Some applications related to Chapter 11 material:

1

• Some applications related to Chapter 11 material
• We will see how the kind of basic science we
  discussed in Chapter 11 will probably lead to
  good advances in applied areas such as
• 1- Design of efficient solar cell dyes based on
  charge transfer absorption.
• 2- Strongly luminescent materials based on the
  Jahn-Teller effect.

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1- Design of efficient solar cell dyes based on
charge transfer absorption
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diimine
dithiolate
These complexes should have charge transfer from
metal or ligand orbitals to the p orbitals.
4
CT-band for Pt(dbbpy)tdt
Data from Cummings, S. D. Eisenberg, R. J. Am.
Chem. Soc. 1996, 118 1949-1960
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X- Chloride
X-thiolate
dx2-y2
?bpy
hv
CT to diimine

? (thiolate) d ? (Pt)
dxy
dxz-yz
dxz-yz
dz2
Connick W. B. Fleeman, W. L. Comments on
Inorganic Chemistry, 2002, 23, 205-230
? bpy
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Electronic absorption spectra for dichloromethane
solutions of (dbbpy)Pt(dmid), 1, (thin line) and
(dbbpy)Pt(dmid)2TCNQ, 3, (thick line) in the
UV/VIS region (left) and NIR region (right).
Smucker, B Hudson, J. M. Omary, M. A. Dunbar,
K. Inorg. Chem. 2003, 42, 4717-4723
7

• So our data for Pt(dbbpy)(dmid) suggest that the
  lowest-energy absorptions are transitions so the
  LUMO is dx2-y2
• The literature for Pt(dbbpy)(tdt) and for the
  M(diimine)(dithiolates) as a class assigns the
  LUMO to be diimine p instead of dx2-y2
• So is there something magical about dmid that
  changes the electronic structure from that for
  analogous complexes with tdt and other
  dithiolates???
• Or is the difference simply due to an
  instrumental technicality as Eisenberg and
  Connick used UV/VIS instruments that only go to
  800 nm while we used a UV/VIS/NIR instrument that
  goes deep into the NIR (down to 3300 nm)?
• Lets see.. we made Pt(dbbpy)(tdt) !!

Pt(dbbpy)(dmid)
Pt(dbbpy)(tdt)
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563
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LUMO
Clearly a dx2-y2 orbital, not a diimine p
hv
HOMO
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MO diagram for the M(diimine)(dithiolates)
class!!!
So the lowest-energy NIR bands are d-d
transitions and the LUMO is indeed dx2-y2, not
diimine p
dx2-y2
?bpy
?bpy
dx2-y2


? (thiolate) d ? (Pt)
? (thiolate) d ? (Pt)
dxy
dxz-yz
dxz-yz
dz2
? bpy
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Lets hear it to Brian Prascher who did the
calculations!!
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WHO CARES!!

• The above was science, lets now see a potential
  application

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Solar Energy Conversion

• Silicon cells
• 10-20 efficiency
• Corrosion
• Expensive (superior crystallinity required)
• Wide band gap semiconductors (e.g. TiO2 SnO2
  CdS ZnO GaP)
• Band gap gtgt 1 eV (peak of solar radiation)
• Solution tether a dye (absorbs strongly across
  the vis into the IR) on the semiconductor
• Cheaper!! used as colloidal particles

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Literature studies to date focused almost solely
on dyes of Ru(bpy)32 derivatives gt Strong
absorption across the vis region (Grätzel Kamat
T. Meyer G. Meyer others)
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Anchoring groups on diimine to allow adsorption
on TiO2 surface.
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dmeobpy (MeOOC)2bpy Precursor for the
carboxylic acid (the ester is easier to handle in
organic solvents while the acid is soluble only
in aqueous base)
solid
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Cheaper is better!!
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Were testing this as a solar dye in Switzerland
Stay tuned!!
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2- Strongly luminescent materials based on the
Jahn-Teller effect
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0
0
10
Au (5d10)
Au(PR3)3
PR3
Ground-state MO diagram of Au(PR3)3 species,
according to the literature
Forward, J. Assefa, Z. Fackler, J. P. J. Am.
Chem. Soc. 1995, 117, 9103. McCleskey, T. M.
Gray, H. B. Inorg. Chem. 1992, 31, 1734.
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Molecular orbital diagrams (top) and optimized
structures (bottom) for the 1A1 ground state
(left) of the Au(PH3)3 and its corresponding
exciton (right).
Barakat, K. A. Cundari, T. R. Omary, M. A. J.
Am. Chem. Soc. 2003, 125, 14228-14229
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lem 496 nm
lem 478 nm
lem 772 nm
lem 640 nm
Au(TPA)3
QM/MM optimized structures of triplet Au(PR3)3
models.
Barakat, K. A. Cundari, T. R. Omary, M. A. J.
Am. Chem. Soc. 2003, 125, 14228-14229
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WHO CARES!!

• The above was science, lets now see a potential
  application

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RGB bright emissions in the solid state and at RT
are required for a multi-color device.
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AuL3 as LED materials?

• Glow strongly in the solid state at RT.
• But Au(PR3)3 X- dont sublime into thin films
  (ionic).
• How about neutral Au(PR3)2X?
• Do they also luminesce in the solid state at RT?
• Do they also exhibit Jahn-Teller distortion?
• lets see the latest thing that made the Omary
  group honors list!!

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Omary group honors list, posted 11/22/03
BRAVO PANKAJ!
Experiment Theory makes a good combo!
DFT calculations (B3LYP/LANL2DZ) for full model.

• In a recent paper (Barakat, K. A. Cundari, T.
  R. Omary, M. A. J. Am. Chem. Soc. 2003, 125,
  14228-14229), it was discovered that a
  Jahn-Teller distortion takes place for cationic
  AuL3 complexes (LPR3) such that the trigonal
  geometry changes toward a T-shape in the
  posphorescent triplet excited state.
• Pankaj shows in the figure above that the same
  rearrangement toward a T-shape also takes place
  in the phosphorescent triplet excited state of
  the neutral Au(PPh3)2Cl complex.
• This result explains the large Stokes shift in
  the experimental spectra on the left.
• Well be probing the structure of the excited
  states of both AuL3 and AuL2X directly by
  photocrystallography and time-resolved EXAFS to
  verify these calculated structures.

• Experimental findings based on the solid-state
  luminescence spectra at RT shown above
• 1- The large Stokes shift (11, 200 cm-1), large
  fwhm (4, 700 cm-1), and the structurless profile
  all suggest a largely distorted excited state.
• 2- The lifetime (21.6 0.2 ms) suggests that the
  emission is phosphorescence from a formally
  triplet excited state.
• To understand the nature of the excited state,
  Pankaj did full quantum mechanical calculations
  (DFT) to fully optimize the triplet excited state
  of the same compound he is studying without any
  approximation in the model.