Activation and regioselectivity of five-membered cyclic thionocarbamates to nucleophilic attack

The cyclic thionocarbamate of alaninol undergoes nucleophilic attack by sulfur nucleophiles at 5-C to give 1-thiopropyl-2-amine derivatives when derivatised on nitrogen with a Boc group. Iodide under microwave conditions causes a rearrangement to the isomeric thiazolidinone, while "hard" nucleophiles react at the thione group to yield a variety of product types by subsequent C–N or C–O cleavage. X-ray crystallography studies showed that the N-Boc group reduces delocalisation of electron density from nitrogen into the thione group, and thus promotes activation of the ring to nucleophilic attack

Synthesis of new chiral organosulfur donors with hydrogen bonding functionality and their first charge transfer salts

The syntheses of a range of enantiopure organosulfur donors with hydrogen bonding groups are described including TTF related materials with two, four, six and eight hydroxyl groups and multiple stereogenic centres and a pair of chiral N-substituted BEDT-TTF acetamides. Three charge transfer salts of enantiopure poly-hydroxy-substituted donors are reported, including a 4:1 salt with the meso stereoisomer of the dinuclear [Fe2(oxalate)5 ]4- anion in which both cation and anion have chiral components linked together by hydrogen bonding, and a semiconducting salt with triiodide

Applications for the activation of hydroxyl groups to nucleophilic attack

This thesis investigates the applications of the activation of hydroxyl groups to nucleophilic attack within three key areas: Cyclic five-membered thionocarbamates bearing a N-Boc group undergo ring opening reactions at the 5-C with soft nucleophiles such as thiophenolate, pyridine-2-thiolate and potassium thioacetate. Hard nucleophiles react at the thiocarbonyl group followed by a variety of successive reactions involving breakage of C-N ( e. g. with n-BuLi) or C-O bond (e. g. with PhLi). Treatment with iodide under microwave conditions led to a rearrangement to a thiazolidin-2-one. Two approaches to the synthesis of vic-dithiols were investigated. The more successful approach involves reaction of the trithiocarbonate dianion with cyclic sulphate esters of vic-diols to yield a protected version of the vic-dithiols. In a second approach, rearrangement of thionocarbonates with bromide gave the oxathiolan-2-one. Under thionation conditions with (e. g. Lawesson‟s reagent and HMDO) it was possible to replace both oxygens, while with Lawesson‟s reagent and HMDO in dry xylene only the carbonyl group was replaced. It was not possible to rearrange this material again with bromide or iodide. New chiral organosulphur donors related to TTF and bearing multiple hydroxyl groups (from two to eight) were prepared starting from reaction of [(4R)-2,2-dimethyl-1,3-dioxolan-4-yl]methyl trifluoromethanesulphonate with 2-thioxo-1,3-dithiole-4,5-dithiolate and several further steps. A triiodide complex of a tetrahydroxy substituted donor was prepared and structurally characterized

Stereoisomeric semiconducting radical cation salts of chiral bis(2-hydroxypropylthio)ethylenedithioTTF with tetrafluoroborate anions

The new chiral TTF-based donor molecule bis(2-hydroxypropylthio)ethylenedithiotetrathiafulvalene has produced enantiopure R,R and S,S radical cation salts with the tetrafluoroborate anion as well as the nearly isostructural meso/racemate mixture. The enantiopure R,R or S,S salts are both 1:1 semiconducting salts with activation energies of 0.19–0.24 eV, both crystallising in the orthorhombic space group C2221. The semiconducting salt containing both meso and racemic donor cations has a very similar crystal structure but crystallising in the monoclinic space group C2/c (β = 91.39°) with similar S⋯S interactions but a smaller activation energy of 0.15–0.17 eV. This is in contrast to previous families of this type where the disordered racemate has a larger activation energy than its enantiopure salts

Chirality in charge-transfer salts of BEDT-TTF of tris(oxalato)chromate(III)

Crystallisation from chiral electrolyte (R)-(−)-carvone has produced three new chiral semiconducting salts of BEDT-TTF from racemic anion tri(oxalato)chromate(III)

Synthesis and DFT Study of Newly Schiff Base and Fused Heterocyclic Compounds as Antibacterial Agent

Treatment of 2,3-di-(4-chlorophenyl) oxirane-2,3-dicarbonitriles(1) with nitrogen nucleophiles, e.g. N2H4, NH2OH afforded pyrazole 2, 1.2oxazole 3 derivatives respectively The 3-amino pyrazole-4-one derivatives 2 can be used as a key starting materials to synthesize some important Schiff base 4 and fused heterocyclic compounds e.g. Imidazolo-[4,5-c]pyrazole 5, Pyrazolo[3,4-e]1,2,4-triazine 6, pyrazol[1,2-a] 1,3,5-triazine 7, 8 and 9. The electromeric effect of the halogen atom in the aryl moieties can be controlled upon the rate of reaction and the yield of the product. The structures of synthesized new compounds were characterized by spectral data and screened for their antimicrobial activities against various bacteria and fungi strains. The heterocyclic compounds 7, 8 and 9 that contained bridgehead nitrogen gave an excellent result.&nbsp

Contrasting crystal packing arrangements in triiodide salts of radical cations of chiral bis(pyrrolo[3,4-d])tetrathiafulvalenes

Crystal structures of six 1 : 1 triiodide salts of a series of enantiopure bis(pyrrolo[3,4-d])TTF derivatives, the first structures of radical cation salts reported for this bis(pyrrolo) donor system, show three different arrangements of triiodide ions, organised either in head-to-tail pairs, in infinite lines, or in a castellated arrangement. The complex crystal structures, obtained by electrocrystallisation, are influenced by the presence of solvent, for example changing an ABCABC packing arrangement to ABAB with inclusion of THF, as well as by the size of the chiral side chain

On-line estimation of first order plus dead time process parameters based on under or over-parameterized models

Simple on-line process identification methods that can be used in tuning PID controllers or any other controllers have been studied in this work. The underlying continuous-time first order plus dead time FOPDT process model parameters ('k', [tau], [tau]'d') have been estimated effectively at every sampling period from the frequency response of an under or over-parameterized model assigned for the process and enhanced with recursive least squares. It is shown that for any under or overparameterized model structure and with any SNR as low as 0dB, the parameters of the FOPDT model are estimated reliably. This has been accomplished by using either the Nelder-Mead optimization approach or the line fitting approach. Line fitting approach provides better estimation results and faster parameter convergence than the Nelder-Mead optimization approach especially when small sampling periods are used. Line fitting approach is applied experimentally to a distillation column and evaluated successfully in this thesis

A structural investigation of novel thiophene-functionalized BEDT-TTF donors for application as organic field-effect transistors

Three new unsymmetrical thiophene-functionalized bisIJethylenedithio)tetrathiafulvalene (BEDT-TTF) donors (1–3) have been synthesized, characterised and examined as semiconducting materials for organic field-effect transistor (OFET) devices. The X-ray crystal structures of (1) and (2) reveal both neutral donors pack as dimers with lateral S⋯S contacts. For (1) the molecules are co-facially stacked in a head-to-tail manner with some degree of latitudinal slippage. A device prepared from a crystalline thin film of (1) deposited on unmodified silicon wafer substrate displays a mobility of 5.9 × 10−3 cm2 V−1 s−1 with an on/off ratio of 11. The shorter CH2 linker in (2) results in poorer orbital overlap, likely due to significant longitudinal and latitudinal slippage between molecules in the crystal lattice. As a consequence, no field-effect response was observed for the device fabricated from (2)

A family of unsymmetrical hydroxyl-substituted BEDT-TTF donors: syntheses, structures and preliminary thin film studies

Three new unsymmetrical hydroxyl-functionalized donors H1–H3 closely related to hydroxymethyl-BEDT-TTF have been synthesised and characterised. Cyclic voltammetry studies showed that the compounds exhibit reversible two one-electron redox processes typical for BEDT-TTF derivatives. X-ray diffraction studies of H1 and H2 reveal π-stacking interactions between pairs of donors that are organized into distinct H-bonded square motifs and DFT calculations indicate that the HOMO is located on the central 1,3-dithiole rings. Protection of the hydroxyl group with acetyl in 13 eliminates co-facial S...S interactions between the dimers to accommodate the bulkier side chains, but short edge-to-edge S...S contacts offer an alternative pathway for electron mobility. Chemical oxidation of H1 and HMET 2 with I2 afforded single crystals of two 1 : 1 charge transfer salts, 18 and 19. The molecules pack as dimers with close π-stacking interactions between pairs of radical cations whose crystal structures are further stabilized via an interplay of S...S and S...I contacts. Iodine-doped surface conducting polystyrene blend films of H3 deposited on a silica substrate exhibit quasiconducting properties, but afford no OFET response when fabricated into devices. Visible-NIR studies of a doped polystyrene blend film of H3 cast on a glass substrate show absorption bands at λ =9 50 and 3000 nm, consistent with mixed valence states due to the presence of charge-transfer species on the surface of the films