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Dissertation Information for Sarah Dunbar McMullen

NAME:
- Sarah Dunbar McMullen

DEGREE:
- Ph.D.

DISCIPLINE:
- Chemistry

SCHOOL:
- Emory University (USA) (2002)

ADVISORS:
- Karl S. Hagen

COMMITTEE MEMBERS:
- Craig L. Hill
- Luigi G. Marzilli

MPACT Status: Fully Complete

Title: Solid-state structures and NMR studies of exchange reactions in paramagnetic divalent metal carboxylates

Abstract: Fundamental studies of structure and reactivity of carboxylate bridged dinuclear complexes with Fe(II), Co(II), Ni(II) are presented. Reactivity of these paramagnetic complexes was monitored by 1 H, 2 H, and 19 F NMR 1D and 2D spectra of reactions involving carboxylate and metal ion exchange between and within complexes.

The exchange rates on complexes of the type M 2 (H 2 O)(RCOO) 4 (tmen) 2 , ( 1 ) R = CF 3 , Me 3 C, Ph, and p -FPh were reexamined at higher fields and with 2D COSY techniques (including the first application of COSY techniques using 19 F). These rapid exchange rates resulted in three or ten species, for metal and carboxylate exchange, respectively that reached equilibrium within minutes. Greater control of reactivity was obtained with a new series of ì-carboxylato dimers using the strapped, dinucleating ligand 1,3-bis[(2-dimethylaminoethyl)iminomethyl]benzene (baib) were the general formula is [M 2 (baib)(RCOO) 3 ](BPh 4 ), ( 2 ). Extensive characterization of crystalline solids by X-ray crystallography revealed multiple polymorphs and temperature dependant phase transitions with some of the Co(II) complexes. Concentration dependant inter-molecular metal and carboxylate exchange was shown with 2 but with dramatically slower rates than for 1 . Exchange reactions of acetate and benzoate with 2 -Fe were fast on the NMR timescale, but reactions of bulkier carboxylates were slower. Metal exchange rates could be slowed to minutes, hours, or days with increasing size of carboxylate or going from Fe to Co to Ni.

This dinucleating ligand was also used in the synthesis of isostructural ì 4 -OH Fe(II) and Co(II) tetranuclear complexes: [M 4 (ì 4 -OH)(ì-OH) 4 (baib) 2 ](OTf) 3 . Their decomposition within hours in solution was monitored by 1 H NMR.

Template Schiff base formation reactions of isophthalaldehyde with N,N -dimethylethylenediamine Fe(II) and Co(II) complexes [M(PhCOO) 2 (dmen) 2 ], [M 3 (PhCOO) 6 (dmen) 2 ], afforded [M 2 (baib)(PhCOO) 4 ]. Reactions were monitored by NMR and crystals characterized by crystallography. Also studied were the Fe(II), Co(II) and Ni(II) complexes [M 5 (OH) 2 (PhCOO) 6 (L) n ](OTf) 2 , ( 3 -L-M) with L = ethylenediamine (en, 3 -en), N,N -dimethylethylenediamine (dmen, 3 -dmen), acetonitrile (MeCN, 3 -MeCN) and 1,3-bis[(aminoethyl)iminomethyl]benzene (baib-4Me, 3 -baib-4Me). Reaction of the 3 -en-Fe and 3 -en-Co with isophtalaldehyde led to the formation of the pentamer with the new ligand baib-4Me ( 3 -baib-4Me-Fe and 3 -baib-4Me-Co). But neither 3 -en-Ni or 3 -dmen-M reacted with isophthalaldehyde.

A direct measure of the magnetic anisotropy mono-, di, and pentanuclear complexes was demonstrated with quadrupolar splitting using 2 H NMR.

MPACT Scores for Sarah Dunbar McMullen

A = 0
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A+C = 0
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TD = 0
TA = 0
calculated 2008-03-23 21:22:03

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