Thesis

Novel imidazolium salts, N-Heterocyclic carbenes and their coordination polymers

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Awarding institution
  • University of Strathclyde
Date of award
  • 2012
Thesis identifier
  • T13329
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Abstract
  • N-heterocyclic carbenes (NHCs) have been developed in the last two decades as an important material in homogenous catalysis. Also MOFs have recently been receiving a great deal of attention due to their potential applications e.g. gas storage, adsorption and catalysis. This study involved the synthesis of new imidazolium salt functionalised with nitriles, carboxylates and pyridyl and their conversion into NHC complexes and porous coordination polymers. A series of nitrile substituted imidazolium salts were synthesised. 1,1-bis(4-cyanophenyl)-3,3-methylenediimidazolium and 1-bromomethyl-3-(4-cyanophenyl)imidazolium salts were synthesised by N-arylation and N-alkylation of 4-cyanophenyl imidazole. The bisimidazolium salt was used to synthesise a dimeric silver(I) NHC complex. Reaction of this silver complex with [Ru(p-cy)Cl₂]₂ results in transmetallation and the formation of the NHC complex [Ru(L)Cl]BF₄. A platinum diNHC complex, [Pt(L)Br₂], was synthesized by in situ deprotonation of the bisimidazolium salt precursor, using NaOAc and [Pt(COD)Cl₂]. All were characterised crystallographically. Picolyl substituted imidazolium salts were synthesised, 1,3-bis(4-picolyl)imidazolium, 1,3-bis(2-picolyl)imidazolium and 1-(4-cyanophenyl)-3-(4-picolyl)imidazolium salt were synthesised using solvothermal synthesis and were characterised spectroscopically, by elemental analysis and X-ray crystallographic analysis. 1,3-bis(2-picolyl)imidazolium chloride was prepared according to literature method while the 1-methyl-3-(4-picolyl)imidazolium salt was synthesised from the methyl imidazole and 4-picolyl chloride. All the picolyl substituted imidazolium salts were converted to Ag(I) NHC complexes of the type [Ag(NHC₂]⁺. The bis 4-picolyl imidazolium was used to synthesise two isostructural highly porous coordination polymers of Ag(I) and Cu(I). New carboxylate imidazolium salts, 3,3'-methylenebis(1-(4-carboxyphenyl)-1H-imidazol-3-ium), 1,3-bis(4-carboxyphenyl)-1H-imidazol-3-ium, 1,3-bis(3-carboxyphenyl)-1H-imidazol-3-ium, 3-(4-carboxyphenyl)-1-methyl-1H-imidazol-3-ium and 1-benzyl-3-(4-carboxyphenyl)-1H-imidazol-3-ium salts were prepared from hydrolysis of the corresponding nitrile imidazolium salts in HX (X = Br, Cl). The 1-benzyl-3-(4-carboxyphenyl)-1H-imidazol-3-ium imidazolium salt formed a rhodium diNHC complex [Rh(L)₂Br(CO)] by reacting the ligand with rhodium acetate in a solvothermal process. The 1,3-bis(4-carboxyphenyl)imidazolium salt reacted with LnCl₃.XH₂O in DMF under a solvothermal process to give two isostructural MOFs of La(III) and Ce(III).
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DOI
Date Created
  • 2012
Former identifier
  • 967046

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