and liquid states.     

Efficient route to hybrid polypyridine–carboxylate ligands for lanthanide complexation

An efficient methodology for the preparation of aminobutyl-bromo-terpyridine is described using a preformed imine prepared from a gem-dibromomethyl terpyridine derivative and the primary amine and further reduced to the secondary amine. Alkylation with pyridine, bipyridine, or terpyridine residues in the presence of a mineral base provides highly functionalized asymmetrical and symmetrical N-heterocyclic ligands. All bromo-containing products were subjected to a carboalkoxylation/hydrolysis sequence of reactions, providing the desired carboxylic acids. Stable Eu complexes were prepared under neutral aqueous conditions and some of them display interesting spectroscopic properties.     

Controlled ring‐opening polymerization of trimethylene carbonate and access to PTMC‐PLA block copolymers mediated by well‐defined N‐heterocyclic carbene zinc alkoxides

Four novel Zinc–NHC alkyl/alkoxide/chloride complexes ( 4 , 5 , 9 and 9′ ) were readily prepared and fully characterized, including X‐ray diffraction crystallography for 5 and 9′ . The reaction of N‐methyl‐N′‐butyl imidazolium chloride ( 3.HCl ) with ZnEt₂ (2 equiv.) afforded the corresponding [(C_NHC)ZnCl(Et)] complex ( 4 ) via a protonolysis reaction, as deduced from NMR data. The alcoholysis of 4 with BnOH led to quantitative formation of the dinuclear Zn(II) alkoxide species [(C_NHC)ZnCl(OBn)]₂ ( 5 ), as confirmed by X‐ray diffraction analysis. The NMR data are in agreement with species 5 retaining its dimeric structure in solution at room temperature. The protonolysis reaction of N‐(2,6‐diisopropylphenyl)‐N′‐ethyl methyl ether imidazolium chloride ( 8.HCl ) with ZnEt₂ (2 equiv.) yielded the [(C_NHC)ZnCl(Et)] species 9 . The latter was found to be reactive with CH₂Cl₂ in solution and to cleanly convert to the corresponding Zn(II) dichloride [(C_NHC)ZnCl₂]₂ ( 9′ ), whose molecular structure was also elucidated using X‐ray diffractometry. Unlike Zn(II)–NHC alkoxide species 1 and 2 , which contain a NHC flanked with an additional N‐functional group (i.e. thioether and ether, respectively), the Zn(II) alkoxide species 5 incorporates a monodentate NHC ligand. The Zn(II) complexes 1 , 2 and 5 were tested in the ring‐opening polymerization (ROP) of trimethylene carbonate (TMC). All three species are effective initiators for the controlled ROP of trimethylene carbonate, resulting in the production of narrow disperse PTMC material. Initiator 1 (incorporating a thioether moiety) was found to perform best in the ROP of TMC. Notably, the latter also readily undergoes the sequential ROP of TMC and rac‐LA in the presence of a chain‐transfer agent, leading to well‐defined and high‐molecular‐weight PTMC/PLA block copolymers. Copyright © 2014 John Wiley & Sons, Ltd.     

Unified path integral treatment for generalized Hulthén and Woods-Saxon potentials

A rigorous path integral discussion of the s states for a diatomic molecule potential with varying shape, which generalizes the Hulthén and the Woods-Saxon potentials, is presented. A closed form of the Green’s function is obtained for different shapes of this potential. For λ ? 1 and (1/η)lnλ<r<∞, the energy spectrum and the normalized wave functions of the bound states are derived. When the deformation parameter λ is 0 < λ < 1 or λ < 0, it is found that the quantization conditions are transcendental equations that require numerical solutions. The special cases corresponding to a screened potential (λ = 1), the deformed Woods-Saxon potential (λ = q e^ηR), and the Morse potential (λ = 0) are likewise treated.     

Bridging of bipyridine units by phenylphosphine links: linear and cyclic oligomers and some acid derivatives

[structures: see text] Reaction of 6,6'-dibromo-2,2'-bipyridine with phenylphosphine under palladium-promoted cross-coupling conditions provides a variety of linear oligomers bearing two reactive bromo substituents as well as a cyclic dimer, characterized by X-ray crystallography, in which the bipyridine units are constrained to a cis configuration by two phenylphosphine oxide bridges. Derivatives of the linear species containing both carboxylate and phosphonate substituents are readily obtained.     

Lanthanide/ATP interaction in water mediated by luminescent hemispherical-shaped complexes

Ligand LH(2), composed of two bipyridylcarboxylate fragments linked to an amino butyl chain, reacts with europium and terbium to form luminescent complexes in water at neutral pH. When testing these unsaturated complexes as anion sensors with NO(3)(-), HPO(4)(2)(-), AMP, ADP, and ATP, a marked selectivity is observed for HPO(4)(2)(-) and ATP(4)(-) at pH = 7.0. The interaction of these anions with the complex was investigated by means of absorption and emission spectroscopies. With ATP(4)(-), ES-MS and (31)P NMR experiments revealed the formation of a [Ln.L.(ATP)](3)(-) ternary species.     

Assisted Self-Assembly to Target Heterometallic Mn-Nd and Mn-Sm SMMs: Synthesis and Magnetic Characterisation of [Mn7Ln3(O)4(OH)4(mdea)3(piv)9(NO3)3] (Ln=Nd,Sm, Eu,Gd)**

In an assisted self-assembly approach starting from the [Mn₆O₂(piv)₁₀(4-Me-py)₂(pivH)₂] cluster a family of Mn−Ln compounds (Ln=Pr−Yb) was synthesised. The reaction of [Mn₆O₂(piv)₁₀(4-Me-py)₂(pivH)₂] ( 1 ) with N-methyldiethanolamine (mdeaH₂) and Ln(NO₃)₃ ⋅ 6H₂O in MeCN generally yields two main structure types: for Ln=Tb−Yb a previously reported Mn₅Ln₄ motif is obtained, whereas for Ln=Pr−Eu a series of Mn₇Ln₃ clusters is obtained. Within this series the Gd^III analogue represents a special case because it shows both structural types as well as a third Mn₂Ln₂ inverse butterfly motif. Variation in reaction conditions allows access to different structure types across the whole series. This prompts further studies into the reaction mechanism of this cluster assisted self-assembly approach. For the Mn₇Ln₃ analogues reported here variable-temperature magnetic susceptibility measurements suggest that antiferromagnetic interactions between the spin carriers are dominant. Compounds incorporating Ln=Nd^III( 2 ), Sm^III( 3 ) and Gd^III ( 5 ) display SMM behaviour. The slow relaxation of the magnetisation for these compounds was confirmed by ac measurements above 1.8 K.