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Symposium on Graph Theory in Chemistry. Topological indexes, elementary graph-theoretical concepts, definitions of selected topological indices, and designing QSPR models.

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Structurally different ferrocene peptides I-VI exhibit considerable conformational differences. This study has explored the structural properties of VII [Y-AA-Fca-OMe; Y = di-tert-butyl dicarbonate (Boc), acetyl (Ac); AA = L-Ala, D-Ala; Fca = 1Ј-aminoferrocene-1-carboxylic acid] with an exchanged sequence of constituent amino acids relative to VI (Y-Fca-AA-OMe; Y = Boc, Ac; AA = L-Ala, D-Ala). The ferrocene peptides VII were obtained by coupling C-protected Fca with Boc-L-Ala-OH and Boc-D-Ala-OH, respectively. The Boc protecting groups of the obtained conjugates Boc-AA-Fca-OMe (2a, AA = L-Ala; 2b, AA = D-Ala) were converted to sterically less demanding Ac groups to give Ac-AA-Fca-1820 Avance 300 MHz spectrometer in CDCl 3 solutions with Me 4 Si as the internal standard. Double resonance experiments (COSY, NOESY, and HMBC) were performed in order to assist in signal assignment. CD spectra were recorded using a Jasco-810 spectropolarimeter in CH 3 CN. Molar ellipticity coefficients, [θ], are in degrees, concentration, c, is given in molL -1 , and path length, l, is given in cm, to give units for [θ] of deg cm 2 dmol -1 . Computational Details:The starting geometries of 2a and 3a were generated by the MacroModel v9.8 [26] molecular modeling program using several different search methods and force fields. The conformers were fully optimized at the B3LYP/LanL2DZ level of theory. [23] The most stable were reoptimized in chloroform (using IEF-PCM to describe implicit solvent effects) with the B3LYP method and 6-311+G(d,p) basis set. [24] Iron was modeled using the ECP set LanL2DZ. Quantum mechanical calculations were performed with Gaussian 09, v.A.02. [27] Molecules were visualized using GaussView [28] and Chem 3D (CambridgeSoft, Cambridge, MA) programs. The topological analysis of the selected compounds was performed with the AIM2000 program. [29] Boc-AA-Fca-OMe (2a/2b): The syntheses of 2a and 2b were performed according to our recent paper: [9] the fully protected ferrocene amino acid Boc-Fca-OMe [5] (1) was N-deprotected by gaseous HCl in EtOAc to give the hydrochloride salt, which was treated with NEt 3 and coupled with Boc-AA-OH (AA = l-, d-Ala, previously activated by using EDC and HOBt). After standard workup and TLC-purification, Boc-l-Ala-Fca-OMe (2a) and Boc-d-Ala-Fca-OMe (2b) were obtained as orange resins.

By using cyclopropyl bromide as precursor, the allyl cation C3H 5+ can be generated at low temperature in an SbF5 matrix and observed by IR spectroscopy; the experimental IR spectrum agrees well with that computed by ab initio methods. Characterization by 13C NMR spectroscopy failed, but the 13C NMR chemical shifts of this and other allyl cations could be predicted accurately for the first time by the GIAO/MP‐2 method.