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Joachim Sieler

Publications and source records attributed to Joachim Sieler.

12 recordsLinked to original sources
PubMed2006

Cadmium nitrate coordination polymers with substituted pyridazino[4,5-d]pyridazines.

catena-Poly[[aquabis(nitrato-kappa2O,O')cadmium(II)]-mu-1,2,3,6,7,8-hexahydrocinnolino[5,4,3-cde]cinnoline-kappaN1:kappaN6], [Cd(NO3)2(C12H12N4)(H2O)]n, (I), and catena-poly[[[bis(nitrato-kappa2O,O')cadmium(II)]-mu-2,2,7,7-tetramethyl-1,2,3,6,7,8-hexahydrocinnolino[5,4,3-cde]cinnoline-kappaN1:kappaN6] chloroform solvate], {[Cd(NO2)2(C12H12N4)].CHCl3}n, (II), are the first structurally examined cadmium-pyridazine coordination compounds. They possess one-dimensional polymeric structures supported by the bidentate bridging function of the cinnolino[5,4,3-cde]cinnoline ligands, which lie about inversion centres. The Cd atoms are seven-coordinated in (I) and six-coordinated in (II), involving two bidentate nitrate groups [Cd-O = 2.229 (2)-2.657 (2) A], two N atoms of the cinnoline ligands [Cd-N = 2.252 (2)-2.425 (2) A], and, additionally, a water O atom in (I) [Cd-O = 2.284 (2) A]. In (I), the coordinated organic and aqua ligands form an intramolecular O-H...N hydrogen bond [O...N = 2.730 (3) A].

Journal Article↗
PubMed2004

Synthesis, characterization, and crystal structures of novel intramolecularly base-stabilized borane derivatives with six- and seven-membered chelate rings.

The reaction of (2-dimethylaminophenyl)alcohols 1-HOX-2-NMe(2)C(6)H(4) [X = CPh(2) (1), X = CCy(2) (2), X = CPh(2)CH(2) (4)] and 1-phenylaminoalkyl-2-dimethylaminobenzene 1-HN(Ph)X-2-NMe(2)C(6)H(4) [X = C(H)Ph (3), C(H)PhCH(2) (5)] with BH(3)(THF) yielded the BH(2) derivatives 1-H(2)BOX-2-NMe(2)C(6)H(4) [X = CPh(2) (6), CCy(2) (7), CPh(2)CH(2) (9)] and 1-H(2)BN(Ph)X-2-NMe(2)C(6)H(4) [X = C(H)Ph (8), C(H)PhCH(2) (10)]. Treatment of 1-H(2)BOCPh(2)-2-NMe(2)C(6)H(4) (6) with acetic acid gave 1-(CH(3)COO)HBOCPh(2)-2-NMe(2)C(6)H(4) (11). Compounds 6-11 were characterized spectroscopically (NMR, IR, MS). Crystal structure determinations were carried out on 6-11, which are novel examples of structurally characterized BH(2) derivatives containing six- or seven-membered chelate rings. For the chiral compounds 8, 10, and 11, both enantiomers are present in the unit cell.

Journal Article↗
PubMed2004

Extended coordination frameworks incorporating heterobimetallic squares.

The molecular structure of aluminium and iron(III) complexes with 3-phenyl and 3-(4-pyridyl) (HL) substituted acetylacetonate ligands is appreciably distorted. For AlL3 and FeL3 this shows that the orientation of the side pyridyl-N donor atoms lone pairs is about 90 and 135 degrees which favours the assembly of heterobimetallic square patterns in Al(Fe)L3 complexes with metal ions. This was employed for the modular construction of semi-regular heterobimetallic networks, in which the pyridyldiketonate ligands bridge pairs of Fe(Al)/Cd(Co) metal ions and support the structure of 1D and 2D coordination polymers. The unprecedented 2D structure of [Cd[AlL3](CH3OH)[NO3]2].2CHCl3 and Cd[AlL3](CH3OH)Br2].2CHCl3 . 2CH3OH is based upon plane tiling by a set of heterobimetallic squares and octagons, while [Cd[FeL3]2(NO3)2].2H2O and [Co[AlL3]2Cl2].4CHCl3 . 2CH3OH are 1D polymers and exist as chains of heterobimetallic squares sharing opposite vertices.

Journal Article↗
PubMed2004

Fused pyridazines: rigid multidentates for designing and fine-tuning the structure of hybrid organic/inorganic frameworks.

Fused pyridazines (1,2,3,6,7,8-hexahydro-cinnolino[5,4,3-cde]cinnoline, L and its 2,2,7,7-tetramethyl derivative, Me4L) are designed as rigid multidentate ligands for the construction of framework solids. In combination with copper(I) bromide (iodide) they provide excellent structural examples for predictive engineering and the possibilities for further fine-tuning of the framework architectures facilitated by the tetradentate function of the ligands and effective cooperation of organic and inorganic bridges. This study features control over helical structures for (CuX)n chains and homo/heterochiral combination of the helices in the lattice, the design of a range of channelled and tubular CuX networks and the structural significance of ligand shape complementarity. 3D tetragonal Cu2X2(L) frameworks exist either as chiral or achiral supramolecular isomers Cu2I2(Me4L) and Cu12I12[Cu(CH3CN)]3(L)(6-)Cu3I6.CH3CN illustrate 3D hexagonal channelled and tubular arrays; Cu2I2(Me4L)(CH3CN) and Cu4I4(L)(CH3CN)2 complexes are 1D polymers.

Journal Article↗
PubMed2004

Self-assembly sodalite-like framework.

The dense packing of shape complementary N-donor molecules dominates the self-assembly of coordination polymers possessing sodalite-like topology and supports nanosize molecular cages.

Journal Article↗
PubMed2004

Fluoro-modified chemotactic peptides: fMLF analogues.

A small library of peptide analogues of the chemotactic tripeptide For-Met-Leu-Phe-NH2 modified by substitution of Leu at position 2 by three different fluorinated amino acids varying in content of fluorine, length of the fluorinated side chain, and alkylation degree at the alpha-carbon atom was synthesized. The influence of the fluorine substitution on the biological activity was investigated by measuring the oxidative activity of neutrophils using a luminol-dependent chemiluminescence assay.

Chemotaxis↗
PubMed2004

Conformational flexibility in a triazole nucleoside derivative: 4-cyano-5-cyanomethyl-1-(2,3,5-tri-O-acetyl-beta-D-ribofuranosyl)-1,2,3-triazole.

The crystal-structure determination of the molecular structure of the hydrophobic compound, 4-cyano-5-cyanomethyl-1-(2,3,5-tri-O-acetyl-beta-D-ribofuranosyl)-1,2,3-triazole, C16H17N5O7, provides us with two different conformations of ribofuranosyl moieties [(C2'-exo, C3'-endo) and C2'-exo] with two markedly different N-glycosidic angles. There are two molecules in the asymmetric unit of the crystal and the overall stereochemistry of the molecules are influenced predominantly by weak intramolecular bifurcated and trifurcated hydrogen bonds of the type C-H...O and C-H...N, where endo-H atoms attached to C2' and C3' are involved. The molecules in the crystal are interconnected with longer intermolecular bonds of the same type. There are empty channels (occupying 14.0% of the whole volume of the unit cell), which are extended along b-axis of the entire crystal.

Crystallography, X-Ray↗
PubMed2002

Mixed-anion complexes with a bipyrazolyl ligand. A new entry to a realm of three-dimensional five-connected coordination topologies.

Cross-linking of corrugated square grid coordination layers by anionic bridging groups generates five-connected coordination networks; the 3D topologies of mixed-anion cobalt(II) and nickel(II) complexes with a tetramethyl-substituted 4,4'-bipyrazolyl ligand are supported by mu-SO4(2-) functions and exist as neutral or cationic five-connected arrays involving additional terminal (NCS-) or non-coordinated (NO3-, ClO4-) groups.

Journal Article↗
PubMed2002

A mechanistic dehydration study with [2-(13)C]-DIMBOA.

Dehydration of a 2-(13)C-labeled synthetic sample of the natural aglucone 2,4-dihydroxy-7-methoxy-2H-1,4-benzoxazin-3(4H)-one ([2-(13)C]-DIMBOA, 10) using N-ethoxycarbonyltrichloroacetaldimine led to 3-formyl-6-methoxybenzoxazolin-2(3H)-one ((13)C-labeled FMBOA, 11) with complete transfer of the (13)C label into the -CHO group. On the basis of this finding, a mechanism for the dehydration is proposed.

Benzoxazines↗