Investigation of gaseous metabolites from moulds by Ion Mobility Spectrometry (IMS) and Gas Chromatography-Mass Spectrometry (GC-MS)

The metabolism of moulds results in the formation of various microbial volatile organic compounds (MVOCs). These substances can be used as an indicator for the presence of moulds in the indoor environment. Three different mould strains were cultivated on culture media and IMS spectra of gaseous mould metabolites were recorded using a portable mini system with a tritium source and a 5 cm drift cell. The headspace spectra are characteristic for mould species and their age. Typical gaseous components of the metabolites were identified and compared with results obtained from gas chromatography using a mass spectrometer detector. It was observed that the MVOCs formation depends on mould species and their growing stage with a maximum of MVOCs emission occurring during the first 10 days. These preliminary results show that IMS can be applied to detect MVOCs in indoor environment and indicate hidden mould growth.     

Localized Orbitals vs. Pseudopotential-Plane Waves Basis Sets: Performances and Accuracy for Molecular Magnetic Systems

 Density functional theory, in combination with a) a careful choice of the exchange-correlation part of the total energy and b) localized basis sets for the electronic orbitals, has become the method of choice for calculating the exchange-couplings in magnetic molecular complexes. Orbital expansion on plane waves can be seen as an alternative basis set especially suited to allow optimization of newly synthesized materials of unknown geometries. However, little is known on the predictive power of this scheme to yield quantitative values for exchange coupling constants J as small as a few hundredths of eV (50–300 cm⁻¹). We have used density functional theory and a plane waves basis set to calculate the exchange couplings J of three homodinuclear Cu-based molecular complexes with experimental values ranging from +40 cm⁻¹ to −300 cm⁻¹. The plane waves basis set proves as accurate as the localized basis set, thereby suggesting that this approach can be reliably employed to predict and rationalize the magnetic properties of molecular-based materials. Corresponding author. E-mail: Carlo.Massobrio@ipcms.u-strasbg.fr Received August 5, 2002; accepted August 9, 2002     

Lattice-dynamical calculations for tetracene and pentacene

Lattice-dynamical, calculations for evidently non-rigid molecules of aromatic hydrocarbons have been carried out on tetracene and pentacene. In these substances, “out-of plane” vibrations mix extensively with lattice vibrations, and significant differences can be noted between results from a “rigid-body” and a “non-rigid” treatment. For tetracene crystals, whose Raman spectral data are given in the literature, the agreement with experiment is satisfactory. This confirms the validity of such procedures for interpreting and/or predicting spectroscopic behaviour, starting from empirical atom—atom potentials and valence force fields.     

Theoretical investigations on the solvation process

A model to facilitate the computation of the most stable conformer of associated M · H₂O (M being a polar molecule) which depends upon the electrostatic interaction energy between the two associated molecules is proposed and tested. SCF electrostatic potentials for the M molecule and a suitable point charge distribution for H₂O were employed in the model computations. Energies predicted by the model are found to be in good agreement with those resulting from an ab initio minimal STO basis SCF treatment of some conformations of the H₂O dimer.

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Zusammenfassung Ein Modell zur Durchführung der Berechnung des stabilsten Konformeren eines Assoziationskomplexes M · H₂O, wobei M ein polares Molekül ist, wird vorgeschlagen und untersucht. Es basiert auf der elektrostatischen Wechselwirkung zwischen beiden Partnern, und zwar wird für das Molekül M der elektrostatische Anteil seines SCF-Potentials und für H₂O eine angemessene Punktladungsverteilung zugrunde gelegt. Die resultierenden Energien sind in guter Übereinstimmung mit denen, die sich bei einer ab initio Rechnung mit minimaler STO Basis ergeben.

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Work performed with the financial support of the Consiglio Nazionale delle Ricerche, through its Laboratorio di Chimica Quantistica ed Energetica Molecolare.     

An ab initio analysis of the electronic structure and harmonic frequencies of nickel porphyrin

Ab initio calculations are performed to understand the geometry, electronic structure, and vibrational frequencies of nickel porphyrin (NiP). Hartree-Fock (HF) and second-order perturbation (MP2) theories are applied with polarized basis sets. The calculated geometrical parameters are in very good agreement with the crystal structure determination. The electronic structure and bonding are analyzed in terms of complexation and correlation effects. Not unexpectedly, the HF depiction of the metal-porphyrin interaction is rather ionic while ligand σ donation is dominant at the MP2 level. Scaled HF frequencies of NiP and its isotopomers are in very good agreement with observed infrared and resonance Raman data. Received: 7 January 1997 / Accepted: 6 May 1997     

Synthesis, Chemical Characterization, and Molecular Structure of Au8{Fe(CO)4}4(dppe)2 and Au6Cu2{Fe(CO)4}4(dppe)2

The new Au₈{Fe(CO)₄}₄(P^P)₂ and Au₆Cu₂{Fe(CO)₄}₄(P^P)₂ (P^P=dppm, dppe) neutral cluster compounds were isolated in good yields by condensation of the [Au₃{Fe(CO)₄}₂(P^P)]^- anions with Au(SEt₂)Cl and CuCl, respectively, and have been characterized by IR, NMR and microanalyses. The molecular structures of Au₈{Fe(CO)₄}₄(dppe)₂ and Au₆Cu₂{Fe(CO)₄}₄(dppe)₂ have been determined by X-ray diffraction studies. Both molecules adopt a stereogeometry of the heavy atoms consisting of a triangulated and corrugated ribbon twisted around the elongation direction. Contrary to the expectations the latter displays the two copper atoms in the sites of highest connectivity. This implies that site exchange between copper and gold occurs during the synthesis.     

Biphenyl ether and biphenyl quinolizidine lactone alkaloids from Heimia salicifolia

Three new biphenyl ether quinolizidine lactone alkaloids (1–3) and 13 new biphenyl quinolizidine lactone alkaloids (4–16) were isolated from Heimia salicifolia (Lythraceae) together with seven known alkaloids. Their structures were determined by spectroscopic analyses and chemical conversions.     

A new method of using supercritical carbon dioxide as a green solvent for synthesis and purification of 5,5‴-bis(tridecafluorohexyl)-2,2′:5′,2″:5″,2‴-quaterthiophene,which is one of n-type organic semiconducting materials

We have investigated synthesis as well as purification of 5,5?-bis(tridecafluorohexyl)-2,2′:5′,2″:5″,2?-quaterthiophene (BFH-4?T, n-type organic semiconducting material) using supercritical carbon dioxide (scCO₂) as a green solvent. BFH-4T was obtained in good selectivity and high yield by TDAE/PdCl₂-catalyzed reductive coupling reaction of 5-bromo-5′-(tridecafluorohexyl)-2,2′-bithiophene in scCO₂. We have also successfully established purification of the reaction mixture by passing scCO₂ in the reaction vessel. The product was yellow powder of BFH-4T with purity of more than 99% and Pd catalyst was not contained.     

Electron impact mass spectrometry of some macrocyclic polyether lactones

Electron impact mass spectrometry has been used together with linked scans, exact mass measurements and mass-analysed ion kinetic energy spectrometry to study nine inacrocyclic polyether lactones in detail. The presence of abundant hydrogenated oxirane ions has been observed for all the compounds examined, and confirmed by kinetic energy release measurements.