The Design, Synthesis, Luminescence And Magnetic Properties Of Mixed-valance Eu(?)/Ln(?) Lanthanide Complexes

Over the past decades,researchers have been paying more and more attention to the study of the low-valent europium complexes.These complexes show great potential on the development of functional solid materials with targeted optical,magnetic,catalytic and medical applications.A series of coordination polymers with novel structures and magnetic or photo properties have been reported.Here,we designed and synthesized a novel macrocyclic ligand H₄L and its series of mixed-valent 2Eu???/4Ln???complexes and trivalent 5Ln???complexes.The existence and oxidation stability of these mixed-valent complexes have been investigated by X-band electronic paramagnetic resonance?EPR?,inductively coupled plasma?ICP?and cyclic voltammetry?CV?techniques.The luminescence and magnetic behaviors of these complexes have been tested and discussed.This dissertation is divided into six chapters.Chapter one is a brief introduction of the research.In this chapter,some basic concepts and the recent progress of mixed-valance lanthanide complexes are stated.And some related complexes are enumerated.In chapter two,the design and synthesis of macrocyclic ligand H₄L?H₄L =N,N',N,",N,"'-tetra?2-hydroxy-3-methoxy-5-methylbenzyl?-1,4,7,10-tetra-10-azacyclododecae?)are introduced.In chapter three,the self-assembly of divalent europium and trivalent lanthanide with H₄L and nicotinic acid ligand?HNIC?is discussed.At argon atmosphere,the reaction gave a series of hexanuclear molecular mixed-valance lanthanide complexes Eu^?₂Ln^?₄?OH?₄L₂?NIC?₄?Ln = La?2?,Sm?3?,Eu?4?,Tb?5?,Dy?6??.In chapter four,we used the same method and same reagents but replaced HNIC with HBZA as the second ligand.A series of hexanuclear molecular mixed-valance lanthanide complexes Eu^?2Ln^?₄?OH?₄L₂?BZA?₄?Ln = La?7?,Sm?8?,Eu?9?,Tb?10?,Dy????were obtained.In chapter five,a series of pentanuclear molecular trivalent lanthanide complexes Ln^?₅?OH?₄L₂?BZA?₄?NO₃?₃?H₂O?·CH₃OH?Ln = Y?12?,Sm?13?,Eu?14?,Tb?15?,Dy?16??were synthesized and their structures were discussed.In chapter six,the existence and oxidation stability of divalent europium in these mixed-valent 2Eu???/4Ln???complexes have been investigated by EPR,ICP and CV.Then,the luminescence and magnetic behaviors of these complexes have been investigated and discussed.It is noted that the 2Eu???/4Ln???lanthanide complexes shown interesting emission spectra composed the characteristic peaks of trivalent lanthanide ion and broad band of divalent europium ion.In addition,the pentanuclear 5Dy???complex shown slow magnetic relaxation and to be an single molecular magnet.In the last chapter,a brief conclusion and an outlook on this work are presented.