Electromembrane extraction (EME) and HPLC determination of non-steroidal anti-inflammatory drugs (NSAIDs) in wastewater samples

In this paper, an electromembrane extraction (EME) combined with a HPLC procedure using diode array (DAD) and fluorescence detection (FLD) has been developed for the determination of six widely used non-steroidal anti-inflammatory drugs (NSAIDs): salicylic acid (SAC), ketorolac (KTR), ketoprofen (KTP), naproxen (NAX), diclofenac (DIC) and ibuprofen (IBU). The drugs were extracted from basic aqueous sample solutions, through a supported liquid membrane (SLM) consisting of 1-octanol impregnated in the walls of a S6/2 Accurel^® polypropylene hollow fiber, and into a basic aqueous acceptor solution resent inside the lumen of the hollow fiber with a potential difference of 10 V applied over the SLM. Extractions that were carried out in 10 min using a potential of 10 V from pH 12 NaOH aqueous solutions shown concentration enrichments factors of 28-49 in a pH 12 NaOH aqueous acceptor solution. The proposed method was successfully applied to urban wastewaters. Excellent selectivity was demonstrated as no interfering peaks were detected. The procedure allows very low detection and quantitation limits of 0.0009-9.0 and 0.003-11.1 μg L⁻¹, respectively.     

Synthesis, crystal structures and magnetic properties of M(II)Cu(II) chains (M = Mn and Co) with sterically hindered alkyl-substituted phenyloxamate bridging ligands

A series of neutral oxamato‐bridged heterobimetallic chains of general formula [MCu(L^x)₂(S)₂] ? p S ? q H₂O [p=0–1, q=0–2.5; L¹=N‐2,6‐dimethylphenyloxamate, S=DMF with M=Mn ( 1 a ) and Co ( 1 b ); L²=N‐2,6‐diethylphenyloxamate, S=DMF with M=Mn ( 2 a ) and Co ( 2 b ) or S=DMSO with M=Mn ( 2 c ) and Co ( 2 d ); L³=N‐2,6‐diisopropylphenyloxamate, S=DMF with M=Mn ( 3 a ) and Co ( 3 b ) or S=DMSO with M=Mn ( 3 c ) and Co ( 3 d )] were prepared by treating the corresponding anionic oxamatocopper(II) complexes [Cu(L^x)₂]^2? (x=1–3) with M²⁺ cations (M=Mn and Co) in DMF or DMSO as the solvent. The single‐crystal X‐ray structures of 2 a and 3 a reveal the occurrence of well‐isolated, zigzag, oxamato‐bridged manganese(II)–copper(II) chains. The intrachain Cu ??? Mn distances across the oxamato bridge are 5.3761(7) and 5.4002(17) Å for 2 a and 3 a , respectively, whereas the shortest interchain Mn ??? Mn distances are 9.4475(16) and 8.1649(14) Å for 2 a and 3 a , respectively. All of these M^IICu^II chains (M=Mn and Co) exhibit 1D ferrimagnetic behaviour with moderately strong intrachain antiferromagnetic coupling between the square‐planar Cu^II and octahedral high‐spin M^II ions across the oxamato bridge [?J=31.4–35.2 and 33.4–44.8 cm^?1, respectively; H =∑_i?J S _M,i( S _Cu,i+ S _Cu,i?1)]. Only the Co^IICu^II chains show slow magnetic relaxation effects characteristic of single‐chain magnets (SCMs). Analysis of the magnetic relaxation dynamics of 3 d shows a thermally activated mechanism (Arrhenius law dependence) with values of the pre‐exponential factor (τ₀=2.6×10^?9 s) and activation energy (E_a=7.7 cm^?1) that are typical of SCMs. In contrast, two relaxation regimes are observed for 2 d in different temperature regions (τ₀=3.2×10^?10 s and E_a=24.7 cm^?1 for T<4.5 K and τ₀=3.2×10^?14 s and E_a=37.5 cm^?1 for T>4.5 K).     

Highly trifluoromethylated platinum compounds

The homoleptic, square‐planar organoplatinum(II) compound [NBu₄]₂[Pt(CF₃)₄] ( 1 ) undergoes oxidative addition of CF₃I under mild conditions to give rise to the octahedral organoplatinum(IV) complex [NBu₄]₂[Pt(CF₃)₅I] ( 2 ). This highly trifluoromethylated species reacts with Ag⁺ salts of weakly coordinating anions in Me₂CO under a wet‐air stream to afford the aquo derivative [NBu₄][Pt(CF₃)₅(OH₂)] ( 4 ) in around 75 % yield. When the reaction of 2 with the same Ag⁺ salts is carried out in MeCN, the solvento compound [NBu₄][Pt(CF₃)₅(NCMe)] ( 5 ) is obtained in around 80 % yield. The aquo ligand in 4 as well as the MeCN ligand in 5 are labile and can be cleanly replaced by neutral and anionic ligands to furnish a series of pentakis(trifluoromethyl)platinate(IV) compounds with formulae [NBu₄][Pt(CF₃)₅(L)] (L=CO ( 6 ), pyridine (py; 7 ), tetrahydrothiophene (tht; 8 )) and [NBu₄]₂[Pt(CF₃)₅X] (X=Cl ( 9 ), Br ( 10 )). The unusual carbonyl–platinum(IV) derivative [NBu₄][Pt(CF₃)₅(CO)] ( 6 ) is thermally stable and has a ν_CO of 2194 cm^?1. The crystal structures of 2? CH₂Cl₂, 5 , [PPh₄][Pt(CF₃)₅(CO)] ( 6′ ), and 7 have been established by X‐ray diffraction methods. Compound 2 has shown itself to be a convenient entry to the chemistry of highly trifluoromethylated platinum compounds. To the best of our knowledge, compounds 2 and 4 – 10 are the organoelement compounds with the highest CF₃ content to have been isolated and adequately characterized to date.     

PtII Coordination to N1 of 9‐Methylguanine: Why it Facilitates Binding of Additional Metal Ions to the Purine Ring

The preparation and X‐ray crystal structure analysis of {trans‐[Pt(MeNH₂)₂(9‐MeG‐N1)₂]} ? {3 K₂[Pt(CN)₄]} ? 6 H₂O ( 3 a ) (with 9‐MeG being the anion of 9‐methylguanine, 9‐MeGH) are reported. The title compound was obtained by treating [Pt(dien)(9‐MeGH‐N7)]²⁺ ( 1 ; dien=diethylenetriamine) with trans‐[Pt(MeNH₂)₂(H₂O)₂]²⁺ at pH 9.6, 60 °C, and subsequent removal of the [(dien)Pt^II] entities by treatment with an excess amount of KCN, which converts the latter to [Pt(CN)₄]^2?. Cocrystallization of K₂[Pt(CN)₄] with trans‐[Pt(MeNH₂)₂(9‐MeG‐N1)₂] is a consequence of the increase in basicity of the guanine ligand following its deprotonation and Pt coordination at N1. This increase in basicity is reflected in the pK_a values of trans‐[Pt(MeNH₂)₂(9‐MeGH‐N1)₂]²⁺ (4.4±0.1 and 3.3±0.4). The crystal structure of 3 a reveals rare (N7,O6 chelate) and unconventional (N2,C2,N3) binding patterns of K⁺ to the guaninato ligands. DFT calculations confirm that K⁺ binding to the sugar edge of guanine for a N1‐platinated guanine anion is a realistic option, thus ruling against a simple packing effect in the solid‐state structure of 3 a . The linkage isomer of 3 a , trans‐[Pt(MeNH₂)₂(9‐MeG‐N7)₂] ( 6 a ) has likewise been isolated, and its acid–base properties determined. Compound 6 a is more basic than 3 a by more than 4 log units. Binding of metal entities to the N7 positions of 9‐MeG in 3 a has been studied in detail for [(NH₃)₃Pt^II], trans‐[(NH₃)₂Pt^II], and [(en)Pd^II] (en=ethylenediamine) by using ¹H NMR spectroscopy. Without exception, binding of the second metal takes place at N7, but formation of a molecular guanine square with trans‐[(Me₂NH₂)Pt^II] cross‐linking N1 positions and trans‐[(NH₃)₂Pt^II] cross‐linking N7 positions could not be confirmed unambiguously, despite the fact that calculations are fully consistent with its existence.     

Binap-gold(I) versus Binap-silver trifluoroacetate complexes as catalysts in 1,3-dipolar cycloadditions of azomethine ylides

The 1,3-dipolar cycloaddition between azomethine ylides and alkenes is efficiently catalysed by [{(S(a))-Binap-Au(tfa)}(2)] (Binap=2,2'-bis(diphenylphosphino)-1,1'-binaphthyl; tfa=trifluoroacetyl). Maleimides, 1,2-bis(phenylsulfonyl)ethylene, chalcone and nitrostyrene were suitable dipolarophiles even when using sterically hindered 1,3-dipole precursors. The results obtained in these transformations improve the analogous ones obtained in the same reactions catalysed by [Binap-Ag(tfa)]. In addition, computational studies have also been carried out to demonstrate both the high enantioselectivity exhibited by the chiral gold(I) complex, and the non-linear effect observed in this transformation.     

Stable N-heterocyclic carbene (NHC)-palladium(0) complexes as active catalysts for olefin cyclopropanation reactions with ethyl diazoacetate

The Pd(0) complexes [(NHC)PdL(n)] (NHC=N-heterocyclic carbene ligand; L=styrene for n=2 or PR(3) for n=1) efficiently catalyse olefin cyclopropanation by using ethyl diazoacetate (EDA) as the carbene source with activities that improve on previously described catalytic systems based on this metal. Mechanistic studies have shown that all of these catalyst precursors deliver the same catalytic species in solution, that is, [(IPr)Pd(sty)], a 14e(-) unsaturated intermediate that further reacts with EDA to afford [(IPr)Pd(=CHCO(2)Et)(sty)], from which the cyclopropane is formed.     

Striking alkenol versus allenol reactivity: metal-catalyzed chemodifferentiating oxycyclization of enallenols

An efficient chemodivergent metal-controlled methodology for the generation of different highly functionalized oxygen heterocycles from common enallenol substrates has been developed. Chemoselectivity control in the O-C functionalization of an enallenol can be achieved through the choice of catalyst: AuCl(3), PdCl(2), and [PtCl(2)(CH(2)=CH(2))](2) exclusively afford dihydrofurans through selective activation of the allenol moiety, whereas FeCl(3) solely gives tetrahydrofurans or tetrahydropyrans through selective activation of the alkenol moiety. We have also shown that a combination of metal-mediated hydroalkoxylation and allenic aminocyclization reactions can lead to a useful preparation of the tetrahydrofuro[3,2-b]piperidine core of the antimalarial alkaloid isofebrifugine. These divergent heterocyclization reactions have been developed experimentally and additionally, their mechanisms have been investigated by a theoretical study.     

Adsorption of arsenic (V) from a water solution onto a surfactant-modified zeolite

In this study a surfactant-modified zeolite (SMZ) was prepared by adsorbing the cationic surfactant hexadecyltrimethylammonium (HDTMA) bromide on a clinoptilolite. The adsorption of the surfactant modified the surface properties of the clinoptilolite and enhanced the anionic capacity of the SMZ. The adsorption equilibrium data of As(V) from the water solution on the SMZ were obtained in a batch adsorber, and the Langmuir isotherm matched the data reasonably well. The As(V) adsorption capacity of the SMZ was 12.5 times greater than that of the clinoptilolite. The adsorption of As(V) on SMZ was mainly due to the interactions between the anionic sites of the SMZ and the As(V) anions in water solution. The adsorption capacity of the SMZ was dependent on the solution pH. The adsorption capacity was increased and decreased by augmenting the pH from 5 to 7 and from 7 to 12, respectively. This unusual behavior was due to the fact that the affinity of the As(V) for the SMZ was dependent on the As(V) species that were present in solution. The adsorption capacity of the SMZ was slightly favored by decreasing the temperature from 25 to 15 °C. The heat of adsorption was estimated to be ΔH _ads=−46.82 KJ/mol, indicating that the adsorption was exothermic and the As(V) was chemisorbed on the SMZ.     

Synthesis and photophysics of silicon phthalocyanine-perylenebisimide triads connected through rigid and flexible bridges

Three new bisperylenebisimide-silicon phthalocyanine triads [(PBI)(2)-SiPcs 1, 2, and 3] connected with either rigid or flexible bridges were synthesized and characterized. A new synthetic approach to connect SiPc and PBI moieties through click chemistry produced triad 3 with an 80% yield. In (PBI)(2)-SiPc 1, PBI and SiPc are orthogonal and were connected with a rigid connector; triads 2 and 3 bear flexible aliphatic bridges, resulting in a tilted (2) or nearly parallel arrangement (3) of PBI and SiPc. Photoinduced intramolecular processes in these (PBI)(2)-SiPcs were studied and the results are compared with those of the reference compounds SiPc-ref and PBI-ref. The occurrence of electron-transfer processes between the SiPc and PBI units was confirmed by time-resolved emission and transient absorption techniques. Charge-separated (CS) states with lifetimes of 0.91, 1.3 and 2.0 ns for triads 1, 2, and 3, respectively, were detected using femtosecond laser flash photolysis. Upon the addition of Mg(ClO(4))(2), an increase in the lifetime of the CS states to 59, 110 and 200 μs was observed for triads (PBI)(2)-SiPcs 1, 2, and 3, respectively. The energy of the CS state (SiPc(·+)-PDI(·-)/Mg(2+)) is lower than the energy of both silicon phthalocyanine ((3)SiPc*-PDI) and perylenebisimide (SiPc-(3)PDI*) triplet excited states, which decelerates the metal ion-decoupled electron-transfer process for charge recombination to the ground state, thus increasing the lifetime of the CS state. The photophysics of the three triads demonstrate the importance of the rigidity of the spacer and the orientation between donor and acceptor units.