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The Synthesis, Characterization and Photophysics of a New Class of Inorganic Ligands for Metal-Metal Multiply Bonded
Compounds
Christopher B. Durr
Metal Based Polymers
Intermediate Energy MLCT 350-500 nm
Low Energy MLCT 500-1200 nm
High Energy -* 250-350 nm
Solar Spectrum
Ground State
hn
*
Exci
tatio
n
S1
Sn
Intersystem Crossing
Trip
let E
miss
ion
Sing
let E
mis
sion T1
Probe hn
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
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
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.
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
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.
Mo2[PTA-ReCl(CO)3]2(TiPB)2: Model Complex
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
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.
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
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.
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.
Acknowledgements
Dr. Malcolm ChisholmDr. Claudia Turro
Dr. Terry GustafsonDr. Vesal Naseri
Samantha Brown-XuThomas Spilker
