Authors:Rodica Olar, M. Badea, E. Cristurean, V. Lazar, R. Cernat, and C. Balotescu
Summary The complexes of the type [M(HDMBG)Cl3] ((1) M:Co; (2) M:Zn;) and [M(DMBG)Cl2] ((3) M:Pd; (4) M:Pt; DMBG: N,N-dimethylbiguanide) present in vitro antimicrobial activity. The modification evidenced in IR and 1H NMR spectra (in the case of complex (2)) was correlated with the presence of N,N-dimethylbiguanide ion as unidentate, coordinated through N3 and of N,N-dimethylbiguanide as chelate, coordinated through N1 and N4 respectively. The electronic reflectance spectrum showed the d-d transition for complex (1) characteristic for the tetrahedral surrounding while the spectra for complexes (3) and (4) have the characteristic pattern for square-planar stereochemistry. The cyclic voltammetric data show the characteristic waves for mononuclear complexes of the metallic ions presented below. The thermal analysis has evidenced the thermal intervals of stability and also the thermodynamics effects that accompany them. The different nature of the ligands generates a different thermal behaviour for complexes.
Three new hydrazinium(1+) fluoro complexes, N2H5AsF6, (N2H5)2ZrF6 and (N2H5)2HfF6, were prepared and characterized by means of chemical analysis, IR and Raman spectroscopy and X-ray powder diffraction. Study of their thermal behaviour via TG, DTG and DTA measurements showed that they decompose in stages; the decomposition of N2H5AsF6 proceeded in two steps, through the intermediate NH4AsF6; (N2H5)2ZrF6. Decomposed in three steps, through (NH4)2ZrF6 and NH4ZrF5. The thermal decomposition of (N2H5)2HfF6 is more complex; in the first step (NH4)2HfF6 with some N2H5HfF5 was obtained, and in the second NH4HfF5. The intermediates were identified by means of chemical analysis and vibrational spectroscopy.
The thermal behaviours of sulphur, selenium and their mixtures have been studied over the range 40–450‡. It has been shown that the polymerization threshold temperature of sulphur,TØ, decreases with increasing selenium content and follows the equilibrium copolymerization model proposed by Tobolsky and Owen. The formation of octa-atomic species Se8−xSx, where 8 >x > 4, takes place only after sulphur is in the liquid state. The rate of polymerization is enhanced by the addition of increasing amounts of selenium and this is reflected in the higher polymerization peak temperatures. The X-ray powder diffractograms show that all the sulphur-selenium melts belong to the same phase as that of SeS, though the constituent atoms are randomly distributed.
Authors:Viorel Cîrcu, Ana S. Mocanu, Constantin Roşu, Doina Manaila-Maximean, and Florea Dumitraşcu
imine group of the Schiff base ligand. The 1 H NMR spectra indicate for all prepared complexes the presence of only one isomer in solution (one set of signals).
The mononuclear palladium(II) complexes were
Authors:Th. Beyrich, M. Schleuder, G. Mietz, H. Wulff, and M. Gruno
The 4-nitrobenzyl ester of acetylphenylhydroxyacetic acid differs in its melting behaviour from other nitrobenzyl esters of
phenylhydroxyacetic or acetylphenylhydroxyacetic acids, the racemate having a higher melting point than the enantiomers. By
means of thermal analysis, IR spectroscopy and X-ray diffractometry the ester can be shown to occur in two crystalline modifications.
In the process of solidification of the molten mass, at first a modification of higher energy is formed, obviously being caused
by an excess of one enantiomer, which is then exothermally rearranged in the lattice of the racemate.
Authors:L. Szirtes, A. Szeleczky, A. Rajeh, and E. Kuzmann
The thermal behaviour of Co(II), Ni(II) and Zn(II)-containing zirconium phosphate of α type was investigated. XRPD analysis
revealed that, for the samples containing Co(II) or Ni(II), the first reflection of the solid phase is split into a doublet.
In contrast, when Zn(II) is present, a single solid phase system is formed. The thermal behaviour of the materials followed
this sequence. For the samples containing Co(II) or Ni(II), phase-transition processes were found and there was also a loss
of crystal water, but for the sample containing Zn(II) there was only one endothermic effect, which corresponded to the decomposition
of phosphate groups.
Authors:Irene Pasquali, R. Bettini, and F. Giordano
This work aims to investigate the thermal behaviour of diclofenac, diclofenac sodium, and NaHCO3 both as single components and binary mixtures. In particular, the melting point and latent heat of fusion binary diagrams
of the diclofenac sodium/diclofenac mixtures at different mole fraction compositions were investigated in order to gain information
about the thermal behaviour of their solid mixtures. A good agreement between liquidus curves, calculated by the Schroeder-Van
Laar equation from fusion enthalpies and temperatures, and the experimental results was found. For all binary compositions,
an endothermic effect at 153�C, probably due to the eutectic fusion, is present.