This thesis presents the synthesis, characterization and reactivity of a series of palladium complexes that contain redox-active verdazyl ligands. This work was motivated by the possibility of discovering new and interesting reactivity that may eventually lead to the development of new chemical reactions. A bidentate verdazyl radical ligand that contains an aryl phosphine was synthesized. Reaction of this ligand with (PhCN)2PdCl2 yielded a square planar (verdazyl)PdCl2 complex. Structural and spectroscopic data suggest that this compound consists of a ligand-centered radical coordinated to a Pd(II) center. The radical complex was chemically reduced by one-electron to generate a binuclear chloride-bridged [(verdazyl)PdCl]2 complex. In this reduced complex, both metals were still Pd(II) and the verdazyl ligand was determined to be in its singly reduced, monoanionic charge state. The original radical PdCl2 complex could be regenerated via one-electron oxidation of the reduced complex using PhICl2. The verdazyl ligands in the reduced complex could also be reversibly protonated to generate “leuco” verdazyl complex (verdazyl-H)PdCl2. Reaction of the radical (verdazyl)PdCl2 complex with water triggers a ligand-centered redox disproportionation reaction. A series of bis(verdazyl) palladium complexes were synthesized using a bidentate pyridine-substituted verdazyl ligand. Reaction of two equivalents of radical ligand with (CH3CN)4Pd2+ yielded a (verdazyl)2Pd(solvent)2+ complex (solvent = CH3CN or DMSO). In this complex, one verdazyl radical ligand chelates to palladium and the other binds as a monodentate ligand. Two-electron reduction of this complex generated a (verdazyl)2Pd complex in which two monoanionic verdazyl ligands are bound to a central Pd(II) ion. This reduced complex could also be made via reaction of 0.5 equivalents of Pd(0)2(dba)3 with two equivalents of radical ligand. In this reaction, the metal is oxidized by two electrons and each ligand is reduced by a single electron. Two-electron oxidation of the reduced complex in the presence of DMSO yielded the original bis(radical)complex, (verdazyl)2Pd(DMSO)2+. Chlorination of the reduced complex using one equivalent of PhICl2 (two-electron oxidation) resulted in dissociation of one verdazyl ligand to afford a 1:1 mixture of free verdazyl : (verdazyl)PdCl2, in which both of the verdazyls are neutral radicals. Reaction of the reduced complex with 0.5 equivalents of PhICl2 (one-electron oxidation) yielded a (verdazyl)2PdCl complex that contained a bidentate reduced verdazyl ligand and a monodentate radical ligand. All three of the oxidation reactions described above adhere to ligand-centered redox chemistry. Reaction of the reduced (verdazyl)2Pd complex with excess HCl resulted in protonation of both the anionic verdazyl ring and the pyridyl group to generate a leuco/pyridinium tetrachloropalladate salt, (verdazyl-H2)2(PdCl4). The protonated salt could be converted back to the original (verdazyl)2Pd complex by deprotonation with water. Palladium complexes of a tridentate NNN-chelating verdazyl ligand were prepared and their redox chemistry was explored. Reaction of the radical ligand with (CH3CN)4Pd2+ yielded radical complex (verdazyl)Pd(NCCH3)2+. The tridentate ligand was also prepared in its reduced, leuco form (verdazyl-H). Reaction of the leuco verdazyl with (CH3CN)2PdCl2 generated HCl and a (verdazyl)PdCl complex in which the ligand is in its monoanionic charge state. The reduced (verdazyl)PdCl complex was reacted with AgBF4 to afford (verdazyl)Pd(NCCH3)+ via chloride abstraction; the verdazyl remained in its reduced charge state following the reaction. Both reduced complexes (chloro and acetonitrile) were oxidized by a single electron to afford the corresponding radical complexes. These radical complexes could be reduced by a single electron to regenerate the original reduced complexes. Like the previous two projects, all of the redox chemistry was ligand-centered. The reactivity of these complexes with primary amines was also explored. Reaction of radical complex (verdazyl)Pd(NCCH3)2+ with n-butylamine resulted in one-electron reduction of the verdazyl ligand. We were unable to determine the mechanism of the reaction, but the reactivity that was observed demonstrates the potential for verdazyl-palladium complexes to be used in the design of new radical reactions. / Graduate / 2018-07-17

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A variety of mononuclear alkene complexes, [Ir{ArNC(NR2)NAr}(cod)], and dicarbonyl complexes, [Ir{ArNC(NR2)NAr}(CO)2] (where R = Me or Et; Ar = Ph, 4-MeC6H4, 4-MeOC6H4, 2,6-Me2C6H3 or 2,6-iPr2C6H3; and cod = 1,5-cyclooctadiene), were synthesized from the neutral N,N-dialkyl-N',N"-diarylguanidines via deprotonation and transmetalation. These complexes were fully characterized by spectroscopic techniques and single-crystal X-ray diffraction. The single-crystal structure determinations show the guanidinato(1—) ligands coordinate the low valent d8 iridium(I) center in an N,N'-chelating binding mode, and the C—N bond lengths indicate a high degree of π-electron delocalization over the CN3 core. The 13C NMR chemical shifts of the alkene carbon atoms in the IrI(cod) complexes and the average CO stretching frequencies for the IrI(CO)2 complexes suggest that the guanidinato ligands function as stronger donors than related monoanionic, bidentate nitrogen-donor ligands. Intermediates in the reactions of the [Ir{ArNC(NR2)NAr}(cod)] complexes with O2 were identified and characterized as (alkene)peroxoiridium(III) species, [Ir{ArNC(NR2)NAr}(cod)(O2)], using multi-dimensional NMR and IR spectroscopy. The (alkene)persulfidoiridium(III) intermediate [Ir{PhNC(NMe2)NPh}(cod)(S2)] was identified and characterized in the reaction of [Ir{PhNC(NMe2)NPh}(cod)] with S8. It was determined that these intermediates are able to transfer oxygen or sulfur to simple organic molecules such as PPh3. The self-decay of the (alkene)peroxoiridium(III) intermediates leads to C—O bond formation and alkene oxidation, and upon addition of excess cod release of 4-cycloocten-1-one was observed. In addition, a mononuclear alkene complex, [Ir{PhNC(Me)NPh}(cod)], and a dinuclear tetracarbonyl complex, [{Ir(CO)2}2{π-PhNC(Me)NPh-κN:κN'}2], with an amidinato ligand, were synthesized and characterized. In the reaction of the IrI(cod) complex with O2, the corresponding (alkene)peroxoiridium(III) intermediate [Ir{PhNC(Me)NPh}(cod)(O2)] was observed. The reactivity of this intermediate and its decay products is similar to that of [Ir{ArNC(NR2)NAr}(cod)(O2)], with the formation of 4-cycloocten-1-one being observed upon addition of cod. Mononuclear (alkene)rhodium(I) complexes, [Rh{PhNC(NMe2)NPh}(cod)] and [Rh{PhNC(Me)NPh}(cod)], and a dinuclear complex, [{Rh(nbd)}2{π-PhNC(NMe2)NPh-κN:κN'}2], were synthesized and characterized (where nbd = norbornadiene or bicyclo[2.2.1]hepta-2,5-diene). Investigation of the reactivity of these complexes with O2 show they react very slowly or not at all.

This research explored the amination reaction of 1,3-bis-chloromethyl-tetramethyl-disiloxane in two different pathways. First, will discuss the synthesis of a new bipodal amino siloxane ligand which was achieved by the reaction of bis-chloromethyl-tetramethyl-disiloxane with t-BuNH3 in the presence of n-BuLi. The new ligand, of t-Butyl-[3-(t-butylamino-methyl)-1,1,3,3-tetramethyl disiloxanylmethyl]-amine (L1), is a model ligand designed to simulate the SOMC model of silica support and bipodal amido ligand that has been presented by the Basset group. Hence, developing this type of siloxane ligand and their complexes will be valuable in the synthesis of new homogenous catalyst, studying the reactivity and attempt to connect them with the SOMC examples. For this, the reaction of L1 with several Lewis acids and afforded several uncommon dimer and cluster complexes in the solid state. The second part of this research found that heating of bis-chloromethyl-tetramethyl-disiloxane with a 4-6 equivalent of amine, affording 4-N-Alkyl-tetramethyl- oxazadisilinane as six heterocycle ring by using a new simple and neat method. Using six different amine functional groups afforded six new oxazadisilinane compounds with different alkyls substituted. Each oxazadisilinane compound was utilized and reacted with four different acids, affording a series of twenty-one examples of new siloxane protic ionic liquids (Si-PILs). Also, the reaction of the cation with methyl iodide provided two examples of siloxane aprotic ionic liquids (Si-AILs). The new family of Si-ILs were well characterized by using NMR, mass, melting point, elemental analysis and thermal gravimetric analyses. Additionally, twelve crystals were suitable for X-ray diffraction as Si-PILs and one for Si-AILs. By studying their chemical and physical properties, a good library of the new Si-ILs has been built. Finally, one group of the new Si-PILs was used for butyl acetate esterification. The 5-X group of new Si-PILs salt was tested for esterification of butanol with acetic acid by thermal heat and under microwave irradiation. The salt 5-BF4- showed a good result in both systems with easy separation from the reaction mixture and recyclability discriminates the 5-BF4- as a good catalyst for the esterification reaction.

Recently, the occurrence of a mammalian endocannabinoid ligand N-arachidonoylethanolamide (anandamide, AEA, NAE20:4), was reported in early land plants. Unlike seed plants, bryophytes such as Physcomitrella patens possess unique fatty acid composition that includes long-chain fatty acids such as arachidonic acid (AA, 20:4) and eicosapentaenoic acid (EPA, 20:5). We performed targeted lipid profiling to discovere long-chain N-acylethanolamines (NAEs) and their corresponding N-acylphosphatidylethanolamine (NAPE) precursors in Physcomitrella and Selaginella. In protonemal tissues, N-arachidonyl-PE and N-20:5-PE contributed to about 49 % and 30 %, respectively. Matured gametophytes on the other hand showed a 12 % increase in N-20:4-PE and 20 % decline in N-20:5-PE, relative to NAPE content in protonemata. In all haploid developmental stages analyzed, NAE20:4 levels contributed to ~ 23 % of the total NAE while NAE 20:5 remained as a minor component (5 %). Interestingly, in Selaginella moellendorffi, an early vascular plant, N-18:2-PE species was most abundant and 20C-NAEs were present in trace amounts. To understand biological implications of anadamide, we examined the effects of exogenously applied AEA and its corresponding fatty acid (AA) on moss protonemata growth. Both AEA and AA inhibit growth of gametophytes and protonemata in a dose dependent manner, while AEA exclusively affected actin-mediated tip growth. Additionally, we identified moss ortholog for NAPE-hydrolyzing phospholipase D (NAPE-PLD) enzyme that likely generates AEA and a fatty acid amide hydrolase (FAAH) that catabolizes AEA. Both putative PpNAPEPLD and PpFAAH are expressed in E. coli for further characterization. Our data demonstrates the occurrence of evolutionarily conserved NAE metabolic pathway in the moss, with unique composition. Functional and evolutionary implications of this mammalian endocannabinoid in early land plants, however, remains elusive.

Ligand design in general enables the formation of coordination compounds with multiple functionalities within a single framework. To date, two of the most widely studied ligands are 2,2′:6′,2′′-terpyridine (terpy) and acetylacetone (acac), whose tridentate and bidentate coordination pockets, respectively, enables the formation of metallic complexes with various geometries. The Brusso group had been incorporating imidoyl amidine (ImAm) ligands to build different materials such as organic radicals and fluorescent materials. In particular, the ligands N-2-pyridylimidoyl-2-pyridylamidine (Py2ImAm) and N-2-pyrimidylimidoyl-2-pyrimidylamidine (Pm2ImAm) were recently synthesized and have great appeal to build metallic complexes, as they poses two coordination sites similar to those in terpy and acac. The work presented herein represents the first studies involving the coordination of Py2ImAm and Pm2ImAm as discrete ligands. Our results demonstrate the versatility of these ligand frameworks, in which discrete mononuclear complexes, homometallic and heterometallic polynuclear complexes may be realized. Chapter one serves as a brief introduction to transition metal chemistry and has a comprehensive review of the coordination chemistry of the ImAm ligand framework. In chapter two, the selective coordination of first row transition metals into the bidentate or tridentate sites of Py2ImAm is explored. The formation of these mononuclear complexes is acid-base driven, where a weak acid induces coordination to the tridentate site and a weak base leads to coordination in the bidentate site. Coordination to both sides of Pm2ImAm with manganese or iron is explored in chapter three. The results show the formation of unusual tetranuclear complexes with the metal ions in both low spin and high spin configurations. Chapter four covers the coordination to cobalt, and the formation of polynuclear complexes with different geometries using Pm2ImAm. The magnetochemistry of these cobalt polynuclear complexes is also presented and reveal a single molecule magnet behaviour for one of the complexes. Finally, in chapter five, a one-pot synthesis of copper-manganese heterometallic complexes is presented. Overall, these imidoyl amidine ligands are able to build complexes with different geometries, different electronic configurations (i.e. low or high spin), and different metal ions. These results show a great versatility of ImAm ligands and suggest the future use of these ligands by other research groups.

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京都大学 / 0048 / 新制・課程博士 / 博士(工学) / 甲第18521号 / 工博第3913号 / 新制||工||1601(附属図書館) / 31407 / 京都大学大学院工学研究科物質エネルギー化学専攻 / (主査)教授 辻 康之, 教授 大江 浩一, 教授 近藤 輝幸 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DGAM

Multicomponent ligand interactions are involved in essentially all nanoparticle (NP) applications. However, the ligand conformation and ligand binding mechanisms on NPs are highly controversial. The research reported here is focused on deepening the fundamental understanding of multicomponent ligand interactions with gold and silver nanoparticles (AuNPs and AgNPs) in water. We demonstrated that AuNPs passivated by saturated layer of poly(ethylene glycol) (PEG-SH) have large fractions of AuNP surface area available for ligand adsorption and exchange. The fraction of AuNP surface area passivated by PEG-SH with molecular weights of 2000, 5000, and 30000 g/mol was calculated to be ~ 25%, ~20%, and ~9% using 2-mercaptobenzimidazole and adenine as model ligands. The effect of both reduced and oxidized protein cysteine residues on protein interactions with AgNPs was investigated. The model proteins included wild-type and mutated GB3 variants with 0, 1, or 2 reduced cysteine residues. Bovine serum albumin containing 34 oxidized (disulfide-linked) and 1 reduced cysteine residues was also included. Protein cysteine content that were found to have no detectable effect on kinetics of protein/AgNP binding. However, only proteins that contain reduced cysteine induced significant AgNP dissolution. We further demonstrated that organothiols can induce both AgNP disintegration and formation under ambient conditions by simply mixing organothiols with AgNPs or AgNO3, respectively. Surface plasmon- and fluorescence-active AgNPs formed by changing the concentration ratio between Ag+ and organothiol. Organothiols also induced AuNP formation by mixing HAuCl4 with organothiols, but no AuNP disintegration occured. Finally, we proposed that multicomponent ligand binding to AuNPs can be highly dependent on the sequence of ligand mixing with AuNPs. Quantitative studies revealed that competitive adenine and glutathione adsorption onto both as-synthesized and PEG-SH functionalized AuNPs is predominantly a kinetically controlled process. Besides providing new insights on multicomponent ligand interactions with colloidal AuNPs and AgNPs, this study opens a new avenue for fabrication of novel nanomaterials in biological/biomedical applications.