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![Page 1: The Synthesis, Characterization and Photophysics of a New Class of Inorganic Ligands for Metal-Metal Multiply Bonded Compounds Christopher B. Durr.](https://reader035.fdocuments.us/reader035/viewer/2022062309/5697bfb71a28abf838c9ec7e/html5/thumbnails/1.jpg)
The Synthesis, Characterization and Photophysics of a New Class of Inorganic Ligands for Metal-Metal Multiply Bonded
Compounds
Christopher B. Durr
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Metal Based Polymers
Intermediate Energy MLCT 350-500 nm
Low Energy MLCT 500-1200 nm
High Energy -* 250-350 nm
Solar Spectrum
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Ground State
hn
*
Exci
tatio
n
S1
Sn
Intersystem Crossing
Trip
let E
miss
ion
Sing
let E
mis
sion T1
Probe hn
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Chromium Carbonyl Model Complex: Synthesis
Electronic Absorption Spectra
Wavelength / nm
300 400 500 600 700 800
No
rma
lize
d In
ten
sit
y /
A.U
.
0.0
0.2
0.4
0.6
0.8
1.0 Mo2(TiPB)2[O2C-(C6H5)Cr(CO)3]2
W2(TiPB)2[O2C-(C6H5)Cr(CO)3]2
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L *
Mo2*
Mo2-5.03 eV
-1.84 eV
-5.35 eV
-2.21 eV
Cr d–CO *
L *, Mo2
Mo2(O2C Ph)2 Mo2[O2CBnCr(CO)3]2
3.19
eV
3.14
eV
Mo2 , Cr dx2-y2
LUMO+1
LUMO
HOMO
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fs-Transient Absorption Spectroscopy Mo2[O2CBnCr(CO)3]2 , ex = 515 nm in DCM
3.5 ps
-1 ps
0.4 ps
1.8 ps
0.9 ps
9.5 ps
500 ps
2000 ps
1000 ps
25 ps
100 ps
fs-TA Spectroscopy shows a transient at ~575 nm that decays with a lifetime of ~17 ps which indicates a 1MLCT singlet state.
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35 min
0 min
45 min
10 min
150 min
5 min
105 min
90 min
170 min
20 min
Light
Dark
210 min20 hours
5.50 ps
-6.8 ps
264 ps
0.53 ps
2.53 ps
2830 ps
1.35 ps
11.7 ps
948 ps
29.4 ps73.6 ps
fs Time-Resolved Infrared SpectroscopyMo2[O2CBnCr(CO)3]2, ex = 515 nm
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ns-Transient Absorption
= 24 s
• ns-Transient Absorption showed a bleach at ~500 nm which indicates a long lived excited state that lasts for 24.3 1.9 s
• Near IR emission indicates a * Triplet State due to its location ~1100 nm and its vibronic features which correlate to the MM stretch.
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Mo2[PTA-ReCl(CO)3]2(TiPB)2: Model Complex
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L *
Mo2*
Mo2
-3.5
-3
-2.5
-2
-5.09 eV
-2.33 eV
-5.86 eV
L
-3.58 eV
Re d-CO *, Mo2-5.97 eV
Re d-CO *
Re d-CO *
L *, Mo2
-2.76 eV
Mo2PTA Mo2[PTAReCl(CO)3]2
2.76
eV
2.28
eV
LUMO+1
LUMO
HOMO
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fs-Transient Absorption SpectroscopyMo2[PTAReCl(CO)3]2 , ex = 675 nm in THF
τ = 16.8 ± 0.8 ps
40 ps
-1 ps
1500 ps
0.3 ps
2.5 ps0.6 ps
17.5 ps7.5 ps
150 ps500 ps
fs-TA Spectroscopy shows a transient at ~475 nm that decays with a lifetime of ~17 ps which indicates a 1MLCT singlet state.
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fs Time-Resolved Infrared SpectroscopyMo2[PTAReCl(CO)3]2, ex = 675 nm
29.1 ps
-6 ps
1140 ps
0.39 ps
2.24 ps0.80 ps
11.4 ps5.21 ps
73.3 ps
2830 ps
264 ps
gs IR
τ = 16.4 ± 0.2 ps
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ns-Transient Absorption = 21 s
• Near-IR Emission confirms a * triplet state due to vibrational transitions corresponding to MM bond stretch.
• The transient absorption shows both a bleach and a transient that lasts for ~21 s.
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Conclusions
• DFT calculations show that molecular orbitals can be tuned based on the metals used and their interactions with the ligands.
• Singlet states are 1MLCT based lasting less than 20 ps, and can be studied in greater depth using TR-IR. (Friday, Infrared/Raman Symposium: 11:25 AM)
• Triplet states are relatively long lived (~25 s), and are * in the case of Mo2 dinuclear centers.
• Further studies with different metals and bonding interactions could shed light on the photophysics of both the MM multiple bond and previously studied inorganic systems.
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Acknowledgements
Dr. Malcolm ChisholmDr. Claudia Turro
Dr. Terry GustafsonDr. Vesal Naseri
Samantha Brown-XuThomas Spilker