Chemistry

 RESEARCH PROJECTS 
 ARTICLES, BOOKS AND REPORTS 
 ABSTRACTS, PRESENTATION AND PROCEEDINGS 
 MASTER'S THESES 
 
 

RESEARCH PROJECTS
 

Amplitude equations from hyperbolic reaction-diffusion equations

Amplitude equations are derived from hyperbolic reaction-diffusion equations using multiple time scale perturbation theory. Two different equations are obtained in the oscillatory regime (Hopf bifurcation) and in stationary regime (Turing bifurcation). Those Ginzburg-Landau equations retain the same form as the amplitude equations derived from parabolic reaction-diffusion equations. However, the coefficients are more complicated in the hyperbolic case and possess singularities when a critical value of the reaction-diffusion number is achieved. Moreover, in the limit of infinite reaction-diffusion number, we regain the amplitude equations from parabolic equations. The newly derived equations exhibit complicated patterns like oscillations, traveling waves and spatio-temporal chaos. M. Al-Ghoul. (Supported by URB.)
 
 

Shock wave structure in a diatomic gas: generalized hydrodynamics approach

The structure of a shock wave in a diatomic gas is investigated using generalized hydrodynamics. Different shock wave properties, like pressure, density, heat, stress and density are computed as a function of distance. The shock thickness is computed versus the Mach number. Dissipation along the shock is calculated. The results are compared with those of different theories and with Monte Carlo simulations of the Boltzmann equation. M. Al-Ghoul. (Supported by URB.)
 
 

Mechanism and irreversible thermodynamics of Turing instability from hyperbolic reaction-diffusion equations for glycolysis in different geometries

Numerical algorithms based on the finite-element method are developed to study Turing Instabilities in different geometries like square, triangle, circle, star, etc. … The effect of the boundaries is thoroughly investigated. Periodic, fixed, flux and no-flux boundary conditions are implemented to solve hyperbolic reaction-diffusion equations. This investigation helps understand better the effects of the boundaries on propagating waves on the cellular level. The effects of nonlinear diffusion are also studied in such small geometries. M. Al-Ghoul. (Supported by URB.)
 
 

Normal forms for a nonlinear oscillator with multiplicative noise

A stochastic complex Ginzburg-Landau equation is derived using normal form transformations to a chemical oscillator with multiplicative noise. In the case of very weak noise and under certain assumptions, the equations for the radial and the phase components of the amplitude separate and can be solved exactly. We show that the radial part fluctuates near the average value for long times. However, the phase is found to be a Gaussian random variable with time dependent mean and variance. For noise amplitudes high enough to push the system away from the oscillatory region, the system exhibits high amplitude intermittent bursts in the concentrations for different realizations of the noise; on the other hand, in this case, the average concentrations also exhibit intermittent bursts but with smaller amplitude relative to the aforementioned case. This behavior may be due to continuous random flips of the system when a parameter varies randomly between the saddle and focus regions. M. Al-Ghoul. (Supported by URB.)
 
 

Chlorosulphonation of a ,b -unsaturated carbonyl compounds-synthesis of sulphur, nitrogen heterocycles

Reaction of 3-methoxy and 3,4-dimethoxychalcone-6-sulphonyl chloride with a series of aliphatic and aromatic amines has been investigated resulting in the formation of 1,2-benzisothiazole-1,1-dioxide and 1,2-benzothiazine-1,1-dioxide derivatives via a intramolecular Michael addition. Reaction of the chalcone sulphonyl chlorides with aromatic ortho-diamines gave a novel route to tetracyclic heterocycles; benzoisothiazolo moiety fused to 1,5-benzodiazepines. J. P. Bassin, K. Al-Nawwar and M. J. Frearson*. (Supported by URB.)
 
 

Chlorosulphonation of styrylpyridine

Reaction of styrylpyridine with chlorosulphonic acid and subsequent treatment of the sulphonyl chloride with morpholine resulted in the formation of 2-(2-pyridyl)-3-morpholino-2, 3-dihydrobenzo[b]thiophene 1,1-dioxide-6-sulphonylmorpholidate. This synthetic route offers a simple method of introducing a 2-pyridyl group into the 2-position in benzo[b]thiophene. This work is in print in Phosphorus, Sulphur and Silicon. J. P. Bassin, R. J. Cremlyn* and S. Graham*. (Supported by URB.)
 
 

Skin cancer photoprotective quinoxaline 1, 4-dioxides

Recent studies in this laboratory have shown that topical application of differently substituted quinoxaline 1,4-di-N-oxides (QdNOs) to the skin inhibits in a dose-dependent fashion radiation-induced skin damage. This work is currently being extended to in vitro studies to determine the ability of these compounds to inhibit cell proliferation and to affect cell cycle distribution of various cell lines and cancer cells. Our data indicate that the QdNOs cause up to 90% inhibition of the growth of various cell lines and induce cell cycle arrest with striking differences in effectiveness between the different substituents. M.J. Haddadin , H. Gali-Muhtasib and D. Rahhal. (Supported by royalties from the Beirut Reaction.)
 
 

Synthesis of new heterocyclic clefts

The reaction of tetracyclo- and pentacyclo undecane diones with nitrobenzaldehydes, benzofurazan oxides, tetrazines, and related compounds, with the aim of synthesizing novel cleft compounds containing chelating centers is studied. The effect of bases and solvents on the reaction products is investigated. M. J. Haddadin and M. Z. Nazer*. (Supported by URB.)
 
 

Photocatalysis at semiconductors

Semiconductor research has led to a multitude of advances over the past few decades. High efficiency lasers, light emitting diodes, solar cells and photocatalysis are only a few of these advancements. Photocatalysis can provide potential new sources of energy, applications for the treatment of waste for environmental cleaning. In this work, semiconductor particles are being assembled as part of multicomponent systems with various surface modifications: sensitizer dyes, metal catalysts, sacrificial electron or hole scavengers, and the effectiveness of such systems in catalyzing various reactions is explored. Part of this project involves studying photocatalysis at quantum confined semiconductor particles, where quantum confinement has the dual advantage of increasing the surface to volume ratio, and of tuning the band gap energy and band edge positions. In addition, films of semiconductor particles are assembled into polymer films with electrostatic links; the spectroscopic and photoelectrochemical properties of these films are under research. L. I. Halaoui. (Supported by URB.)
 
 
 

Hydroxylamine formation studied by scanning electrochemical microscopy

Scanning electrochemical microscopy was used to study the electrochemical formation of hydroxylamine. Hydroxylamine is a material of paramount significance in the industry. In the agricultural and pharmaceutical realms, it serves as an intermediate for various synthetic end products. The semiconductor industry benefits from its use in stripper formulation for photoresist removal. It also finds applications as a component in liquid propellants, as a reducing agent, and as a photographic developer amongst other usage. The formation of hydroxylamine from the reduction of nitric acid at modified surfaces other than liquid mercury was accomplished, and various surface changes accompanying this process were investigated. This work was conducted at the University of Texas at Austin in the laboratory of A. J. Bard, it is completed and a manuscript is under preparation. L. I. Halaoui, A. J. Bard,* H. Sherifian*. (Supported by Sachem Chemical Company.)
 
 

Quantum confinement in semiconductors

Scanning Tunneling Microscopy (STM), Atomic Force Microscopy (AFM), and Tunneling Spectroscopy were used to probe the size and quantum confinement effects in nanometer size semiconductors. STM and AFM probed the topography of InAs (and GaAs) quantum dots deposited as films or as single particles on metal surfaces. Tunneling spectroscopy data onanometer size InAs particles, and of single crystal InAs with sulfide passivated surfaces showed a significant increase in the conductivity gap for the particles, relative to the single crystals. Energy gaps three times as large as the band gap of the bulk solid were measured. Results were consistent with theoretical models describing quantum confinement for particles of the size. This work was conducted at Duke University in the laboratory of L. A. Coury, Jr. Results have been submitted to Chemistry of Materials. L. I. Halaoui, L. A. Coury, Jr.,* R. Wells*. (Supported by the Airforce Office of Scientific Research and Duke University.)
 
 

Photoelectrochemical and electroluminescence studies of nitride films

Electroluminescence and photoelectrochemical studies of GaN and Ga_xIn_1-xN thin films, and of GaN single crystals were the subjects of this research study. These have potential applications in light emitting diodes (LEDs), lasers, photoelectrochemical cells (PECs), and as photocatalysts. The positioning of the band edges and the state of the band gap region of these semiconductors, and their dependence on the solution interface is of crucial significance. Both solution electroluminescence and photoelectrochemical measurements in different electrolytes were used to probe band edge positioning and band gap energies. Solution Electroluminescence showed significant yellow luminescence attributed to mid gap states. Photoelectrochemical measurements showed significant photocurrent density, and lead to flat band potential measurements and hence band edge determination in solution. Work was conducted in the laboratory of Professor A. J. Bard, University of Texas, Austin. Work on solution electroluminescence resulted in a publication (Electrochem. Solid. State Lett.). Work on the photoelectrochemical properties of films and single crystal GaN is under preparation. L. I. Halaoui, C. Hung*, A. J. Bard*. (Supported by the National Science Foundation.)
 
 

The interaction of di- and trinuclear heterogroups (e.g. diphosphonates, tripolyphosphate) with tungstate, molybdate and vanadate

The synthesis of new polyoxometalates with novel structures containing external di- and trinuclear heterogroups will be performed. The advantage of heteropolyanions with external heterogroups (as opposed to the compact ones with internal heterogroups) is that a slight modification of the heterogroup (e.g. O₃PCXYPO₃^4-, X = Y = H; X = CH₃, Y = NH₂; X = H, Y = N(CH₃)₂) might lead to the same overall polyanion-structure, but a difference in the electrostatic surface-potential could result in a more selective HIV-1 inhibition. Then the anti-bacterial and anti-viral (e.g. HIV) properties of all newly synthesized heteropolyanions will be tested and I hope to find a compound which, perhaps by systematic modification of the heterogroups ("drug design"), will become a selective and potent inhibitor of HIV and therefore a cure for AIDS. U. Kortz. (Supported By URB.)
 
 

Introduction of second- and third-row transition metals (e.g. Ru, Rh, Os, Ir) in lacunary heteropolyanions

Transition metal substituted polyoxometalates exhibit many of the properties of metalloporphyrins (e.g. multidentate and reversibly reducible ligand system, co-binding or co-activation of the substrate) without being thermodynamically unstable with respect to oxidative degradation ("inorganic metalloporphyrin analogs"). A number of polyoxometalates with d-electron-transition metal ions (e.g. [MXW₁₁O₃₉]^x-, X = P, Si; M = Co, Cu, Fe, Mn) have been investigated using different substrates (e.g. alkanes, alkenes, alkylphenols), oxidants (e.g. O₂, PhIO, H₂O₂) and solvents (e.g. H₂O, CH₃CN) with good results. There have been very few reported examples of polyoxometalate-metal complexes that contain a 4d or 5d transition-metal cation and in most cases their syntheses are not well established. To date only three heteropolyanion-complexes that contain Ru have been reported. These species can be expected to display significant redox and potential catalytic activity. U. Kortz. (Supported By URB.)
 
 

Synthesis of transition-metal substituted molybdopyrophosphate heteropolyanions

The 18-molybdopyrophosphate, [P₂O₇Mo₁₈O₅₄]^4-, is the first structurally characterized polyoxoanion containing pyrophosphate. Recently the syntheses of a 15- and a 12-molybdopyrophosphate have been reported, but the structures of the species remain unknown. Most likely both are compact lacunary polyoxoanions related to the parent 18-molybdopyrophosphate and if the structures of these novel anions could be elucidated a rational approach to synthesize the first examples of transition metal (e.g. W, V, Ru, Rh) substituted molybdopyrophosphates could be attempted. I am planning to determine the structures of the novel compounds using IR and NMR-spectroscopy (³¹P, ⁹⁵Mo, ¹⁸³W) and single-crystal X-ray crystallography. The catalytic red/ox activity of the new compounds will then be tested. U. Kortz. (Supported By URB.)
 
 

Interaction of ethylenediphosphonate with tungstate, molybdate and vanadate.

The macrocyclic dodecatungstate, [(O₃PCH₂PO₃)₄W₁₂O₃₆]^16-, has a unique structure and very interesting biological properties (e.g. anti-HIV-1). In order to synthesize an inhibitor that is more specific towards reverse transcriptase I am planning to study the interaction of ethylenediphosphonate, (O₃PCH₂CH₂PO₃^4-), with tungstate, molybdate and vanadate. The synthesis of novel heteropolyanions seems likely and also a combination of both heterogroups, methylenediphosphonate and ethylenediphosphonate, might lead to interesting new structures. The analytical techniques used for the synthetic and structural investigations will include IR and NMR-spectroscopy (¹H, ¹³C, ³¹P, ¹⁸³W, ⁹⁵Mo) as well as X-ray crystallography. The biological activity of the new compounds will then be tested. U. Kortz. (Supported By URB.)
 
 

Interaction of the dilacunary gamma-decatungstophosphate, [g -PW₁₀O₃₆]^7-, with first-row transition metals

Based on the unexpected and exciting results that I obtained by reacting the dilacunary heteropolyanion gamma-decatungstosilicate, [g -SiW₁₀O₃₆]^8-, with first-row transition metals it is now of interest to investigate the interaction of the structurally analogous gamma-decatungstophosphate, [g -PW₁₀O₃₆]^7- with the same type of transition metals (e.g. Ni²⁺, Mn²⁺, Cu²⁺). The synthesis of the lacunary precursor ion [g -PW₁₀O₃₆]^7- has been published and is straightforward. The products are expected to be di-metal substituted Keggin-type polyoxoanions, [g -M₂(H₂O)₂PW₁₀O₃₈]^7- (M = Ni²⁺, Mn²⁺, Cu²⁺ etc.), with the two metal ions in neighboring, edge-shared octahedra. However, there is a possibility that the reaction path will involve isomerization and dimerization; perhaps analogous to the observations for the gamma-decatungstosilicate. In this case the product formed would be even more interesting since the number of paramagnetic transition metal centers enclosed by the two diamagnetic silicotungstate fragments would be larger. U. Kortz. (Supported By URB.)
 
 

Synthesis and characterization of substituted 2,2¢ -bipyridine derivatives

The work involves the synthesis of new mono-and disubstituted 2,2¢ -bipyridine derivatives and their uses in a variety of synthetic projects ranging from solar materials to supramolecular complexes. A. Salameh.
 
 

Synthesis and characterization of 5,5¢ -disubstituted 2,2¢ -bipyridine ligands and their mono and polynuclear ruthenium (II) complexes

The reactions of cis-dichloro bipyridine ruthenium (II) (bpy)₂ RuCl₂ with several 5,5¢ -disubstituted-2,2¢ -bipyridine derivatives were attempted and gave the corresponding mononuclear ruthenium (II) complexes. Several polymers were synthesized from the 5,5¢ -disubstituted-2,2¢ -bipyridines: a polyamide polymer was synthesized from the reaction of 5,5¢ -diamino-2,2¢ -bipyridine and 2,2¢ -bipyridine-5,5¢ -diacid Chloride. A polyamine polymer was synthesized from the reaction of 5,5¢ -diamino-2,2¢ -bipyridine and 5,5¢ -bis(bromomethyl)-2,2¢ -bipyridine. A Schiff base polymer was synthesized from the reaction of 5,5¢ -diformyl-2,2¢ -bipyridine and 5.5¢ -bis(aminomethyl) 2,2¢ -bipyridine. The reaction of tpolymers with (bpy)₂ RuCl₂ gave the corresponding polynuclear ruthenium (II) complexes. Coupling of the mononuclear ruthenium (II) complexes also yielded the corresponding ruthenium bipyridine polymers directly. A. Salameh.
 
 

Polyelectrolyte structures

We are using charged polymers, polyelectrolytes, to make thin films on substrates, including silicon wafers. The polymers are assembled in a layer-by-layer fashion, providing for precise control over layer thickness. These materials have applications as corrosion protection layers, antistatic coatings, sensors, and controlled-permeability membranes. We are also investigating the use of diblock polymers as surfactants and dispersants (“polysoaps”). J. Schlenoff. (Supported by the National Science Foundation and URB.)
 
 

Structure and variety in multiple-precipitate Liesegang systems

Periodic precipitation of ions in gelled media is extended to a broad variety of two- and three-salt systems. Precipitate bands could overlap or alternate or form a diverse collection of exotic patterns. The band content is analyzed using different techniques such as potentiometry (ion-selective electrodes), spectrophotometry and even image analysis of the patterns’ pictures. The systems studied include lead halides, hydroxides of nickel, cobalt and magnesium, sulfides (MnS, CuS and CdS), dichromates of silver and lead, oxinates of cobalt, silver and copper and other precipitate systems. R. Sultan. (Supported by URB.)
 
 

Traveling waves on a ring in chemical systems

A scaling reaction-diffusion model is extended from a linear to a circular spatial geometry (a ring). The reaction scheme includes one slow (X) and one fast (Y) variables, with the fast variable experiencing sudden jumps across two reaction interfaces. The solution of the problem yields both static and traveling waves on the ring. The oscillations are compared with those obtained in the Belousov-Zhabotinskii (BZ) reaction, and thus suggest novel experiments where the BZ reagent is placed in a toroidal container with a very thin cross-section (to simulate the ring). R. Sultan. (Supported by URB.)
 
 

Modeling of chaotic dynamics in a Co(OH)₂ Liesegang experiment

A pattern of Co(OH)₂ bands from CoCl₂ and NH₄OH propagates in space and displays chaotic oscillations in the number of precipitate bands. A model incorporating diffusion, nucleation, kinetics of particle growth and precipitate redissolution due to complexation of the metal ion with ammonia is developed to account for the front propagation and the observed chaotic dynamics. R. Sultan. (Supported by URB.)
 
 
 
 

ARTICLES, BOOKS AND REPORTS

 

Attieh, M., Al-Kassem, N. and Sultan, R., Periodic and chaotic patterns in nonequilibrium PbI₂/PbF₂ systems. Journal of the Chemical Society, Faraday Transactions, 94, 2187-2194, 1998.

Graul*, T. and Schlenoff, J. B., Ion exchange in ultrathin layers. Journal of Physical Chemistry B, 103, 2718-2723, 1999.

Hung, C.*, Halaoui, L. I., Bard, A. J.*, Grudowski, P. A.*, Dupuis, R. D.*, Molstad, J.*, and Disalvo, F. J.*, Electroluminescence at GaN and GaxIn1-xN electrodes in aqueous electrolytes. Electrochemical Solid-State Letters, 1, 142-144, 1998.

Kolega*, R. , and Schlenoff, J. B., Self-assembled monolayers of an aryl thiol: formation, stability, and exchange of adsorbed 2-naphthalenethiol and bis(2-naphthyl) disulfide  on gold. Langmuir, 14, 5469-5478, 1998.

Kortz, U., Tézé, A. and Hervé, G., A cubane substituted polyoxoanion: structure and magnetic properties of Cs₂[H₂PW₉Ni₄O₃₄(OH)₃(H₂O)₆].5H₂O. Inorganic Chemistry, 38, 2038, 1999.

Kortz, U., Jeannin, Y. P., Tézé, A., Isber, S., and Hervé, G., A Novel dimeric ni-substituted beta-keggin silicotungstate: structure and magnetic properties of K12[{beta-SiNi2W10O36(OH)2(H2O)}2]*20H2O. Inorganic Chemistry, 38, 3670, 1999.

Laurent*, D. and Schlenoff, J. B., Multilayer assemblies of redox polyelectrolytes. Langmuir, 13, 1552-1557, 1997.

Mateeva*, N., Niculescu*, H., Schlenoff, J. B. and Testardi*, L., Thermoelectric behavior of conducting polymers: on the possibility of off-diagonal thermoelectricity. Materials Research Society Symposium Proceedings, 478, 243-248, 1997.

Mateeva*, N., Niculescu*, H., Schlenoff, J. B. and Testardi*, L. R. , Correlation of Seebeck coefficient and electric conductivity in polyaniline and polypyrrole. Journal of Applied Physics, 83, 3111-3117, 1998.

Nasreddine, V. and Sultan, R., Propagating fronts and chaotic dynamics in Co(OH)₂ Liesegang systems. Journal of Physical Chemistry A, 103, 2934-2940, 1999.

Salameh, A. S., Ghaddar T., and Isied S., Hydrogen bonding association of a ruthenium (II) bipyridine barbituric acid guest to complementary 2,6-di-aminopyridine amide hosts: guidelines for designing high binding hydrogen bonding cavities in both high and low polarity solvents. Journal of Physical Organic Chemistry, 12, 247-254, 1999.

Salameh, A. S., Nassif, N. and Tayim H., The influence of some platinum (II), palladium (II) and rhodium (III) coordination compounds on humoral immune response on white mice. The Arabian Journal for Science and Engineering, 23, 175-182, 1998.

Schlenoff, J. B. and Wang*, R., Adsorption of random and diblock hydrophilic/hydrophobic copolymers at the liquid-liquid interface. Polymer Materials Science and Engineering Proceedings, 77, 654-655, 1997.

Schlenoff, J. B., Laurent*, D., Ly*, H. and Stepp*, J. , Redox-active polyelectrolyte multilayers. Advanced Materials, 10, 347-349,1998.

Schlenoff, J. B., Radiochemical methods for polymer adsorption. In Colloid-Polymer Interactions, ed. Dubin, P. and Farinato, R., 225-253. New York: John Wiley and Sons, 1999.

Schlenoff, J. B., Laurent*, D., Ly*, H. and Stepp*, J. Redox-active polyelectrolyte multilayers. Chemical and Engineering Technology, 21, 757-759, 1998.

Schlenoff, J. B., Ly*, H. , and Li*, H., Charge and mass balance in polyelectrolyte multilayers. Journal of the American Chemical Society, 120, 7626-7634, 1998.

Stepp*, J. and Schlenoff, J. B. , Electrochromism and electrocatalysis in viologen polyelectrolyte multilayers. Journal of the Electrochemical Society, 144, L155-L157, 1997.

Sultan, R., The structural variety of chemical spike-electric field interactions. Chemical Physics Letters, 266, 145-152, 1997.

Wang*, R. and Schlenoff, J. B., Adsorption of a radiolabeled random hydrophilic/hydrophobic copolymer at the liquid/liquid interface: kinetics, isotherms and self-exchange. Macromolecules, 31, 494-500, 1998.

Wen*, L., Li*, M. and Schlenoff, J. B., Polyporphyrin thin films from the interfacial polymerization of mercaptoporphyrins. Journal of the American Chemical Society, 119, 7726-7733, 1997.

Zhang*, X., Tarkka*, R. M., Jenekhe*, S. A., and Schlenoff, J. B., Toward electrically pumped organic diode lasers: electroluminescence of proton transfer polymers. Materials Research Society Symposium Proceedings, 488, 545-550, 1998.
 
 
 
 

Garwatoski, M. J.*, Halaoui, L. I., and Coury, L. A., Jr.*, Measurements on nanocrystals immobilized in polymer films on electrode. 1997 Pittsburgh Conference and Exposition on Analytical Chemistry and Applied Spectroscopy, Atlanta , GA, USA, March 1997.

Halaoui, L. I., Wells, R. L.*, and Coury,L. A., Jr.*, Optical and electrical characterization of InAs quantum dots. Pittsburgh Conference and Exposition on Analytical Chemistry and Applied Spectroscopy, Atlanta, GA, USA, March 1997.

Nasreddine, V. and Sultan, R., Effect of an electric field on Co(OH)₂ Liesegang patterns. 13^th International Congress of Chemical and Process Engineering (CHISA), Prague, Czech Republic, August 1998.

Rahhal, D., Haddadin, M. J., and Gali-Muhatsib, H., In vitro effects of quinoxaline 1,4-dioxidin a mouse papilloma derived cell line. Abstract, 4^th Middle East Oncology Congress, Beirut, Lebanon, April 28-May 1, 1999.

Sultan, R. and Al-Kassem, N., Periodic trends in MX₂ precipitate patterning schemes involving two salts. 13th International Congress of Chemical and Process Engineering (CHISA), Prague, Czech Republic, August 1998.

Sultan, R. and Jaafar, S., Traveling chemical waves on a ring. Gordon Research Conference on "Oscillations and Dynamic Instabilities in Chemical Systems", Il-Ciocco, Barga, Italy, June 1999.