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Synthesis and structural characterisation of polynuclear d-block metal complexes
Godfrin, Sylvie
THESIS 7832 The research presented in this thesis lies within the area of coordination chemistry and the study of polynuclear metal complexes. More specifically, this project involves the synthesis and structural and magnetic (for some examples) characterisation of novel polynuclear d-block metal complexes, featuring either C3-symmetric tripodal Schiff base ligands or small tridentate ligands. Chapter 2 details the attempts at the complexation of the C3-symmetric tripodal hexadentate Schiff base ligands, cis,cis- and cis,trans-tris(salicylideneamino)cyclohexane (H3L2a and H3L2b), which consist of phenol groups appended to a 1,3,5-triaminocyclohexane (L1) backbone. The crystal structure of L1a.3HBr and H3L2a are described and show the formation of 3D networks through hydrogen bonding. Linear trinuclear d-block metal complexes (L2a)2M3 (M(II) = Cd (1), Mn (2), Ni (solvates 3 and 4), Zn (5), Co (solvates 6 and 7), as well as (HL2b)2Co3(OAc)2·CHCl3 (8) were isolated and structurally characterised. Moreover, the complexation of H3L2a and H3L2b with Cu(II) was studied, resulting in the isolation of the tetranuclear complex (L2b)2Cu4 (solvates 9 and 10) and the mononuclear complex (HL2a)Cu (11), even though a 2:3 ligand-to-metal ratio was used. However, no trinuclear Cu(II) complex was isolated. Single crystals of all these complexes were isolated and structurally characterised. Magnetic measurements for the Mn(II) and Ni(II) trinuclear complexes revealed an antiferromagnetic coupling for the former and a ferromagnetic coupling for the latter. Chapter 3 describes the synthesis and structural characterisation of paramagnetic first row transition metal complexes incorporating 2,6-pyridinedimethanol (H2L3) or 2,6-bis(hydroxymethyl)-4-methylphenol (H3L6). A discrete novel manganese undecanuclear cluster incorporating H2L4, [Mn11(L4)2(OAc)13O6(H2O)4]·MeOH·3.8H2O (12), was synthesised. It is a mixed-valence MnII 4MnIII7 compound. The most remarkable feature of this reaction is the in situ formation of H2L4 from the reaction of two molecules of H2L3. A mononuclear manganese complex featuring H2L4, [Mn(H2L4)(OAc)(H2O)](OAc) (13), was also isolated from the same reaction, whose noticeable feature is the presence of two enantiomers in the non-chiral space group P-1. Moreover, hydrogen bonding of the mononuclear complex of H2L4 with an acetate molecule led to the formation of a pseudo-macrocycle, which is then further hydrogen bonded into 2D sheets. H2L3 also yielded a tetranuclear manganese and nickel complex, [Mn4(HL3)4(OAc)4(OMe)2]·1.6MeOH·3.4H2O (14) incorporating a mixed valence MnII 2MnIII 2 planar diamond core and [Ni4(HL3)3(OAc)5(HOMe)2]·3H2O·MeOH (15) featuring a novel open cubane core due to a m3-bridging acetate. However, attempts to get a similar nickel complex to 14 featuring the bidentate ligand pyridine-2-methanol (HL5) failed, only mononuclear complex Ni(HL5)2(OAc)2 (16) was isolated. Furthermore H3L6 led to the isolation of the novel 1D linear copper(II) polymer {Cu3(HL6)2(OAc)2(MeOH)}n (17), whose crystal structure was determined. The chains result from the bridging of adjacent Cu(II) centres via two m2-oxygen atoms and then assemble into 2D sheets via hydrogen bonding interactions. Chapter 4 contains results of the synthesis and complexation of C3-symmetric tripodal Schiff base ligands, heptadentate H3L7 and L8, and hexadentate L9a and L9b. These ligands incorporate either an L1 or a tren backbone, to which are appended three phenol or pyridine groups. The crystal structure of the ligand H3L7 is described herein. A linear trinuclear complex (L7)2Cd3 (18), whose structure is very similar to complex 1, was isolated. Futhermore, L8 formed both a trinuclear and a mononuclear complex featuring Ag(I), [(L8)2Ag3](PF6)3 (19) and [(L8)Ag](PF6) (20). Finally, complex 20, along with mononuclear complexes [(L8)Cu](PF6)2 (21) and [(L9a)Fe](PF6)2 (22), whose structures are described herein, exist as two enantiomers due to the ability of L8 and L9a to form a twist towards the left or towards the right by coordination. Chapter 5 provides the experimental details for the synthesis of the compounds described herein.
Keyword(s): Chemistry, Ph.D.; Ph.D. Trinity College Dublin
Publication Date:
Type: Doctoral thesis
Peer-Reviewed: Unknown
Language(s): English
Institution: Trinity College Dublin
Citation(s): Sylvie Godfrin, 'Synthesis and structural characterisation of polynuclear d-block metal complexes', [thesis], Trinity College (Dublin, Ireland). School of Chemistry, 2006, pp 219
Publisher(s): Trinity College (Dublin, Ireland). School of Chemistry
Supervisor(s): Kruger, Paul E.
First Indexed: 2017-09-14 06:51:21 Last Updated: 2020-07-28 08:26:49