The syntheses of three structurally isomeric pentacoordinate [special characters omitted]-donor macrobicyclic ligands are reported. The isomers differ only in the identity of the two nitrogen atoms of the cyclam ring across which the [special characters omitted] fragment ("sulphur bridge") has been linked. The first isomer, 15-Thia-1,5,8,12- tetraazabicyclo[10.5.2]nonadecane (L1), consists of a 9-membered [special characters omitted]-donor ring fused to the 14-membered 1,5,8,11-tetraazacyclotetradecane (cyclam) ring. The ligand was synthesized by a copper(II) templated ring closure followed by borohydride reduction. A novel side product (4), a monoamide derivative of (L1), was also isolated and characterized. The second isomer, 17-Thia-1,5,8,12-tetraazabicyck)[6.6.5]nonadecane (L2), consists of linking the sulphur bridge across the diagonally opposed [1,8]-nitrogens. The ligand was synthesized by cyclizing cyclam (1,4,8,11-tetraazacyclotetradecane) with thiodiglycolic acid chloride under high dilution conditions. The third isomer, 14-Thia- 1,4,8, 11-tetraazabicyclo[9.5.3]nonadecane (L3), consists of linking the sulphur bridge across the adjacent [1,5]-nitrogens of the cyclam ring. The ligand was synthesized by cyclization of 1-thia-4,8-diazacyclododecane (20) with N,N’ –bis(α-chloro amido)diaminopropane (27) which afforded the diamide derivative, 14-Thia-1,4,8,11- tetraazabicyclo[9.5.3]nonadecane-3,9-dione (30), in high yield. Reduction of 30 with diborane gave the third structural isomer, (L3). A novel, convenient synthesis of 1-thia-4,8-diazacyclododecane-3,9-dione (23) from diaminopropane and thiodiglycolic acid chloride was developed. It was shown that high dilution conditions were necessary to obtain high product yields. The nature of the product obtained from reduction of 23 was shown to depend on the conditions used. In the presence of excess borane and methanol, the major product was a boron complex of the reduced ligand. Several changes to the conditions used avoided production of the boron complex and yielded the intended product (20) in sufficient quantity. The parent 1-Thia-4,7-diazacyclononane ([9][special characters omitted]) and 1,4,8,11- tetraazacyclotetradecane ([14][special characters omitted]) ligands exhibit first order coupling behaviour as a result of time averaging of molecular motions. However, the ambient temperature [special characters omitted] spectrum of the [9][special characters omitted] bicyclic free ligand (L1) exhibited second-order couplings and line broadening indicative of an exchange process. This result indicates that the rigidity of the macrobicyclic structure has hindered certain molecular motions. The variable-temperature [special characters omitted] spectra of (L1) were recorded in deuterated chloroform. It was found that the geminal coupling (> 15 Hz) of the [special characters omitted] (propylene fragment) methylene group approached 0 Hz as the temperature was raised beyond 40°C. It is believed that nitrogen inversion processes are responsible for the collapse of these signals. In order to determine if the rigidity of the [special characters omitted] macrobicyclic free ligand structure would have a significant effect on the chemistry of the metal complexes, the copper(II) and nickel(II) complexes of each of the [special characters omitted] isomers (L1-L3) were prepared and characterized. Any differences observed between these isomers can be attributed to ring strain effects. Electronic spectroscopy of the copper(II) complexes determined the absorption maxima of the [special characters omitted] isomers to be 532, 532.5 and 603 nm respectively. ESR spectroscopy showed each complex to have similar [special characters omitted] values (2.092, 2.090 and 2.089), and the frozen solution (77 K) spectra were indicative of tetragonally elongated axial symmetry [special characters omitted] with the unpaired electron predominantly in the [special characters omitted] orbital. The synthesis and characterization of the corresponding nickel(II) complexes of each ligand are reported. The electronic spectra of each of the [special characters omitted](acetate)2 and [special characters omitted] isomers were consistent with that expected for [special characters omitted] coordination of nickel(II). Electrochemical studies of the nickel(II)/(III) oxidations showed that there was a 170 mV difference between the [special characters omitted] values of the [special characters omitted] and [special characters omitted] complexes. These results implied that the (L1) and (L3) bicycle isomers are similar in coordination properties such that significant differences were not observed. The coordination properties of the third [special characters omitted] bicycle (L2) differ markedly from those of the other two isomers. That the unique diagonally bridged structure resulted in significantly different absorption maxima and redox potentials, indicates that the coordination of the [special characters omitted] donor set has been perturbed (relative to the (L1) and (L3) bicyclic ligands) by the strain energies unique to that isomer. The molecular structures of the [special characters omitted] and [special characters omitted] complexes were determined by X-ray crystallographic techniques. The cobalt(Ill) complex was shown to contain "true" octahedral coordination. The palladium(ll) complex was shown to consist of square planar [special characters omitted] coordination with the axial sulphur donor positioned 2.87Å from the palladium atom with the M-S vector deviating 16° from the perpendicular to the [special characters omitted] plane. / Graduate

No description available.

Treatment of [1,4-(PhS)2C6H4] and [1,2-(PhS)2C6H4] with the appropriate amount of O-mesitylenesulfonylhydroxylamine (MSH) yields the corresponding protonated sulfimides, both of which may be deprotonated with 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) to give the hydrated free sulfimides [1,4-(PhS{NH2})2C6H4] and [1,2-(PhS{NH2})C6H4PhS]. It would seem that both products display the ability to give two distinct types of material, anhydrous and hydrated forms. The hydrated type [1,4-(PhS{NH2})2C6H4].2H2O has been found by crystallography to form an extended array system; whereas the crystal structure of the dehydrate exhibits extra structural "rigidity" brought about by having two hydrogen-bonded sulfimide units per molecule. The ligand [1,2-(PhS{NH2})C6H4PhS] also exhibits two distinct types of formation, one a dehydrate (exhibited as an oil) and the other a hydrated type (present as a crystalline solid).

Various axially substituted Silicon octaphenoxyphthalocyanines were synthesised as potential photosensitisers in the photodynamic therapy of cancer. Conventional reflux reactions were used for synthesis as well as new microwave irradiation reactions, wherein the reaction times were decreased tenfold with a marginal increase in reaction yield and product purity. An interesting series of oligomeric (dimer to a nonamer) silicon octaphenoxyphthalocyanines were also successfully synthesised in a reaction similar to polymerisation reactions. These compounds were found to undergo an axial ligand transformation upon irradiation with red light (> 600 nm) in dimethylsulphoxide solution. All the ligands were transformed into the dihydroxy silicon octaphenoxyphthalocyanine with varying degrees of phototransformation quantum yields ranging in order from 10⁻³ to 10⁻⁵ depending on the axial ligand involved. During and after axial ligand transformations a photodegredation of the dihydroxy silicon octaphenoxy phthalocyanine was observed upon continued irradiation. The oligomers were found to undergo the same axial ligand transformation process with a phototransformation quantum yield of 10⁻⁵ The singlet oxygen quantum yields of the unaggregated monomeric silicon octaphenoxy phthalocyanines were all found to be approximately 0.2 with the exception of a compound with two (trihexyl)siloxy axial substituents that had a singlet oxygen quantum yield of approximately 0.4 in dimethylsulphoxide solutions. The oligomers showed a surprising trend of an increase in singlet oxygen quantum yield with an increase in phthalocyanine ring number up to the pentamer and then a dramatic decrease to the nonamer. The triplet quantum yield and triplet lifetime were determined by laser flash photolysis for selected compounds and no correlation was observed with any of these properties and the singlet oxygen quantum yields. These selected compounds all fluoresce and a very good correlation was found between the fluorescence lifetimes determined experimentally by laser photolysis and the Strickler-Berg equation for the non-aggregated compounds. Electrochemical measurements also indicate the importance of the axial ligands upon the behaviour of the phthalocyanines as cyclic voltammetric behaviour was determined by the nature of the axial ligand.

A series of optically active tertiary phosphorus ligands, [special characters omitted] (R = bornyl, menthyl, or isopinocamphyl; n = 1, 2, or 3, 1 – 9), containing chiral alkoxy groups derived from natural terpene alcohols, menthol, borneol, and isopinocampheol, are synthesized and characterized by various spectroscopic techniques. The reactions of these ligands with iron and cobalt carbonyl complexes are carried out, giving monomeric mono- and di-substituted iron(0) and dimeric di-substituted cobalt carbonyl complexes [special characters omitted]. The characterization of these complexes by IR and NMR spectrometries is discussed. Results of preliminary studies on hydroformylation reaction under oxo conditions catalysed by several cobalt complexes are presented. Pyrazolyl bridged di-iridium(I) systems, [special characters omitted], are prepared as diastereomers with unequal thermodynamic distribution. The X-ray crystal structure of 41 shows cocrystallization of the two diastereomers in the same unit cell, which provides 1:1 kinetic distribution of the two isomers. Kinetic studies of the interconversion from the kinetic ratio to the thermodynamic ratio of the two diastereomers in 41 indicates the existence of a slow inversion process of the six-membered central metallocycle in 41. Oxidative addition of Mel to 41 generates a pair of diastereomeric adducts (43) in kinetic distribution, which is slowly converted to its thermodynamic distribution, implying a very slow reductive elimination of Mel. Oxidative additions of exo- and endo-norbornyl iodide to [special characters omitted] results in same product (44). Possible mechanisms for this process are discussed. Bisdiphenylphosphinoalkylsilane containing chiral menthoxy group [special characters omitted] is prepared and characterized. Its four-coordinate square planar platinum complex [special characters omitted] and five-coordinate iridium(I) complex [special characters omitted] are synthesized. Isomerizations of 49 and its CO adducts, [special characters omitted] (55 and 56), are studied in relation to their methyl analogues. / Graduate

Macrocyclic ligands containing nitrogen and sulphur donor atoms, as well as with pyridine or thiophene pendant arms were synthesized. The Co(II), Ni(II), Cu(II) and Pd(II) complexes have been characterized by crystallography, UV/Vis, NMR or ESR spectroscopy and the redox chemistry have been studied by cyclic voltammetry (CV). The Pd(II) complex of [14]aneNS3 (1,4,7-trithia-11-azacyclotetradecane), is square-planar whereas the structures of Pd(II) macrocyclic complexes with pyridine or thiophene pendent arms may be described as pseudo five-coordinate. There is considerable interaction between the apical sulphur donor atom and the palladium metal centre. In solution, the Pd(II) complex of py[14]aneNS3 (N-(2’-pyridylmethyl)- 1,4,7-trithia-11-azacyclotetradecane) exhibits fluxional behavior. There is an exchange process involving the metal-coordinated and -uncoordinated thioether atoms. By analyzing the NMR spectra obtained at different temperatures, the mechanism for the fluxional process is proposed. The cyclic voltammograms of the Pd(II) macrocyclic complexes showed irreversible reduction to Pd(I) and no oxidation to Pd(III) could be detected in the potential range studied. In the case of the Pd(II) complex with thiophene pendent arms, a quasi-reversible reduction to Pd(I) was observed. This unique behavior is rationalized as due to the proximity of a thiophene moiety in the apical position which inhibits dimerization to the Pd(I) generated, due to steric reasons. The Ni(II) complex of py[14]aneS3 is peudo-octahedral whereas the Co(Il) complex exists as two linkage isomers. In the nitrate salt, [special characters omitted], the cobalt centre is octahedral, being coordinated to only the nitrogen donors from the ligand and the remaining coordination sites are occupied by acetonitrile and oxygen atoms from two nitrate groups. In the perchlorate salt, [special characters omitted], solution studies (ESR and CV) suggest that the cobalt(II) ion is being coordinated by the nitrogen and sulphur donor atoms from the ligand. The Cu(II) complexes of these mixed donor ligands have also been studied and their spectroscopic (UV/Vis and ESR) characteristics and Cu(II)/Cu(I) reduction potential were compared to the type I Blue copper protein. / Graduate

A series of pendant arm tris-catecholate macrocyclic ligands were synthesized. The first, based on 1,4,7- triaminopropyl-1, 4, 7-triazacyclononane, was prepared via condensation with 2,3-dimethoxybenzoyl chloride. The deprotection of the catechol moieties was achieved with boron tribromide in 80% yields. The ferric complexes were characterized by electronic absorption spectroscopy. The second series of ligands described are based on the pendant arm macrocyclic ligand, 1, 4, 7-triaminoethyl-1, 4, 7- triazacyclononane. New routes to the preparation of this ligand were investigated; the best approach used chloroacetyl chloride as the reagent in functionalizing the nitrogen atoms of the triazacyclononane ring. The ligands, 1, 4, 7-tris-((2, 3- dihydroxyphenethyl) aminoethyl)-1, 4, 7-triazacyclononane (34) and 1, 4, 7-tris-((2, 3-dihydroxybenzyl)aminoethyl)-1, 4, 7- triazacyclononane (36) were prepared through a series of acid chloride condensation reactions, followed by reduction of the amides with diborane. The mononuclear ferric complexes of compounds 34 and 36 Were prepared and characterized by uv-visible spectroscopy. Mononuclear nickel, cobalt, and copper complexes of these ligands were also characterized by uv-visible spectroscopy. The binuclear complexes, Na[NiFe(34)] and Na[NiFe(36)], were prepared and characterized by electronic absorption spectroscopy. Tris-((2, 3-dihydroxybenzylamino)ethyl) amine, tris-((2, 3- dihydroxybenzoyl)aminoethyl)amine, and tris-((2 ,3-dihydroxyphenethyl)aminoethyl)amine were prepared by Schiff base condensation reactions, or acid chloride condensation of tris-(2-aminoethyl)amine and the appropriate catecholate moiety. The ferric complexes of these ligands were prepared and characterized by uv-visible spectroscopy. The A1(III) tris-((2,3-dihydroxybenzyl)aminoethyl)amine complex was examined by nmr spectroscopy. The Ni(II), Cu(Il) and Co(III) complexes were investigated by electronic absorption spectroscopy. The rates of base hydrolysis of [Co(tacn) (en)Cl]2+ (tacn=1, 4, 7-triazacyclononane), [Co(tacn) (amp)Cl]2+ (amp=2- aminomethylpyridine), [Co(tacn) (tn)Cl]2+, ufac-I- [Co(dien) (amp)Cl]2+ (dien=l,4,7-triazaheptane), ufac-Il- [Co (dien) (amp)]2+ and [Co (bicycloN5) C1]2+ (bicycloN5=1, 5, 8, 12, 15-pentaazabicyclo [10.5.2] nonadecane), were measured using stopped flow techniques. The base hydrolysis rates (kCH, M-1s-1; [ionic strength (M)]) are 9.66 [0.1], 154 [0.1], 40.6 [0.1], 334 [0.1], 762 [0.1], and 3X103 [1.0], respectively. The rate of [NCS-] anation of [Co (bicycloN5) (OH2)]3+, and the rates of [Br-] and [NCS-] anation of [Co (tacn) (en) (OH2)]3+ were measured as a function of pH. The pKa of the coordinated water molecules are 3.8 ([Co (bicycloN5) (OH2)]3+) and 6.5 ((Co(tacn) (en) (OH2)]3+) . The anation rates increase as the pH increases, indicating a base catalysed anation reaction through the deprotonation of the coordinated amine. In the case of the [Co(tacn) (en) (OH2)]3+ complex, the rate increases as the pH increases until the pH ~ 7, then there is no reaction after that point, suggesting some sort of blockage at the five-coordinate intermediate. / Graduate

Irradiation of [special characters omitted] at 313 nm in basic solution at 10°C in the presence of free SCN yields the products [special characters omitted], and [special characters omitted]. Analysis of product distribution was done by HPLC using a [special characters omitted] column and ion pairing reagents with methanol and water as the eluent. The aquation/anation product ratio is independent of X, but depends linearly on the concentration of SCN. A specific ion effect is observed, the aquation/anation ratio showing a correlation with the radius of the cation. The ratio of sulfur to nitrogen thiocyanato product is 10±2, independent of X, concentration of SCN, and cation, but is different that measured in the thermal anation of [special characters omitted] which gives a S/N ratio of 4. A limiting dissociative mechanism is proposed for the photosubstitution, involving a five coordinate intermediate of sufficient kinetic stability to discriminate among entering groups. The constant S/N ratio for the photosubstitution leads to the conclusion that the intermediate formed in the photoreaction is different from that formed in the thermal reaction. Direct anation has been reported previously for aquopentacyanocobaltate, but not for hexacyanocobaltate. Quenching of the emission lifetime of [special characters omitted] in the presence of chloride salts shows the same order of cation assistance with cation radius as observed for the aquation/anation ratio. / Graduate

M.Sc. / The main objective of the research described in this dissertation was to prepare a range of triaryl phosphine ligands having systematically changing stereo-electronic properties using Grignard reagents and P-Cl derivatives. These ligands were utilised in the Rh-catalysed hydroformylation reaction in order to determine the effects of stereo-electronic properties of these ligands on the outcome of the reaction. Initially, a first series of tri-aryl phosphine ligands having methyl or ethyl groups substituted on the ortho or para position of the phenyl rings was successfully synthesised. The stereoelectronic properties of these ligands were probed by determining the P=Se coupling constants of the Se-phosphine derivatives and the CO vibrational frequencies of the Vaskatype complexes of these ligands. It was shown that the substitution of alkyl groups on the phenyl rings of the phosphine ligands resulted in the formation of more electron-rich ligands. In the Rh-catalysed hydroformylation reaction a systematic decrease in the yields of aldehydes were observed as the basicity of the phosphine ligand increased. Inspired by the outcome of the first series, a second series of tri-aryl phosphine ligands having both methyl and fluoro groups variously substituted (ortho, meta and para positions) on the phenyl rings was successfully synthesised. It was observed that the group substituted on the ortho position electronically dominated over the group substituted in the meta and para position of the phenyl rings. Substitution of fluorine atoms on the ortho position and methyl on the para position of the phenyl rings resulted in the formation of less electron-rich phosphine ligands, while the opposite substitution pattern (p-F-o-Me) resulted in the formation of more electron-rich ligands. The former caused an increase in the yields of aldehydes obtained in the Rh-catalysed hydroformylation reaction compared to triphenylphosphine. viii A third series of tri-aryl phosphine ligands having trifluoromethyl groups substituted on the ortho, meta or para positions of the phenyl rings was successfully synthesised. It was observed that substitution of the trifluoromethyl groups on the meta and para positions of the phenyl rings resulted in the formation of less electron-rich phosphine ligands, while substitution on the ortho position resulted in the formation of more electron-rich ligands. The hydroformylation reaction with these ligands followed the same trend as with the first and second series of tri-aryl phosphine ligands. A series of tri-aryl phosphine-borane adducts of the first series of phosphine ligands was also successfully synthesised using BH3·THF. These ligands were employed in the Rh-catalysed hydroformylation reaction with the aim to determine whether in situ deprotection of the phosphine-borane adducts with CO was possible. The hydroformylation results with these adducts provided yields of aldehydes similar to those of the free phosphines. This suggested that deprotection had occurred to release the free phosphine which complexed to the Rh catalyst. This indicated that phosphine-borane complexes can be directly applied to carbonylation reactions eliminating the use of common deprotection methods and provides an opening for more research in this regard.

No description available.