Herman O. Desseyn

Vibrational analysis of arsenic acid and its anions: I. Description of the Raman spectra

Abstract The Raman spectra of arsenic acid and its anions have been recorded. For some regions in the spectra, where overlapping bands arise, a band profile analysis has been performed using the damped least square procedure. The vibrational assignments for the observed frequencies have been proposed and discussed.

Thermal decomposition of the ammonium zinc acetate citrate precursor for aqueous chemical solution deposition of ZnO

The thermal decomposition of an aqueous chemical solution deposition Zn2+-precursor is studied by HT-DRIFT (high temperature diffuse reflectance infrared Fourier transform spectroscopy), on-line coupled TGA-EGA (thermogravimetric analysis - evolved gas analysis by Fourier transform infrared spectroscopy (FTIR) and mass spectrometry (MS)), and HT-XRD (high temperature X-ray diffraction). Using these complementary techniques, it is found that the α-hydroxyl group of the citrate ligand plays a significant role in the decomposition pathway of the ammonium zinc acetate citrate precursor. TEM (transmission electron microscopy) shows that crystalline ZnO (zincite) is formed at 390°C, after dehydroxylation of the α-hydroxyl group and subsequent decarboxylation of the Zn2+-precursor complex. Before total calcination, ZnO particles are already formed and a residual organic backbone thereby remains. The results obtained by these complementary techniques clearly indicate the importance of thermal analysis in the preparation of ceramics through chemical solution deposition.

The Characteristic Pattern of Thioamides in Infrared and Raman Spectra

A number of simple products, containing the thioamide functional groups, have been investigated in infrared and Raman spectra; from the average appearance and potential energy distribution values, a pattern characteristic for the thioamide groups has been given.

The vibrational spectra of complexes with planar monothio-oxamides—I. The Ni(II), Pd(II), Pt(II), Cu(II) and Zn(II) complexes of N,N′-dimethylmonothio-oxamide

Abstract The new complexes M(LH) 2 (M = Pd,Pt), ML(M = Pd,Cu) and ML · H 2 O (M = Ni,Zn), where LH 2 = N , N ′-dimethylmonothio-oxamide, have been prepared. The complexes were characterized by metal analyses, thermal methods and spectral (i.r., Raman, u.v.—vis.) studies. The vibrational analyses of the complexes are given using NH/ND, CH 3 /CD 3 and metal isotopic substitutions. The Ni(II), Pd(II), Pt(II) and Cu(II) compounds are square planar. The monoanion LH − shows a chelated bidentate S,O-coordination, while the doubly deprotonated L 2− acts as a bridging S,N/N,O-tetradentate ligand giving polymeric structures.

MODELLING THE VIBRATIONAL BEHAVIOUR OF THE CYCLIC CARBOXYLIC ACID DIMER. SQM FORCE FIELD OF THE FORMIC ACID DIMER

Abstract The vibrational behaviour of the cyclic carboxylic acid dimer is modelled through the scaled quantum mechanical (SQM) force field of the cyclic formic acid dimer. The results indicate that the SQM force field technique is very well applicable to hydrogen bonded molecules. The frequency shifts observed on hydrogen bonding can be related to the shifts observed on lowering the temperature. This study also confirms that a clear distinction between cyclic carboxylic acid dimers and catamers can be made through the difference between infrared and Raman frequencies, and it is proved here that these conditions are also valid for weaker hydrogen bonded cyclic carboxylic acid dimers.

CHARACTERISTIC VIBRATIONAL PATTERN FOR THE CYCLIC DIMER CARBOXYLIC ACID FUNCTION IN THE SOLID STATE

The infrared and Raman characteristics of the cyclic dimer hydrogen-bonded carboxylic acid function in the solid state are fully reported. Some dicarboxylic acids (e.g., malonic, methylmalonic, di-methylmalonic, succinic, glutaric, and adipic acid) are reported as typical examples. The vibrational characteristics of the cyclic dimer hydrogen-bond pattern are studied through the effect of deuteration on the position of infrared and Raman bands and through the temperature effect on the behavior of the vibrational bands. The fundamentals can very well be compared with the fundamentals of the trans secondary amide function, and are therefore assigned as the acid I to acid VII fundamentals.

The synthesis, spectroscopic and thermal study of oxamic acid compounds of some metal(II) ions

SummaryThe preparation of oxamic acid complexes of general formula M(H2NCOCOO)2·xH2O (M = MnII, CoII, NiII, CuII or ZnII; x = 1 for CuII, x = 2 for the other metals) is reported. The i.r. and Raman spectra are discussed considering a trans-octahedral structure, formed by five-membered chelate rings with the amide oxygen and one carboxylic oxygen as donor atoms. The apical positions are occupied by water molecules. The thermal degradation process is very similar for the different complexes, first losing H2O in one or different steps, then the fragments of the organic ligand to give the metal oxide as residue. The thermal degradation of the CuII and ZnII compounds results in the formation of a new polymeric compound by deprotonation of the primary amide function in an endothermic process, the polymer further decomposes to form the metal oxide.

Vibrational analysis of the oxaniides—the characteristic pattern of amides in i.r. and Raman spectra

Abstract The i.r. and Raman spectra of the oxamides R 1 R 2 NCOCONR 3 R 4 (where R = CH 3 , H or D), have been recorded and the fundamental vibrational frequencies have been assigned; the spectra have been compared with those of other simple amides and we have been able to describe a pattern, characteristic for the amides, in infrared and Raman; these results could be useful in qualitative analysis.

Preparation, structural characterization and properties of malonamato(−1) complexes

Abstract The complexes trans-[M(LH)2(H2O)2] (M = Mn, Co, Ni, Cu, Zn; LH− = the monoanion of malonamic acid) have been synthesized and the X-ray crystal structures of the copper (II) and zinc (II) complexes show an octahedral geometry around the metal ion in both molecules. The ligand LH− acts as a bidentate chelate with ligated atoms being the amide and one of the carboxylate oxygens. Both structures are stabilized through similar, intermolecular 2D hydrogen bonds. The thermal decomposition data, magnetic susceptibilities, and electronic, variable-temperature ESR and FT-IR spectra of the complexes are discussed in terms of the nature of bonding and known structures.

The vibrational spectra of complexes with planar monothio-oxamides—II. Complexes of N(s)-methylmonothio-oxamide

Abstract The new complexes Pd(SH 2 ) 2 · H 2 O, M(SH) · H 2 O (M = Ni, Pd, Pt) and M(SH) · 0.5H 2 O (M = Cu, Zn), where SH 3 = N ( s ) -methylmonothio-oxamide, have been prepared. The complexes were characterized by metal analyses, thermal methods and i.r., Raman and u.v./vis spectroscopic studies. The vibrational analyses of the complexes are given using NH/ND, CH 3 /CD 3 and metal isotopicsubstitutions. The Ni(II), Pd(II), Pt(II) and Cu(II) compounds are square planar. The vibrational spectra show that in Pd(SH 2 ) 2 · H 2 O the coordination occurs via the sulphur atom of the deprotonated thioamide group and the oxygen atom of the neutral primary amide group, in a bidentate chelated fashion. The doubly deprotonated SH 2− ion behaves as a bridging bis -bidentate ligand giving polymeric structures.