Bahareh Khalili Najafabadi

New Polydentate Trimethylsilyl Chalcogenide Reagents for the Assembly of Polyferrocenyl Architectures

A series of polychalcogenotrimethylsilane complexes Ar(CH2ESiMe3)n, (Ar = aryl; E = S, Se; n = 2, 3, and 4) can be prepared from the corresponding polyorganobromide and M[ESiMe3] (M = Na, Li). These represent the first examples of the incorporation of such a large number of reactive -ESiMe3 moieties onto an organic molecular framework. They are shown to be convenient reagents for the preparation of the polyferrocenylseleno- and thioesters from ferrocenoyl chloride. The synthesis, structures, and spectroscopic properties of the new silyl chalcogen complexes 1,4-(Me3SiECH2)2(C6Me4) (E = S, 1; E = Se, 2), 1,3,5-(Me3SiECH2)3(C6Me3) (E = S, 3; E = Se, 4) and 1,2,4,5-(Me3SiECH2)4(C6H2) (E = S, 5; E = Se, 6) and the polyferrocenyl chalcogenoesters [1,4-{FcC(O)ECH2}2(C6Me4)] (E = S, 7; E = Se, 8), [1,3,5-{FcC(O)ECH2}3(C6Me3)] (E = S, 9; E = Se, 10) and [1,2,4,5-{FcC(O)ECH2}4(C6H2)] (E = S, 11 illustrated; E = Se, 12) are reported. The new polysilylated reagents and polyferrocenyl chalcogenoesters have been characterized by multinuclear NMR spectroscopy ((1)H, (13)C, (77)Se), electrospray ionization mass spectrometry and, for complexes 1, 2, 3, 4, 7, 8, and 11, single-crystal X-ray diffraction. The cyclic voltammograms of complexes 7-11 are presented.

Luminescent CdSe Superstructures: A Nanocluster Superlattice and a Nanoporous Crystal

Superstructures, combining nanoscopic constituents into micrometer-size assemblies, have a great potential for utilization of the size-dependent quantum-confinement properties in multifunctional electronic and optoelectronic devices. Two diverse superstructures of nanoscopic CdSe were prepared using solvothermal conversion of the same cadmium selenophenolate precursor (Me4N)2[Cd(SePh)4]: the first is a superlattice of monodisperse [Cd54Se32(SePh)48(dmf)4]4- nanoclusters; the second is a unique porous CdSe crystal. Nanoclusters were crystallized as cubic crystals (≤0.5 mm in size) after solvothermal treatment at 200 °C in DMF. UV-vis absorption and PLE spectra of the reported nanoclusters are consistent with previously established trends for the known families of tetrahedral CdSe frameworks. In contrast to these, results of PL spectra are rather unexpected, as distinct room temperature emission is observed both in solution and in the solid state. The porous CdSe crystals were isolated as red hexagonal prisms (≤70 μm in size) via solvothermal treatment under similar conditions but with the addition of an alkylammonium salt. The presence of a three-dimensional CdSe network having a coherent crystalline structure inside hexagonal prisms was concluded based on powder X-ray diffraction, selected area electron diffraction and electron microscopy imaging. Self-assembly via oriented attachment of crystalline nanoparticles is discussed as the most probable mechanism of formation.

Crystallization of Esomeprazole Magnesium Water/Butanol Solvate

The molecular structure of esomeprazole magnesium derivative in the solid-state is reported for the first time, along with a simplified crystallization pathway. The structure was determined using the single crystal X-ray diffraction technique to reveal the bonding relationships between esomeprazole heteroatoms and magnesium. The esomeprazole crystallization process was carried out in 1-butanol and water was utilized as anti-solvent. The product proved to be esomeprazole magnesium tetrahydrate with two 1-butanol molecules that crystallized in P63 space group, in a hexagonal unit cell. Complete characterization of a sample after drying was conducted by the use of powder X-ray diffraction (PXRD), 1H-nuclear magnetic resonance (NMR), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), infrared spectroscopy (IR), and dynamic vapor sorption (DVS). Investigation by 1H-NMR and TGA has shown that the solvent content in the dried sample consists of two water molecules and 0.3 butanol molecules per esomeprazole magnesium molecule. This is different from the single crystal X-ray diffraction results and can be attributed to the loss of some water and 1-butanol molecules stabilized by intermolecular interactions. The title compound, after drying, is a true solvate in terms of water; conversely, 1-butanol fills the voids of the crystal lattice in non-stoichiometric amounts.