CMDITR Review of Undergraduate Research - Pluto - University of ...

Synthesis of Azaindoly-phenanthroline Spirooxazine
Lea Dankers, University of Wisconsin-River Falls
Dinesh G. Patel and Natia L. Frank
Frank Lab, Dept. of Chemistry, University of Washington
The synthesis of azaindoly-phenanthroline
spirooxazine was begun. The proposed
spirooxazine should isomerize upon exposure to
UV light then revert to its original state
thermally or upon exposure to visible light. A
metal will be attached to the molecule and the
molecule should then exhibit changes in
magnetic properties as well as optical properties
depending on isomerization state.
Introduction
With the growing need for ultra-high density
storage methods, research into data storage
technologies has begun to focus on
multifunctional materials in which two or more
functionalities, such as optical, magnetic, and
conducting functionalities have been
incorporated into one material. Such systems
allow the interfacing of optical data transfer and
storage with magnetic recording technologies
(photomagnetic), or semiconductor technologies
with magnetic recording (magnetoelectronics).
Photomagnetism has its mesoscopic partner in
magneto-optics, the state of the art for ultra- high
density storage. In such systems, changes in
magnetic anisotropy lead to changes in the
polarization dependent optical properties of a
material. There is great interest however, in
developing optically tunable materials in which
irradiation with specific wavelengths leads to
changes in magnetic state, leading to truly
photomagnetic read/write processes.
Certain molecules, known as photochromes,
have the ability to change properties when
exposed to either ultraviolet or visible light. The
changes in electronic structure accompanying
photochromism can be engineered to lead to
changes in optical or magnetic properties. We
are currently studying a class of photochromes,
the spirooxazines, due to their synthetic
versatility, ease of derivatization, and their high
fatigue resistance. Upon irradiation with UV
light, cleavage of the C spiro -O bond of the
oxazine ring portion of the molecule occurs, as
shown in Figure 1. The resulting
photomerocyanine has an absorbance band in the
visible range (~600 nm). The reformation then
occurs either thermally, or upon exposure to
visible light (λ > 500 nm) causing ring closure.
The synthesis of two new spirooxazines is
proposed in which nitrogen incorporation and
metal binding moieties may lead to interesting
photochromic and magnetic metal complexes.
The experiments proposed will examine if
changes in magnetic behavior can be optically
induced and if the optically induced states are
stable.
The target spirooxazines are shown in
Figure 2. The first spirooxazine, azaindolylphenanthroline
spirooxazine (SPITNO),
proposed is one in which an azaindolyl moiety
will be incorporated into the spirooxazine
structure. Incorporation of nitrogen into the
indolyl moiety is expected to lead to increased
electron withdrawing ability of the indolyl ring
system, leading to increased stability of the
spirooxazine closed form. The second
spirooxazine proposed is one in which a
bipyridyl moiety will be incorporated into the
spirooxazine structure (2). Incorporation of
bipyridine into the oxazine moiety is expected to
lead to effective binding of metal ions with a
decreased ligand field from that of the parent
phenthroline ligands studied in the Frank lab.
Figure 1. Photochromism in spirooxanzines: C-O
bond cleavage when exposed to UV light and
reformation when exposed to visisble light.
Figure 1. Photochromism in spirooxanines:
C-O bond when exposed to UV light and
reformation when exposed to visible light.
Figure 2. Target Molecules
CMDITR Review of Undergraduate Research Vol. 1 No. 1 Summer 2004 29