Self-assembled monolayers on gold and glass substrates are employed as templates to direct the crystal growth and polymorphism of active pharmaceutical ingredients. Orthogonal approaches are used to control polymorphism either through complementary hydrogen-bonding interactions or through repulsive interactions.

The reaction of hydroquinone and 1,12-dibromododecane affords 4-(12-bromo-dodecyloxy)phenol (4, 7% yield). The alkyl bromide (4) was converted to the corresponding thiol with thiourea to afford 4-(12-mercaptododecyloxy)phenol (1) in 52% yield. The reaction of t-butyllithium with 4-bromoanisole followed by reaction with 1-12-dibromododecane affords a mixture of 4-bromoanisole, 1,12-dibromododecane ,and 4-(12-bromododecyl)-anisole (6). Silica gel chromatography resulted in an inseperable mixture of 4-bromoanisole and (6). Reaction of the mixture with BBr3 afforded 4-(12-bromododecyl)phenol (7) in 34% yield. The alkyl bromide (7) was converted to the corresponding thiol with thiourea to afford 4-(12-mercaptododecyl)phenol (2) in 9% yield. Reduction of 16-mercaptohexadecanoic acid with BH3â hTHF afforded 16-mercaptohexadecanol (3) in 53% yield. All new compounds were characterized by ¹H NMR, ¹³C NMR, transmission IR, HRMS, and, where possible, elemental microanalysis. Self-assembled monolayers (SAMs) on gold were prepared using thiols 1, 2, and 3. SAMs were characterized using reflectance-absorbance infrared spectroscopy (RAIRS). Diagnostic vibrational modes were assigned by comparing RAIRS spectra to normal mode frequencies and intensities calculated using DFT methods at the 6-31G* level using commercial software. Water droplet goiniometry found contact angles of 52o, 53o, and 64o for SAMs prepared from 1, 2, and 3, respectively. SAMs of 1 and 2 were found to be hydrophilic. When SAMs prepared from 1, 2, and 3 were silylated with phenyldimethylchlorosilane, the resulting contact angles were 78o, 74o, and 75o respectively. A significant increase in contact angles for silylated SAMs of 1 and 2 indicated facile silanization of the surface hydroxides. RAIRS spectra were also obtained for the functionalized SAMs. Silylated SAMs prepared from 1, 2, and 3 are currently under investigation as models for silica-immobilized metallocene olefin polymerization catalysts. / Master of Science

The cyclic voltammogram of complex 6 shows one successive reversible one-electron redox wave corresponding to the oxidation of the Ruthenium moiety and peak-to-peak separations are smaller than 59 mV(ideal value of one electron transfer with diffusing controlling). In addition, the peak currents are linear to scan rate, i.e., i £\ V. This observation is corresponding to the electrochemical property of SAM, and we would like to suggest that the electron transfer process in the electrochemical measurements is direct controlling. Furthermore, we synthesized a nano-material by using of redox stable Ru(II)-Terpyridyloctanethiol attached to gold cluster (complex 7). The clusters are stable in air, soluble in nonpolar organic solvents and the characters could be examining by traditional chemical instruments such as NMR, UV/Vis, TEM. Finally, complex 7 seif-assembled on gold electrode (complex 8). This observation is corresponding to the electrochemical property of SAM, and we would like to suggest that the electron transfer process in the electrochemical measurements is direct controlling. we would like to suggest that the complex 5 has bi-functionalized property.

Self-assembled monolayers (SAMs) were investigated with regard to their application as templates to control processes down to the nanometre length scale. With applications of SAM for electrochemical nanotechnology in mind, the range of aspects studied comprises patterning on different length scales, behaviour of SAMs under the conditions of electrochemical metal deposition, and the influence of the head and tail groups on formation and structure of SAMs. On a micrometre scale, laser scanning lithography (LSL) was used to pattern SAM covered Au surfaces. With this technique, localized regions of a SAM are desorbed by scanning the focal spot of a laser beam. Thermal desorption occurs as a result of the high substrate temperature produced by the laser pulses. Patterns with line width as small as 0.9 µm were produced by LSL. It is demonstrated that SAM can not only be patterned by laser radiation but can also be rendered more passive as revealed by electrochemical metal deposition. Such blocking effect is explained by annealing of defects upon irradiation at the appropriate laser energy. This effect can block deposition of bulk copper particles, but does not prevent the underpotential deposition. Based on this passivation effect, large passivation areas can be created, which can be used as substrate for further nano/micro fabrication. The combination of SAM patterning and electrochemical metal deposition was also demonstrated to be an effective way to prepare superhydrophobic surfaces, exhibiting a contact angle of 165° (water droplet). Aiming for the generation of smaller structures, scanning tunneling microscopy (STM) is used as a tool to pattern SAMs. Several phenomena observed in STM based manipulation of SAMs are addressed. The first one is sweeping effect. Deposited metal particles on top of SAM and SAMs are swept by STM tip by choosing appropriate I/V parameters. The closer the tip (higher current, lower bias), the more effective it is. Molecularly resolved images confirm that after sweeping, the scanned area is still covered by SAM molecules. This is explained by diffusion. The sweeping process can be repeated, thus, resulting in a layer by layer etching. The second effect is field-induced desorption. Applying a positive voltage (2.5-5V), a SAM is damaged beneath the area of the tip. The damage depends not only on the bias applied, but also on the current setpoint right before applying the bias. The third effect is nanografting. Nanografting was observed that a SAM having a stronger assembling ability can replace the weaker one (matrix layer) in hexadecane solution by STM scanning under normal I/V parameters combination that are usually used for imaging. It is found that longer chain can replace the shorter chain thiol, alkanethiol can replace biphenyl thiol. This method can be applied to pattern SAM. Defects (punched holes) were created purposely on the SAMs covered Au surface and in situ STM was used to investigate the process of Under-Potential Deposition (UPD) and bulk metal deposition. Bulk metal deposition on punched holes depends on the size. Small scale patterning by punching is sufficient for applications based on UPD but not for bulk metal deposition. Several SAMs assembled on Au(111) surface (1-mercaptoundecanoic acid (MUA), Dodecyl Thiocyanate (C12SCN) and bis(pyrazol-1-yl)pyridine-substituted thiol (bpp-SH) and thiocyanate (bpp-SCN)) were investigated with the aim to expand the type of SAMs that can be used as template for further application, such as metal coordination. High quality thiolate monolayers formed by cleavage of the S-CN bond can be obtained on Au(111). Thus, organothiocyanates appear to be a promising alternative to thiols. Well-ordered MUA monolayers are formed in a few hours at the temperature range of 323-363 K by Physical Vapour Deposition (PVD). Self-assembled monolayers of bpp-SH and bpp-SCN on Au(111)/mica were studied with STM. Preparation conditions such as temperature, solvent, and contamination affect the formation of SAMs on Au(111) much more than other common thiols such as alkanethiols and biphenythiols.

The field of organic-based opto-electronic devices such as organic light- emitting diodes (OLEDs) or field-effect transistors (OFETs) has grown in interest over the past two decades. Optimizing the performance of these applications requires a better understanding of the processes taking place inside the devices and especially at their interfaces. We focused in this Ph.D. work on the electronic structure of metal/organic interfaces where the charge injection mechanism occurs. The latter process can be modulated and fine tuned by the control of the work function of the metallic electrodes. Chemisorption of self-assembled monolayers (SAMs), i.e., a two-dimensional layer of polar molecules deposited onto metal surfaces proves to be an efficient way to tune the work function of electrodes in OLED and OFET devices. However, the role played by the dipole moment of the adsorbed molecules as well as the description of the electronic effects taking place at the metal/SAM interfaces are not yet well understood. Our Ph.D. work aims at rationalizing at a theoretical level (via quantum- chemical calculations) the electronic processes occurring at metal/organic interfaces. For this goal, we focused our investigations on a well-characterized system : a methanethiolated SAM on gold-(111) surface. The adsorption energy and the influence of the anchoring site on the work function shift were evaluated beforehand in order to validate our methodology. The decomposition of the interfacial dipole moment into its interfacial and molecular components was assessed in a second stage for this system following two different procedures which differ by the treatment of the molecular backbone. The incorporation of a third component, generally not treated in an explicit way, was taken into consideration to unify the description of the interface dipole. The influence of the packing density was also described. In a next step, we have extended this study by changing the SAM chemical structure and by investigating the influence of a modification of the anchoring atom, a fluorination of the methyl group and a change in the nature of the metal surface (Ag, Cu, Pt). In order to probe the influence of intermolecular interactions, we have finally considered longer alkanethiol chains having various terminal chemical functions and analyzed the influence of the structural geometry on the change in the electrostatic potential.

Self-assembled monolayers (SAMs) of 4-aminothiophenol (4-ATP) has been successfully deposited onto nanometer-sized gold (Au) electrodes. The cyclic voltammograms obtained on a 4-ATP SAMs modified electrode show peaks and the peak height is proportional to the scan rate, which is similar to that on an electroactive SAMs modified macro electrode. The electrochemical behavior and mechanism of outer-sphere electron transfer reaction on the 4-ATP SAMs modified nanometer-sized electrode has also been studied. The 4-ATP SAMs modified electrode is further modified with platinum (Pt) nanoparticles. Electrochemical behaviors show that there is electrical communication between Pt nanoparticles and Au metal on the Pt nanoparticles/4-ATP SAMs/Au electrode. However, scanning electron microscopic image shows that the Pt nanoparticles are not evenly covered the electrode.

This work has centered on the interface dipoles arising at heterojunctions between metals, semiconductor nanoparticles, self-assembled monolayers, and organic semiconductor materials. Alkanethiol self-assembled monolayers, CdSe nanocrystals, and the organic semiconductors zinc phthalocyanine (ZnPc) and Buckminster fullerene (C60) were the basis of these investigations. UV photoemission spectroscopy has proven to be an invaluable tool to observe the vacuum level shifts for these analyses while using XPS to corroborate surface structure. With a full evaluation of these surfaces, the shifts in the vacuum level, valence ionizations, and core ionizations, the impact of these interfaces, as well as their influence on the subsequent deposition of organic semiconductor layers is established.Alkanethiols possessing varying dipole moments were examined on gold and silver substrates. The viability of these alkanethiols was demonstrated to predictively adjust the work function of these metals as a function of their intrinsic dipole moments projected to surface normal, and established differences between Ag--S and Au--S bonds. The capability of the SAMs to modify the work function of gold provided an opportunity for mixed monolayers of the alkanethiols to produce a precise range of work functions by minimal adjustments of solution concentration, which were examined with a simple point dipole model.Photoemission spectroscopy offers a thorough analysis of CdSe nanoparticle films. Despite a plethora of research on these nanocrystals, there still is controversy on the magnitude of the shift in the valence band with diameter. In our research we found the majority of the valence band shift could be attributed to the interface dipole, ignored previously. Meanwhile, the valence band tethered films was obscured by the sulfur of the thiol tether.Finally, organic semiconductor layers deposited on SAMs on gold exhibited various interface dipole effects at these heterojunctions. Charge transfer states of ZnPc did not favor energy level alignment on the SAM/Au substrates used; C60 demonstrated vacuum level shifts on C15 and C12ph alkanethiol monolayers consistent with the interface charge transfer (ICT) model. These results provide credibility to models recently demonstrated in the literature for other passivated metal surfaces, and include the viability of SAMs in these discussions.

The design, effectiveness and versatility of the self-assembled monolayer-immobilized aza-bis(oxazoline) catalysts was explored here. The first part of this dissertation focuses on the immobilization of aza-bis(oxazoline) ligand with three different C2 groups onto self-assembled monolayer support material. In the homogeneous phase, the more steric bulk present at the C2 position of the catalytic system, the greater the selectivity. In the heterogeneous systems, those with the least amount of steric bulk had the greatest increase in selectivity compared to their respective homogeneous phase. The supports not only allowed for selectivity enhancements not observed in the homogeneous phase, but also demonstrated the effectiveness of this support material in the cyclopropanation reaction. <br>Self-assembled monolayer supports allowed for modification of the surface steric environment around the catalytic site. This was accomplished by varying the length of the background alkenethiol chains so that three steric environments were created. The three steric environments were the catalyst above the monolayer surface, level with the monolayer surface, and below the monolayer surface. Modification of the steric environment around the catalyst, in turn allows for control of the selectivity of the heterogeneous catalytic system. <br>Modification of the surface electronic environment around the catalytic site is accomplished by modification of alkanethiol tail groups. The five background tail groups investigated were hydroxyl, bromide, carboxylic acid, methyl ester, and nitrile. Modification of the background tail groups allows for control of the enantioselectivity in the cyclopropanation reaction. <br>Self-assembled monolayer supports also allow for the generation of effective reusable heterogeneous catalytic systems. One of the main positive aspects of heterogeneous catalysis is the ability to recycle the catalytic system multiple times without major reduction in selectivity. The duration of these heterogeneous aza-bis(oxazoline) systems is dependent on the stability of the gold substrate layer and the reaction solvent. <br>The last section of this dissertation focuses on the versatility of the aza-bis(oxazoline) copper complex immobilized onto self-assembled monolayers. The homogeneous and heterogeneous catalysts were investigated in the carbonyl-ene reaction of ethyl glyoxylate and á-methylstyrene. The three heterogeneous catalytic systems were the carboxylic acid surface, hydroxyl surface, and the catalyst above the methyl monolayer surface. / Bayer School of Natural and Environmental Sciences / Chemistry and Biochemistry / PhD / Dissertation

The ability to produce monomolecular coatings with well-defined structural and functional properties is of key importance in biosensing, drug delivery, and many recently developed applications of nanotechnology. Organic chemistry has proven to be a powerful tool to achieve this in many research areas. Herein, we present the synthesis of three oligo(lactosides) glycosylated in a (1 → 3) manner, and which are further functionalized with amide-linked short alkanethiol spacers. The oligosaccharides (di-, tetra-, and hexasaccharide) originate from the inexpensive and readily available lactose disaccharide. These thiolated derivatives were immobilized onto gold surfaces, and the thus formed self-assembled monolayers (SAMs) on planar gold were characterized by wettability, ellipsometry and infrared reflection–absorption spectroscopy. Further, the ability of these SAMs to stabilize gold nanoparticles in saline solutions was also demonstrated, indicating that the oligosaccharides may be used as stabilizing agents in gold nanoparticle-based assays.

Switchable surfaces, also called smart surfaces or controllable surfaces, respond to changes in their local environment resulting in altered surface properties. There are various environmental perturbations that can cause changes to the surface properties but the focus of this thesis is on the affect of electrostatic potential. Significant evidence is provided from previous reports on electrochemical and infrared spectroscopic experiments suggesting that self-assembled monolayers (SAMs) of 4-mercaptobenzoic acid (4-MBA) undergo protonation-deprotonation by the application of an electric field. However, there are plenty of aspects of this electric field driven protonation-deprotonation mechanisms using carboxylic acid terminated SAMs that are not well understood. Most importantly, there is a lack of model independent measurements to validate this process. As such, experimental techniques utilizing infrared spectroscopy were employed to correlate electrochemical measurements and models.<p> This body of work demonstrates the importance of the intermolecular hydrogen bonding network on the measured voltammetric peak associated with the protonation-deprotonation of these SAMs. The voltammetric peak height diminishes with increasing exposure to an electrolyte solution. This behaviour is attributed to the replacement of the carboxylic acid protons with electrolyte cations and ultimately the disruption of the hydrogen bonded network.<p> We attempted to further our ex-situ infrared measurements by using an in-situ spectroelectrochemical technique. We had some initial successes, presented within, but more work is needed to complete this picture and is beyond the scope of this thesis. To summarize, the protonated state of SAMs of 4-MBA can be driven by the application of an electric field providing a potential platform to build a controllable smart surface.