Studies of Rotaxanes Consisting of 1,10-Phenanthroline-Based Macrocycles and Platinum-Capped Polyynediyl Complexes: a Steric and Dynamic Approach to Insulated Molecular Wires
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The objective of this dissertation is the steric insulation of diplatinum polyynediyl complexes through the assembly of rotaxanes, a class of mechanically interlocked molecules (MIMs). The synthetic approach to these MIMs takes advantage of the active metal template employing a copper(I) iodide macrocycle complex as the site of an oxidative homocoupling of two terminal alkynes. Various structural modifications to the macrocyclic precursors are explored. Firstly the chemistry of polyynes emphasizing diplatinum polyynediyl complexes as model compounds for molecular wires is presented. Previous studies have revealed a need for steric insulation of these unsaturated linkers and earlier attempts in this direction are introduced. Here, a new approach to the steric insulation employing rotaxanes will be discussed. Following, a series of macrocyclic precursors to rotaxanes equipped with a 1,10- phenanthroline moiety available for coordination with copper(I) iodide are described. These complexes serve as active templates in the syntheses of rotaxanes. Various α,ω- bis(bromoalkoxy)aryl precursors are prepared via Williamson ether synthesis. These dibromides are condensed with 2,9-bis(4-hydroxyphenyl)-1,10-phenanthroline in the presence of K2CO3 to give the corresponding 31- to 35-membered macrocycles. When the macrocycles are treated with copper(I) iodide, mononuclear 1:1 complexes form in which the metal cation chelates to the nitrogen donor atoms of the phenanthroline moiety. The crystal structures of the synthesized macrocycles and their corresponding complexes are determined and analyzed in the context of DFT calculations and rotaxanes that can be formed by treatment of the copper(I) iodide macrocycle complexes with terminal alkynes (e.g., macrocycle dimensions, void volumes). The copper and iodide atoms significantly protrude from the least squares plane of the phenanthroline moiety (0.46-0.63 Å and 1.65-2.07 Å). Lastly, the syntheses of various platinum-capped polyynediyl containing rotaxanes by the oxidative homocoupling of the monoplatinum polyynyl complexes trans-(Cv6Fv5)(p-tolv3P)v2Pt(C≡vC)n/2H in the presence of copper(I) iodide adducts of the 1,10-phenanthroline-based macrocycles 2,9-(1,10-phenanthrolinediyl)(p- Cv6Hv4O(CHv2)v6O)v2(1,3-Cv6Hv4) or 2,9-(1,10-phenanthrolinediyl)(p-Cv6Hv4O(CHv2)v6O)v2(2,7- naphthdiyl) are described. All of these MIMs feature a Pt(C≡vC)vnPt unit (n = 4, 6, 8) that is threaded through the macrocycle. Crystal structures of three rotaxanes are determined and analyzed in detail, particularly in regards to geometric perturbations and the degree of steric Cvsp chain insulation. The ^1H NMR spectra show a number of noteworthy shielding effects. UV-visible spectra exhibit negligible electronic interactions between the Pt(C≡C)vnPt axles and macrocycles, although cyclic voltammetry data suggest rapid reactions following oxidation. Finally, the findings of this work are summarized and a perspective on potential future studies in this area is offered.
mechanically interlocked molecules
platinum alkynyl complex
Williamson ether synthesis
Baranova, Zuzana (2017). Studies of Rotaxanes Consisting of 1,10-Phenanthroline-Based Macrocycles and Platinum-Capped Polyynediyl Complexes: a Steric and Dynamic Approach to Insulated Molecular Wires. Doctoral dissertation, Texas A & M University. Available electronically from