Biomedical subjects

Lucjan B Jerzykiewicz

Publications and source records attributed to Lucjan B Jerzykiewicz.

10 recordsLinked to original sources

PubMed2006

Structural, spectroscopic, and magnetic study of bis(9,10-dihydro-9-oxo-10-acridineacetate)bis(imidazole)bis(methanol) nickel(II).

The mixed ligand complex [Ni(CMA)2(im)2(MeOH)2] (where CMA = 9,10-dihydro-9-oxo-10-acridineacetate ion, im = imidazole) was prepared, and its crystal and molecular structure were determined. The nickel ions are hexa-coordinated by four oxygen atoms of the carboxylate and hydroxyl groups and by two imidazole nitrogen atoms, to form a distorted octahedral arrangement. The structure consists of a one-dimensional network of the complex molecules connected by strong intermolecular hydrogen bonds. The weak intermolecular C-H...X hydrogen bonds and stacking interactions make up the 2-D structure. Very strong intramolecular hydrogen bonds significantly affect the geometry and vibrational characteristics of the carboxylate group. The UV-vis-NIR electronic spectrum was deconvoluted into Gaussian components. Electronic bands of the Ni(II) ion were assigned to suitable spin-allowed transitions in the D4h symmetry environment. The single ion zero-field splitting (ZFS) parameters for the S = 1 state of Ni(II), as well as the g components, have been determined by high-field and high-frequency EPR (HF-HFEPR) spectroscopy over the frequency range of 52-432 GHz and with the magnetic fields up to 14.5 T: D = 5.77(1) cm-1, E = 1.636(2) cm-1, gx = 2.29(1), gy = 2.18(1), and gz = 2.13(1). These values allowed us to simulate the powder magnetic susceptibility and field-dependent magnetization of the complex.

Magnetics↗

PubMed2006

Deoligomerization by cocomplexation: syntheses and structures of aluminum-calcium alkoxides and aryloxides.

Reactions of oligomeric "Ca(dbbfo)2" and Ca9(CH3OCH2CH2O)18(CH3OCH2CH2OH)2 with Al(CH3)3 in toluene gave tetranuclear heterobimetallic [Ca(mu-dbbfo){(mu-dbbfo)(mu-CH3)Al(CH3)2}]2 (71%) and polymeric Ca{(mu-CH3OCH2CH2O)(mu-CH3)Al(CH3)2}2 (86%). The latter can be obtained as monomeric THF adduct Ca{(mu-CH3OCH2CH2O)Al(CH3)3}2(THF)2 (78%) when a mixture of solvents is used. The results, including an initial L-lactide polymerization test, are discussed in the context of calcium alkoxo cluster degradation in solution.

Journal Article↗

PubMed2005

Structural characterization of a methylaluminoxane (MAO)-magnesium dichloride cluster: model of MAO grafted onto a MgCl2 support.

The study outlines our initial results that contribute to a better understanding of MAO/MgCl2 (MAO=methylaluminoxane) incorporation in the Cp2ZrCl2/MAO/MgCl2 catalytic system, which is currently of global industrial use. We show here that the[Al3(mu3-O)(Me)5]2+ moiety can be trapped by the tetrapodal [Mg3Cl4(thffo)4(THF)]2- macrounit to form a cluster [Al3Mg3(mu3-O)(thffo)4(Me)5Cl4(THF)] (thffo=2-tetrahydrofurfuroxide). From this perspective, this macrounit might be considered as a part of the MgCl2 support surface, which fulfills the requirement of a Al3(mu3-O) core.

Journal Article↗

PubMed2005

X-ray structure of the dipotassium salt of D-mannose 1-phosphate 3.25 hydrate.

The first crystal structure of mannose 1-phosphate is described. The dipotassium hydrate salt crystallizes in the P2(1)2(1)2 space group. There are two independent dianions (I and II) in the asymmetric unit, which are alpha anomers adopting the 4C(1) chair conformation. The main difference between the two mannose 1-phosphate dianions is the orientation of the phosphate group with relation to the pyranosyl ring. In I, one of the phosphate oxygen atoms is antiperiplanar positions with respect to carbon atom C-1, whereas the two others are situated synclinally. The corresponding orientations of the terminal phosphate oxygen atoms in II are synperiplanar and anticlinal. The potassium cations are six- and seven-coordinate, mainly with O atoms of hydroxyl groups and water molecules. There are potassium channels extending along the c-axis. In the packing arrangement, water molecules and mannose phosphate groups also define two different types of layers parallel to a-axis. Within water channels there are extensive hydrogen-bonding networks.

Carbohydrate Conformation↗

PubMed2005

Synthesis of homoleptic barium alkoxides and aryloxides and their reactions with Al(CH(3))(3): a convenient route to heterometallic species.

Reactions of metallic Ba with benzofuranol (dbbfoH) or diethylene glycol give homoleptic and homonuclear complexes Ba(dbbfo)(2)(dbbfoH)(2).3dbbfoH and Ba{O(CH(2)CH(2)O)(2)}{O(CH(2)CH(2)OH)(2)}(2) (60-89%). Both compounds and formerly described Ba{O(CH(2)CH(2)O)(2)Me}(2) react with Al(CH(3))(3) to yield trinuclear heterobimetallic low-coordinated barium compounds with structure and geometry depending on the reaction stoichiometry and crystallization procedure.

Aluminum↗

PubMed2005

Highly efficient magnesium initiators for lactide polymerization.

Two monomeric, six-coordinated magnesium complexes with bulky aminophenolate ligands [(Htbpoa)2Mg] (1) and [(Htbpca)2Mg(THF)2] (2), where Htbpoa =N-[methyl(2-hydroxy-3,5-di-tert-butylphenyl)]-N-methyl-N-methyl-1,3-dioxolaneamine and Htbpca =N-[methyl(2-hydroxy-3,5-di-tert-butylphenyl)]-N-methyl-N-cyclohexylamine have been prepared, characterized and employed as initiators for lactide polymerization. The crystal structure of the homoleptic compound 1 has been determined and shows that the six-coordinate magnesium atom in 1 is surrounded by two tridendate tbpoa ligands. In the solution, however, complex 1 exists in equilibrium with a five-coordinate species 1a having one oxolane fragment dangling. The tbpoa and tbpca ligands in 1 and 2 play a dual role, as the ancillary ligand stabilizing the monomeric magnesium species and as the initiating polymerization group.

Journal Article↗

PubMed2004

Adenine ribbon with Watson-crick and Hoogsteen motifs as the "double-sided adhesive tape" in the supramolecular structure of adenine and metal carboxylate.

The cocrystals of adenine and metal (II) quinoline-2-carboxylates (M = Mn2+, Fe2+, Co2+) have been obtained by self-assembly. The complexes are composed of adenine ribbons with the AA22 pairing pattern involving both Watson-Crick and Hoogsteen faces in hydrogen bonding and the neutral molecules of carboxylate positioned in inorganic layers. The very compact supramolecular structure is made by the extensive system of hydrogen bonds and face-to-face pi-pi interactions.

Adenine↗

PubMed2003

The first structurally characterized nonorganometallic titanium(III) alkoxo-bridged dinuclear complexes.

The reaction of [Ti4(OMe)14Cl2] (1) with an excess of AlMe3 gave the cocrystallite [Ti2(mu-OMe)2(mu-Cl)Cl3(thf)3].[Ti2(mu-OMe)3Cl3(thf)3] (2.3) species in a 1:1 ratio. Similar to 2, [Ti2(mu-OEt)2(mu-Cl)Cl3-(thf)3] (4) was obtained in the reaction of an equimolar mixture of TiCl4 and Ti(OEt)4 with Al/AlMe3. The short distance [2.543(1)av A in 2.3 and 2.599(1) A in 4] between "Ti(+3)" atoms, their diamagnetism, and ELF analysis indicate the presence of a Ti-Ti bond.

Journal Article↗

PubMed2003

A family of Group 4 metal alkoxo complexes with an M3(mu3-O) core relevant to Ziegler-Natta catalyst intermediates.

Reactions of [Mg(thffo)(2)] (1) or [Ca(thffo)(2)] (2) with ZrCl(4) or HfCl(4) in a CH(2)Cl(2)/THF/CH(3)CN mixture give thermally stable neutral heterobimetallic tetranuclear complexes [M(3)M'(mu(x)-O)(mu,eta(2)-thffo)(6)(Cl)(6)] (thffo=tetrahydrofurfuroxide; M/M'/x: 3, Zr/Mg/3; 4, Hf/Mg/3; 5, Zr/Ca/4; 6, Hf/Ca/4) as colorless crystals in 75-82 % yield. X-ray diffraction studies show complexes 3-5 to contain oxo-bridged M(3) triangles that are capped by an alkaline earth metal-containing moiety to form species of C(3) symmetry. Reactions of ZrCl(4) and HfCl(4) with pure tetrahydrofurfuryl alcohol in EtOH and MeOH provide ionic complexes [M(3)(mu(3)-O)(mu,eta(2)-thffo)(3)(L)(3)(Cl)(6)]Cl (M/L: 8, Zr/EtOH; 9, Hf/EtOH; 10, Zr/MeOH) in 66-79 % yield. Complexes 8-10 consist of M(3) triangles that are analogous to those in 3-6 and possess similar overall symmetry, as shown by X-ray crystallography. Changes in the reaction conditions afforded the asymmetric neutral dimer [Zr(2)(mu-thffo)(2)(thffoH)(Cl)(6)] (7) and the homometallic [Zr(3)(mu(3)-O)(mu,eta(2)-thp)(3)(thf)(2)(Cl)(7)] (11).

Journal Article↗

PubMed2002

Five-coordinate iron(III) porphycenes: (1)H NMR, magnetic, and structural studies.

Five-coordinate iron(III) 2,7,12,17-tetrapropylporphycene (TPrPc)Fe(III)X (X = C(6)H(5)O(-), Cl(-), Br(-), I(-), ClO(4)(-)) complexes have been investigated. The (1)H NMR spectra demonstrate downfield shifts for pyrrole resonances [(TPrPc)Fe(III)(C(6)H(5)O), 65.3 ppm; (TPrPc)Fe(III)Cl, 28.5 ppm] but large upfield ones for (TPrPc)Fe(III)Br (-7.8 ppm), (TPrPc)Fe(III)I (-49.4 ppm), and (TPrPc)Fe(III)ClO(4) (-77.1 ppm) (294 K, CD(2)Cl(2)). The pyrrole chemical shifts span the remarkable +70 to -80 ppm range. The variable-temperature (1)H NMR spectra of (TPrPc)Fe(III)X demonstrate anti-Curie behavior with a sign reversal for (TPrPc)Fe(III)Cl. These behaviors are consistent with the admixed S = 3/2, 5/2 ground electronic state with a dominating contribution of the S = 3/2 one. In terms of the chemical shift, (TPrPc)Fe(III)(ClO(4)) can be considered as an example of the purest S = 3/2 state in the investigated series. The extent of the S = 5/2 contribution in the admixed S = 3/2, 5/2 ground electronic state, as gradated solely the basis of the pyrrole proton paramagnetic shifts, is controlled by the strength of the axial ligand, following the magnetochemical series (Evans, D. R.; Reed, C. A. J. Am. Chem. Soc. 2000, 122, 4660). Significantly iron(III) 2,7,12,17-tetrapropylporphycene, soluble in typical organic solvents, can be considered as a universal framework to classify the ligand strength in a magnetochemical series, consistently using the beta-H pyrrole paramagnetic shifts as a fundamental criterion. The structure of (TPrPc)Fe(III)Cl has been determined by X-ray crystallography. The iron is five-coordinate with bonds of nearly equal length to the four pyrrole nitrogen atoms (Fe-N in the range 1.983(5)-2.006(6) A). The iron lies 0.583(1) A out of the mean plane of the macrocycle and 0.502(5) A out of the mean N(4) plane. In the solid, pairs of molecules are positioned about the center of symmetry so there is face-to-face pi-pi contact. The mean plane separation is 3.38 A, and the lateral shift of the porphycene center along the Fe-N bond is 4.490 A. The distance from one porphycene center to the other is 5.62 A, and the iron-iron separation is 6.304(2) A.

Journal Article↗