Дисертації з теми "Ligands scorpionates"

Tripodal borate ligands, including Tp and Tm, are some of the most widely used in organometallic chemistry and were originally prepared, as anions, from the reaction of the relevant heterocycle with an alkali metal borohydride. However, an alternate route, allowing access to zwitterionic, charge-neutral, scorpionates was recently developed within the Bailey group using tris(dimethylamino)borane as the boron source. This thesis describes the expansion of the borane synthetic route to create new, charge-neutral, zwitterionic, tris(methimazolyl)borate (ZTm) ligands containing B-N, B-O and B-C coordinate bonds. Unusual reactivity with isonitrile donors is also presented which has allowed access to boron substituted anionic Tm ligands from the charge-neutral starting material, (HNMe2)ZTm. Attempts to control the helical chirality of ZTm complexes, by using chiral imidazoline donors on the central boron are also described. The borane synthetic route has allowed access to the novel ligand ZThp, the first example of a tripod based on 2-hydroxypyridine ligand arms. As with Tm, this ligand exhibits helical chirality upon complexation and demonstrates how individual atom hybridisation within the ligand arms affects the helicity and thus the chirality of flexible scorpionate ligands. Coordination studies of both zwitterionic and boron-substituted anionic Tm ligands have shown a tendency for the formation of ‘sandwich’ complexes of the form L2M with some metal precursors, whilst the formation of the corresponding ‘half-sandwich’ complexes of these ligands with ruthenium and rhodium was found to be disfavoured.

Cette thèse porte sur la synthèse et les applications catalytiques des complexes de cobalt(III) contenant des ligands chélatants de type scorpionate. Des ligands tris(pyrazolyl)borate (Tp) ont été utilisés pour former des complexes de cobalt présentant une diversité de propriétés structurelles et électroniques. Une exploration systématique de ces complexes révèle leur potentiel dans les transformations catalytiques, notamment dans les réactions de couplage carbone-carbone. En outre, le phénomène de spin-crossover observé dans les complexes de cobalt permet des transitions dynamiques entre les états de spin élevé et de spin faible, influençant de manière significative les mécanismes réactionnels et l’efficacité catalytique. Cette propriété facilite l’activation des substrats et des intermédiaires, tout en abaissant les barrières énergétiques des étapes clés de la catalyse. Ces caractéristiques permettent des voies réactionnelles efficaces dans des conditions douces, mettant en avant le potentiel du cobalt en tant que catalyseur multifonctionnel et durable
This thesis focuses on the synthesis and catalytic applications of cobalt(III) complexes containing scorpionate chelating ligands. Tris(pyrazolyl)borate (Tp) ligands were utilized to form cobalt complexes with diverse structural and electronic properties. Systematic exploration of these complexes reveals their potential in catalytic transformations, particularly in carbon-carbon coupling reactions. The spin-crossover phenomenon observed in cobalt complexes allows for dynamic transitions between high-spin and low-spin states, significantly influencing reaction mechanisms and catalytic efficiency. This property facilitates the activation of substrates and intermediates, lowering energy barriers in key catalytic steps. Additionally, the oxidation of cobalt to higher oxidation states enhances its catalytic performance. These features enable efficient reaction pathways under mild conditions, highlighting cobalt's potential as a multifunctional and sustainable catalyst

The nature of ligands coordinated to the metal ion mostly determines the properties of the inorganic, organometallic or bioinorganic model compounds. The pyrazole is one of the most studied heterocyclic aromatic compounds in coordination chemistry as single ligand or incorporated in polidentate ligands, such as in poly(pyrazolyl)borates (‘scorpionates'), poly(pyrazolyl)alkanes, etc. The great versatility of the pyrazole allows the formation of several ligands with different functionalizations, which mainly influence the geometry and nuclearity of the diverse coordination complexes afforded by the reaction of the pyrazole-based chelating ligands and a metal ion. Another of the most studied heterocyclic aromatic compounds in coordination chemistry is an analogue of pyrazole with two non-adjacent nitrogen atoms, the imidazole, which represents the main structure of the most common and studied N-Heterocyclic carbenes (NHCs), in particular the imidazol‐2‐ylidenes. These general informations arouse curiosity in main features and reactivity, synthesis and coordination modes, potential and ensured applications of various N-donor ligands, such as poly(pyrazolyl)borates or scorpionates, their isoelectronic and isosteric neutral analogues poly(pyrazolyl)alkanes and N-heterocyclic carbenes, presented, thus, in detail, in Chapter 1. The focus on the electronic and steric properties, the coordinating behaviour and several applications of scorpionates metal complexes, the state-of-art on coordination chemistry and reactivity of the poly(pyrazolyl)alkanes derivatives, the advantages of NHCs over phosphines, including ease of handling, minimal toxicity and powerful electron-donating properties, as enhanced stability of their transition metal complexes, which lead to the synthesis of highly active derivatives in homogeneous catalysis, anticipate the research work of this thesis on the nitrogen pyrazole- and imidazole-based ligands and their organometallic compounds. Beginning from Chapter 2, which describes the aims of the research work, all the chapters are divided in four sub-chapters. In the first sub-chapter differently halogen substituted bis- and tris-(pyrazolyl)borate ligands (BpBr3, TpBr3 and TpiPr,4Br) are compared in terms of electron-donor character through their interactions with various ruthenium(II) arene dimers, as also through electrochemical studies. Interestingly, an unexpected dinuclear ionic compound accounted for by its low thermodynamic stability, confirmed by theoretical calculations at the DFT level, due to steric reasons. The second sub-chapter is centered on the synthesis, characterization and crystal structure of the complexes of the second-lowest steric hindrance scorpionate ligand, TpTn, towards CuI, CuII, ZnII and CdII acceptors. A remarkable coordinative aspect of this ligand is pointed out, as well as the thermal and air stability of the relative complexes, confirmed by thermogravimetric and differential thermal analysis (TGA-DTA). By contrast, the interaction between TpTn and PtI2 proceeded through ligand decomposition, affording a monomeric complex. In the third sub-chapter, the varying, different stoichiometries and the N,N-chelating coordination modes of the bis(pyrazolyl)methanes, in particular of the two indazolyl-based regio-isomeric ligands, L1, bis(1H-indazol-1-yl)methane, and L2, bis(2H-indazol-2-yl)methane, toward XI group metal centers are studied. The synthesis and full characterization of analogous adducts of both regio-isomers allow a systematic comparison of their structural and spectral features, depending on the regio-isomeric ligand and counter-ion used, and the reaction conditions employed. The synthesis and characterization of a new series of stable, cationic gold(I/III) NHC complexes, as well as their catalytic activity in five well-established organic gold-mediated transformations, performed at the University of Strasbourg, under guidance of Director of Research Pierre Braunstein and coworkers (Laboratoire de Chimie de Coordination, Institut de Chimie (UMR 7177 CNRS), Universita'© de Strasbourg, France) is described in the fourth sub-chapter. Interestingly, various attempts to synthesize gold(III) NHC bis- or tris-pyridine complexes, as also the comparative behaviour of NHCs respect to phosphine ligands, are presented. Going further on the thesis structure, all the general procedures and experimental data are reported in Chapter 3, while the discussion and elaboration of the results are described in Chapter 4. Concluding remarks and future perspectives are discussed in Chapter 5, whereas all the references and some notes are given in Chapter 6. In Annexes section, the Curriculum Vitae, the List of Pubblications and the Contributions to Congresses are presented.

Alkylation of the soft scorpionate anions, TmR, Tbz and tzTtz have been successfully carried out. The resulting cationic species of TmMe were fully characterised. However, the formation of the cationic species is not always favourable and the alkylated products of Tbz and tzTtz were found to be unstable. The structures and degradation pathways of the three species were interrogated using ab-initio DFT calculations. This suggested that the B-N bond can lengthen when the scorpionate is alkylated and that this leads to thio-imidazole elimination. This work was extended to the synthesis of cyclic ring system initially by linking two sulphurs in the anion using dihalo-alkane species. Ring formation can also be effected using mild oxidising agents and treatment of TmMe and TmPh with NO+ and I₂ leads to the synthesis of a series of unique polycyclic heterocycles. The importance of B-N bond elongation to complex stability is investigated further using the Tbz anion. As expected Tbz is unable to form complexes with the hard metals e.g. cobalt. Treatment with soft metals (mercury, antimony and bismuth) does produce complexes but these are not stable. These metal complexes rearrange to form a new class of polycyclic rings. Studies using NO+ are extended to its chemistry of soft scorpionate metal complexes. A study was conducted which sought to use ruthenium complexes as nitric oxide scavengers. This chemistry failed to materialise and NO+ acts as a mild oxidising agent rather than a π acceptor with these species. % Buried volume analysis is performed using a series of soft scorpionates (TmR R = Me, iPr, tBu, and Ph) to calculate the steric demand of the ligands at the central metal atom. The study reveals that there is a modest effect when the scorpionate is supporting a four coordinated metal (e.g. zinc). However, for six coordinated metals (e.g. manganese as its tricarbonyl) the scorpionate has minimal influence.

Cette thèse porte sur la synthèse et la caractérisation de complexes octaédrique de fer(II) et fer(III) coordinés par un ligand tridente de type scorpionate (symétrie fac) et par trois ligands cyanures. Leur utilisation en tant que metalloligand face à des ions métalliques partiellement bloqués est étudiée. Les ligands cyanures, de par leur caractère ambidente, permettent un accès facile aux espèces hétérobimétalliques. De plus, ces ligands sont connus pour transmettre efficacement l'interaction d'échange magnétique et donc pour favoriser la communication électronique intramoléculaire entre les ions métalliques qu'ils relient. La fonctionalisation des ligands scorpionates permet de contrôler les propriétés électroniques intrinsèques des complexes précurseurs de fer, et donc de moduler les propriétés des espèces polynucléaires obtenues à partir de ces dernières par auto-assemblage. Dans cette thèse, un intérêt particulier est porté aux systèmes {FeCo} en raison de leur capacité à présenter une bistabilité électronique (propriétés photomagnétiques ou de molécules/chaines aimants). Les systèmes cyanuré {FeCo} sont particulièrement adaptés pour l'observation de réarrangements électroniques thermo- et/ou photo-induit, comme en témoignent le nombre important de composés cyanurés photomagnétiques dans la littérature
The work presented in this PhD dissertation focuses on the synthesis and the characterisation of octahedral iron(II) and iron(III) complexes coordinated by a tridentate ligand of the scorpionate family (fac- geometry) and three cyanide ligands. Their use as metalloligands in respect to partially blocked metal ions is studied. Because of their ambidentate character, cyanide ligands open the door to facile synthesis of heterobimetallic species. Moreover, these ligands are known to be efficient magnetic exchange interaction transmitter, thus favouring intramolecular electronic communication between the metal ions they are bridging. The functionalisation of scorpionate ligands allows control over the intrinsic electronic properties of the iron precursor complexes, thus allows to tune the properties of the obtained polynuclear species from the latter by self-assembly. In this PhD dissertation, a particular interest was taken in {FeCo} systems because of their potential ability to exhibit electronic bistability (photomagnetic properties or SMM/SCM behaviour). Cyanide-bridged {FeCo} systems are particularly suitable for the observation of thermally or light-induced electron rearrangements, as testified by the wide range of photomagnetic cyanide-bridged compounds in the literature

Deux machines moléculaires technomimétiques, dont la forme et la fonction miment des objets macroscopiques, ont été développées au cours de cette thèse : un moteur moléculaire et un nanovéhicule. La première de ces machines est destinée à générer un mouvement de rotation azimutal. C'est une famille de complexes de ruthénium coordinés par un ligand de type scorpionate jouant le rôle de stator et par un ligand pentaphénylcyclopentadiényl jouant le rôle de rotor. Afin de favoriser un mouvement de rotation unidirectionnel du rotor, l'introduction de chiralité a été effectuée dans la structure de la molécule. De plus, un stator fonctionnalisé par un groupement azobenzène et son complexe de ruthénium modèle ont été synthétisés afin d'arrêter de manière contrôlée la rotation du rotor. La seconde machine est quant à elle destinée à générer un mouvement de rotation altitudinal. Pour cela, une nouvelle génération de roues a été élaborée à partir de fragments subphthalocyanine dont la forme de bol ne présente pas d'interactions trop importantes avec la surface. Dès lors, la synthèse d'un nanovéhicule a été envisagée autour d'un plateau polyaromatique
Two technomimetic molecular machines, which have the shape and the function of macroscopic objects, were developed during this thesis: a molecular motor and a nanovehicle. The first one was designed in order to control an azimutal rotational motion. This machine is based on a family of ruthenium complexes coordinated by a scorpionate ligand acting as a stator and a pentaphenylcyclopentadienyl ligand acting as a rotor. In order to favor a unidirectional rotation of the rotor, introduction of chirality was achieved in the design of the molecule. Besides, a stator functionalized with an azobenzene functional group and its ruthenium model complex were synthesized in order to lock the rotation of the rotor in a controlled manner. The second machine was designed to control an altitudinal rotational motion. To achieve this goal, a new generation of wheels was synthesised based on subphthalocyanine fragments which have a bowl shape structure avoiding too many interactions with the surface. The synthesis of a nanovehicle was considered around a polyaromatic core

I and my research group have focused our attention on the study of the coordinative ability of monoanionic heteroscorpionate ligands based on bis(pyrazol-1-yl)methanes containing acetate or sulfonate groups as the third coordinating moiety in particular toward rhenium. The similarity between technetium and rhenium chemistry, in fact, determined a widespread use of the latter as a technetium surrogate to perform macroscopic chemistry of potential radiopharmaceuticals. In this way, a ‘‘cold'' material (the natural isotopic mixture of 185Re and 187Re) can be advantageously manipulated instead of the radioactive nuclide 99gTc (t1/2 = 2.12 105 y, Ea'¢ = 292 keV). On the other hand, rhenium has two a'¢- emitters isotopes 186Re (a'¢-max = 1.07 max = 2.10 MeV; t1/2 = 17 h) which are of great interest to nuclear medicine due to their physical and nuclear properties finalized to a potential application in the radiopharmaceutical. For this reason, a renewed interest in rhenium coordination chemistry fluourished, finalized to a potential application in the radiopharmaceutical field of rhenium itself, which was no longer considered as a mere technetium substitute for chemical investigations at macroscopic level. In the past few years the so-called ‘‘metal fragment'' strategy for the synthesis of new technetium and rhenium radiopharmaceuticals revealed to be a promising approach. This methodology is based on the preparation of intermediate species comprising a stable building- block constituted by the metal and suitable ancillary ligands and labile modentate groups (e.g., water molecules or halide groups), which can be easily replaced by chelating bi- or tri-dentate ligands eventually conjugated to a specific biomolecule. According to this strategy, we have reported on a new class of compounds containing the stable metal fragment [Re(O)(NNO)]2+ (N,N,O = tripodal heteroscorpionate ligand). In fact, in order to stabilize the monooxo rhenium core, heteroscorpionate ligands were chosen due to their coordinative flexibility and proper (facial) stereochemical arrangement. In particular, monoanionic bis(pyrazol-1-yl)methane derivatives, containing acetate (Hbpza = bis(pyrazol-1-yl)acetate; Libdmpza = Lithium[Bis(3,5-dimethylpyrazol-1-yl)acetate]) or sulfonate groups (Libdmpzs = Lithium[Bis(3,5-dimethylpyrazol-1-yl)methanesulfonate]), by reaction with [NBu4][Re(O)Cl4], gave a series of intermediate compounds Re(O)(NNO)Cl(X), where the octahedral coordination sphere is filled with two modentate groups (X = Cl or OR) whose structure depends on the type of NNO ligand and solvent utilized. Besides, we have seen that the effectiveness of replacement of two modentate groups of intermediate species with a bidentate chelate (ethylene glycol, malonic acid and 1,3-propandiol) depends on the nature of the heteroscorpionate, and that the substitution takes place easily when N,N,O ligand bear methylated pyrazolyl rings

Dans le domaine des NanoSciences, la synthèse d'un moteur monomoléculaire rotatif reste, à ce jour, un défi à relever. Un moteur moléculaire rotatif est une molécule qui, de manière continue, transforme une énergie en travail via un mouvement de rotation unidirectionnel contrôlé. Nous avons décidé de synthétiser un moteur moléculaire à énergie électrique adapté à une étude en tant que molécule unique, déposée sur une surface entre les électrodes d'une nanojonction, par microscopie à sondes locales. Ce sera un complexe de ruthénium comprenant une partie fixe (stator), un ligand trisindazolyborate fonctionnalisé pour interagir avec les surfaces d'étude et une partie mobile (rotor) constitué d'un ligand cyclopentadiényle qui possèdera des bras espaceurs terminés par des groupements électroactifs. Le rôle des groupements électroactifs sera de transférer les électrons d'une électrode à l'autre et de convertir l'énergie électrique fournie en mouvement de rotation de l'ensemble du rotor
In the field of nanosciences, the conception and the construction of a molecular motor at the nanometric scale is a conceptual and synthetic challenge. A molecular motor is a molecule which can transform energy into an unidirectional movement. We decided to synthesized a molecular motor electrically addressed, designed to be studied as a single molecules between the electrodes of a nanojunction by near field microscopy. It will be a ruthenium organometallic complex bearing two different ligands which would act as a rotor and a stator. The stator is an hydrotrisindazolylborate ligand with a tripodal shape which have been functionalized to interact strongly with oxide surface currently used in AFM experiments. The rotor is a cyclopentadienyl ligand connected to five electroactive group by linear and rigid arms. Electroactive group will transfer electrons from the cathode to the anode and convert the electrical energy into an rotational motion of the rotor

This thesis is concerned with the synthesis and coordination chemistry of· a range of poly(pyrazolyl)borate 'scorpionate' ligands and examines their suitability in facilitating rapid [llC]carbonylation reactions to form radiotracers for application in positron emission tomography (PET). Author (full names): Steven Kealey Title of thesis: Synthesis and Coordination Chemistry of Scorpionate Ligands and their Applications in He-Positron Emission Tomography The second part of this thesis concerns the use of a copper(I)-Tp system for selectively solubilising llCO from nitrogen-rich gas streams for subsequent use in palladium-catalysed carbonylation reactions between amines and aryl-halides to form amides. These reactions were performed on a microfluidic device and in Schlenk apparatus using unlabelled carbon monoxide. These reactions ~were transferred to the radiochemical laboratory whereby efficient llCO trapping was observed prior to the formation of llC-radiolabelled amides. The third part of this thesis explores the coordination chemistry of palladium(II) towards a novel hybrid ligand consisting of pyrazolyl and triphenylphosphine moieties. The potential hemilabile behaviour of this ligand and its derivatives towards palladium was investigated and the use of these complexes as catalysts for carbonylation reactions is described. The final part of this thesis examines the coordination chemistry of poly(pyrazolyl)borates bearing additional coordinating groups appended to the 3- or 5~position ofthe pyrazolyl rings. Reactions ofthe 3-substituted derivatives were carried out with a range of metals and found to display varied coordination behaviour depending on the specific coordination requirements ofthe metal.

Une famille de moteurs moléculaires rotatifs a été synthétisée en vue de leur étude au niveau de la molécule unique par microscopie en champ proche. Le moteur est basé sur un complexe de ruthénium de géométrie en tabouret de piano avec deux ligands constituant un rotor et un stator. Le stator est un ligand tripodal hydrotris(indazolyl)borate fonctionnalisé pour s'accrocher à la surface d'étude. Le rotor est un ligand cyclopentadiényle (Cp) connecté à cinq groupements électroactifs ferrocényles via des espaceurs rigides et linéaires. Le moteur sera déposé entre deux électrodes d'une nanojonction afin de contrôler la rotation par le passage d'un courant. Deux ligands hydrotris(indazolyl)borate fonctionnalisés par des groupements ester ou thio-éther ont été synthétisés afin de permettre un accrochage du moteur respectivement sur des surfaces d'oxydes ou métalliques. Ces ligands ont été incorporés à une première génération de moteurs où les ferrocényles sont connectés par un lien conjugué au Cp central. L'utilisation de fragment isolant trans-platine ou biyclo[2,2,2]octane entre les groupements électroactifs a été étudiée afin de minimiser les transferts d'électrons intramoléculaires. Une étude expérimentale et une étude théorique a montré la diminution du paramètre de couplage électronique, par rapport à un lien conjugué d'un facteur trois avec un fragment trans-platine et d'un ordre de grandeur avec un bicyclo[2,2,2]octane. Ces espaceurs isolants ont ainsi été introduits dans les bras du rotor pour conduire à des moteurs moléculaires totalement fonctionnels. Afin de mettre en évidence la rotation, des moteurs ayant un rotor dissymétrique ont été également été synthétisés
A family of electrically fuelled rotary molecular motors has been synthesised to be studied by near field microscopy at the level of a single molecule. The motor is based on a ruthenium complex with a piano stool geometry bearing two different ligands that act as a rotor and a stator. The stator is a tripodal hydrotris(indazolyl)borate ligand functionalized to interact strongly with the surface. The rotor is a cyclopentadienyl (Cp) ligand connected to five electroactive groups (ferrocene) by linear and rigid arms. The motor will be deposited between two electrodes of a nanojonction to control the rotation by a flow of current. Two hydrotris(indazolyl)borate ligands functionalised with ester or thio-ether groups have been synthesised to anchor the motor respectively to an oxide or to a metallic surface. These ligands have been incorporated into a first generation of motors where the ferrocenes are connected by a conjugated linker to the central Cp. .

Scorpionate and terpyridine ligands are of importance in inorganic chemistry for their metal-binding properties. Tris-pyrazolylborate (Scorpionate) ligands that show facial binding mode and steric protection have been extensively used to synthesize complexes modeling the active site structure and biological function of various metalloproteins and as catalysts in C-H and NO activation and carbine transfer reactions. Terpyridine and modified terpyridine ligands showing meridional binding mode have been used in bioinorganic chemistry where Pt-terpyridine complexes are known to inhibit the activity of thiordoxin reductase (TrxR) besides showing interaction with G-quadruplex. The thesis work stems from our interest to use these ligand systems to design and prepare new 3-d metal-based photodynamic therapeutic (PDT) agents to explore their visible light-induced DNA cleavage activity and photocytotoxicity. Efforts have been made in this thesis work to design and synthesize Co(II) and Cu(II) complexes having scorpionate (Tpph) abd terpyridine (tpy) ligands. Ternary 3d-metal complexes having Tpph and planar phenanthroline bases have been synthesized and structurally characterized. The steric encumbrance of Tpph has led to the reduction in chemical nuclease activity along with enhanced photo-induced DNA cleavage activity, particularly of the Cu(II) and Co(II) complexes. The Co(II), Cu(II) and Zn(II) complexes of Tpph and a pyridyl ligand having a photoactive naphthalilmide moiety show molecular light-switch effect on binding to calf thymus DNA or BSA protein. The complexes do not show any chemical nuclease activity. The Cu(II) complex shows significant DNA cleavage activity in red light. The Co(II) complex displays significant photocytotoxicity in UV-A light. Ternary Cu(II) complexes of ph-tpy and heterocycylic bases are prepared and their DNA binding and cleavage activity studied. The complexes are avid binders to CT-DNA. The dipyridoquinoxaline (dpq) and dipyridophenazine (dppz) complexes are photocleavers of DNA in visible light. A significant enhancement in cytotoxicity in HeLa cancer cells is observed on exposure of the dppz complex to light. The binary Cu(II) complexes are also prepared to reduce the dark toxicity using phenyl and pyrenyl substituted terpyridine ligands. The pyrenyl substituted complex shows DNA cleavage activity in the visible light, low dark toxicity and unprecedented photocytotoxicity in visible light. The copper(II) complexes generally show dark cellular toxicity due to the presence of reducing thiols. The present terpyridine copper(II) complex having pendant pyrenyl moiety shows significant PDT effect that is similar to that of the PDT drug Photofrin. Binary Co(II) complexes show efficient DNA cleavage activity in visible light, significant photocytotoxicity in visible light and cytosolic uptake behaviour. Considering the bio-essential nature of the cobalt and copper ions, the present study opens up new strategies for designing and developing 3d-metal-based photosensitizers for their potential applications in PDT.

Scorpionate and terpyridine ligands are of importance in inorganic chemistry for their metal-binding properties. Tris-pyrazolylborate (Scorpionate) ligands that show facial binding mode and steric protection have been extensively used to synthesize complexes modeling the active site structure and biological function of various metalloproteins and as catalysts in C-H and NO activation and carbine transfer reactions. Terpyridine and modified terpyridine ligands showing meridional binding mode have been used in bioinorganic chemistry where Pt-terpyridine complexes are known to inhibit the activity of thiordoxin reductase (TrxR) besides showing interaction with G-quadruplex. The thesis work stems from our interest to use these ligand systems to design and prepare new 3-d metal-based photodynamic therapeutic (PDT) agents to explore their visible light-induced DNA cleavage activity and photocytotoxicity. Efforts have been made in this thesis work to design and synthesize Co(II) and Cu(II) complexes having scorpionate (Tpph) abd terpyridine (tpy) ligands. Ternary 3d-metal complexes having Tpph and planar phenanthroline bases have been synthesized and structurally characterized. The steric encumbrance of Tpph has led to the reduction in chemical nuclease activity along with enhanced photo-induced DNA cleavage activity, particularly of the Cu(II) and Co(II) complexes. The Co(II), Cu(II) and Zn(II) complexes of Tpph and a pyridyl ligand having a photoactive naphthalilmide moiety show molecular light-switch effect on binding to calf thymus DNA or BSA protein. The complexes do not show any chemical nuclease activity. The Cu(II) complex shows significant DNA cleavage activity in red light. The Co(II) complex displays significant photocytotoxicity in UV-A light. Ternary Cu(II) complexes of ph-tpy and heterocycylic bases are prepared and their DNA binding and cleavage activity studied. The complexes are avid binders to CT-DNA. The dipyridoquinoxaline (dpq) and dipyridophenazine (dppz) complexes are photocleavers of DNA in visible light. A significant enhancement in cytotoxicity in HeLa cancer cells is observed on exposure of the dppz complex to light. The binary Cu(II) complexes are also prepared to reduce the dark toxicity using phenyl and pyrenyl substituted terpyridine ligands. The pyrenyl substituted complex shows DNA cleavage activity in the visible light, low dark toxicity and unprecedented photocytotoxicity in visible light. The copper(II) complexes generally show dark cellular toxicity due to the presence of reducing thiols. The present terpyridine copper(II) complex having pendant pyrenyl moiety shows significant PDT effect that is similar to that of the PDT drug Photofrin. Binary Co(II) complexes show efficient DNA cleavage activity in visible light, significant photocytotoxicity in visible light and cytosolic uptake behaviour. Considering the bio-essential nature of the cobalt and copper ions, the present study opens up new strategies for designing and developing 3d-metal-based photosensitizers for their potential applications in PDT.

This thesis describes investigations into tridentate facial or meridional ligand frameworks that feature unconventional ‘donors’ including boron, aluminium and silicon and their coordination chemistry with transition metals. Inclusion of electropositive elements within the ligand framework are of interest as they impart unique properties to their corresponding complexes and contrasts that of conventional donors such as phosphorus, nitrogen and sulfur. Chapter one provides an introduction that includes a survey of relevant literature of pincer and scorpionate chemistry. In Chapter two, the series of complexes [Ru(X)(CO)(PPh3){3-H,S,S’-H2B(mt)2}] (X = H, Cl, SePh, BCat, SiCl3, SiMe3) was synthesised for spectroscopic and structural comparisons to gain insight into perturbations on the B–H–Ru interaction affected by the trans X ligand. The trans influence of the X ligand on the H chemical shift of the borohydride B–H–Ru group was assessed. Ligands of strong trans influence resulted in a B–H…Ru interaction consisting of more borohydride character while those of weaker trans influence resulted in a B…H–Ru interaction with metallohydridic character. The osmium complex [OsH(CO)(PPh3){3-H,S,S’-H2B(mt)2}] served as a further (5d transition metal) point of comparison. When the trans ligand was a -organyl (X = Ph, CH=CHPh), the complexes [Ru(X)(CO)(PPh3){3-H,S,S’-H2B(mt)2}] were observed as transient species en route to the ruthenaboratrane [Ru{3-B,S,S’-BH(mt)2}(CO)(PPh3)2]. In Chapter three, a convenient one-pot synthesis from [RuHCl(CO)(PPh3)3] was developed for the first doubly-bridged ruthenaboratrane [Ru{3-B,S,S’-BH(mt)2}(CO)(PPh3)2] (Ru→B), which can alternatively be obtained using [Ru(Ph)Cl(CO)(PPh3)2]. Trace amounts of [Ru(C≡CPh)(CO)(PPh3){3-H,S,S’-BH(mt)2}] and [Ru(2-N,S-mt)(Ph)(CO)(PPh3)2] were crystallographically identified during the syntheses. The reactivity of the Ru→B bond was explored for oxidative conversion to the 3-H,S,S mode of coordination. The reactions revealed either a plethora of products indicative of ligand degradation or no reaction, which suggests a robust M→B interaction. The complex [Ru{3-B,S,S’-BH(mt)2}(CO)(PPh3)2] was shown to serve as a useful precursor to access further examples of doubly-bridged ruthenaboratrane complexes. Phosphine substitution reactions of [Ru{3-B,S,S’-BH(mt)2}(CO)(PPh3)2] afforded the monosubstituted products [Ru{3-B,S,S’-BH(mt)2}(CO)(PPh3)(L)] (L = CO, PMe2Ph) and the disubstituted products [Ru{3-B,S,S’-BH(mt)2}(CO)(L)2] (L = PMe2Ph, P(OMe3)) and [Ru{3-B,S,S’-BH(mt)2}(CO)(Z-Ph2PCH=CHPPh2)]. These complexes consistently feature an elongated ruthenium phosphorus bond trans to boron compared to that trans to sulfur, confirming a pronounced trans influence exerted by the Ru→B bond. Comparisons were made to sulfur-based metallaboratranes, including the triply-bridged series [Ru{4-B,S,S’,S’’-B(mt)3}(CO)(PR3)] (PR3 = PMe2Ph, PCy3, P(OMe)3), which were synthesised and characterised. No general trends concerning the M→B interaction were identified from the complexes assessed, reflecting the constraints of chelation in different ligand frameworks and metals. In Chapter four, the synthesis of aluminium based ligands was explored and yielded the novel aluminium pro-ligand, Li[H2Al(mt)2].THF. Coordination of the [H2Al(mt)2]‒ ligand to transition metal precursors allowed spectroscopic observation of the desired products on ruthenium, osmium and rhenium, but ligand degradation precluded isolation of complexes with an intact [H2Al(mt)2]‒ unit. The greater reactivity and metal-mediated lability of Li[H2Al(mt)2].THF compared to the Na[H2B(mt)2] ligand was a recurrent feature. In Chapter five, coordination of the o-phenylenediamine-based silane HPhSi(NCH2PPh2)2C6H4-1,2 to metal precursors afforded rhodium(III), rhodium(I), iridium and osmium complexes. A third preparatory method toward the reported complex [RhHCl{SiPh(NCH2PPh2)2C6H4-1,2}(PPh3)] was discovered with use of [RhCl(CO)(PPh3)2]. The iridium analogue [IrHCl{SiPh(NCH2PPh2)2C6H4-1,2}(PPh3)] and [RhHCl{SiCl(NCH2PPh2)2C6H4-1,2}(PPh3)] were similarly synthesised. Preparative routes to rhodium(I) square planar complex [Rh{SiPh(NCH2PPh2)2C6H4-1,2}(PPh3)] were explored and include dehydrohalogenation of octahedral rhodium(III) complexes and a direct synthesis pathway from [RhH(PPh3)4]. The strong -donating properties of the silyl unit was evident by elongation of the bond trans to silicon in crystallography studies. Complex [Rh{SiPh(NCH2PPh2)2C6H4-1,2}(PPh3)] displayed facile ligand addition and substitution with dihydrogen, carbon monoxide and norbornadiene to give [RhH2{SiPh(NCH2PPh2)2C6H4-1,2}(PPh3)], [Rh{SiPh(NCH2PPh2)2C6H4-1,2}(CO)(PPh3)], [Rh{SiPh(NCH2PPh2)2C6H4-1,2}(CO)2] and [Rh{SiPh(NCH2PPh2)2C6H4-1,2}(C7H8)]. Direct synthesis resulted in the first benzosiladiazole based osmium complex [OsCl{SiPh(NCH2PPh2)2C6H4-1,2}(PPh3)] from [OsCl2(PPh3)3] and HPhSi(NCH2PPh2)2C6H4. The Appendix Chapter details the reaction of pro-ligands H2C(NCH2PR2)2C10H6-1,8 (R = Cy, Ph) with iridium precursors. Pro-ligand H2C(NCH2PCy2)2C10H6-1,8 was found to readily react with iridium(I) chloro-bridged dimers through double C–H activation to afford iridium(III) NHC complex trans-[IrH2Cl{C(NCH2PCy2)2C10H6}]. The trans hydrides in [IrH2Cl{C(NCH2PCy2)2C10H6}] hindered reductive elimination of dihydrogen. However, the complex underwent spontaneous hydride substitution upon solvation in chloroform, which afforded cis-[IrHCl2{C(NCH2PCy2)2C10H6}]. Hydride replacement reactions were similarly observed for the diphenylphosphine supported trihydride complex, [IrH3{C(NCH2PPh2)2C10H6}].

碩士
國立彰化師範大學
化學系
95
In order to mimic the function and active site structure of copper proteins such as：nitrite reductase, nitrous oxide reductase, amine oxidase, dopamine ß-monooxygenase and peptidylglycine α-hydroxylating monooxygenase, the N2S scorpionate ligand with methyl as substituents [{Li(bdmpzdta)(H2O)}4] (bdmpzdta = bis(3,5-dimethylpyrazol-1-yl)dithioacetate) and with t-butyl as substituents bdtbpzdta have been synthesized. Three copper complexes , Cu(Ⅱ)(bdmpzdta)2 (1), [Cu(Ⅰ)(bdtbpzdta)Br]2 (2) and {Cu(Ⅰ)2[µ-S-(bdtbpzdta)2]}2 (3) have been obtained . During the characterization of copper complexes we found an exchange reaction that the dithioacetate moiety has been slowly converted to acetate group in the presence of carbon dioxide. There is no precedent example on the C-C bond cleavage in either [{Li(bdmpzdta)(H2O)}4] or mental complex of N2S ligand . Our observation represents an unique example of CC bond activation promoted by metal ion and, more importantly, this type of compound might be able to carry out the CO2 fixation reaction. In the second part of research, multidentate N2O ligands are used to bridge metal centers to form clusters or polymeric structures via coordination bonds. The N2O scorpionate ligand bdmpza (= bis(3,5-dimethylpyrazol-1-yl) has been used because carboxylate group can bridge to metal centers. The silver complexes, K4{[Ag(bdmpza)2]2}(ClO4)2(Acetone)2 (4), [Ag4(bdmpza)3]2(OH)(ClO4) (5), and ({Na[Ag(bdmpza)]2BF4(H2O)}2)n (6) have been synthesized and structure characterized. These silver complexes demonstrate the importance of cation and anion on controlling the three dimensional structure. In the case of complex (6) linear chain structure forms. It is optimistic that other two dimensional or three dimensional supramolecular structures can be constructed using this type of N2O coordinating ligand.

A series of uranium benzyl compounds supported by two hydrotris(3,5-dimethylpyrazolyl) borate (Tp*) ligands has been synthesized and characterized. In addition to the previously reported Tp*₂U(CH₂Ph) (2-Bn), examinations of both steric (tert-butyl, iso-propyl) and electronic (methoxy, picolyl) changes on the aromatic ring led to the formula Tp*₂U(CH₂Ar) (Ar = 4-tert-butylphenyl (2-^tBu), 4-isopropyl (2-ⁱPr), 2-picolyl (2-pyr), 3-methoxyphenyl (2-OMe). Treatment of the entire series of benzyl compounds with azidotrimethylsilane results in the formation of a neutral, monomeric U(III) compound, Tp*₂U(N₃) (3-N₃), and substituted benzyltrimethylsilane. While there was no observed change in reactivity among the benzyl compounds and Me₃SiN₃, treatment of these compounds with triphenylphosphine oxide saw unique carbon-carbon coupling occur for three of the substituted benzyl compounds. With a single equivalent of OPPh₃, the following products were isolated: Tp*₂U[OP(C₆H₅)(C₆H₅CH₂C₆H₅)] (4-Ph), Tp*₂U[OP(C₆H₅)(C₆H₅-p-iPrC₆H₄)] (4-ⁱPr), Tp*₂U[OP(C₆H₅)(C₆H₅-p-tBuC₆H₄)] (4-^tBu), Tp*₂U[OP(C₆H₅)(C₆H₅-m-OCH₃C₆H₄)] (4-OMe).

A family of uranium(IV) imido complexes of the form Tp*₂U(NR) (R = benzyl (7-Bn), para-tolyl (7-Tol), para-methoxyphenyl (7-OMe), 2,6-diethylphenyl (7-detp), 2,6-diisopropylphenyl (7-dipp)) have been generated by bibenzyl extrusion from 2-Bn. When 7-Bn and 7-Tol, along with previously reported Tp*₂U(N-Ph) (7-Ph) and Tp*₂U(N-Ad) (7-Ad), are treated with isocyanates or isothiocyanates, they readily undergo [2π+2π]-cycloaddition to generate κ²-ureato and κ²-thioureato derivatives, respectively. Use of phenylisoselenocyanate with 7-Tol and 7-Ph generates a rare κ²-selenoureato complex. Treating 7-Tol and 7-OMe with benzonitrile or 4-cyanopryidine results in unusual products of multiple bond metathesis, namely κ¹-amidinate U(IV) complexes.

A family of dinuclear bis(Tp*) (Tp* = hydrotris(3,5-dimethylpyrazolyl)borate) uranium compounds with conjugated organic linkers was synthesized to explore possible electronic communication between uranium ions. Trivalent diuranium phenyl alkynyl compounds, Tp*₂UCC(1,3-C₆H₄)CCUTp*₂ (14-meta) or Tp*₂UCC(1,4-C₆H₄)CCUTp*₂ (14-para), and tetravalent diuranium phenylimido compounds, Tp*₂U(N-1,3-C₆H₄-N)UTp*₂ (15-meta) and Tp*₂U(N-1,4-C₆H₄-N)UTp*₂ (15-para), were generated from trivalent Tp*₂UCH₂Ph. All compounds were fully characterized both spectroscopically and structurally. The electronic structures of all derivatives were interrogated using magnetic measurements, electrochemistry, and were the subject of computational analyses. All of this data combined established that little electronic communication exists between the uranium centers in these trivalent and tetravalent diuranium molecules.

Uranium mono(imido) species have been prepared via oxidation of Cp*U(^MesPDI^Me)(THF) (16-Cp*) and [Cp^PU(^MesPDI^Me)]₂ (16-Cp^P) (Cp* = η⁵-1,2,3,4,5-pentamethylcyclopentadienide; Cp^P = 1-(7,7-dimethylbenzyl)cyclopentadienide; ^MesPDI^Me = 2,6-((Mes)N=CMe)₂C₅H₃N, Mes = 2,4,6-trimethylphenyl) with organoazides. Treating either with N₃DIPP formed uranium(IV) mono(imido) complexes, Cp^PU(NDIPP)(^MesPDI^Me) (17-Cp^P) and Cp*U(NDIPP)(^MesPDI^Me) (17-Cp*), featuring reduced [^MesPDI^Me]^1-. Addition of electron-donating 1-azidoadamantane (N₃Ad) to 16-Cp* generated a dimeric product, [Cp*U(NAd)(^MesHPDI^Me)]₂ (18), from radical coupling at the para-pyridine position of the pyridine(diimine) ligand and H-atom abstraction, formed through a monomeric intermediate that was observed in solution but could not be isolated. To support this, Cp*U(^tBu-^MesPDI^Me)(THF) (16-^tBu), which has a tert-butyl group protecting the para-position, was also treated with N₃Ad, and the monomeric product, Cp*U(NAd)(^tBu-^MesPDI^Me) (17-^tBu), was isolated. All isolated complexes were analyzed spectroscopically and structurally, and dynamic solution behavior was examined using electronic absorption spectroscopy.

Reported in Chapter 2 of this thesis is the reliable and tolerant synthesis of a small library of pyrazole and triazole heterocycles. This synthesis was achieved in two steps in good yields from the reaction of acetophenone and benzamide derivatives with dimethyl formamide-dimethyl acetal followed by a cyclization with hydrazine. Also reported is the synthesis and characterization of their corresponding scorpionate ligands. Preliminary co ordination chemistry was done with a variety of lanthanide metals and was studied by standard spectroscopic methods as well as variable temperature 1H NMR, which revealed that Curie-Weiss behaviour was followed for these complexes in solution. An X-ray crystal structure of a nine co-ordinate ytterbium metal centre with eight nitrogen atom (four pyrazole, four pyridine) donors and one chloride atom was obtained, which may have been a product of decomposition during crystal growth. The bond lengths of this structure were compared with other lanthanide complexes of similar structural motifs. This comparison supported the theory of decomposition as the pyridine nitrogen atom-ytterbium bond lengths were longer than the average ytterbium-nitrogen atom bond length. Reported in Chapter 4 of this thesis is the synthesis and partial characterization of a new organic dye named perinaphthindigo. Perinaphthindigo was synthesized with adapted iv Baeyer-Drewson reaction conditions for the synthesis of indigo which involved the treatment of 1,8-nitronaphthaldehyde with acetone under basic conditions, and was found to be an intense green colour in solution. Perinaphthindigo was produced in poor yields, so efforts were undertaken to improve the yields through an alternative two-step synthesis, first between 1,8-nitronaphthaldehyde and nitromethane in a Henry reaction followed by oxidative coupling. The synthesis of perinaphindigo was adapted so as to structurally modify the final compound, either through incorporation of solubilizing tert-butyl groups or bromine atoms for future cross-coupling chemistry. The brominated derivatives of perinaphthindigo were also synthesized in low yields so cross-coupling conditions were scanned on model precursor compounds. The brominated perinaphthindigo compounds were found to have a bathochromically shifted absorbance maximum from the parent perinaphthindigo. This bathochromic shift was more pronounced in our compounds than in the comparison of indigo and 6.6’-dibromoindigo which indicates our compounds are more sensitive to perturbation by substitution. Reported in Chapter 5 of this thesis is the study of the acid and base chemistry of Nindigo, a previously reported compound. The treatment of Nindigo with a series of strong acids led to an interesting “protoisomerization”, or trans to cis isomerization of the central olefin, with ultimate structural determination through X-ray crystallographic methods. This isomerization was studied through absorbance stopped-flow methods which identified a probable pathway of the isomerization through a neutral, cis species. The investigation of neutral Nindigo was undertaken to attempt to identify two peaks which are red-shifted from the π-to-π transition at 586 nm. These two peaks appear at 657 nm and 741 nm and are present in all solvents. The preparative acid chemistry allowed us to assign the first red shifted peak at 657 nm to the cationic species. Aggregation studies showed concentration dependent behaviour of the ratio between the peaks at 586 nm and 657 nm with little effect on the species at 741 nm. In order to probe whether an autoionization process was occurring, variable temperature NMR and UV-Vis experiments were performed which did not provide a definitive answer to the species at 741 nm.
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