Synthesis, molecular and solid state structures, and magnetic properties of sandwich lanthanide phthalocyanines lacking C-H bonds

Author

Wycliffe A. Graham, New Jersey Institute of Technology

Document Type

Dissertation

Date of Award

Spring 5-31-2012

Degree Name

Doctor of Philosophy in Materials Science and Engineering - (Ph.D.)

Department

Committee for the Interdisciplinary Program in Materials Science and Engineering

First Advisor

Joseph W. Bozzelli

Second Advisor

Trevor Tyson

Third Advisor

N. M. Ravindra

Fourth Advisor

S. G. Greenbaum

Fifth Advisor

Ken Keunhyuk Ahn

Sixth Advisor

Haidong Huang

Abstract

A new class of sandwich phthalocyanine (Pc) compounds without C-H bonds was synthesized and characterized. They are the bis[octakis(perfluoro i-C₃F₇) octakis(perfluoro)phthalocyaninato(2−)]M(III) complexes, formulated as (F₆₄Pc)₂MH, M = Tb, Dy, Lu, Y. Single molecular magnetic (SMM) behavior in the (F₆₄Pc)₂TbH and (F₆₄Pc)₂DyH complexes was confirmed through slowed relaxation response of their magnetization in an applied time varying magnetic field during alternating current (AC) magnetic testing in the range 2 - 50 K. The energy barrier to magnetic reversal, Δ = 215 cm^-1 and the pre-exponential factor, τ₀^-1 = 2.7 x 10^7-1 were estimated for the undiluted (F₆₄Pc)₂TbH with direct current bias magnetic field (Hdc) of 1000 Oe applied. Undiluted (F₆₄Pc)₂DyH gave estimated values of Δ = 31 cm^-1 and τ₀^-1 = 1.6 x 10⁵ s^-1 at Hdc = 500 Oe. These respective values are within the range observed for the unsubstituted Tb and Dy analogues. Magnetic hysteresis testing at 0.04 K exhibited hysteresis in both of these complexes. Magnetic circular dichroism (MCD) tests on (F₆₄Pc)₂Tb frozen in acetone at 1.8-1.9 K exhibited a “butterfly shaped” hysteresis which appeared to depend on the oxidation state of the complex and which also provided evidence of quantum tunneling of magnetization. The chemical tuning of the Pc macrocycle of these complexes through the replacement of the H atoms with the electron withdrawing fluorine atom and i-C₃F₇ group has created additional functionalities. Thermal analysis in the forms of thermogravi metric analysis and differential scanning calorimetry showed the complexes to be stable up to 450°C in air and N₂. Cyclic voltammetry revealed four reduced and one oxidized states, the oxidized state occurring at > 1.2 V, showing the complexes’ resistance to oxidation. The (F₆₄Pc)₂MH compounds derive their uniqueness as [(F₆₄Pc)₂M]− sandwich phthalocyanine complexes with exceptional thermal and oxidative stability.

Recommended Citation

Graham, Wycliffe A., "Synthesis, molecular and solid state structures, and magnetic properties of sandwich lanthanide phthalocyanines lacking C-H bonds" (2012). Dissertations. 319.
https://digitalcommons.njit.edu/dissertations/319