Title

Electrochemistry of molecular dyads containing fullerenes, porphyrins, or phthalocyanines and electrocrystallization of transition metal complexes

Date of Award

1999

Availability

Article

Degree Name

Doctor of Philosophy (Ph.D.)

Department

Chemistry

First Committee Member

Luis Echegoyen, Committee Chair

Abstract

Novel covalently linked "parachute-shape" C60-porphyrin dyads show appreciable electronic interactions between the two chromophores from electrochemical experiments. These C60-porphyrin dyads exhibit more of an effect on the oxidation of the porphyrin moiety due to the neighboring groups than those previously reported (by the Diederich and Hirsch groups), where the porphyrin rings were held much closer to the fullerene core. Electrochemical reductions of new C60-donor and C60-acceptors appear to be highly localized, taking place either on the fullerene core or on the addend, depending on the relative electron affinities. ESR spectra are consistent with the electrochemical observations except for the penta-anion of the C 60-acceptors. The notable regioselectivity of template-mediated hexa-additions of malonates to octahedral [6,6] double bonds of C60 allows for the facile synthesis of globular functional dendrimers with high core branching multiplicities involving a porphyrin chromophore. The neighboring dendra determine the nanoenvironment of the fullerene causing the shift of the first reduction potential to more negative values with increasing generation number. A fullerene-fused 2,9-diphenyl-1,10-phenanthroline was prepared by the reaction of 5,6-bis(bromomethyl)-2,9-diphenanthroline with C60 in the presence of I-. The compound reacts with Ag(CF3SO3) in chloroform to form a complex, which is the first example of a non-covalent dimer of [60]fullerene. [60]Fullerene reacts with 1,8-bis(bromomethyl)naphthalene in the presence of KI/18-crown-6 to form a C60 derivative with a seven-membered ring fused to a [6,6] junction. A cycloaddition mechanism is suggested. To our knowledge, this C60 derivative is the first example of [60]fullerene derivative containing a fused seven-membered ring.The electronic properties of a series of molecular dyads, consisting of two homo- or heterodimetallic (M = M' = Zn II or M = ZnII, M' = Co II) phthalocyaninato complexes bridged by mono- and bis-DEE [DEE = (E)-1,2-diethynylethene, (E)-hex-3-ene-1,5-diyne] fragments were investigated electrochemically, and data were compared to those of previously prepared phthalocyanine (Pc) dyads. Substantial electronic communication between the two Pc units in the dyads across the DEE bridges was revealed in the electrochemical studies.Reductive electrocrystallization of [Ru(terpy)2](PF6 )2 (where terpy = 2,2'--6 ',2″-terpyridine) results in the formation of black crystals. X-ray analysis reveals that the crystals consist exclusively of [Ru(terpy)2]0, with no solvent or counteranion present in the lattice. [Ru(terpy)2]0 units are structurally very similar to the parent [Ru(terpy)2]2+. Analysis of the crystal packing shows that [Ru(terpy)2] 2+ crystals have close intermolecular distances, while [Ru(terpy) 2]0 crystals show only intermolecular interactions along the c axis with contacts that are less than 3.5 A. Analysis of molecular volumes and empty spaces reveals the presence of cavities, which could contain substantial electron density.

Keywords

Chemistry, Analytical; Chemistry, Physical

Link to Full Text

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