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Date of Award

1994

Document Type

Dissertation - Pacific Access Restricted

Degree Name

Doctor of Philosophy (Ph.D.)

Department

Chemistry

First Advisor

Larry Spreer

First Committee Member

John Otvos

Second Committee Member

Patrick Jones

Third Committee Member

Donald Wedegaertner

Fourth Committee Member

Michael Minch

Abstract

The study of macrocyclic ligands for complexation of alkali metals (macrobicyclic polyether cryptands) and transition metals (tetraaza macrocycles) is reported. The synthesis of a new bis(phosphotriester) macrobicyclic polyether cryptand, O = P (O(CH$\sb2)\sb2\rm O(CH\sb2)\sb2O(CH\sb2)\sb2O\rbrack\sb3$ P = O, 1, called phosphocrypt, and its acyclic tripodal precursor O = P (O(CH$\sb2)\sb2\rm O(CH\sb2)\sb2O(CH\sb2)\sb2OH\rbrack\sb3$, 2, is described. Aqueous stability constants (K$\sb{\rm s}$) measured with a cation selective electrode with potassium and rubidium are 10$\sp{3.7}$ and 10$\sp{3.6}$ for 1, and are 10$\sp{3.6}$ and 10$\sp{3.0}$ for 2, respectively. The K$\sb{\rm s}$ values for phosphocrypt are 1000 fold greater than comparably sized nitrogen bridgehead cryptands. $\sp1$H and $\sp{13}$C NMR indicate 1 is flexible at 20$\sp\circ$C. Molecular mechanics calculations confirm the flexibility of 1. Also reported are the synthesis and characterization of (1) a new mixed-valence bimetallic ruthenium complex, Ru$\sb2\rm (C\sb{20}H\sb{36}N\sb8)Cl\sb{4}\sp{+}$, 3, that contains a cross-conjugated bridge that links two tetraaza macrocycles; and (2) the formation, physical properties, and reduction chemistry of a new iron $\beta$-diimine keto macrocyclic complex, Fe(C$\rm \sb{10}H\sb{18}N\sb{4}O)(CH\sb3CN)\sb{2}\sp{2+},$ 4. The ruthenium dimer 3 was formed by oxidative dehydrogenation of Ru(C$\rm\sb{10}H\sb{24}N\sb4)(Cl\sb2)\sp+$ and its mass was determined by positive ion fast atom bombardment mass spectrometry. The binuclear species 3 is assigned as a Robin and Day strongly coupled class III mixed-valence species based on cyclic voltammetry, electronic spectroscopy, and X-ray photoelectron spectroscopy (XPS). The XPS photopeaks of 3 for the binding energies from the Ru 3p$\sb{1/2}$ and Ru 3p$\sb{3/2}$ regions show only a single peak, indicating the unpaired electron is delocalized on the short (10$\sp{-17}$ s) timescale of the XPS experiment. The keto complex 4 was formed in high yields ($>$90%) from the reaction of Fe$\rm\sb2(C\sb{20}H\sb{36}N\sb8)(CH\sb3CN)\sb{4}\sp{4+}$, 5, (the diiron analog of 3) with molecular oxygen. Its mass was determined by electrospray mass spectrometry and its structure by NMR spectroscopy ($\sp1$H, $\sp{13}$C, COSY, NOE DIFF). The complex is rigid at room temperature in CD$\sb3$CN and this allows the assignment of the ten distinct protons. Reduction of the keto group in 4 under anaerobic conditions, followed by aerobic oxidation, leads to the reformation of 5.

Pages

133

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