FAB Mass Spectrometry Research Articles

Fluorinated‐Thiolate Osmium(III) and Osmium(IV) Complexes Bearing N,N‐diethyldithiocarbamate and Substituted Phosphines. Synthesis, Crystal Structures and DFT‐Studies

AbstractThe paramagnetic osmium(III) [Os(SRF)(S2CNEt2)2(P(C6H4X‐4)3)] (RF=C6F4H−4, C6F5; X=OCH3, CH3, F) (1–6) along with diamagnetic osmium(IV) [Os(SRF)2(S2CNEt2)2] (7–8) complexes were obtained from [Os(SRF)4(P(C6H4‐X)3)] and NaS2CNEt2, which were characterized by FAB mass spectrometry, IR spectroscopy, single crystal X‐ray diffraction, and for the diamagnetic 7 also by NMR. TD‐DFT calculations were performed to simulate the absorption spectra of complexes. In the visible region, LMCT transitions contribute to the calculated intensities, which are somewhat related to the color of the synthesized compounds. In the ultraviolet region, the phosphine ligand plays a significant role in MLCT transitions, which results in Os(III) complexes exhibiting an intense band in that region. Topological analysis and electron localization function (ELF) maps calculated for 6 and 7 confirm the strong ionic character of the Os−S coordination bonds formed by the thiophenolate and dithiocarbamate ligands. This comprehensive study provides information on the structure, bonding, and electronic properties of osmium complexes, for potential applications in catalysis, materials science, and biological systems.

Synthesis of methotrexate-betulonic acid hybrids and evaluation of their effect on artificial and Caco-2 cell membranes

An efficient protocol for the synthesis of novel methotrexate-betulonic acid hybrids with a (tert-butoxycarbonylamino)-3,6-dioxa-8-octanamine (Boc-DOOA) linkage has been developed. Reaction of N-(2-(2-(2-aminoethoxy)ethoxy)ethyl)-betulonamide with methotrexate resulted in a mixture of isomeric conjugates which were separated by column chromatography. Their structures and composition have been fully established by 1H NMR, 13C spectra, FAB mass spectrometry and elemental analysis. The identity of conjugates was confirmed by LC-MS data. Membranotropic properties of the new hybrids were assessed on the basis of their interactions with artificial lipid membranes by differential scanning calorimetry (DSC) method. The ability of the conjugates to penetrate Caco-2 cells is inferior to methotrexate. Probably, this is due to the increasing lipophilicity, the affinity of these hybrid molecules for the lipid bilayer increases, which is confirmed by experiments with artificial membranes.

Synthesis, Characterization and Biological Properties of Mn (II) and Cu (II) Complexes with Sulfonamide and Imidazole Derivatives: Genotoxicity, ADME Profile, and Molecular Docking Studies**

AbstractThe synthesis, characterization, and comparative biological properties of manganese (II) and copper (II) complexes formed with two heterocyclic ligands used in the pharmaceutical field are reported. The characterization of the metal complexes involved elemental analysis, FAB mass spectroscopy, ESR, FTIR, UV‐Visible spectroscopy, and conductometry. The spectroscopic data allowed the determination of the coordination mode and the geometry of all the coordination compounds.

SYNTHESIS METHOD OF OPTICALLY PURE ENANTIOMERS OF 5-ARYL SUBSTITUTED3-METHYL‑7- NITRO‑1,2-DIHYDRO‑3H‑1,4-BENZODIAZEPIN‑2-ONES

The aim of this work is to develop a simple, fast and efficient method for the synthesis of optically pure enantiomers of some 5-aryl-substituted 3-methyl‑7-nitro‑1,2-dihydro‑3H‑1,4-benzodiazepin‑2-ones using simple reagents. In the course of the study, we found that the interaction of 2-amino‑5-nitrobenzophenone or 2-amino‑2’-chloro‑5-nitrobenzophenone with optically active L- or D‑α-alanine N‑carboxyanhydrides in the presence of two equivalents of trifluoroacetic acid does not leads to the formation of the corresponding reaction intermediates (2-amino-N-(2-benzoylphenyl)propanamide), even when refluxed for 24 hours in xylene. Acylation of 5-nitro‑2-aminobenzophenones with hydrochlorides of L- or D‑α-alanine acid chlorides, followed by cyclization under mild conditions, leads to target 3-methyl‑7-nitro‑1,2-dihydro‑3H‑1,4-benzodiazepin‑2-ones characterized by high optical purity. It is noteworthy that these reactions allow the coupling of acid chlorides derived from stereospecific α-alanines with weakly reactive 5-nitro derivatives of 2-aminobenzophenone without racemization. It is important to note that the acid chloride hydrochlorides of optically active α-alanines, which are chemically unstable and extremely sensitive to moisture, are used as building blocks in the work. In this case, acid chlorides of individual antipodes of L- or D‑α-alanine were synthesized in absolute chloroform using phosphorus pentachloride and the products were isolated by simple filtration of precipitates, without applying additional purification to them. The structure of the title compound was confirmed by spectroscopy 1H and 13C NMR, and FAB mass spectrometry methods, purity was controlled by HPLC. To analyze the optical purity of the1,2-dihydro‑3H‑1,4-benzodiazepines synthesized in this work, HPLC was applied using stationary chiral phase CiraDex®. This simple preparation method is of potential practical importance for the design and synthesis of optically pure enantiomers of various 3-alkyl derivatives of 1,2-dihydro‑3H‑1,4-benzodiazepin‑2-ones with a wide spectrum of biological activity.

Prodigiosin R3, a new multicyclic prodigiosin formed by prodigiosin cyclization genes in the roseophilin producer.

The rph gene cluster for prodigiosin biosynthesis has been identified in Streptomyces griseoviridis 2464-S5, which produces cyclic prodigiosin derivatives including roseophilin (2), prodigiosin R1 (3) and prodigiosin R2 (4). A new cyclic prodigiosin, prodigiosin R3 (1), was produced by the redG redP double disruptant of Streptomyces coelicolor M511 expressing four cyclization gene candidates (rphG, rphG2, rphG3 and rphG4) in the rph cluster. The same compound was isolated from Streptomyces griseoviridis 2464-S5. The molecular formula of 1 was established as C27H33N3O by ESI and FAB mass spectrometry. The structure was determined to be a multicyclic prodigiosin with three alkyl linkages by NMR spectroscopic analysis. Prodigiosin R3 (1) showed cytotoxicity against HeLa human cervical carcinoma cells and HT1080 human fibrosarcoma cells with IC50s of 2.1 µM and 3.2 µM, respectively.

SYNTHESIS, SPECTROSCOPIC CHARACTERISATION, AND KINETIC PARAMETER STUDY OF LABILE CHROMIUM COMPLEXES USING BENZOIC ACID AS A LIGAND

Ethanol was used as the solvent in the process of producing chromium benzoic acid complexes by combining CrO3 (chromium trioxide) and benzoic acid. Its spectrum characteristics were evaluated by the use of elemental analysis, FAB-Mass Spectroscopy,1 HNMR spectroscopy, FTIR Spectroscopy, UV-Vis Spectroscopy, and ICP-OES, and its thermal decomposition has been studied through DSC. The Objective was to get inside of thermal stability, the heat of energy, and the rate of decomposition of the complexes. The kinetic parameter, low amount of activation energy, and enthalpy of reaction, all pointed to the complexes having a high degree of liability.

2-Propyl-N′-[1,7,7-trimethylbicyclo[2.2.1]hept-2-ylidene]pentanehydrazide

2-Propyl-N′-[1,7,7-trimethylbicyclo[2.2.1]hept-2-ylidene]pentanehydrazide was obtained in 80% yield via the Einhorn variation of the Schotten–Baumann method by (+)-camphor hydrazide condensation with valproic acid (VPA) chloride. The structure of the titled compound was verified by Raman, FTIR, 1H-NMR, and 13C-NMR spectral analysis along with FAB-mass spectrometry. Thermal properties of synthesized derivative were elucidated by DSC and its purity by HPLC. The compound was successfully tested as a potential anticonvulsant agent based on models of chemically- and electrically-induced seizures.

Two cytotoxic squalene-derived polyethers from the Japanese red alga Chondria armata

The red alga Chondria armata is known to produce and contain a rich diversity of secondary metabolites, such as domoic acid-related alkaloids and triterpene polyethers. Our investigation on red alga C. armata from Kagoshima coast, Japan, resulted in the isolation of two new triterpene polyethers, bandokorols A (1) and B (2). The structures of these compounds were determined based on spectroscopic data such as infrared (FTIR), 1H-NMR, APT, 1H–1H-COSY, HSQC, HMBC, NOESY and FAB mass spectrometry (HRFABMS). The anticancer potentials of these compounds were tested against adult T-cell leukaemia (ATL), S1T cells and their IC50 values are reported here.

Synthesis, Spectroscopic, Thermal and in vitro Antimicrobial Activity of Fe(III) and Mn(III) Metal Complexes of Semicarbazone

In this work novel pyrazolone based semicarbazone derivatives and their spectroscopic and biological activities were investigated. Pyrazolone based semicarbazone ligands and their Fe(III) and Mn(III) heterochelates were synthesized. The structure of semicarbazone ligands were confirmed by 1H NMR, IR, elemental analysis and their heterochelates were confirmed by thermal studies (TGA/DTG & DSC) and FAB mass spectroscopy. All the ligands and heterochelates were screened for antimicrobial study against Gram positive (Bacillus megaterium, Bacillus subtilis) and Gram negative (E. coli, Klebsiella) microorganisms. The results confirmed that semicarbazone based heterochelates have a great potential and significant for further investigation.

Novel tris-buffer based Schiff base bearing long flexible alkoxy arm and its lanthanide complexes: Mesomorphism and photoluminescence

A new liquid crystalline salicylaldimine Schiff base having pendant hydroxymethyl (CH2OH) groups and a series of lanthanide(III) complexes of the type, [Ln(LH)3(NO3)3] {Ln = La, Pr, Sm, Gd, Tb; LH=(E)-2-((1, 3-dihydroxy-2-(hydroxyl methyl) propan- 2-ylimino)methyl)-5-(hexadecyloxy) phenol} have been synthesised. The compounds were characterised by FT-IR, 1H NMR, 13C NMR, UV–Vis, and FAB-mass spectroscopy. Thermal behaviour of these compounds was studied using polarising optical microscopy (POM) and differential scanning calorimetry. The phase confirmation and molecular organization in the mesophase was ascertained by variable temperature powder X-ray diffraction (XRD) study. The ligand and the complexes both showed highly viscous smecticA and columnar mesophase, respectively. A bilayer self organization of the ligand molecules with interdigitation of the alkyl chains in the mesophase is proposed. Molecular organizations of the complexes in the mesophase involve arrangement of all the aliphatic chain pointing in same direction leading to lamellar columnar phase. The ligand showed an intense blue emission at 452 nm while the gadolinium(III) complex exhibited an intense emission at 458 nm (λex = 310 nm). The samarium(III) complex is a bright orange light emitter over a wide range upon UV irradiation.

A NEW METHOD FOR PREPARING 6-NITRO-2-(4-BOC-PIPERAZIN-1-YL)-3H-QUINAZOLIN-4-ONE

The 2-amino-3H-quinazolin-4-one scaffold is found in a large number of molecules with physiological significance and pharmaceutical utility. Previously we synthesized a series of potent antagonists of fibrinogen receptor, derivatives of 2-(piperazin-1-yl)-3H-quinazolin-4-one. The key building block for preparing the above series of compounds is 6-amino-2-(4-Boc-piperazin-1-yl)-3H-quinazolin-4-one, which was synthesized by hydrogenation of 6-nitro-2-(4-Boc-piperazin-1-yl)-3H-quinazolin-4-one. In turn, the nitro derivative was obtained starting from isatoic anhydride in four stages, by a method that can be considered classical, but difficult. The purpose of this work is to simplify the preparation of 6-nitro-2-(4-Boc-piperazin-1-yl)-3H-quinazolin-4-one. We proposed an effective method for the synthesis of 6-nitro-2-(4-Boc-piperazin-1-yl)-3H-quinazolin-4-one based on a sequential process, C-N cross-coupling and intramolecular amidation. As the arylhalogenide, 2-bromo-5-nitrobenzoic acid methyl ester was used, as the N-nucleophile, 4-Boc-piperazine-1-carboxamidine, a guanidine derivative, was used. In the study, we used two types of catalytic systems, which both gave good results. The application of the third generation of Palladacycleprecatalyst –[(4,5-Bis(diphenylphosphino)-9,9-dimethylxanthene)-2-(2′-amino-1,1′-biphenyl)] palladium(II) methanesulfonate, leads to the production of the target product in a high yield, in comparison with the use of the catalytic system: precatalyst – Tris(dibenzylideneacetone) dipalladium(0) chloroform adduct and Buchwald Ligands – 4,5-Bis(diphenylphosphino)-9,9-dimethylxanthene. The structure of the title compound was confirmed by spectroscopy 1H and 13C NMR, and FAB mass spectrometry methods, purity was controlled by HPLC. This method has potential implications for the design of various 2-amino-3H-quinazolin-4-ones.

Corrosion resistance and thermal behavior of acetylacetonato-oxoperoxomolybdenum(VI) complex of maltol: Experimental and DFT studies

Corrosion and thermo-chemistry is a prominent discipline of physical science. In the conspicuous fascination to design potent durable materials herein, we report the synthesis of an oxoperoxomolybdenum(VI) complex containing maltol and acetylacetone as co-ligands. Magnetic susceptibility measurements, FAB mass spectrometry, FT-IR spectroscopy and thermal analysis are the main characterization techniques that have been used to arrive at the proposed structure of the compound. Experimental data have been compared with density functional theory (DFT) based theoretical outcomes by applying B3LYP functional, and basis set LanL2DZ for Mo and 6311 + G for all other atoms. A close agreement has been found between computed data and the experimental results. From the overall study, it can be found that the complex bears hepta-coordinate pseudo-pentagonal bipyramidal geometry. Based on combined experimental-DFT calculations, the possible role of the complex in designing smart materials has been evaluated. In addition to satisfactory anticorrosive potential, thermo-gravimetry based excellent heat resistance has been shown by the complex. The article also focuses on the calculation of various thermodynamic and kinetic parameters of the respective pyrolysis (TG curve).

Synthesis and spectroscopic studies of Ru(II) complexes of steroidal thiosemicarbazones by multi step reaction: As anti-bacterial agents

Ru(II) steroidal metal complexes were synthesized by the reaction of dichlorodicarbonyl ruthenium(II) [Ru(CO)2Cl2]n with Steroidal thiosemicarbazones. Coordination via the thionic sulfur and the azomethine nitrogen atom of the thiosemicarbazone to the Ru(II) metal. Steroidal thiosemicarbazone derivatives were obtained by the thiosemicarbazide with steroidal ketones. Structures of the steroidal thiosemicarbazone and their metal complexes were confirmed by the FT-IR, 1H NMR, 13C NMR, Fab-Mass spectroscopy and elemental analysis. The antibacterial activity of these compounds were first tested in vitro by the disk diffusion assay against two Gram-positive and two Gram-negative bacteria, and then the minimum inhibitory concentration (MIC) was determined. The results showed that steroidal Ru(II) complexes are better inhibit growth as compared to steroidal thiosemicarbazones of both types of the bacteria (gram-positive and gram-negative).

Synthesis and Photochromic Studies of Dithienylethene-Containing Cyclometalated Alkynylplatinum(II) 1,3-Bis(N-alkylbenzimidazol-2'-yl)benzene Complexes.

Several photochromic cyclometalated alkynylplatinum(II) complexes with tridentate 1,3-bis(N-alkylbenzimidazol-2'-yl)benzene (bzimb) ligands have been synthesized by the reaction of the corresponding chloroplatinum(II) bzimb precursor complexes with the photochromic ligand TMS-C≡C-Th-DTE in the presence of sodium hydroxide. They have been characterized by (1)H NMR spectroscopy and positive-ion FAB or ESI mass spectrometry and confirmed by elemental analysis. One of the complexes has also been characterized by X-ray crystallography. Their photophysical, photochromic, and electrochemical properties have been studied. Upon photoexcitation, the yellow solutions in benzene display green phosphorescence originating from the triplet intraligand ((3)IL) excited state. All the cyclometalated alkynylplatinum(II) bzimb complexes exhibit reversible photochromism with solution colors changing between yellow and purple upon photoirradiation. The thermal bleaching kinetics of complex 2 has been studied in toluene at various temperatures with the activation barrier for the thermal cycloreversion reaction determined.

Phenylmercury(ii) sulfanylpropenoates: an example of symmetrization with the 3-(2-methoxyphenyl)-2-sulfanylpropenoato ligand

Some new phenylmercury(ii) sulfanylpropenoate complexes were prepared and characterized. The identification of diphenylmercury(ii) reveals the existence of a symmetrization process, which was followed in solution by NMR.

Photoluminescent tetrahedral d10-metal Schiff base complexes exhibiting highly ordered mesomorphism

A series of four-coordinate d10-metal complexes of the type [ML2] {M=Zn, Cd, Hg; L=4-nitro-2-((octadecylimino)methyl)phenol}, incorporating a new N-alkylated bidentate [N,O]-donor salicylaldimine Schiff base ligand, has been synthesized and characterized by elemental analyses, FT-IR, UV–Vis, 1H NMR and FAB-mass spectroscopies. The ligand is non-mesomorphic and devoid of any photoluminescence. The zinc(II) and cadmium(II) complexes displayed highly ordered mesophases reminiscent of soft crystals. The phases have been characterized by polarizing optical microscopy (POM), differential scanning calorimetry (DSC) and powder X-ray diffraction (PXRD) studies. The complex of mercury(II) decomposed prior to melting. An orthogonal symmetry with a ‘herringbone’ array for the zinc complex and a primitive triclinic symmetry (p1) for the cadmium complex, respectively, has been proposed. The complexes exhibited fluorescence at room temperature, both in the solution and in the solid state, with emission maxima in the blue region. Density functional theory (DFT) calculations carried out using the gaussian 09 program at the B3LYP level revealed a distorted tetrahedral geometry around the metal center in all the complexes. Natural bond orbital (NBO) analysis suggested appreciable charge transfer from the ligand to the metal center in the complexes.

A hyperbranched mechanically interlocked rotaxane-type polymer

The interaction of the diacid chloride (2) of N,N’-bis(5″-carboxypentyl)-4,4′bipyridnium bis(hexafluorophosphate) (1) with m-phenylene-5′-hydroxymethyl-1′,3′-phenylene-32-crown-10 (3) at −70 °C led to the in situ formation of a pseudorotaxane 4 as an AB2 monomer, which was allowed to polymerize by raising the temperature and adding a catalytic amount of pyridine. The resulting hyperbranched polymer was held together via mechanical bonds formed by threading of the crown ether units by the bipyridinium (paraquat) moieties. The polymer was initially precipitated into aqueous NH4PF6 to remove any unreacted, water soluble diacid 1 to form 5b and then precipitated from DMSO into aqueous NH4PF6 to remove any pyridinium monoester 8 complexed with crown ether units in the polymer, leading to 6. The hyprerbranched polyester was characterized by 1H NMR and NOESY spectroscopies, FAB and MALDI-TOF mass spectrometry and viscometry. NMR spectroscopy confirmed complete esterification of the crown ether alcohol; 5b contained 60% monoesterified paraquat units (8) and 40% diester moieties (9), while 6 contained only 24% monoester moieties, which existed primarily as “focal point” units (10), but also as uncomplexed linker units (11). A variety of mechanically linked structures containing cyclic units is possible, including 17–19. Mass spectrometry on 6 detected masses up to 16.3 kDa, corresponding to a degree of polymerization of 11 units of the diester repeat unit in 17 (and/or isomeric structures).

English

English

Synthesis and physico-chemical characterization of a β-cyclodextrin conjugate for sustained release of Acyclovir

We report the synthesis of an oligomeric prodrug of the antiviral agent Acyclovir (Acy) conjugated to β-cyclodextrin (β-CyD). The drug was selectively linked through a succinic spacer to one of the primary hydroxyl groups of β-CyD by ester linkage in a 1:1 molar ratio. The conjugate was purified by semipreparative reverse-phase chromatography and characterized by FAB mass spectrometry and NMR experiments. The release of Acy from the conjugate was evaluated both in acidic and in neutral conditions and in the presence of porcine liver esterase. In all cases we observed the release of both free Acy and Acy succinate (AcySucc) at differing rates as a function of the hydrolysis conditions. In the presence of esterase the release of free Acy was favoured over AcySucc, showing a release rate of 100% of Acy within 7 days.

Synthesis, characterization, crystal structure and antimicrobial activity of copper(II) complexes with the Schiff base derived from 2-hydroxy-4-methoxybenzaldehyde.

A novel Schiff base, ethyl 4-[(E)-(2-hydroxy-4-methoxyphenyl)methylene-amino]benzoate (HL), was prepared and structurally characterized on the basis of elemental analyses, 1H NMR, 13C NMR, UV-Vis and IR spectral data. Six new copper(II) complexes, [Cu(L)(NO3)(H2O)2] (1), [Cu(L)2] (2), [Cu(L)(OAc)] (3), [Cu2 (L)2Cl2(H2O)4] (4), [Cu(L)(ClO4)(H2O)] (5) and [Cu2(L2S)(ClO4)(H2O)]ClO4·H2O (6) have been synthesized. The characterization of the newly formed compounds was done by IR, UV-Vis, EPR, FAB mass spectroscopy, elemental and thermal analysis, magnetic susceptibility measurements and molar electric conductivity. The crystal structures of Schiff base and the complex [Cu2(L2S)(ClO4)(H2O)]ClO4·H2O (6) have been determined by single crystal X-ray diffraction studies. Both copper atoms display a distorted octahedral coordination type [O4NS]. This coordination is ensured by three phenol oxygen, two of which being related to the µ-oxo-bridge, the nitrogen atoms of the azomethine group and the sulfur atoms that come from the polydentate ligand. The in vitro antimicrobial activity against Escherichia coli ATCC 25922, Salmonella enteritidis, Staphylococcus aureus ATCC 25923, Enterococcus and Candida albicans strains was studied and compared with that of free ligand. The complexes 1, 2, 5 showed a better antimicrobial activity than the Schiff base against the tested microorganisms.