We have employed combined density functional theory and multi-reference configuration interaction methods including spin–orbit coupling (SOC) effects to investigate the photophysics of the green phosphorescent emitter fac-tris-(2-phenylpyridine)iridium (fac-Ir(ppy)3). A critical evaluation of our quantum chemical approaches shows that a perturbational treatment of SOC is the method of choice for computing the UV/Vis spectrum of this heavy transition metal complex while multi-reference spin–orbit configuration interaction is preferable for calculating the phosphorescence rates. The particular choice of the spin–orbit interaction operator is found to be of minor importance. Intersystem crossing (ISC) rates have been determined by Fourier transformation of the time correlation function of the transition including Dushinsky rotations. In the electronic ground state, fac-Ir(ppy)3 is C3 symmetric. The calculated UV/Vis spectrum is in excellent agreement with experiment. The effect of SOC is particularly pronounced for the metal-to-ligand charge transfer (MLCT) band in the visible region of the absorption spectrum which does not only extend its spectral onset towards longer wavelengths but also experiences a blue shift of its maximum. Pseudo-Jahn-Teller interaction leads to asymmetric coordinate displacements in the lowest MLCT states. Substantial electronic SOC and a small energy gap make ISC an ultrafast process in fac-Ir(ppy)3. For the S1T1 non-radiative transition, we compute a rate constant of kISC = 6.9 × 1012 s−1 which exceeds the rate constant of radiative decay to the electronic ground state by more than six orders of magnitude, in agreement with the experimental observation of a subpicosecond ISC process and a triplet quantum yield close to unity. As a consequence of the geometric distortion in the T1 state, the T1S0 transition densities are localized on one of the phenylpyridyl moieties. In our best quantum chemical model, we obtain phosphorescence decay times of 264 μs, 13 μs, and 0.9 μs, respectively, for the T1,I, T1,II, and T1,III fine-structure levels in dichloromethane (DCM) solution. In addition to reproducing the correct orders of magnitude for the individual phosphorescence emission probabilities, our theoretical study gives insight into the underlying mechanisms. In terms of intensity borrowing from spin-allowed transitions, the low emission probability of the T1,I substate is caused by the mutual cancellation of contributions from several singlet states to the total transition dipole moment. Their contributions do not cancel but add up in case of the much faster T1,IIIS0 emission while the T1,IIS0 emission is dominated by intensity borrowing from a single spin-allowed process, i.e., the S2S0 transition.

1.
S.
Kappaun
,
C.
Slugovc
, and
E. J. W.
List
,
Int. J. Mol. Sci.
9
,
1527
(
2008
).
2.
K.
Goushi
,
Y.
Kawamura
,
H.
Sasabe
, and
C.
Adachi
,
Jpn. J. Appl. Phys.
43
,
937
(
2004
).
3.
Y.
Kawamura
,
K.
Goushi
,
J.
Brooks
,
J. J.
Brown
,
H.
Sasabe
, and
C.
Adachi
,
Appl. Phys. Lett.
86
,
071104
(
2005
).
4.
T.
Sajoto
,
P. I.
Djurovich
,
A. B.
Tamayo
,
J.
Oxgaard
,
W. A.
Goddard
, and
M. E.
Thompson
,
J. Am. Chem. Soc.
131
,
9813
(
2009
).
5.
T.
Hofbeck
and
H.
Yersin
,
Inorg. Chem.
49
,
9290
(
2010
).
6.
S.-J.
Su
,
C.
Cai
, and
J.
Kido
,
Chem. Mater.
23
,
274
(
2011
).
7.
C.
Adachi
,
M. A.
Baldo
,
M. E.
Thompson
, and
S. R.
Forrest
,
J. Appl. Phys.
90
,
5048
(
2001
).
8.
K.-C.
Tang
,
K. L.
Liu
, and
I.-C.
Chen
,
Chem. Phys. Lett.
386
,
437
(
2004
).
9.
G. J.
Hedley
,
A.
Ruseckas
, and
I. D.
Samuel
,
Chem. Phys. Lett.
450
,
292
(
2008
).
10.
W. J.
Finkenzeller
and
H.
Yersin
,
Chem. Phys. Lett.
377
,
299
(
2003
).
11.
P. J.
Hay
,
J. Phys. Chem. A
106
,
1634
(
2002
).
12.
H.
Yersin
,
A. F.
Rausch
,
R.
Czerwieniec
,
T.
Hofbeck
, and
T.
Fischer
,
Coord. Chem. Rev.
255
,
2622
(
2011
).
13.
T.
Matsushita
,
T.
Asada
, and
S.
Koseki
,
J. Phys. Chem. C
111
,
6897
(
2007
).
14.
K.
Nozaki
,
J. Chin. Chem. Soc.
53
,
101
(
2006
).
15.
E.
Jansson
,
B.
Minaev
,
S.
Schrader
, and
H.
Ågren
,
Chem. Phys.
333
,
157
(
2007
).
16.
S.
Koseki
,
T.
Asada
, and
T.
Matsushita
,
J. Comput. Theor. Nanosci.
6
,
1352
(
2009
).
17.
B.
Minaev
,
H.
Ågren
, and
F. D.
Angelis
,
Chem. Phys.
358
,
245
(
2009
).
18.
B.
Minaev
,
V.
Minaeva
, and
H.
Ågren
,
J. Phys. Chem. A
113
,
726
(
2009
).
19.
N.
Tian
,
D.
Lenkeit
,
S.
Pelz
,
L. H.
Fischer
,
D.
Escudero
,
R.
Schiewek
,
D.
Klink
,
O. J.
Schmitz
,
L.
González
,
M.
Schäferling
 et al,
Eur. J. Inorg. Chem.
2010
,
4875
4885
.
20.
X.
Li
,
B.
Minaev
,
H.
Ågren
, and
H.
Tian
,
Eur. J. Inorg. Chem.
2011
,
2517
2524
.
21.
X.
Li
,
B.
Minaev
,
H.
Ågren
, and
H.
Tian
,
J. Phys. Chem. C
115
,
20724
(
2011
).
22.
A. R. G.
Smith
,
P. L.
Burn
, and
B. J.
Powell
,
ChemPhysChem
12
,
2429
(
2011
).
23.
J.
Fine
,
K.
Diri
,
A. I.
Krylov
,
C.
Nemirow
,
Z.
Lu
, and
C.
Wittig
,
Mol. Phys.
110
,
1849
1862
(
2012
).
24.
D.
Andrae
,
U.
Häussermann
,
M.
Dolg
,
H.
Stoll
, and
H.
Preuss
,
Theor. Chim. Acta
77
,
123
(
1990
).
25.
F.
Weigend
and
R.
Ahlrichs
,
Phys. Chem. Chem. Phys.
7
,
3297
(
2005
).
26.
A.
Schäfer
,
C.
Huber
, and
R.
Ahlrichs
,
J. Chem. Phys.
100
,
5829
(
1994
).
27.
J. P.
Perdew
,
K.
Burke
, and
M.
Ernzerhof
,
Phys. Rev. Lett.
77
,
3865
(
1996
).
28.
J. P.
Perdew
,
K.
Burke
, and
M.
Ernzerhof
,
Phys. Rev. Lett.
78
,
1396
(
1997
).
29.
C.
Adamo
and
V.
Barone
,
J. Chem. Phys.
110
,
6158
(
1999
).
30.
F.
Furche
and
R.
Ahlrichs
,
J. Chem. Phys.
117
,
7433
(
2002
).
31.
TURBOMOLE V6.3 2011, a development of University of Karlsruhe and Forschungszentrum Karlsruhe GmbH, 1989–2007, TURBOMOLE GmbH, since 2007; available from http://www.turbomole.com.
32.
A.
Klamt
and
G.
Schüürmann
,
J. Chem. Soc., Perkin Trans. 2
1993
,
799
.
33.
A.
Schäfer
,
A.
Klamt
,
D.
Sattel
,
J.
Lohrenz
, and
F.
Eckert
,
Phys. Chem. Chem. Phys.
2
,
2187
(
2000
).
34.
S.
Grimme
and
M.
Waletzke
,
J. Chem. Phys.
111
,
5645
(
1999
).
35.
M.
Kleinschmidt
,
C. M.
Marian
,
M.
Waletzke
, and
S.
Grimme
,
J. Chem. Phys.
130
,
044708
(
2009
).
36.
A. D.
Becke
,
J. Chem. Phys.
98
,
1372
(
1993
).
37.
C.
Lee
,
W.
Yang
, and
R. G.
Parr
,
Phys. Rev. B
37
,
785
(
1988
).
38.
M.
Gerenkamp
, “
Entwicklung und Anwendung quantenchemischer Methoden zur Berechnung komplexer chemischer Systeme
,” Ph.D. thesis (
Universität Münster
,
2005
).
39.
C.
Marian
, in
Reviews in Computational Chemistry
, edited by
K.
Lipkowitz
and
D.
Boyd
(
Wiley-VCH
,
Weinheim
,
2001
), Vol.
17
, pp.
99
204
.
40.
B. A.
Heß
,
C. M.
Marian
,
U.
Wahlgren
, and
O.
Gropen
,
Chem. Phys. Lett.
251
,
365
(
1996
).
41.
AMFI is an atomic spin–orbit integral program written by B. Schimmelpfennig, University of Stockholm, 1996.
42.
F.
Rakowitz
and
C. M.
Marian
,
Chem. Phys. Lett.
257
,
105
(
1996
).
43.
R. M.
Pitzer
and
N. W.
Winter
,
J. Phys. Chem.
92
,
3061
(
1988
).
44.
H.
Stoll
,
B.
Metz
, and
M.
Dolg
,
J. Comput. Chem.
23
,
767
(
2002
).
45.
S.
Koseki
,
D. G.
Fedorov
,
M. W.
Schmidt
, and
M. S.
Gordon
,
J. Phys. Chem. A
105
,
8262
(
2001
).
46.
W. J.
Stevens
,
M.
Krauss
,
H.
Basch
, and
P. G.
Jasien
,
Can. J. Chem.
70
,
612
(
1992
).
47.
M.
Kleinschmidt
,
J.
Tatchen
, and
C. M.
Marian
,
J. Comput. Chem.
23
,
824
(
2002
).
48.
M.
Kleinschmidt
,
J.
Tatchen
, and
C. M.
Marian
,
J. Chem. Phys.
124
,
124101
(
2006
).
49.
M.
Kleinschmidt
and
C. M.
Marian
,
Chem. Phys.
311
,
71
(
2005
).
50.
A. V.
Mitin
and
C.
van Wüllen
,
J. Chem. Phys.
124
,
064305
(
2006
).
51.
L. L.
Lohr
, Jr.
,
J. Chem. Phys.
45
,
1362
(
1966
).
52.
L.
Goodman
and
B. J.
Laurenzi
,
Adv. Quantum Chem.
4
,
153
(
1968
).
53.
J.
Neugebauer
,
M.
Reiher
,
C.
Kind
, and
B. A.
Hess
,
J. Comput. Chem.
23
,
895
(
2002
).
54.
M.
Etinski
,
J.
Tatchen
, and
C. M.
Marian
,
J. Chem. Phys.
134
,
154105
(
2011
).
55.
C. M.
Marian
,
WIREs Comput. Mol. Sci.
2
,
187
(
2012
).
56.
M.
Etinski
,
J.
Tatchen
, and
C. M.
Marian
,
Phys. Chem. Chem. Phys.
16
,
4740
(
2014
).
57.
M. R.
Silva
Junior
,
M.
Schreiber
,
S. P. A.
Sauer
, and
W.
Thiel
,
J. Chem. Phys.
128
,
104103
(
2008
).
58.
D.
Escudero
and
W.
Thiel
,
J. Chem. Phys.
140
,
194105
(
2014
).
59.
R. J. F.
Berger
,
H.-G.
Stammler
,
B.
Neumann
, and
N. W.
Mitzel
,
Eur. J. Inorg. Chem.
1613
1617
(
2010
).
60.
R.
Englman
and
J.
Jortner
,
Mol. Phys.
18
,
145
(
1970
).
61.
See supplementary material at http://dx.doi.org/10.1063/1.4913513 for data relating to the assessment of the methods and approximations, equilibrium geometry parameters, and pictures of molecular orbitals and difference densities.

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