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Synthesis, structures and magnetic properties of mono- and polynuclear coordination compounds with ligands based on 2-formylpyridine and salicylaldehyde


Author: Palamarciuc Oleg
Degree:doctor of chemistry
Speciality: 02.00.01 - Inorganic chemistry
Year:2012
Scientific adviser: Mihail Revenco
doctor habilitat, professor, Moldova State University
Scientific consultant: Rodolphe Clérac
doctor habilitat în fizico - chimie, cercetător CNRS, Bordeaux, Franţa
Institution: Moldova State University
Scientific council: DH 05-02.00.01
Institute of Chemistry of the ASM

Status

The thesis was presented on the 6 April, 2012
Approved by NCAA on the 23 May, 2012

Abstract

Adobe PDF document13.00 Mb / in romanian

Keywords

coordination compounds, polyfunctional ligand, manganese, magnetic properties, template reaction

Summary

The thesis consists of introduction, 5 Chapters, Conclusions and Recommendations, Bibliography list with 119 references. It comprises 170 pages, 26 tables, 99 figures and 12 annexes. The results were published in 15 scientific papers.

Field of study and thesis objectives. The thesis is devoted to the use of new coordination agents for synthesis and investigation of polynuclear coordination compounds of Cu, Ni, Fe and Mn with ligands derived from salicylaldehyde and 2 - formylpyridine as potential precursors for assembling magnetic materials, to develop reproducible methods of synthesis, separation and purification, to determine the crystal structure and magnetic properties of obtained compounds.

To achieve the proposed goal a number of tasks were planed and realised: synthesis of organic species with versatile coordination behavior, using traditional and template reaction methods, elaboration of new and improvement of the known methods permiting to prepare the polynuclear coordination compounds of Cu(II), Ni(II), Fe(III), Mn(II) and Mn(III), to find the conditions to obtain monocrystals for X-Ray determination of their structure, to determin the magnetic properties and establish the nature of the magnetic interaction between the paramagnetic centers.

Scientific novelty and originality. Original methods of synthesis and separation of 31 new coordination compounds with increased nuclearity were developed and their crystal structures and magnetic properties were determined. It was shown that the Girard T reagent hidrazones prepared on the base of 2- formylpyridine and salicylaldehyde avoid the coordination in cationic form, as a results of strengthening the acid-base properties after coordination. An increased reactivity was observed for the thiosemicarbazidic fragment by highlighting three new types of transformations (addition, amidation and disulfurization reactions), providing the formation of new coordination copper(II), nickel(II) and manganese(III) compounds of high nuclearity. A new family of unidimensional polymer coordination compounds based on salicylaldehyde thiosemicarbazone, containing paramagnetic centers of Mn(III) with high anisotropy and possessing the molecular magnets properties has been developed.

Theoretical significance and practical value. New aspects of reactivity of the thiosemicarbazidic fragment has been described and the mechanism of the reactions resulting in template formation of asymmetric previously unknown ligands was proposed. These reactions and different coordination agents, were used for the synthesis of more than 30 new coordination compounds. Among them, a new family of polymeric chain coordination compounds with properties of molecular magnets, was found.