Jarosław Jaźwiński

Tricyclic tetraamines by glyoxal - linear tetraamine condensation

Abstract New perhydrotetraaza- -naphtacenes, -phenalenes, phenantrenes, etc., have been obtained. The preference of formation of six- over five- and seven-membered ring structures, the cis-trans isomerisation, and the ring inversion in cis -isomers have been observed.

Structure and NMR Spectra of Some (2.2)Paracyclophanes. The Dilemma of (2.2)Paracyclophane Symmetry

Density functional theory (DFT) quantum chemical calculations of the structure and NMR parameters for highly strained hydrocarbon [2.2]paracyclophane 1 and its three derivatives are presented. The calculated NMR parameters are compared with the experimental ones. By least-squares fitting of the (1)H spectra, almost all J(HH) coupling constants could be obtained with high accuracy. Theoretical vicinal J(HH) couplings in the aliphatic bridges, calculated using different basis sets (6-311G(d,p), and Huz-IV) reproduce the experimental values with essentially the same root-mean-square (rms) error of about 1.3 Hz, regardless of the basis set used. These discrepancies could be in part due to a considerable impact of rovibrational effects on the observed J(HH) couplings, since the latter show a measurable dependence on temperature. Because of the lasting literature controversies concerning the symmetry of parent compound 1, D(2h) versus D(2), a critical analysis of the relevant literature data is carried out. The symmetry issue is prone to confusion because, according to some literature claims, the two hypothetical enantiomeric D(2) structures of 1 could be separated by a very low energy barrier that would explain the occurrence of rovibrational effects on the observed vicinal J(HH) couplings. However, the D(2h) symmetry of 1 with a flat energy minimum could also account for these effects.

A multinuclear NMR study of some mesoionic 1,3-dimethyltetrazoles, 1- and 2-methyltetrazoles and related compounds

Mesoionic 1,3-dimethyltetrazoles of the type A with sulfur, oxygen and nitrogen exocyclic groups, and related mono- and di-methylated tetrazoles have been investigated by means 1H, 13C, 14N and 15N NMR spectroscopy. The measurements were carried out in Me2SO and/or CF3CO2H solutions. The location of the protonation sites of the tetrazoles has been determined. The hydrogen atom is located on the exocyclic group of the mesoionic aminotetrazole 1, whereas the monomethylated and unsubstituted tetrazoles are protonated at the N-4 position (compounds 4,6, 8, 11–13). The monomethylated and non-ring substituted tetrazoles (compounds 4–8, 11–14 and 16) exist as non-mesoionic compounds, but compounds 1, 2, 9, 10 and 15 have a mesoionic structure.

Dimolybdenum Tetracarboxylates as Auxiliary Chromophores in Chiroptical Studies of vic-Diols

The aim of the present work was to check the suitability of dimolybdenum carboxylates, other than commonly used [Mo2(OAc)4], as auxiliary chromophores for determining the absolute configuration of optically active vic-diols by means of electronic circular dichroism (ECD). To this end, a set of dimolybdenum tetracarboxylates was synthesized, and subsequently, the two most promising compounds were selected, namely dimolybdenum tetrakis(μ-pivalate) and tetrakis(μ-isovalerate). The selection was based on their solubility in commonly used solvents, their stability in solution, their tolerance to air exposure, as well as their utility for dichroic studies. The stability of the obtained in situ chiral complexes was verified by measuring the dependence of ECD, UV-vis, and NMR spectra on time, temperature, and concentration. We have shown that the ECD spectra of diverse vic-diols with these complexes are suitable for configurational assignment based on the correlation between signs of Cotton effects (CEs) arising in the spectra and the stereostructure of the ligand. Furthermore, to aid in the interpretation of experimental results, a separate set of DFT calculations has been incorporated to provide additional insight into the structure of the chiral complexes involved. In contrast to the earlier assumptions, experiments showed that the chelating mode of ligation is preferred for the studied complexes.

A structural study of some mesoionic type A oxa- and thiatriazoles in the solid state by CP-MAS NMR and X-ray crystallography

Abstract 13C and 15N CP-MAS NMR measurements are reported for four mesoionic type A oxa- and thiatriazoles. X-ray structures are also reported for compounds 1 and 2. The results obtained show close similarity between the solid and solution structures for these molecules. The phenyl and mesoionic rings are nearly coplanar and the bond orders of the C5-Y− bonds are close to 1.5. The relative cis and trans positions of the components of the exocyclic groups, with respect to the mesoionic ring sulphur atom, are also reported.

Mesoionic compounds — structure and NMR parameters

It has been shown that1H,13C,14N,15N,17O, and77Se NMR are very successful techniques for the identification and investigation of potential valence tautomerism in all types of mesoionic compounds. Especially the combined use of14N and15N NMR studies has been shown to be very effective in solving structural problems. From15N NMR it is possible to obtain accurate chemical shifts and spin-spin couplings, whereas the14N NMR spectra provide us with nuclear relaxation and some chemical shift data. In particular14N NMR is very useful for the identification of charged nitrogen atoms in molecules containing non equivalent nitrogen positions. This information is available from the relative14N signal widths, which depend upon the rates of14N relaxation, positively charged nitrogen atoms usually have relatively slow14N relaxation rates thus giving rather sharp NMR signals. Some solid state, CP MAS,13C and15N NMR results are available for comparison with the solution NMR data.

A nitrogen NMR and X-ray investigation of some mesoionic 1,3-diazoles, 1,3-oxazoles and 1,3-thiazoles

Abstract 14 N, 15 N and 17 O NMR and data are reported for some mesoionic 1,3-diazoles, 1,3-oxazoles and 1,3-thiadiazoles. Additionally, 15 N CP/MAS NMR data are also given for five mesoionic 1,3-diazoles. The relation between compound structures and NMR parameters has been discussed. 15 N chemical shift values for diazoles, taken from CP/MAS NMR measurements, are very similar to the values observed for compounds in the solution. These imply the structure similarity of compounds in both phases, and allow excluding the chain–ring equilibrium in the solution. The cyclic, ‘mesoionic’ structure of 1,3-diazole have been confirmed by X-ray diffraction study.

Synthesis and multinuclear magnetic resonance study of some derivatives of mesoionic 1,2,3,4-thiatriazolo-5-aminide

Abstract Five derivatives of mesoionic 1,2,3,4-thiatriazolo-5-aminide and its salts were synthesized. The structures of the compounds were examined by 1 H, 13 C, 14 N and 15 N NMR techniques. The protonation of the compounds occurs on the nitrogen atoms of the exocyclic group; one or two molecules of acid are bonded, depending on the compound structure. The investigated derivatives are supposed to be a chelate type ligand binding metal cation. Some preliminary investigations on compound interaction with metal cation were performed by VIS/UV technique.

Multinuclear NMR study of some mesoionic 3-phenyl-1-thia-2,3,4-triazol-3-ium-5-ylmethanides with various exocyclic groups

Six mesoionic 3-phenyl-1-thia-2,3,4-triazol-3-ium-5-ylmethanides (3,5–9) have been synthesized for the first time. 13C, 14N and 15N NMR data have been collected and interpreted in terms of molecular structure. The 1J13C–13C coupling constants of the ring–exocyclic group bond have been determined and are discussed.

Synthesis of some ligands containing 1,2,3,4-thiatriazolium-5-aminide unit and their interactions with metal cations

Abstract Five new compounds, 6–10, derivatives of mesoionic 3-phenylo-1,2,3,4-thiatriazolium-5-aminide, have been obtained. The structures of the compounds have been investigated by 1H, 13C, 15N NMR and X-ray diffraction. The 15N NMR technique has been used for identification of a heteroatomic backbone of the mesoionic unit. The 15N chemical shifts observed are typical for this class of compounds. However, some unusual 15N shift values have been observed for 9. The structures of compounds 2 and 7–9 have been confirmed by X-ray diffraction. The interactions of the thiatriazoles 6–9 with some salts, CoCl2, Ni(ClO4)2 and Cu(CH3COO)2 in acetonitrile solution, have been studied by visible electronic spectroscopy.