Anilate-based Functional Molecular Materials with Conducting and Magnetic Properties

This work reports on the design, synthesis and characterization of novel anilate-based functional molecular materials showing magnetic and conducting properties. The family of anilate ligands comprises several derivatives obtained by introducing various substituents (H, F, Cl, Br, I, CN, Me, NO2, etc.) at the 3 and 6 positions of a common 2,5-dihyroxy- 1,4-benzoquinone framework. Their electronic/structural features, coordination modes and ability to mediate magnetic exchange interactions between coordinated metal centers make them suitable candidates for the preparation of the above-mentioned materials. In Chapter 1, the syntheses of novel anilate-based ligands (anilate = An) having thiophene (Th), 3,4-ethylenedioxy-thiophene (EDOT), or Cl/CN as substituents are presented, along with their crystal structures, the investigation of the emission (Cl/CN derivative) or charge-transfer (Th, EDOT derivatives) properties and preliminary coordination chemistry studies. Chapter 2 reports on a general synthetic strategy to achieve rationally designed tris-chelated octahedral paramagnetic metal complexes, based on the combination of CrIII and FeIII as metal ions with chloranilate, bromanilate, iodanilate, hydranilate and chlorcyananilate as ligands. The crystal structure analyses, spectroscopical and electrochemical features, density functional theory calculations, and the magnetic properties of these metal complexes of general formula [A]3[MIII(X2An)3] (A = (n-Bu)4N+, (Ph)4P+; MIII = Cr, Fe; X = Cl, Br, I, H, Cl/CN) are described. In Chapter 3 a novel class of molecule-based ferrimagnets formulated as [A][MnIIMIII(X2An)3] (A = [H3O(phz)3]+, (n-Bu)4N+; MIII = Cr, Fe; X = Cl, Br, I, H), obtained according to the “complex-asligand” approach by combining MnII metal ions with the [M(X2An)3]3- molecular building blocks described in Chapter 2, is reported. The crystal structures and the magnetic properties for these compounds are described, and the structure/properties correlation observed between the ordering temperature values and the electron density on the ligand ring, associated with the electron withdrawing properties of the X substituents, is particularly highlighted. Chapter 4 reports on the structural diversity and the physical properties of three new paramagnetic molecular conductors obtained combining the BEDT-TTF organic donor and the [Fe(Cl2An)3]3- metal complex as conducting and magnetic building blocks, respectively. The correlation between the crystal structure and conductivity behavior is reported. Finally, in Chapter 5, the crystal structures and the physical properties of a complete series of isostructural chiral molecular conductors obtained by combining the TM-BEDT-TTF organic donor in its (S,S,S,S) and (R,R,R,R) enantiopure forms, or their racemic mixture (rac), with 2D heterobimetallic anionic layers obtained in situ by association of tris(chloranilato)ferrate(III) metal complexes and potassium cations are described. As far as the framework of the thesis is concerned, this work is organized as follows. Part I contains a general introduction on molecular materials, the state of the art and the aim of the work. Part II contains the obtained results and their discussion divided in 5 Chapters whose content has been summarized above. Part III contains the conclusions and the perspectives for this work. Finally, Part IV contains 5 Appendixes where additional information (basic principles of conductivity and magnetism, details on the electrocrystallization technique, etc.) are given.