Stickstoffheterocyclen als Chelatliganden

In this thesis, crystal structures of metal complexes of various five membered heterocyclic compounds are presented. The heterocyclic compounds were either already literature known or newly synthesized, in which case crystal structures of the compounds are also included. The investigation was concentrated on compounds that might show photoisomeric behaviour. Here, nitrosyl and nitrito comlexes were considered, since both are known to undergo isomerization reactions by the influence of light. Experimental and computational chemical investigations on some model compounds lead to the conclusion that the sterical demand of the equatorial ligands and the shape and the electrostatic properties of the cavity around the nitrosyl or nitrito ligand in the crystal have a large influence on the relative stability of the different isomers and the reaction pathways between them as well on the electronic ground state potential hypersurface as on those of the excited states

Methyl 1H-pyrrole-2-carboxyl­ate

The title compound, C6H7NO2, is essentially planar with a dihedral angle of 3.6 (3)° between the pyrrole ring and the methoxy­carbonyl O/C/O/C plane. In the crystal structure, the N atom is a hydrogen-bond donor to the carboxylate C=O O atom of the neighboring mol­ecule. These inter­molecular hydrogen bonds lead to the formation of helical chains along the b axis

Poly[[μ-1,4-anhydro­erythritolato-di-μ-aqua-sodium(I)] monohydrate]

In the title compound, {[Na(C4H7O3)(H2O)2]·H2O}n, the sodium ion is octa­hedrally coordinated by two bridging 1,4-anhydro­erythritolate ligands, unexpectedly coordinated by the ring oxygen and four water ligands. This bonding pattern leads to one-dimensional anti­tactical polymeric chains along [010]. One of the exocyclic O atoms of the anhydro­erythritolate group is an acceptor in four hydrogen bonds, giving further evidence that it is deprotonated

tert-Butyl imidazole-1-carboxyl­ate

In the title compound, C8H12N2O2, mol­ecules are inter­connected by weak C—H⋯O contacts with H⋯O distances of 2.30 Å, resulting in the formation of chains along [100]. According to graph-set analysis, the unitary descriptor of these chains is C(5). In addition, there are π–π stacking inter­actions between pyrazole rings (centroid distance = 3.878 Å and ring plane distance = 3.26 Å)

(1S*,2S*)-1,2-Di-tert-butyl­glycol

In the crystal structure of the title compound, C10H22O2, co-operative chains of O—H⋯O hydrogen bonds are established by intra- as well as inter­molecular inter­actions. These hydrogen bonds connect the mol­ecules into infinite strands along [100], with a binary level graph-set descriptor C 2 2(4). Excluding the H atoms on the hydr­oxy groups, the mol­ecule shows non-crystallographic C 2 symmetry

Quasiliving cationic ring-opening polymerization of 2-ethyl-2-oxazoline in benzotrifluoride, as an alternative reaction medium

Cationic ring-opening polymerization (CROP) of 2-ethyl-2-oxazoline (EtOx) was systematically investigated in benzotrifluoride (BTF), which is considered as an environmentally less harmful solvent than many conventional reaction media. Simultaneously, polymerizations in conventional solvents, such as acetonitrile, N,N-dimethylacetamide and toluene, were also carried out for comparison in the 80-100 degrees C temperature range. Kinetic experiments revealed that the monomer consumption occurs by first order kinetics and the number average molecular weights linearly increase in line with the theoretical molecular weight as a function of monomer conversion. These findings indicate that the polymerization takes place by quasiliving CROP in all the investigated solvents, including BTF as well, resulting in PEtOx with prederminded molecular weights and polydispersities of 1.3-15. The highest polymerization rates were obtained in BTF, resulting in high conversions in short reaction times at 100 degrees C reaction temperature. The Arrhenius parameters of the polymerization of EtOx in BTF indicates relatively high activation energy in comparison with other applied solvents, however, a compensation effect between the activation energies and frequency factor is observed for such polymerization in a variety of solvents. Our findings are expected to enable the convenient synthesis of polyoxazolines and polyoxazoline-based well-defined polymer architectures in BTF, an environmentally advantageous alternative solvent to harmful polymerization media, with high polymerization rates in short reaction times without the need for any special conditions or equipment.Peer reviewe

Pyrrolidinium chloride

The title compound, C4H10N+·Cl−, was obtained as a decomposition product from 2,6-bis­(pyrrolidin­yl)pyridine. The anion lies on the same cristallographic mirror plane as the N atom of the cation, the complete cation being generated by mirror symmetry. The anions and cations are connected by N+—H⋯Cl− hydrogen bonds into chains along [100]. The pyrrolidinium cation is puckered in an envelope conformation E N1

Trispyrazol-1-ylmethane

In the title compound, C10H10N6, the three N atoms in the 2-positions of the pyrazole rings (the ones not bridging to the central C atom are acceptors for weak C—H⋯N contacts with H⋯N distances ranging from 2.49 to 2.59 Å). These furnish the formation of layers perpendicular to [100]. An ortho­rhom­bic polymorph of the title compound has already been described [McLauchlan et al. (2004 ▶). Acta Cryst. E60, o1419–o1420]