Polymorphism and Red Photoluminescence Emission from 5s2 Electron Pairs of Sb(III) in a New One-Dimensional Organic-Inorganic Hybrid Based on Methylhydrazine: MHy2SbI5.

We explore the crystal structure and luminescent properties of a new 1D organic-inorganic hybrid, MHy2SbI5, based on methylhydrazine. The compound reveals the red photoluminescence (PL) originating from the 5s2 electron pairs of Sb(III) as well as complex structural behavior. MHy2SbI5 crystalizes in two polymorphic forms (I and II) with distinct thermal properties and structural characteristics. Polymorph I adopts the acentric P212121 chiral space group confirmed by SHG, and, despite a thermally activated disorder of MHy, does not show any phase transitions, while polymorph II undergoes reversible low-temperature phase transition and high-temperature reconstructive transformation to polymorph I. The crystal structures of both forms consist of 1D perovskite zig-zag chains of corner-sharing SbI6 octahedra. The intriguing phase transition behavior of II is associated with the unstable arrangement of the [SbI5]2-∞ chains in the structure. The energy band gap (Eg) values, estimated based on the UV-Vis absorption spectra, indicate that both polymorphs have band gaps, with Eg values of 2.01 eV for polymorph I and 2.12 eV for polymorph II.

Structural, Electric and Dynamic Properties of (Pyrrolidinium)3[Bi2I9] and (Pyrrolidinium)3[Sb2I9]: New Lead-Free, Organic-Inorganic Hybrids with Narrow Band Gaps.

Hybrid organic-inorganic iodides based on Bi(III) and Sb(III) provide integrated functionalities through the combination of high dielectric constants, semiconducting properties and ferroic phases. Here, we report a pyrrolidinium-based bismuth (1) and antimony (2) iodides of (NC4H10)3[M2I9] (M: Bi(III), Sb(III)) formula which are ferroelastic at room temperature. The narrow band gaps (~2.12 eV for 1 and 2.19 eV for 2) and DOS calculations indicate the semiconducting characteristics of both materials. The crystal structure consists of discrete, face-sharing bioctahedra [M2I9]3- and disordered pyrrolidinium amines providing charge balance and acting as spacers between inorganic moieties. At room temperature, 1 and 2 accommodate orthorhombic Cmcm symmetry. 1 displays a complex temperature-induced polymorphism. It is stable up to 525 K and undergoes a sequence of low-temperature phase transitions (PTs) at 221/222 K (I ↔ II) and 189/190 K (II ↔ III) and at 131 K (IV→III), associated with the ordering of pyrrolidinium cations and resulting in Cmcm symmetry breaking. 2 undergoes only one PT at T = 215 K. The dielectric studies disclose a relaxation process in the kilohertz frequency region, assigned to the dynamics of organic cations, described well by the Cole-Cole relation. A combination of single-crystal X-ray diffraction, synchrotron powder diffraction, spin-lattice relaxation time of 1H NMR, dielectric and calorimetric studies is used to determine the structural phase diagram, cation dynamics and electric properties of (NC4H10)3[M2I9].

Solution studies of some new oxamides - co-ordination behaviour towards Cu(II) ions.

The co-ordination chemistry of some new oxamides towards Cu(II) ions was studied using various techniques: potentiometry, voltammetry, spectroscopy (UV-Vis, CD and EPR) and ESI-MS spectrometry. All tested compounds chelate the copper(II) ions with formation of 1:1 and 1:2 (metal-to-ligand ratio) complexes. The Cu(II) ions are bound by 1N, 2N or 3N nitrogen donor systems. Additionally, an unusual co-ordination to amide N-atoms without additional anchoring site is suggested. The (14)N hyperfine splitting observed for the system ox6-Cu(II) above pH 10 clearly indicates the involvement of at least three N donor atoms in the copper ion binding. Moreover, the surrounding by three amide-N and one carbonyl-O stabilizes the high oxidation state of copper(III), although such complexes are very unstable in solution.

Synthesis of bis-(methyl 3,4,6-tri-O-acetyl-D-glucopyranosid-2-yl)-oxamides.

The synthesis of a new bis-(D-glucopyranosid-2-yl)oxamides via the key intermediate, N-acetyl N-(methyl 3,4,6-tri-O-acetyl-alpha-D-glucopyranosid-2-yl) oxamic acid chloride (2alpha) is described. Treatment of compound 2alpha with methyl 3,4,6-tri-O-acetyl-2-amino-2-deoxy-beta-D-glucopyranoside afforded N-(methyl 3,4,6-tri-O-acetyl-alpha-D-glucopyranosid-2-yl)-N'-(methyl 3,4,6-tri-O-acetyl-beta-D-glucopyranosid-2-yl)-oxamide. Reaction of 2alpha with 1,2-diaminoethane afforded 1,2-bis-[N,N'-(methyl 3',4',6'-tri-O-acetyl-alpha-D-glucopyranosid-2'-yl)]ethyloxamide as a main product, while 2-N-[N'-(methyl 3',4',6'-tri-O-acetyl-alpha-D-glucopyranosid-2'-yl)oxamide]-ethyl acetamide was formed as a side product. Reaction of 2alpha with 1,3-diamino-2-hydroxypropane gave only 1,3-bis-N,N-[N'-(methyl 3',4',6'-tri-O-acetyl-2'-deoxy-alpha-D-glucopyranosid-2'-yl)-oxamido]-2-propanol.

Synthesis and solid state 13C and 1H NMR analysis of new oxamide derivatives of methyl 2-amino-2-deoxy-alpha-D-glucopyranoside and ester of amino acids or dipeptides.

The syntheses of new oxamide derivatives of methyl 2-amino-2-deoxy-alpha-D-glucopyranoside and amino acid or peptide esters are presented. The reaction of methyl 3,4,6-tri-O-acetyl-2-acetamido-2-deoxy-alpha-D-glucopyranoside and oxalyl chloride gave N-(methyl 3,4,6-tri-O-acetyl-2-deoxy-alpha-D-glucopyranosid-2-yl) oxamic acid chloride which on reaction with the ester of Gly, L-Ala, L-Phe, GlyGly, Gly-L-Phe and Gly-L-Ala afforded N-(methyl 3,4,6-tri-O-acetyl-2-deoxy-alpha-D-glucopyranosid-2-yl), N'-oxalyl-amino acid or dipeptide esters. The structure of the oxamides was studied using 1H, 13C NMR in solution and solid state.

Liquid crystal membranes for serum-compatible diabetes management-assisting subcutaneously implanted amperometric glucose sensors.

Membranes formed of thermodynamically stable cubic phase lyotropic liquid crystals (LLCs) could replace the presently used polymeric membranes, applied to reduce the flux of glucose in semicontinuous, subcutaneously implanted, user-replaced, miniature, amperometric glucose sensors, assisting in the management of diabetes. LLC-forming amphiphilic compounds set and toughen spontaneously after mixing with water, without undergoing chemical change. When applied by doctor-blading, they form membranes having three-dimensionally interconnected water channels of uniform diameter, with reproducible glucose transport-characteristics. We find that the best studied cubic phase LLCs, which are formed of monoolein and water, are not useful in their intended application because they are hydrolyzed by serum lipases. Those formed of phytantriol, a liquid at ambient temperature, and water, are not hydrolyzed but change their shape and size in a dehydration and rehydration cycle. Because glucose sensors are sterilized and stored in a sealed package in a dry atmosphere, drying and rehydration must not change the transport characteristics. A third, novel, LLC-forming, amphiphile 1-O-beta-(3,7,11,15-tetramethylhexadecyl)-d-ribopyranoside, I, was synthesized, and its phase diagram was tailored by adding Vitamin E acetate, to form a cubic phase. The phase was stable through the 20 degrees C-90 degrees C temperature range in excess of water and had the desired glucose-transport characteristics. A preferred LLC, II, was formed of water and I containing 7 wt % of Vitamin E acetate. When II was applied to a wired glucose oxidase bioelectrocatalyst, sensors of reproducible glucose-sensitivity were formed. At a 0.1 mm thickness of II, the membrane reduced the glucose flux 5-fold and increased the 90% response-time by less than 2 min. The membrane was mechanically rugged, withstanding the approximately 1 N m(-2) maximal shear stress at 5 mm diameter electrodes rotating at 4000 rpm. The activation energy for glucose permeation through II was reduced to 15.6 kJ/mol, making the sensors's current less temperature-dependent than that of the polymeric-membrane overcoated implantable glucose sensors.