Cristina Ferreira

Bifunctional activation of cyanoguanidine. Synthesis and molecular structure of the azametallacycle cis-[(PPh3)2Pt{NHC(OMe)=NC(NH2)=NH}][BPh4]

Abstract The cyanoguanidine complex cis-[Pt(NCNC(NH2)2)2(PPh3)2][BPh4]2, prepared by reacting cis-[PtCl2(PPh3)2] with cyanoguanidine in the presence of Na[BPh4], readily reacts with methanol to give cis-[(PPh3)2PtNHC(OMe) = NC(NH2) = NH)] [BPh4] containing a novel type of azametallcycle whose molecuar structure is established by X-ray crystallography. Its formation involves metal-promoted nucleophilic addition of the alcohol to the cyano group of a cyanoguanidine ligand, combined with deprotonation of the guanidine unit which then chelates the Pt(II) centre.

Microwave plasma source operating with atmospheric pressure air-water mixtures

The overall performance of a surface wave driven air-water plasma source operating at atmospheric pressure and 2.45 GHz has been analyzed. A 1D model previously developed has been improved in order to describe in detail the creation and loss processes of active species of interest. This model provides a complete characterization of the axial structure of the source, including the discharge and the afterglow zones. The main electron creation channel was found to be the associative ionization process N + O → NO+ + e. The NO(X) relative density in the afterglow plasma jet ranges from 1.2% to 1.6% depending on power and water percentage, according to the model predictions and the measurements. Other types of species such as NO2 and nitrous acid HNO2 have also been detected by mass and Fourier Transform Infrared spectroscopy. The relative population density of O(3P) ground state atoms increases from 8% to 10% in the discharge zone when the input microwave power increases from 200 to 400 W and the water percent...

Cationic phenyl and chloro-platinum(II) complexes with cyanamides and cyanoguanidine. X-ray structure of trans-[Pt(Ph)(NCNMe2)(PPh3)2][BPh4]

The phenyl-platinum(II) organocyanamide trans -[Pt(Ph)(NCNR 2 )(PPh 3 ) 2 ][BPh 4 ] (R=Me 1a , Et 1b ) or cyanoguanidine cis -[Pt(Ph){NCNC(NH 2 ) 2 }(PPh 3 ) 2 ][BPh 4 ] ( 2 ) complexes have been prepared by treatment of cis -[PtCl 2 (PPh 3 ) 2 ] in THF with NCNR 2 or NCNC(NH 2 ) 2 , respectively, in the presence of Na[BPh 4 ], whereas the cyanoguanidine chloro-complex cis -[PtCl{NCNC(NH 2 ) 2 }(PPh 3 ) 2 ][BF 4 ] ( 3 ) has been obtained by using Tl[BF 4 ] instead of Na[BPh 4 ]. Complex 3 reacts further with cyanoguanidine, in the presence of Na[BPh 4 ], to produce the di(cyanoguanidine) cis -[Pt{NCNC(NH 2 ) 2 } 2 (PPh 3 ) 2 ][BPh 4 ] 2 complex 5 , whereas the amine complex cis -[PtCl(NH 2 R′)(PPh 3 ) 2 ][BF 4 ] (R′=CH 2 C 6 H 4 Me-4, 4 ) is formed on reaction of the former with NH 2 R′ in CH 2 Cl 2 . The X-ray structure of 1a is also reported.

2-Amino-2-oxazoline and trialkylisourea Pt(II) complexes derived from organocyanamides

In the di(organocyanamide) complexes trans-[PtCl2(NCNR2)2] (R = Me 1a, Et 1b), prepared by reaction of PtCl2 with the appropriate NCNR2, the cyanamide ligands, activated by coordination, undergo an unprecedented nucleophilic addition, at room temperature, of an haloalcohol (ClCH2CH2OH/LiBun) or of an alcohol (MeOH) to give the corresponding 2-amino-2-oxazoline cis-[PtCl2{NC(OCH2CH2)NR2}2] (R = Me 2a, Et 2b) or trialkylisourea trans-[PtCl2{NHC(OMe)NR2}2] (R = Me 3a, Et 3b) complexes. The X-ray crystal structure of 2b is also reported, indicating a π-bond delocalization along the NCN group of the aminooxazoline ligands.

Hot and super-hot hydrogen atoms in microwave plasma

“Super-hot” (kinetic energy ∼4–8 eV) and “hot” (kinetic energy ∼0.3 eV) H atoms were detected in a surface wave (500 MHz) generated H2 plasma column, at pressure p=0.01 mbar, from the analysis of the Hβ, Hγ, Hδ, and He emission line profiles. These profiles were found to evolve from single Gaussian to bi-Gaussian toward the plasma column end. Population inversion between the levels 5→4 and 6→4 was detected. At pressure p=0.2 mbar, super-hot atoms were not detected and the temperature of the hot atoms was found to increase with the upper level principal quantum number.

Vacuum ultraviolet emission from microwave Ar-H2 plasmas

Vacuum ultraviolet emission from Ar-H2 wave driven microwave (2.45 GHz) plasmas operating at low pressures (0.1–1 mbar) has been investigated. The emitted spectra show the presence of the Ar resonance lines at 104.8 and 106.7 nm and of the Lyman-α,β atomic lines at 121.6 nm and 102.6 nm, respectively. The increase of the hydrogen amount in the mixture results in an abrupt increase of the Werner and Lyman molecular bands intensity. The Lyman-β intensity shows little changes in the range of 5%–30% of hydrogen in the mixture while the Lyman-α intensity tends to decrease as the percentage of hydrogen increases.

Energetic hydrogen atoms in wave driven discharges

Doppler broadened Hγ emission was detected in high frequency (350 and 500 MHz) hydrogen surface wave sustained discharges, revealing the presence of fast excited H atoms with kinetic energies in the range 4–9 eV. Spatially resolved measurements of the Doppler-broadened emission indicate that these fast atoms are predominantly formed near the wall, which suggests that their generation may result from acceleration of H+ ions in the radial dc space charge field followed by recombination at the wall and the return of the neutral atom to the gas phase.

Travelling Wave Discharges in Nitrogen: Modelling and Experiment

This work is concerned with the study of travelling wave discharges in molecular gases. Specifically, as an illustrative example a theoretical and experimental study of a surface wave (SW) discharge in nitrogen is presented which incorporates a detailed self-consistent analysis of plasma kinetics and wave electrodynamics.

Energetic Hydrogen Atoms in High Frequency Plasmas

Generation of energetic hydrogen atoms, with energy in the range 4-8 eV, was detected throughout the volume of a surface wave generated (500 MHz) plasma column in H2 at pressure p = 0.01 mbar. The Hβ, Hγ, Hδ, and H, line profiles were found to be bi-Gaussian towards the plasma column end. The kinetic temperatures corresponding to the Doppler broadening of the Hβ, Hγ, Hδ, lines are higher than the rotational temperature of the hydrogen molecular Fulcher-α band and the wall temperature. At pressure p = 0.2 mbar, the kinetic temperature of excited H (n = 4-7) atoms, as determined from the fitting of the spectral lines with a single-Gaussian profile, increases with upper level principal quantum number. The experimental results have been analyzed in the framework of a global self-consistent kinetic model describing this surface wave sustained plasma column.

Bidirectional converter for distributed generation with grid-supporting capacity

Distributed generation systems are growing, and their power converters and how they deal with the power flow when connected to the grid are key knowledge in this field. This work shows some technical and functional characteristics about a bidirectional converter, developed to assist the grid providing active or reactive power. The converter and control algorithms are presented, as well as a relation between the converter and synchronous generators, showing active and reactive power control capability. Simulation and practical results in a single-phase prototype demonstrate the system behavior.