Qualitative analysis of organic compounds is expedited by third-derivative processing of diode array UV/vis spectra which can locate Xmax with ±0.02 nm precision, or 1/100 of the present diode interval. The technique was applied to over 50 metalloporphyrins, primarily geological residues of ancient chlorophyll, and the results suggest broader applicability. Among metalloporphyrins, the Soret band wavelength, X(Soret), varies with the type of functional group structure on the periphery of the 20-carbon porphyrin chromophore. Distinctive X(Soret) ranges are defined by exocyclic structure (butano, propano, ethano), or lack thereof (etio). Among etioporphyrins X(Soret) varies with the number of alkyl substituents. Etioand ethanoporphyrin isomers with the same alkyl groups are least differentiated. Fifty or more spectral classes can be specified by including ( ) and (ß), or higher than that when other data, i.e., molecular mass or chromatographic data, are added. Moreover, such results can be obtained 1000-fold faster than conventional NMR and MS structure determinations.The new technique allows one to differentiate quickly among congeners, homologues, and isomers, to use wavelength data to guide chemical isolations of known components from mixtures, and to expedite the isolation of unknowns or new structures when the technique is adjoined to HPLC separations.
Solubility of polyaromatic hydrocarbons (PAH) and carbon nanostructures is important both from the technical and environmental points of view. In the present work, two general quantitative structure-property relationship (QSPR) models were developed, describing the solubility of PAH-s and fullerene (C60) in two different condensed media (1-octanol and n-heptane). Statistically good QSPR models were obtained by using forward selection techniques from large space of theoretical molecular descriptors. The physical meaning of the models is discussed and analyzed.
Polarizability is one of the key properties determining the nonlinear optical effects of the new materials. In the current study, a quantitative structure-property relationship approach is used to model the polarizability of polyaromatic hydrocarbons (PAHs) and fullerenes. The model is derived using the data set of 40 PAHs and fullerenes and includes just one molecular descriptor, the AM1-calculated total molecular two-center exchange energy. The model is externally validated, and the obtained results are in good agreement with both the ab initio calculated and the experimental polarizabilities of these compounds. The reported quantitative structure-property relationship is a quick tool for finding an estimate of polarizability for different PAHs and fullerenes.
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