Synthesis, structure and magnetism of discrete coordination clusters using carboxylate-appended (2-pyridyl)alkylamine ligands

Manda, Munirathnam (2024) Synthesis, structure and magnetism of discrete coordination clusters using carboxylate-appended (2-pyridyl)alkylamine ligands. PhD thesis, Indian Institute of Science Education and Research Kolkata.

Text (PhD thesis of Munirathnam Manda (14RS083)) 14RS083.pdf - Submitted Version Restricted to Repository staff only Download (12MB)

Abstract

Discrete polynuclear coordination complexes with carboxylate-appended (2-pyridyl)alkylamine ligands or their Schiff base derivatives remain of interest for magneto-structural research. The structural diversity and topological beauty of polynuclear coordination clusters draw attention in addition to their intriguing magnetic properties. Bioinorganic modelling and magnetic materials provide the drive for the fabrication and structural characterization of 3d-metal bi- and poly-nuclear coordination clusters connected by carboxylates. The aim of this area of research is to understand the fundamental structural elements that control the magnetic-exchange interaction between paramagnetic centers via carboxylate-bridge mediation. Carboxylates have distinct triatomic syn-syn, syn-anti, anti-anti, and monoatomic bridging properties, which make them ideal linkers between metal ions for the propagation of metal-ligand coordination units. The research results presented in this thesis explore detailed coordination chemistry between the deprotonated form of carboxylate-appended (2-pyridyl)alkylamine ligands i.e., {L¹-(CO₂⁻)}Li⁺, {L³-(CO₂⁻)}Li⁺, {L⁷-(CO₂⁻)₂}2Li⁺ and {L⁸-(CO₂⁻)}Li⁺ with first-row transition-metal ions. Using{L⁸-(CO₂⁻)}Li⁺ ligand, four novel dimeric complexes of Mn(II), Co(II), Ni(II) and Cu(II) and three tetrameric mix bridged complexes of Mn(II), Co(II) and Ni(II) have been synthesized and characterized. {L¹-(CO₂⁻)}Li⁺ is used to make tetranuclear tetrahedral cage-like Co(II) complex. Two rectangular type Ni(II) pentamers have been synthesized using {L¹-(CO₂⁻)}Li⁺ and {L³-(CO₂⁻)}Li⁺ ligands. {L⁷-(CO₂⁻)₂}2Li⁺ ligand with appended two carboxylate moieties used to create two high-nuclearity discrete tridecanuclear Co(II) and Ni(II) complexes. All these complexes characterized by elemental analysis, IR and UV/Vis spectroscopy. Purity of the complexes tested by PXRD. Temperature-dependent magnetic susceptibilities for the above complexes are measured in the temperature range of 2–300 K.

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