On the determination of empirical absolute chiral structure: chiroptical spectrum correlations for D3 lanthanide (III) complexes.

Circularly polarized luminescence (CPL) from selected transitions of Eu(III) in resolved single crystals of Na3[Eu(ODA)3].2NaClO4.6H2O are compared to CPL results obtained from solutions containing perturbed racemic mixtures of Eu(2,6-pyridine-dicarboxylate)3 (3-) and enantiomerically pure d-f helicate LambdaLambda-(-)EuCr(L8)3] in order to determine an empirical relationship between helicity and CPL spectra. Comparison of the CPL results, even for the magnetic dipole allowed transitions of Eu(III) where one measures large chiral discrimination, shows that the signs and magnitudes do not correlate with the overall helicity of the Eu(III) site. It is concluded that the symmetry of the Eu(III) site in LambdaLambda-(-)EuCr(L8)3 is not close enough to D3 to allow for the confirmation of the presumed spectra:structure correlation.

Beta-alanine-hydrochloride (2:1) crystal: structure, 13C NMR and vibrational properties, protonation character.

The crystal structure of beta-alanine-hydrochloride (2:1) complex (2A-HCl) has been determined by X-ray diffraction method at 298 and 100 K as monoclinic, space group C2/c, Z=4. The crystal comprises chloride anions and protonated beta-alanine dimers: two beta-alanine zwitterions are joined by strong, symmetric (Ci) hydrogen bond with the O...O distance of 2.473 A at room temperature. Powder FT-IR and FT-Raman as well as solid state 13C NMR spectra provide insights into the solid structure of this complex, character of its hydrogen bonds and the beta-alanine protonation.

Pyrrole-inverted isomer of 5,10,15,20-tetraaryl-21-selenaporphyrin

A novel 5,10,15,20-tetraaryl-21-selenaporphyrin isomer with an inverted pyrrole ring, i.e., 5,10,15, 20-tetraaryl-2-aza-21-carba-22-selenaporphyrin (SeC-TArPH) has been produced by a [3 + 1] condensation of 2, 5-bis(phenylhydroxymethyl)selenophene and 5,10-ditolyltripyrrin. The reaction yielded 5,20-diphenyl-10,15-bis(p-tolyl)-21-selenaporphyrin Se-DPDTPH (19%) and its isomer with an inverted pyrrole ring, i.e., 5,10-diphenyl-15,20-bis(p-tolyl)-2-aza-21-carba-22-selenaporphyrin, SeC-DPDTPH (1%). Mechanistically the synthesis of SeC-DPDTPH requires one beta-condensation at the pyrrole moiety of 5, 10-ditolyltripyrrin instead of the stereotypical alpha-condensation. The identity of inverted selenaporphyrin has been confirmed by high-resolution mass spectrometry and (1)H NMR spectroscopy. A saddle distortion mode for the inverted selenaporphyrin macrocycle SeC-DPDTPH has been determined by X-ray crystallography. NMR spectra are consistent with the existence of tautomeric equilibria that involve three tautomeric species of the neutral form of SeC-DPDTPH. The preference for the tautomer with the labile proton located at the peripheral N(2) nitrogen atom has been detected in pyridine-d(5) solution. The density functional theory (DFT) has been applied to determine the molecular and electronic structure of three tautomers of 2-aza-21-carba-22-selenaporphyrin: 2-N, 23-N, 24-NH, 2-N, 23-NH, 24-N, and 2-NH, 23-N, 24-N formally created from SeC-DPDTPH by a replacement of phenyl and tolyl groups with hydrogen. The total energies calculated using the B3LYP/6-311G//B3LYP/6-311G approach, demonstrate that relative stability of postulated tautomers decreases in the order 2-N, 23-NH, 24-N > 2-N, 23-N, 24-NH > 2-NH, 23-N, 24-N. The small energy differences between tautomeric species suggests their simultaneous presence in equilibrium.

Lactones. 9. Synthesis of terpenoid lactones-active insect antifeedants.

Starting from (+)- and (-)-perillyl alcohols, via Claisen rearrangement and iodolactonization, four enantiomeric pairs of gamma-lactones were obtained. The structures of compounds were established by both spectroscopic and crystallographic methods. The lactones were tested for antifeeding activity toward grain storage pests-the granary weevil beetle (Sitophilus granarius L.), the khapra beetle (Trogoderma granarium Ev.), and the confused flour beetle (Tribolium confusum Duv.). The results of the tests proved that two compounds, (1R,4R, 6R)-(-)-4-(1-methylethenyl)-9-oxabicyclo[4.3.0]nonan-8-one (8a) and its enantiomer (8b), are very active antifeedants against all of the above tested species. The lactone 8b is also active against the peach-potato aphid (Myzus persicae Sulz.). The activity depends on the absolute configurations of compound chiral centers. Additionally, the lactones 8a and 8b are characterized by interesting fragrances.