Microwave-assisted one-pot synthesis of new ionic iridium complexes of [Ir(bzq)2(N^N)]+A- type and their selected electroluminescent properties

Iridium C,N-cyclometalated complexes with an ionic structure are considered to be promising candidates for application in host/guest solid-state phosphorescent single-layer devices because the employment of such dopants offers the possibility of reducing their concentration in organic matrices as well as allows obtaining organic light emitting devices (OLEDs) with interesting emission parameters. We report herein a methodology enabling the synthesis of cyclometalated ionic iridium(iii) complexes of the type [Ir(C^N)₂(N^N)]⁺A^- according to a three-component one-pot strategy involving the acceleration of the reaction via microwave irradiation. The developed protocol allowed efficient synthesis of a series of new cationic iridium(iii) coordination derivatives, which were isolated and spectroscopically characterized, while the structures of two of them were determined by the X-ray method. Moreover, the iridium(iii) derivatives were subjected to the cyclic voltammetry studies in order to determine the energies of the HOMO and LUMO levels as well as to estimate their electrochemical properties and to predict some electronic properties. Additionally, the ONIOM calculation scheme that was used to predict HOMO-LUMO gaps for the studied Ir(iii) complexes showed a good correlation between the experimental and calculated values. In order to determine the influence of the structure and nature of the ancillary ligand on the location of the maximum emission band, the photophysical properties of the synthesized iridium complexes were characterized. Finally, the selected compounds were used as emitters for the construction of polymer light emitting diodes (PLEDs) based on a poly(N-vinylcarbazole)/2-(4-tert-butylphenyl)-5-(4-biphenyl)-1,3,4-oxadiazole (PVK/PBD) matrix. The highest luminance, above 10 000 cd m^-2, was recorded for the device containing only 1.0 wt% of [Ir(bzq)₂(1,10-phenanthroline)]⁺PF₆^- in the PVK/PBD. The fabricated PLEDs exhibit current efficiency in the range of 1.0 to 2.2 cd A^-1.

Tetra-functional double-decker silsesquioxanes as anchors for reactive functional groups and potential synthons for hybrid materials

The preparation of a series of double-decker silsesquioxane (DDSQ) derivatives with four reactive functional groups (FGs) is described. The synthetic approach is based on a highly efficient functionalization of a simple tetrasilanol form of DDSQ.

Unusual cis and trans architecture of dihydrofunctional double-decker shaped silsesquioxane and synthesis of its ethyl bridged π-conjugated arene derivatives

An original family of well-defined molecular and macromolecular double-decker silsesquioxane derivatives with ethyl bridged π-conjugated arenes is obtained via hydrosilylation reaction.

A highly selective synthesis of new alkenylsilsesquioxanes by hydrosilylation of alkynes

In this study a selective synthesis of a series of new di- and trisubstituted ethenes with a POSS moiety was performed.

Ruthenium-catalyzed deaminative redistribution of primary and secondary amines

A ruthenium–hydride complex, [Ru(H)(Cl)(CO)(PCy₃)₂], was found to be active in the highly selective redistribution of primary and secondary amines bearing an α-hydrogen atom.

Synthesis of a new class of silsesquioxanes with alkynyl and germyl functionality

Although there are a variety of functional compounds in the vast family of silsesquioxanes (POSS), the number of protocols describing specific monosubstituted silsesquioxanes is limited. There are even fewer reports on alkynyl and/or germyl functionalities appearing together with the POSS compounds. Here, a series of novel kinds of cubic monosubstituted POSS bearing alkynyl and germyl functionality in one molecule are reported. These compounds were synthesized by effective germylative coupling of terminal alkynes with vinylgermanes in the presence of a Ru-H complex. The structures of the products were determined. Moreover, stoichiometric reactions of a complex possessing Ru-Ge were also performed to propose the general mechanistic scheme of this reaction.

Ruthenium-catalysed hydrosilylation of carbon–carbon multiple bonds

Recent advances in ruthenium-catalysed hydrosilylation of C–C multiple bonds and its application to organic synthesis are highlighted.

An efficient catalytic synthesis and characterization of new styryl-ferrocenes and their trans-π-conjugated organosilicon materials

A selective and efficient catalytic method for the synthesis of new styryl-π-conjugated silyl-ferrocenes in a stereoselective manner is presented.

Synthesis and characterization of functionalized molecular and macromolecular double-decker silsesquioxane systems

Synthesis and characterization of new, molecular and macromolecular DDSQ-based compounds functionalized by substituted styrenes and distyrylarenes (also with heteroatoms) in a stereoselective manner is presented.

Influence of ionising irradiation on clotrimazole in the solid state

The effect of ionising irradiation on the antifungal drug clotrimazole has been studied. The compound was subjected to ionisation irradiation in the form of high-energy electron beam (25-800 kGy) from an accelerator. Before and after the irradiation the compound was subjected to the EPR, TLC, HPLC and HPLC-MS analysis. After irradiation with doses 400-800 kGy the colour of the substance was changed from white to cream. Four products of radiolysis appeared in the HPLC chromatogram at 7.7, 4.2, 6.4 and 14.6 min and the active ingredient content decreased to 96.5%. The irradiation with a dose of 25 kGy resulted in the appearance of trace amounts of the product at 7.7 min and free radicals (2.54 x 10(14)spins/g). On the basis of the HPLC-MS data, the main product of radiolysis (t(R)=7.7 min) is 1-(9-phenylfluoren-9-yl)-imidazole. Besides traces of (2-chlorophenyl)-diphenylmethanol, other impurities listed in the European Pharmacopoeia (European Pharmacopea, 5th edition, Council of Europe, Strasbourg, France, 2004.) have not been detected. Clotrimazole has been found to show relatively high resistance to ionising irradiation (greater than fluconazole) and probably will be suitable for radiation sterilisation but with doses lower than 25 kGy.

The influence of radiation sterilization on thiamphenicol

The effect of ionising radiation, applied in the form of an electron beam, in the doses of 25, 100 and 400 kGy on the physical and chemical properties of thiamphenicol in solid phase has been studied by organoleptic analysis (form, colour, smell, solubility, clarity) and spectroscopic methods (UV, IR, EPR), chromatography (TLC), SEM observations, X-ray diffraction, polarimetry and thermal method (DSC). The above-discussed results have proved that on irradiation with a dose of 25 kGy no significant changes appear in thiamphenicol, apart from the formation of free radicals of the lifetime of over 352 days. On irradiation with much higher doses (100 and 400 kGy) no changes were observed in the IR spectra but the UV line intensities slightly increased at lambda(max)=266 and 273 nm, the colour of the powder changed, the radiolysis products appeared as detected by TLC, changes were also observed in the XRD, SEM pictures, the melting point values (DSC) and optical rotation. On the basis of DSC results a linear relation was found between the irradiation dose and the decrease in the melting point and increase in the enthalpy of melting, characterised by high correlation coefficients of r=0.9839 and 0.9622, respectively. Moreover, a linear relation was established between the optical rotation angle and the irradiation dose, alpha(D) ( degrees )=f(dose), characterised by the correlation coefficient r=0.9874. The results obtained indicate that thiamphenicol can be safely subjected to radiation sterilization by the standard dose of 25 kGy.

Radiochemical stability of fluconazole in the solid state

The effect of ionizing radiation in doses between 20 and 200 kGy on physicochemical properties of fluconazole (alpha-(2,4-diflurophenyl)-alpha-(1H-triazol-1-methyl)-1H-1,2,4-triazole-1-ethanol) in the solid state was examined. A number of qualitative and quantitative methods such as scanning electron microscopy (SEM), nuclear magnetic resonance (NMR), ultraviolet (UV) and infrared (IR) spectroscopy, thin layer chromatography (TLC) and high pressure liquid chromatography (HPLC) and organoleptic analysis were used to determine and analyse any changes resulting from irradiation. A change in colour from white to cream was observed at even smallest dose (20 kGy) and as the dose increased the colour deepened from salmon pink to orange at the highest dose of 200 kGy. The UV method showed an increase in absorbance at lambda(max) and an appearance of an additional band in the range 280-310 nm for irradiated samples. These changes were associated with the appearance of one to two decomposition products observed by TLC. Depending on the dose of radiation, the HPLC method detected between 2 and 3 radiolysis products and the decreasing fluconazole content from 0.48 to 7.12%. The remaining analytical methods (SEM, IR and NMR) did not provide any conclusive information in respect of radiological stability of fluconazole. The results indicate that fluconazole is a compound of low radiological stability and should not be sterilized using gamma, beta or E-beam radiation.

Functionalization of octavinylsilsesquioxane by ruthenium-catalyzed silylative coupling versus cross-metathesis

Functionalization of octavinylsilsesquioxane (Vi(8)T(8), 1) by two reactions catalyzed by ruthenium complexes is reported: a silylative coupling reaction catalyzed by [RuHCl(CO)(PCy(3))(2)] (I) and cross-metathesis catalyzed by first- (II) and second-generation (III) Grubbs' catalysts. The two reactions of 1 with styrene take place highly regio- and stereoselectively (the X-ray structure of the product 2 has also been obtained); the cross-metathesis of 1-hexene and allyltrimethylsilane occurs quite effectively, whereas the silylative coupling with these compounds gives a mixture of isomers. Functionalization of 1 with heteroatom-substituted vinyl derivatives (Si, O, N) by silylative coupling reaction has been found to be highly efficient, but cross-metathesis appears to be the more effective method for the synthesis of S-substituted vinyl-silsesquioxane.

The effect of ionizing radiation on some derivatives of 1,4-dihydropyridine in the solid state

The effect of gamma and beta radiation in doses between 10 and 100 kGy on physico-chemical properties of four derivatives of 1,4-dihydropyridine (nifedipine, nitrendipine, felodipine and nimodipine) in the solid state was analysed. A number of qualitative and quantitative methods such as UV, IR, TLC, GLC, DSC, EPR as well as organoleptic and gravimetric analysis were used to determine and analyse any changes resulting from irradiation. In order to determine the effectiveness of sterilization with ionizing radiation of doses from 10 to 25 kGy, various microbiological tests were used. It was established that only doses 10-20 kGy of both kinds of radiation ensure total sterilization without any degradation of physico-chemical properties of the compounds studied. For the doses 50-100 kGy a decrease in the content of the compounds, appearance of the products of their decomposition and changes in the melting point and IR spectra appeared. Felodipine (with chlorophenyl substituent) was found to be much more sensitive to ionising radiation than nifedipine, nitrendipine and nimodipine (all with nitrophenyl substituent).

The effect of gamma-radiation on nitroimidazole derivatives

The effect of gamma irradiation, in doses from 10 to 50 kGy on physical and chemical properties of metronidazole, ornidazole and tynidazole in solid state has been studied. Results of the measurements by the UV, IR, TLC, EPR, DSC methods revealed the presence of free radicals, products of decomposition, an increase in the melting point and a decrease or increase in the content of the substance studied. Microbiological assays proved that sterilization of the compounds studied was effective even with the smallest irradiation dose applied. The maximum tolerated dose and the safe sterilisation dose were determined.

Free radicals in irradiated drugs: an EPR study

Exposure of dry powder forms of the drugs nitrendipine, nifedipine, felodipine, and nimodipine to gamma-radiation results in the formation of free radicals detected by electron paramagnetic resonance (EPR) spectroscopy. The four structurally related drugs show qualitatively identical EPR spectral features in terms of g-values, the qualitative descriptive parameter. These radicals are very stable, surviving long periods of time in excess of 9 months and possibly beyond conventional shelf-life of the drugs. The residual radical population is high enough to be detectable after long storage. Administration of such radiation-treated drugs may present patients with quantities of free radicals and possibilities of secondary cell damage.

Evaluation of nifedipine preparations by chromatographic-spectrophotometric methods

The content of nifedipine in 10 currently available preparations (tablets, capsules, dragees and drops) was analyzed. In the qualitative analysis, a TLC method was employed, whereas in the quantitative analysis, a chromatographic-spectrophotometric method developed in our laboratory (TLC-UV), a TLC-UV method according to USP XXI, and the method of gas chromatography coupled with mass spectrometry (GC-MS) were employed. For all the preparations under study, the presence of at least one decomposition product as well as a decrease in the content of active component, in most cases proportional to the storage time, were observed. However, in none of the preparations pyridine nitro derivative decomposition products were found, but in each the presence of nitroso derivative was reported. As a result, it was stated that about a half of the preparations studied do not meet the requirements of USP XXI as for as the content of the active substance is concerned, which suggests that the expiration date is shorter by 6 to 12 months.

Photochemical decomposition of phenazone derivatives. Part 7: Mechanism of decomposition in aqueous solutions

Kinetic studies, supplemented by the isolation and identification of the products of decomposition, have proved the process of photochemical decomposition of phenazone derivatives to be a complex reaction, involving several successive parallel reactions, one of which is predominant depending on the concentration of the solution and the atmosphere above it. In an oxygen-free atmosphere and at low concentrations (10(-4) mol/dm3) decomposition is almost wholly the result of second photolysis of zero order to aziridine derivative----aniline----isonitrile. At higher concentrations (10(-3)-10(-2) mol/dm3), the contribution from the reaction of water photoaddition to the double bond C3-C4 increases. Whereas at concentrations of order greater than or equal to 10(-2) mol/dm3, photoisomerization to imidazole derivatives is predominant. In air, one onserves additionally a second reaction of photooxidation to 4-hydroxy-phenazone----1-acetylo-1-methyl-2-phenyl-hydrazine, a reaction of photodemethylation at N2 with simultaneous oxidation to the 4-ketoderivative, and reactions of hydrolysis characteristic for the individual derivatives. The principal primary photolytic reaction for the group of compounds studied consists in cleavage of the N1-N2 bond of the pyrazoline ring.

Photochemical decomposition of phenazone derivatives. Part 6: Effect of substituents on mass fragmentation and photochemical stability

Mass spectra (EI) of phenazone, aminophenazone, 4-aminophenazone, noramidopyrine, isopropyl-aminophenazone, niphenazone, propylphenazone and morazone are obtained. The fragmentation pathways are discussed and the mechanisms of spectrometric fragmentation, as well as their similarities and differences within the group under investigation, are determined. A Hammett relationship is found to hold between the intensity of certain ions and the type of substituent on the C-4 positions. Certain similarities are established between photochemical decomposition and spectroscopic fragmentation, and it is suggested that MS may prove useful when making predictions concerning the photochemical stability of phenazone derivatives.

Photochemical decomposition of phenazone derivatives. Part 5(1): Isolation and identification of decomposition products in aqueous solution

From aqueous solutions of phenazone, aminophenazone, propyphenazone, nifenazone, morazone, noramidopyrine, 4-aminophenazone and isopropylaminophenazone, UV irradiated at lambda = 254 nm in oxygen free atmosphere as well as in the presence of air, 24 decomposition products were isolated and identified as derivatives of pyrazoline, pyrazolidinone, imidazoline, hydantoin, aziridine, phenylhydrazine and aniline.

Kinetics of drug decomposition. Part 73. Kinetics and mechanism of vitamin K3 soluble form thermal decomposition in solid phase

Kinetics of thermal decomposition of trihydrate of sodium salt of 1,2,3,4-tetrahydro-2-methyl-1,4-dioxo-2-naphthalenesulfonic acid (MDS, vitamin K3 soluble form) in solid state by accelerated aging method at elevated temperature has been studied. It was found that the process occurs according to Prout-Tompkins model and its rate depends on temperature, humidity and particle size of the substance. Thermodynamic parameters of the reaction (Q10(0), EA, delta H not equal to, delta S not equal to, delta G) were determined and theoretically predicted stability of MDS at room temperature is given. The reaction mechanism assumes a preliminary dehydration occurring via the successive elimination of one and a half, two and a half and finally three molecules of water. The obtained anhydrous form decomposes thermally forming free radical intermediates and yielding finally 2-methyl-1,4-naphthoquinone (vitamin K3), SO2 and NaOH.

Kinetics of drug decomposition. Part 69: Effect of excipients on the thermal decomposition of the mixture of aminophenazone allobarbital and adiphenine hydrochloride in the solid

By the method of accelerated testing at elevated temperature, the thermal decomposition rate of the mixture of aminophenazone (AP), allobarbital (AB) and adiphenine hydrochloride (AD) and its individual components in the presence of the excipients starch (potato), agar, talcum, kaolin and magnesium stearate is studied. The individual and joint effect of the excipients on the components of the mixture AP + AB + AD as well as on the mixture as a whole is determined and compared. The theoretically predicted stability of the components is discussed and compared with the results of "self-life" tests in the presence and absence of the excipients.

Kinetics of drug decomposition. Part 60. Thermal decomposition of the mixture of aminophenazone, allobarbital and adiphenine hydrochloride in the solid state

Kinetics of decomposition of a mixture of aminophenazone, allobarbital and adiphenine hydrochloride has been examined using accelerated testing at elevated temperatures (333-353 K). The reaction order, rate constants and activation parameters (Q10 degrees, EA, delta H#, delta S#, delta G) have been determined and compared for each component, in the presence of each component of the mixture and in the presence of two components of the mixture. The effect of individual components of the mixture on the rate of decomposition of the other components has been observed, the value of this effect has been determined using the rate constants obtained. The rate constants and times t10% for room temperature were calculated. The "shelf-life time" (t10%) was calculated from accelerated testing data at elevated temperature and compared with that obtained for Vegantalgin ragées in the mixture studied at 293 K.

Chemical characterization of decomposition products of drugs. Part 6. Mass spectrometry of some perazine derivatives

Mass spectra of perazine, prochlorperazine, tiethylperazine, trifluperazine, butaperazine and thioproperazine were obtained. All possible fragmentation routes were discussed. The mechanism of fragmentations, their similarities and differences within the investigated group of compounds were established. The Hammett type relationship was found between the intensities of some ions and the kind of substituents at the C2 position. The utility of mass spectra for the prediction of drug stability was demonstrated.

Kinetics of drug decomposition. Part 46. Photooxidation and photolysis of some perazine derivatives

The rate and type of the photochemical degradation of perazine derivatives in acidic aqueous solutions depends upon the nature of the substituent at C2 atom. Free perazine degrades by two parallel reactions, namely a fast reversible first-order photooxidation and a slow zero-order photolysis. An introduction of the substituent in the C2 position results frequently in the elimination of one of these reactions.

Kinetics of drug decomposition. Part 47. Effect of substituents on photochemical stability of perazine derivatives

A quantum yield phi of photooxidation of perazine derivatives estimated actinometrically and the pKa, values were used for the correlation with the substituent volumes. The Hammett type plots of phi= f(sigma) and phi= f(pKa10--pKa1) are discussed.