Χημική δραστικότητα λειτουργικών ομάδων σε πολυδοντικούς υποκαταστάτες που προάγεται από μεταβατικά μεταλλοϊόντα και λανθανίδια
Authors: Δανέλλη Παναγιώτα 
Published: September 2021

There are many ‘organic’ reactions promoted, catalyzed or initiated by metal ions. Chemists are fascinated by the many and varied reactions that proceed in the presence of metal ions. As a result, many Inorganic Chemistry groups around the world delve deeper and deeper into this subject. Since the movement of electrons characterizes a chemical reaction, anything that alters the distribution, movement or availability of electrons can, in principle, be capable of affecting reactivity. A necessary consequence of the metal-ligand interaction is the perturbation of the electronic configuration of the ligand, to some extent, upon coordination. If changes in the electronic structure may result in changes in the reactivity, an obvious corollary is that the reactivity of coordinated ligands may not necessarily parallel that of the free ligands. There are several ways in which a metal ion might affect the properties of a ligand to which it is coordinated. Today, the effect of the ligands upon a metal ion is well understood and satisfactorily quantified; on the contrary, the converse effect is not so. There are a number of reasons for that. Firstly, a metal ion is a mononuclear center and, to some extent, its orbitals have many of the properties of hydrogen-like atomic orbitals. In contrast, ligands are frequently polynuclear molecular species, in which the orbitals of the donor atoms are also ivolved in intraligand covalent bonding. Secondly, the ligand orbitals are more or less polarizable than metal orbitals. Thus, whereas metal d or f orbitals remain more-or-less recognizable as such in coordination complexes (as seen from d-d or f-f electronic spectra), ligand donor orbitals become more perturbed. For example, it is less meaningful to talk of an electron in the 2p orbital of nitrogen in the complex cation [Ni(NH3)6]2+ than it is to discuss an electron in the NiII 3d orbitals of the same complex. In particular, the change from lone to bonding pair, consequent upon the formation of the coordination bond, has effects upon the other groups which might be bonded to the ligand donor atom(s). A metal ion may alter the properties of a coordinated ligand through three types of changes: Conformational changes, polarization changes and π-bonding changes. Conformational changes involve steric consequences of metal-ligand bonding, geometrical consequences of chelation and chemical consequences of lone pair non-availability. Polarization changes refer mainly to the ligands and often result in ligand polarization and the intrinsic effects that accompany this polarization. Changes in π-bonding refer to ligands possessing a π-bonding systems, whose π- or π*--orbitals may be of the correct symmetry for overlap with metal p or d orbitals. The chemical consequences of these interactions are less readily defined than those resulting from the conformational or polarization changes. In particular, the π-bonding changes often oppose those resulting from the σ-polarization. Interactions involving the π-orbitals also differ from those only involving ligand polarization in another important manner; the symmetry of the orbitals involved has critical effects upon the reactivity of the molecular system.The present Doctoral Thesis had as a goal the study of the reactivity of four coordinated ligands, namely di-2-pyridyl ketone [(py)2CO], 2-acetylpyridine [(py)(me)CO], 2-benzoylpyridine [(py)(ph)CO] and pyridine-2,6-dimethanol [(py)(CH2OH)2 or pdmH2]; the structural formulae of the ligands are shown in Sceme I. The ligands (py)2CO, (py)(me)CO, (py)(ph)CO have as a common feature the existence of a 2-pyridyl group and a carbonyl group, while pdmH2 [or (py)(CH2OH)2] possesses a pyridyl group and two –CH2OH groups at the ortho (or 2- and 6-) positions. Scheme I: The organic ligands whose metal ion-assisted/promoted transformations have been studied in the present Thesis. A large number of reactions of carbonyl compounds has been shown to be sensitive to the presence of metal ions. Carbonyl compounds are of great importance in the formation of C-C bonds in Organic Chemistry and metalion control of their reactivity offers a way to promote, inhibit or even control such reactions. The coordination of the oxygen atom of a carbony compound to a metal center is likely to modify the reactivity of that group. Products formally derived by attack at the carbon atom or by attack at the metal ion followed by attack at carbon by the coordinated nucleophile. There has been (and still is) a scientific debate over the relative importance of these two competing mechanisms in biological and biomimetic systems. These two mechanisms may well both be operative in some cases. The principal reactions of carbonyl compounds are of two types. The first type is that in which the nucleophile reacts with the electrophilic carbon atom of the carbonyl group to generate a new tetrahedral carbon center. The second type involves the generation of a nucleophilic enol or enolate ion. Both of these principal types of reactivity of a carbonyl compound may be modified by coordination to metal ions. The polarization effect results in the increase of the electrophilic character of a carbonyl atom by coordination of the oxygen to a metal ion, and so any reactions in which the rate-determining step is nucleophilic attack upon this site might be accelerated. There are many examples in which a ketone group in a polydentate organic ligand is attacked by water, an alcohol or another nucleophile in the presence of metal ions to give gem-diols or hemiketals, which may be subsequently deprotonated. The reactions of (py)2CO with metal ions have been particularly well studied over the years. A range of nucleophiles have been shown to add to the carbonyl group upon coordination of the oxygen atom and/or the 2-pyridyl rings to the metal ion. On the contrary, the metal-ion assisted/promoted reactivity of the coordinated (py)(me)CO and (py)(ph)CO molecules has much less been studied. Examples of the reactivity of coordinated pdmH2 are very rare. Here, the principal sites of reactivity are the two –CH2OH groups wich may be (one or both) oxidized to aldehyde or carboxylic groups, or alternatively to act as nucleophiles upon deprotonation. For a given general reaction system, we tried to isolate the maximum number of products. The isolated metal complexes have been characterized in the solid state by microanalyses (C, H, N), single-crystal X-ray crystallography, IR spectra and electronic spectra (diffuse reflectance spectra), as well by room temperature magnetic susceptibility measurements (for selected compounds). The emission properties (photoluminescence) of selected lanthanide(III) [Ln(III)] compounds have been also recorded. Some diamagnetic metal complexes have been studied in solution by 1H NMR spectroscopy, while conductivity measurements were performed for few complexes. For a pair of Ni(II) diastereoisomers, theoretical (DFT) calculations have been performed to evaluate the stability of the two complexes in solution. The Thesis consists of six (6) sections. Each section can be read independently; this means that it has its own references list, and the numbering scheme of chapters, figures, tables and compounds starts from the beginning. Section I (Introduction) consists of nine (9) chapters and every chapter has been written in the form of a short review. Chapter A is an overview of the metal-ligand interactions. Chapters B, C, D, E, F and G illustrate the basic features of the reactions of coordinated carbonyl compounds with nucleophiles, other reactions of coordinated ligands with nucleophiles, stabilization of anions and the reactions of coordinated ligands with electrophiles, cyclic ligands and the template effect, reactions of aromatic and heterocyclic ligands, and of oxidation and reduction of coordinated ligands, respectively. Since (i) some complexes were synthesized by solvothermal techniques and (ii) some of the products are polymorphs and pseudopolymorphs, Chapters H and I give basic information about solvothermal synthesis in Coordination Chemistry, and the chemistry of polymorphs/pseudopolymorphs, respectively. Section II provides the members of the jury and the readers with the general and more specific goals of the Thesis, with emphasis on the selection criteria of the organic ligands and the metal ions used. Section III is a general experimental section giving information concerning the solvents and starting materials employed, and details about the instruments used for the characterization of the complexes and the DFT calculations. Sections IV and V are organized in a similar manner. Both contain a specific introduction concerning the already published coordination chemistry of the ligands involved (IV-1, V-1), a detailed experimental part (IV-2, V-2) with all the information for the syntheses of the metal complexes (this is written in a such way that a graduate student can reproduce the results), a ‘Results and Discussion” subsection (IV-3, V-3) in which all the results are explained and discussed, and a final part (IV-4, V-4) which contains the reference list. Section IV refers to the coordination complexes obtained from the reactions of (py)2CO, (py)(me)CO and (py)(ph)CO with some metal ions with emphasis on the reactivity of the coordinated ligands. Section V describes coordination complexes isolated from the reactions of pdmH2 with the chosen metal ions; again emphasis is on the observed metalion assisted/promoted transformation. The final section VI (Final Conclusions-Future Perspectives) summarizes the main results, provides a critical discussion of the finding in terms of the goals (presented in Section II) and gives several ideas (some are in progress) for future research on topics related to the present Thesis. Diagnostic crystallographic data for the compounds of this Thesis are summarized in the Appendix. Some details of the chemistry described in the Thesis are briefly described below. The full synthetic investigation of reaction systems containing (py)2CO, (py)(me)CO and (py)(ph)CO and various metal ions has provided access to complexes [Hg3I6{(py)2C(OMe)(OH)}2]•(py)2CO•MeOH [1•(py)2CO•MeOH], [Hg2(SCN)4{(py)2C(OMe)(OH)}2] (2), [Ni{(py)2C(NH2)(OH)}2][Hg(SCN)4]•H2O (3•H2O), [Ni{(py)2C(NH2)(OH)}{(py)2C(OEt,OH)(OH)}][HgCl4]•H2O•1.5EtOH (4•H2O•1.5EtOH), [Ni{(py)2C(NH2)(OH)}2] [HgCl4]•0.2H2O (5•0.2H2O), [Ni{(py)2C(OMe)(OH)}2]2[Hg2Cl6](ClO4)2 (6), [Ni{(py)2C(NH2)(OMe)}2](ClO4)2 (7), [Ni{(py)2C(NH2) (OEt)}2](ClO4)2•0.9H2O (8•0.9H2O), [Cd2Cl4{(py)2C(OEt)(OH)}2] (9), [CdI2{(py)2CO}2] (10), [Th(NO3)2{(py)2C(OMe)(O)}2(MeOH)] (11), [ΖrCl2{(py)2C(OMe)(O)}2] (12), [Pb2{(py)2C(OH)(O)}2(DMF)2](NO3)2 (13), [Mn{(py)2C(OMe)O}2(MeOH)2](PF6) (14), [Mn{(py)2C(OMe)O}2](PF6) (15), [Mn{(py)2C(OMe)O}2](ClO4) (16), {L[HgCl3}n (17•0.5MeOH), {L[HgBr3]}n (18), (L1)+(ClO4)- (19),trans,trans,trans-[NiCl2{(py)(ph)CO}2]•0.4H2O•0.6EtOH (20•0.4H2O•0.6EtOH),cis,cis,trans-[NiCl2{(py)(ph)CO}2] (21), trans,trans,trans-[NiBr2{(py)(ph)CO}2]•EtOH (22•EtOH),trans,trans,trans-[NiBr2{(py)(ph)CO}2] (23), trans,trans,trans-[NiI2{(py)(ph)CO}2] (24), trans,trans,trans-[Ni(H2O)2{(py)(ph)CO}2](NO3)2 (25), trans,trans,trans-[Ni(H2O)2{(py)(ph)CO}2](NO3)2 (26), [Ni(MeOH)2{(py)(ph)CO}2](ClO4)2 (27), [CdBr2{(py)(ph)CO}2] (28), [HgCl2{(py)(me)CO}]n (29), [HgBr2{(py)(me)CO}]n (30), cis,cis,trans-[CdCl2{(py)(me)CO}2] (31), cis,cis,trans-[CdBr2{(py)(me)CO}2] (32), cis,cis,trans-[CdI2{(py)(me)CO}2] (33), cis,cis,trans-[CdI2{(py)(me)CO}2] (34), trans,trans,trans- -[Ni(H2O)2{(py)(me)CO}2](ClO4)2 (35) and trans,trans,trans-[Ni(H2O)2{(py)(me)CO}2](NO3)2 (36). Concerning the in situ metal-ion promoted/assisted reactivity of the coordinated ligands, the transformations observed are conventionally summarized in Scheme II. No transformation of (py)(me)CO was observed. The (py)2CO→(py)2C(NH2)(OH) and (py)2C(NH2)(OR) transformations (observed only for NiII) are novel, i.e. they are reported for the first time. Sheme II: Metal-ion promoted/assisted transformations of (py)2CO, (py)(me)CO and (py)(ph)CO observed in the present Thesis. Please note that the ligands (py)2C(OR)(OH) [and their monoanions] and (py)2C(NH2)(OR) do not exist as ‘free’ molecules/anions, but they exist only as ligands in metal complexes. The L+ cation behaves as counterion in anionic polymeric halogeno Hg(II) complexes, whereas the (L1+) cation was isolated in the metal-free salt (L1)+ClO4- (19). R = H, Me, Et/M = Hg, Ni, Cd, Th, Zr, Pb, Mn/n = II, III, IV. Salient features concerning the chemistry (except transformations) reported in Section IV are:(1) A minor variation of the synthentic parameters in the reaction system HgI2/(py)2CO in MeOH has led, in addition to the previously known tetranuclear cluster {Hg4I8{(py)2C(OMe)(OH)}2], to the trinuclear complex [Hg3I6{(py)2C(OMe)(OH)}2]•(py)2CO•MeOH [1•(py)2CO•MeOH].(2) Despite the use of SCN-, we could not synthesize heterometallic Hg(II)/Ni(II)/(py)2CO (and its various forms) complexes based on the HSAB model. Our efforts resulted in the isolation of the pseudoheterometallic complex [Ni{(py)2C(NH2)(OH)}2][Hg(SCN)4]•H2O (3•H2O). (3) Complex [CdI2{(py)2CO}2] (10) is the only compound in the present Thesis that contains di-2-pyridyl ketone in its ketone form, a fact that it has been attributed to the solvent used (MeNO2). (4) Compounds [Th(NO3)2{(py)2C(OMe)(O)}2(MeOH)2] (11), [ZrCl2{(py)2C(OMe)(O)}2] (12) and [Pb2{(py)2C(OH)(O)}2(DMF)2](NO3)2 (13) are the first structurally characterized Th(IV), Zr(IV) and Pb(II) complexes containing any form of di-2-pyridyl ketone as ligand. The former two exhibit light emission properties (albeit weak) in the solid state at room temperature.(5) The crystallization method in the 1:1:1 MnF3/(NH4)PF6/(py)2CO reaction system affects the identy of the mononuclear products. In the isolated complexes [Mn{(py)2C(OMe)(O)}2(MeOH)2](PF6] (14) and [Mn{(py)2C(OMe)(O)}2](PF6) (15), the monoanionic (py)2C(OMe)(O)- behave as O,N-bidentate chelating (1.1010) and N,O,N-tridentate chelating (1.1011) ligands, respectively. Complex 15 is one of the relatively few examples in high-spin octahedral Mn(III) complexes where the four equatorial coordination bonds are elongated and the two axial bonds are compressed.(6) Complexes {L[HgCl3]•0.5MeOH}n (17•0.5MeOH) and {L[HgBr3]}n (18) are new, welcome members of the structurally interesting family of anionic polymeric species containing the {HgX3}- (X = Cl, Br) moiety.(7) The preparation and characterization of complexes (20•0.4H2O•0.6EtOH),cis,cis,trans-[NiCl2{(py)(ph)CO}2] (21), trans,trans,trans-[NiBr2{(py)(ph)CO}2]•EtOH (22•EtOH),trans,trans,trans-[NiBr2{(py)(ph)CO}2] (23), trans,trans,trans-[NiI2{(py)(ph)CO}2] (24), trans,trans,trans-[Ni(H2O)2{(py)(ph)CO}2](NO3)2 (25), trans,trans,trans-[Ni(H2O)2{(py)(ph)CO}2](NO3)2 (26), [Ni(MeOH)2{(py)(ph)CO}2](ClO4)2 (27), [CdBr2{(py)(ph)CO}2] (28), [HgCl2{(py)(me)CO}]n (29), [HgBr2{(py)(me)CO}]n (30), cis,cis,trans-[CdCl2{(py)(me)CO}2] (31), cis,cis,trans-[CdBr2{(py)(me)CO}2] (32), cis,cis,trans-[CdI2{(py)(me)CO}2] (33), cis,cis,trans-[CdI2{(py)(me)CO}2] (34), trans,trans,trans- -[Ni(H2O)2{(py)(me)CO}2](ClO4)2 (35) and trans,trans,trans-[Ni(H2O)2{(py)(me)CO}2](NO3)2 (36) contribute significantly to the coordination chemistry of (py)2CO and (py)(me)CO, which is relatively undeveloped.(8) Complexes 20•0.4H2O•0.6EtOH and 21 constitute a pair of diastereoisomers. The former has been isolated from EtOH and the latter from MeCN. DFT studies suggest that the cis,cis,trans diastereoisomer (21) is more stable in solutions of both solvents. The diastereoisomeric character of the two complexes is reflected on their solid-state, d-d electronic (diffuse reflectance) spectra. The two diastereoisomers are very rare in the chemistry of octahedral [MA2((BC)) ̂2] systems, where A is a monodentate ligand, (BC) ̂ is an asymmetric bidentate chelating ligand and M is a metal of any oxidation state.(9) Complexes 22•EtOH and 23 are pseudopolymorphs, the first in the coordination chemistry of (py)(ph)CO.The full synthetic investigation of reaction systems containing pdmH2 and various metal ions, mainly 4f-metal ions, has provided access to complexes [La(NO3)2(pmH2)2](NO3) (1), [La(NO3)3(pmH2)2] (2), [Ce(NO3)2(pmH2)2](NO3) (3), [Pr(NO3)2(pmH2)2](NO3)•H2O (4•H2O), [Nd(NO3)2(pmH2)2](NO3) (5), [Gd(pmH2)3](NO3)3•MeOH (6•MeOH), [Tb(pmH2)3](NO3)3 (7), [Dy(pmH2)3](NO3)3 (8), [Er(pmH2)3](NO3)3 (9), [LaCl(H2O)2(pdmH2)2]Cl2 (10), [Pr(pdmH2)3]Cl3 (11), [Nd(pdmH2)3]Cl3•H2O (12•H2O), Tb[(pdmH2)3]Cl3•H2O (13•H2O), [Εr(pdmH2)3]Cl3 (14), [La(NCS)2(H2O)(pdmH2)2](NO3)•MeCN (15•MeCN), [Pr(NCS)2(H2O)(pdmH2)2](NO3)•MeCN (16•MeCN) [Eu(NCS)2(H2O)(pdmH2)2](NO3)•MeCN (17•MeCN), [Eu(NCS)3(pdmH2)2]•2MeOH (18•2MeOH), [Tb(pdmH2)3](SCN)3•H2O•MeOH (19•H2O•MeOH), [Er(pdmH2)3](SCN)3 (20•H2O•MeOH), [Yb(NCS)2(pdmH2)2](NO3) (21), [La2(O2CMe)3(NO3)2(MeOH)(pdmH2)2(pdmH)]•MeOH (22•MeOH), [Zn2Pr2(O2CPh)6(NO3)2{(py)(CH2OH)(COO)}2] (23), [Zn2Tb2(O2CPh)6(NO3)2{(py)(CH2OH)(COO)}2] (24), [Zn(pdmH2)2](NO3)2 (25), [Zn(pdmH2)2](NO3)2 (26), [Zn(pdmH2)2](NO3)2•Me2CO (27•Me2CO) και [Tb(pdmH2)3][ZnCl4]Cl•3H2O (28•3H2O). Concerning the in situ metal-ion promoted/assisted reactivity of the coordinated pdmH2, our results are relatively poor. However, the novel and very interesting (py)(CH2)(OH) (pdmH2)→{(py)(CH2OH)(COO)}- transformation in the presence of Pr(III)/Zn(II) and Tb(III)/Zn(II) was observed under solvothermal conditions. The transformation is illustrated in Scheme III. The in situ reactivity of coordinated pdmH2 resulted in the isolation of the tetranuclear heterometallic complexes [Zn2Ln2(O2CPh)6(NO3)2{(py)(CH2OH)(COO)}2] (Ln = Pr, 23/Ln = Tb, 24), which have interesting molecular structures. The obvious oxidant is the oxygen of the atmospheric air, with the coordination of one –OH group in solution facilitating its oxidation to the carboxylic group; probably the solvothermal conditions play an important role in the partial oxidation of the coordinated pdmH2. Scheme III: The in situ transformation of pdmH2 which was observed during the solvothermal reaction which resulted in the isolation of the heterometallic complexes 23 and 24. The transformed ligand is monoanionic in the complexes, the PhCO2- ion most possibly being the proton acceptor. Salient features concerning of the chemistry (except transformations) reported in Section IV are:(1) The La(NO3)3•6H2O/pdmH2 reaction system gave two product with different LaIII coordination numbers, depending on the solvent. The 10-coordinate ionic complex [La(NO3)2(pmH2)2](NO3) (1) was isolated in a more polar solvent, whereas the product from the reaction in a less polar solvent is the neutral 12-coordinate complex [La(NO3)3(pmH2)2] (2). The solid-state structures of the two compounds are not retained in DMSO, as evidenced by 1H NMR spectroscopy. The corresponding Ce(III), Pr(III) and Nd(III) systems gave only 10-coordinate ionic complexes, structurally similar to 1; this is propably due to the smaller size of Ce(III), Pr(III) and Nd(III) compared with that of LaIII.(2) The f-f transitions in the near-IR region were observed and assigned in the solid-state (diffuse reflectance) electronic spectrum of [Pr(NO3)3(pdmH2)2](NO3)•H2O (4•H2O).(3) The general LnCl3•xH2O/pdmH2 reaction system gives 9-coordinate complexes with the general formula [Ln(pdmH2)3]Cl3•yH2O (Ln = Pr, y = 0, 11/Ln = Nd, y=1, 12•H2O/Ln = Tb, y=1, 13•H2O/Ln = Er, y=0, 14). Again La(III) is an exception, giving the ionic 9-coordinate complex [LaCl(H2O)2(pdmH2)2]Cl2 (10) in the same solvent (MeOH).(4) Complex 13•H2O emits light in the solid state at room temperature; the emission is TbIII-based but the coordinated ligand doesn’t act as ‘antenna’ for the sensitization of the lanthanide(III), because the free ligand pdmH2 doesn’t emit light.(5) Compounds [Ln(NCS)2(H2O)(pdmH2)2](NO3)•MeCN (Ln = La, 15•MeCN/Ln = Pr, 16•MeCN/Ln = Eu, 17•MeCN), [Eu(NCS)3(pdmH2)2]•2MeOH (18•2MeOH), [Ln(pdmH2)3](SCN)3•H2O•MeOH (Ln = Tb, 19•H2O•MeOH/Ln = Er, 20•H2O•MeOH) and [Yb(NCS)2(pdmH2)2](NO3) (21) are the first structurally characterized Ln(III)/pdmH2 complexes also possessing isothiocyanato ligands or thiocyanate counterions. Again here, the nature of the solvent affects the product identity. The less polar solvent (MeOH) favors the formation and isolation of neutral complexes in the case of lighter Ln(III) ions, whereas the slightly more polar solvent (MeCN) seems to favor ionic complexes. Complexes 17•MeCN and 18•2MeOH are a pair of complexes which have the same LnIII (EuIII) and belong to the above mentioned two general types (ionic and neutral complexes). In both complexes, the EuIII center is 9-coordinate with a spherical capped square antiprismatic geometry. Yb(III) does not give in MeOH the ionic complex [Yb(pdmH2)3](SCN)3•yH2O•zMeOH, like the relatively neighboring Tb(III) and Er(III) ions which give in MeOH the ionic complexes 19•H2O•MeOH and 20•H2O•MeOH, respectively. It seems that YbIII can not adopt the coordination number 9 forming the cation [Yb(pdmH2)3]3+.(6) Weak, Ln(III)-based emission was recorded for the solid complexes 18•2MeOH and 19•H2O•MeOH at room temperature, while the unique 2F7/2→2F5/2 transition of Yb(III) was observed in the near-IR diffuse reflectance spectrum of 21.(7) Efforts to synthesize Ln(III)/MeCO2-/pdmH2 complexes were unsuccessful. The dinuclear complex [La2(O2CMe)3(NO3)2(MeOH)(pdmH2)2(pdmH)]•MeOH (22•MeOH) was isolated during our efforts to prepare heterometallic Hg(II)/Ln(III) compounds. The molecular structure of this complex exhibits some unique characteristics.(8) Complexes [Zn(pdmH2)2](NO3)2 (25, 26) are polymorphs, while [Zn(pdmH2)2](NO3)2•Me2CO (27•Me2CO) is pseudopolymorph to compounds 25 and 26.(9) The structurally interesting complexes [Zn2Ln2(O2CPh)6(NO3)2{(py)(CH2OH)(COO)}2] (Ln = Pr, 23/Ln = Tb, 24) are new, welcome members of the family of Zn(II)/Ln(III) clusters.(10) Compound [Tb(pdmH2)3][ZnCl4]Cl•3H2O (28•3H2O), which was isolated from the ZnCl2/Tb(NO3)3•6H2O/pdmH2 reaction system in MeCN under solvothermal conditions, is one of the rare examples of pseudoheterometallic Ln(III)/Zn(II) complexes. In summary, we believe that this Thesis is a contribution into the reactivity of coordinated 2-pyridyl ketones and pyridine-2,6-dimethanol, as well as into the coordination chemistry of these ligands. We shall be happy if the distinguished examiners and the readers of this PhD Thesis enjoy studying it, in the way we enjoyed obtaining the results and writing the Thesis.