Experimental and DFT evidence for the fractional non-innocence of a β-diketonate ligand

Article abstract of DOI:10.1002/chem.201201785

New compounds [Ru(pap)₂(L)](ClO₄), [Ru(pap)(L) ₂], and [Ru(acac)₂(L)] (pap=2-phenylazopyridine, L ^-=9-oxidophenalenone, acac^-=2,4-pentanedionate) have been prepared and studied regarding their electron-transfer behavior, both experimentally and by using DFT calculations. [Ru(pap)₂(L)](ClO ₄) and [Ru(acac)₂(L)] were characterized by crystal-structure analysis. Spectroelectrochemistry (EPR, UV/Vis/NIR), in conjunction with cyclic voltammetry, showed a wide range of about 2 V for the potential of the Ru^III/II couple, which was in agreement with the very different characteristics of the strongly π-accepting pap ligand and the σ-donating acac^- ligand. At the rather high potential of +1.35 V versus SCE, the oxidation of L^- into L^. could be deduced from the near-IR absorption of [Ru^III(pap)(L ^.)(L^-)]²⁺. Other intense long-wavelength transitions, including LMCT (L^-→Ru^III) and LL/CT (pap^.-→L^-) processes, were confirmed by TD-DFT results. DFT calculations and EPR data for the paramagnetic intermediates allowed us to assess the spin densities, which revealed two cases with considerable contributions from L-radical-involving forms, that is, [Ru ^III(pap⁰)₂(L^-)]²⁺→ [Ru^II(pap⁰)₂(L^.)]²⁺ and [Ru^III(pap⁰)(L^-)₂] ⁺→[Ru^II(pap⁰)(L^·)(L ^-)]⁺. Calculations of electrogenerated complex [Ru ^II(pap^.-)(pap⁰)(L^-)] displayed considerable negative spin density (-0.188) at the bridging metal. Copyright

Full text of DOI:10.1002/chem.201201785

FULL PAPER
DOI: 10.1002/chem.201201785
Experimental- and DFT Evidence for the Fractional Non-Innocence of a
AHCTUNGTREGbNNUN -Diketonate Ligand
Amit Das,[a] Thomas Michael Scherer,[b] Prasenjit Mondal,[a] Shaikh M. Mobin,[a]
Wolfgang Kaim,*[b] and Goutam Kumar Lahiri*[a]
Abstract: New compounds [Ru-
(pap)2(L)](ClO4), [Ru(pap)(L)2], and
[Ru(acac)2(L)] (pap=2-phenylazopyri-
which was in agreement with the very
different characteristics of the strongly
p-accepting pap ligand and the s-do-
nating acacꢀ ligand. At the rather high
potential of +1.35 V versus SCE, the
LMCT
(Lꢀ!RuIII)
and
LL/CT
ꢀ
Cꢀ
N
G
E
(pap !L ) processes, were confirmed
by TD-DFT results. DFT calculations
and EPR data for the paramagnetic in-
termediates allowed us to assess the
spin densities, which revealed two cases
with considerable contributions from
L-radical-involving forms, that is,
ACHTUNGTRENNUNG
dine, Lꢀ =9-oxidophenalenone, acacꢀ =
2,4-pentanedionate) have been pre-
pared and studied regarding their elec-
tron-transfer behavior, both experi-
mentally and by using DFT calcula-
oxidation of Lꢀ into L could be de-
C
duced from the near-IR absorption of
ꢀ
2+
[RuIII
ACUTHGNTRNENU(G pap)(L )(L )] . Other intense
C
0
2+
[RuIII
and
N
(Lꢀ)]2+$
[RuII
ACHUTGTNRENNUG CAHTUNGTRENNUNG
(pap )2(L )]
C
tions. [Ru
G
N
long-wavelength transitions, including
R
[RuIII
U
ACHTUNGTRENNUNG
tal-structure analysis. Spectroelectro-
chemistry (EPR, UV/Vis/NIR), in con-
junction with cyclic voltammetry,
showed a wide range of about 2 V for
the potential of the RuIII/II couple,
A
Keywords: density functional calcu-
lations · EPR spectroscopy · non-in-
nocent ligands · ruthenium · X-ray
diffraction
trogenerated complex [RuII
Cꢀ
ACHTUNGTRENNUNG(pap )-
AHCTUNGTRENNUNG
ative spin density (ꢀ0.188) at the
bridging metal.
Introduction
Widely utilized b-diketonate chelate ligands, such as acacꢀ
(2,4-pentanedionate/acetylacetonate) or its alkylated/fluori-
nated derivatives, have generally been regarded as redox-in-
nocent entities in metal complexes,[1] although DFT calcula-
tions of ruthenium–acac compounds have predicted its parti-
al involvement in intramolecular electron-transfer- or spin-
interaction processes.[2] However, O/NR-exchanged b-diketi-
minate (NacNac) in a nickel complex has recently been ad-
dressed as a “hidden non-innocent” ligand.[3]
On the other hand, the phenalenyl p system of the modi-
fied b-diketonate frameworks in structures A–C has been
reported to undergo stepwise electrochemical reduction in
complexes of positively charged Lewis-acid centers, such as
BIII, AlIII, SiIV, or GeIV.[4]
In this context, our recent work[5] on the first examples of
transition-metal complexes of 9-oxidophenalenone (Lꢀ =A),
[RuII
(bpy)2(Lꢀ)]ClO4
([4]ClO4),
ACTHNGUTERNNUG
[RuIII(bpy)(Lꢀ)2]ClO4
([5]ClO4), and [RuIII(Lꢀ)3] (6) (bpy=2,2’-bipyridine), has
demonstrated through experiments as well as by DFT calcu-
lations that Lꢀ can also participate in oxidation processes,
ꢀ
C
L !L , in combination with ruthenium bonded to the mod-
erately p-accepting bpy co-ligand.
To provide further insight into the potentially non-inno-
cent behavior of 9-oxidophenalenone (Lꢀ =A), we have de-
signed ruthenium complexes of Lꢀ together with co-ligands
with different electronic properties, that is, strongly p-ac-
[a] A. Das, P. Mondal, Dr. S. M. Mobin, Prof. Dr. G. K. Lahiri
Department of Chemistry
cepting
(pap)2(Lꢀ)]ClO4 ([1]ClO4) and [RuII
donating acacꢀ ligands ([RuIII(acac)2(Lꢀ)] (3)).
pap[6]
(pap=2-phenylazopyridine;
[RuII-
Indian Institute of Technology Bombay
Powai, Mumbai-400076 (India)
E-mail: lahiri@chem.iitb.ac.in
A
ACHTUNGTRENNUNG
AHCTUNGTRENNUNG
[b] Dipl.-Chem. T. M. Scherer, Prof. Dr. W. Kaim
Institut fꢀr Anorganische Chemie
Universitꢁt Stuttgart
Herein, we report the synthesis and characterization of
these complexes, as well as the structural characterization of
compounds [1]ClO4 and 3. The potential non-innocent be-
havior of Lꢀ in the accessible redox states of the complexes
has been analyzed both experimentally (electrochemistry,
UV/Vis/NIR spectroelectrochemistry, EPR spectroscopy)
Pfaffenwaldring 55, 70550 Stuttgart (Germany)
E-mail: kaim@iac.uni-stuttgart.de
Supporting information for this article is available on the WWW
under http://dx.doi.org/10.1002/chem.201201785.
Chem. Eur. J. 2012, 00, 0 – 0
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and by using DFT calculations. The specific role of the elec-
range of d=ꢀ30 to +15 ppm, owing to the paramagnetic
contact shift effect[7] (see the Supporting Information, Fig-
ure S2 and the Experimental Section).
tronic nature of the co-ligands (strongly p-accepting pap,
moderately p-accepting bpy, and s-donating acacꢀ) on the
ꢀ
ꢀ
electronic structural aspects of the Ru L moiety in these
complexes will be discussed.
Structural aspects: The identities of complexes [1]ClO4 and
3 have been authenticated by single-crystal X-ray diffraction
(Figure 1 and Figure 2, respectively); selected crystallo-
Results and Discussion
Synthesis and characterization: Diamagnetic complexes
[RuII(pap)2(Lꢀ)]ClO4 ([1]ClO4) and [RuII(pap)(Lꢀ)2] (2), as
ACHTUNGTRENNUNG ACHTUNGTRENNUGN
well as paramagnetic complex [RuIII
been synthesized from precursor complexes ct-[Ru-
ACHTUNGTRENNUNG(pap)2Cl2], [RuACHTUNGTRENNUNG(pap)ACHTUTNGRENNUG(PPh3)2Cl2], and [RuACHTUNGTERN(UNGN acac)2AHCTUNTRGEN(GNUN MeCN)2]
(acac)2(Lꢀ)] (3), have
ACHTUNGTRENNUNG
(pap=2-phenylazopyridine and acacꢀ =2,4-pentanedio-
nate=acetylacetonate), respectively, in the presence of HL
(Lꢀ =9-oxidophenalenone) and NEt3 under a nitrogen at-
mosphere (see the Experimental Section).
Figure 1. ORTEP of the cationic part of [1]ClO4·CH2Cl2. Ellipsoids are
set at 50% probability. Hydrogen atoms, the perchlorate anion, and the
solvent of crystallization are omitted for clarity.
The strongly p-accepting pap ligand stabilizes the metal
ion in the RuII state[6] in compounds [1]ClO4 and 2, whereas
the presence of three electron-donating ligands (two acacꢀ
ligands and one Lꢀ ligand) in the complex framework of
compound 3 stabilizes the metal ion in the RuIII state.[2,5] It
should be noted that unlike complex 2, the reported analo-
gous compound[5] incorporating moderately p-accepting bpy
Figure 2. ORTEP of 3·MeCN. Ellipsoids are set at 50% probability. Hy-
drogen atoms and the solvent of crystallization are omitted for clarity.
ligand in [RuIII
ACHTUNGTRENNUNG
(bpy)(Lꢀ)2]ClO4 results in the isolation of a
ruthenium(III) complex. The 1:1 conducting compound
ACHTUNGTRENNUNG
[1]ClO4 and electrically neutral compounds 2 and 3 exhibit
satisfactory microanalytical data (see the Experimental Sec-
tion). In MS (ESI) experiments, compounds [1]ClO4, 2, and
3 show molecular ion peaks (m/z) at 662.92, 674.36, and
494.86, which correspond to ions 1+, 2+, and 3+ (calculated
masses: 1+: 663.11, 2+: 675.05, 3+: 495.04), respectively (see
the Supporting Information, Figure S1).
graphic and bond parameters are listed in Table 1, Table 2,
and Table 3. In compounds [1]ClO4 and 3, the ligand (Lꢀ)
binds to the central ruthenium atom through oxygen donor
atoms, thereby forming six-membered chelate rings. The
trans- and cis angles around the ruthenium ion deviate con-
siderably from the idealized 1808 and 908, respectively
(Tables 2 and 3), thus implying a distorted octahedral situa-
tion. The crystal structure of compound [1]ClO4 shows that
the ct configuration[6d,e] (ct=cis and trans with respect to the
azo and pyridine nitrogen atoms of the two pap ligands, re-
1
The H NMR spectra of diamagnetic compounds [1]ClO4
and 2 in [D6]DMSO display partially overlapping signals
1
within the chemical-shift range d=6.5–9 ppm. The H NMR
resonances of complex 3 in CDCl3 appear within a wide
spectively) of the precursor complex, [RuACTHNGUTERNNU(G pap)2Cl2], has
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Fractional Non-Innocence of a b-Diketonate Ligand
FULL PAPER
Table 1. Selected crystallographic parameters of [1]ClO4·CH2Cl2 and
3·MeCN.
ꢀ
been retained. In compound [1]ClO4, the average Ru N-
(azo) bond length (1.984(4) ꢃ) is about 0.05 ꢃ shorter than
Compound
[1]ClO4·CH2Cl2
3·MeCN
ꢀ
the average Ru N(py) distance (2.035(4) ꢃ) owing to the
strong p-accepting effect of the azo group.[6] This result was
also reflected in the lengthening of the N=N bond length
empirical formula
Mw
crystal system
space group
a [ꢃ]
b [ꢃ]
c [ꢃ]
a [8]
b [8]
C36H27Cl3N6O6Ru
847.06
monoclinic
P21/n
13.5252(2)
17.5983(4)
15.2125(2)
90
94.089(2)
90
3611.67(11)
4
0.711
150(2)
1.558
C25H24NO6Ru
535.52
orthorhombic
Pbca
8.12510(10)
23.6189(4)
24.0340(4)
90
(average: 1.293(5) ꢃ) with respect to the N=N bond of free
[Hpap]+ (1.258(5) ꢃ).[8] The average Ru N(py) distance
II
ꢀ
(2.035(4) ꢃ) in compound [1]ClO4 is comparable to that of
structurally characterized analogous complex [RuII-
(bpy)2(L)]ClO4 (2.021 ꢃ).[5] The average Ru O(L) distan-
II
ꢀ
90
90
ces in compound [1]ClO4 (2.026(3) ꢃ) match fairly well with
those in the aforementioned compound [4]ClO4 (2.035 ꢃ),
g [8]
V [ꢃ3]
Z
4612.27(12)
8
0.721
150(2)
1.542
but are appreciably longer than the average RuIII O(L) dis-
ꢀ
m [mmꢀ1
T [K]
]
tance in [RuIII
(bpy)(L)2]ClO4 (1.994 ꢃ).[5] The average
RuIII O(L) distance in compound 3 (1.989 ꢃ) is similar to
ꢀ
Dcalcd [gcmꢀ3
]
that in compound [5]ClO4 (1.994 ꢃ).[5] The average RuIII O-
ꢀ
F
A
1712
2184
(acac) distance in compound 3 (2.011 ꢃ) is in agreement
3.38 to 25.00
6353/0/469
0.0509, 0.1445
0.0696, 0.1508
1.047
3.39 to 25.00
4053/0/303
0.0250, 0.0653
0.0342, 0.0671
1.001
with the values for reported structures of RuIII acac deriva-
data/restraints/parameters
R1, wR2 [I>2s(I)]
R1, wR2 (all data)
GOF
ꢀ
tives.[2,9]
ꢀ
The average C O(L) bond lengths in compounds [1]ClO4
largest diff. peak/hole, [e ꢃꢀ3
]
1.424 and ꢀ1.332
0.610 and ꢀ0.298
and 3 (1.301(6) ꢃ and 1.295(3) ꢃ, respectively) are as ex-
pected (cf. compounds [4]ClO4 and [5]ClO4: 1.287(3) ꢃ and
1.288(4) ꢃ, respectively).[5] The bond parameters of coordi-
nated Lꢀ in compounds [1]ClO4 and 3 are in good agree-
ment with the data of structurally characterized GeIV, SiIV,
AlIII, and RuII/III complexes of Lꢀ.[4,5] The DFT (B3LYP/
LANL2DZ/6-31G*)-optimized bond parameters of com-
pounds 1+ and 3 (see the Supporting Information, Figure S3)
confirm the experimentally obtained values (Table 2,
Table 3, and the Supporting Information, Table S1).
Table 2. Selected bond lengths and angles for [1]ACHTUNGTRNEG(UN ClO4)·CH2Cl2.
Bond length [ꢃ]
X-ray
Bond angle [8]
DFT
X-ray
DFT
Ru1–N6
1.981(4)
1.986(4)
2.024(3)
2.028(3)
2.034(4)
2.035(4)
1.302(6)
1.300(5)
1.287(5)
1.298(5)
2.070
2.056
2.067
2.063
2.070
2.089
1.291
1.292
1.283
1.2866
N6-Ru1-N3
N6-Ru1-O2
N3-Ru1-O2
N6-Ru1-O1
N3-Ru1-O1
O2-Ru1-O1
N6-Ru1-N4
N3-Ru1-N4
O2-Ru1-N4
O1-Ru1-N4
N6-Ru1-N1
N3-Ru1-N1
O2-Ru1-N1
O1-Ru1-N1
N4-Ru1-N1
97.24(15)
170.36(13)
85.00(13)
89.58(14)
169.81(13)
89.52(12)
77.15(15)
104.13(14)
93.21(13)
84.72(13)
104.46(15)
77.36(15)
85.17(14)
93.65(14)
177.71(15)
98.02
168.93
86.56
88.87
169.42
88.11
76.37
103.28
92.79
86.09
106.95
76.45
83.89
93.90
176.68
Ru1–N3
Ru1–O2
Ru1–O1
Ru1–N4
Ru1–N1
O1–C1
O2–C11
N2–N3
N5–N6
Electrochemistry: The CVs and DPVs of compounds
[1]ClO4, 2, and 3 are shown in Figure 3 and the data are
listed in Table 4. The CV of compound [1]ClO4 shows one
oxidation (Ox1) and two reduction peaks (Red1 and Red2)
and that of compound 2 displays two successive oxidations
(Ox1 and Ox2) and two reduction couples. Complex 3 how-
ever exhibits one oxidation peak and one reduction peak.
On replacing one strongly p-acidic pap ligand in compound
ACTHNUTRGNEUNG
[1]ClO4 with the negatively charged Lꢀ in [RuII(pap)(Lꢀ)2]
(2), the first oxidation potential is lowered dramatically
from 1.22 to 0.32 V, whilst Red1 shifts to a more-negative
potential (from ꢀ0.50 to ꢀ1.15 V). On the other hand, the
substitution of the strongly p-accepting pap ligands in [RuII-
Table 3. Selected bond lengths (ꢃ) and bond angles (o) for 3·MeCN.
Bond length [ꢃ]
X-ray
Bond angle [8]
DFT
X-ray
DFT
AHCTUNGTRENNUNG
(pap)2(Lꢀ)]ClO4 ([1]ClO4) by s-donating acacꢀ ligands in
Ru1–O1
Ru1–O6
Ru1–O2
Ru1–O5
Ru1–O4
Ru1–O3
O1–C1
O2–C11
O3–C15
O4–C17
O5–C20
O6–C22
1.9838(16)
1.9958(16)
1.9980(15)
2.0040(15)
2.0066(17)
2.0356(15)
1.297(3)
1.292(3)
1.269(3)
1.288(3)
1.273(3)
2.0158
2.0416
2.0442
2.0392
2.034
2.066
1.292
1.277
1.270
1.285
1.280
1.278
O1-Ru1-O6
89.57(7)
90.74(6)
86.33(6)
88.76(6)
94.41(6)
179.10(7)
176.23(7)
87.68(7)
91.67(6)
88.87(6)
90.96(7)
177.32(6)
91.04(6)
88.22(6)
91.91(7)
89.91
88.99
88.14
90.33
92.86
178.79
179.35
89.49
90.75
89.94
90.180
178.78
90.65
88.35
90.41
ACTHNUTRGNEUNG
[RuIII(acac)2(Lꢀ)] (3) causes a large negative potential shift
O1-Ru1-O2
O6-Ru1-O2
O1-Ru1-O5
O6-Ru1-O5
O2-Ru1-O5
O1-Ru1-O4
O6-Ru1-O4
O2-Ru1-O4
O5-Ru1-O4
O1-Ru1-O3
O6-Ru1-O3
O2-Ru1-O3
O5-Ru1-O3
O4-Ru1-O3
of 1.96 V (Ox1 for [1]ClO4 minus Red1 for 3). The differ-
ence in p-acid capacity between the pap and bpy ligands is
nicely reflected in the redox potentials: the Ox1 potential
ACTHNUTRGNEUNG
for [RuII(pap)2(Lꢀ)]ClO4 ([1]ClO4) is about 0.7 V higher
ACTHNUTRGNEUNG
than that of the corresponding [RuII(bpy)2(Lꢀ)]ClO4
([4]ClO4) complex.[5] However, the effect is diminished to
0.47 V on moving to complexes that only contain one pap or
ACTHNUTRGNEUNG
bpy ligand, i.e., [RuII(pap)(Lꢀ)2] (2) versus [RuIII-
1.274(3)
AHCTUNGTRENNUNG
AHCTUNGTRENNUNG
Chem. Eur. J. 2012, 00, 0 – 0
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W. Kaim and G. K. Lahiri et al.
Figure 4. EPR spectra of a) 1, b) 2+, and c) 2ꢀ in MeCN and 0.1m
Bu4NPF6 at 110 K.
lized form, such as in frozen solution, reflect the contribu-
tions of atoms with high spin-orbit coupling constants
through deviations from the free-electron value (ge =
2.0023).[11] DFT-calculated spin densities are available
(Figure 5, Table 6) to support and analyze the ex-
perimental results.
Figure 3. Cyclic voltammograms (solid lines) and differential pulse vol-
tammograms (dashed lines) of a) 1+, b) 2, and c) 3 in MeCN and 0.1m
Et4NClO4 at 298 K. Scan rate: 100 mVsꢀ1
.
Table 4. Electrochemical data.[a]
EPR experiments reveal a dichotomy between
Complex
E2988 [V] (DEp [mV])[b]
Reference
those species with large g anisotropy (Dg>0.25;
12+, 2+, 3) and those with small g anisotropy (Dg<
0.03; 1, 2ꢀ; Dg=g1ꢀg3).[9c] The former set of com-
pounds can be assigned to a first approximation
Ox2
–
Ox1
Red1
Red2
G
G
1.22 (70)[c] ꢀ0.50 (60)
ꢀ1.00 (70)
this work
E
1.35 (90) 0.32 (100)[c] ꢀ1.15 (90)
ꢀ1.66 (130) this work
N
N
–
0.82 (60)
ꢀ0.74 (70)[c]
ꢀ1.48 (70)
ꢀ0.15 (70)
ꢀ0.66 (90)
–
this work
T
(bpy)2(Lꢀ)]+ (4+) 1.78 (ir) 0.50 (70)
ꢀ1.74 (80)
ꢀ0.99 (300)
–
[5]
[5]
[5]
(see below) as rutheniumACHTNUTGRNEUNG
(III) species,[9c] whereas
G
(bpy)(Lꢀ)2]+ (5+) 1.23 (70) 0.49 (60)
the latter set of compounds are typical for radical-
ion complexes of ruthenium(II).[10,17] Similar differ-
ences were noted for previously reported[5] species
42+, 4, 5+, and 6, and are listed in Table 5 and
Table 6.
–
0.71 (90)
[a] From CV analysis in MeCN and 0.1m Et4NClO4 at 100 mVsꢀ1. [b] Potential [V]
versus SCE; the difference between the peak potentials (DEp) [mV] is given in paren-
theses. [c] RuIII/II couple according to EPR spectroscopy.
Considering the ready formation of the pap radi-
cal anion from pap, the distribution of oxidation
EPR and UV/Vis/NIR spectroelectrochemistry: The para-
magnetic redox states of the compounds presented herein
were also analyzed by EPR spectroscopy (Figure 4, Table 5).
The presence of a heavy-metal center with a high spin-orbit
coupling constant[10] can be advantageously used to assess
the amount of spin on that metal (and, by implication, on
the ligands). The g factor and its anisotropy in its immobi-
states in compounds 12+, 2+, 3, 1, and 2ꢀ is straightforward
(Scheme 1). Of the EPR-inactive forms in Scheme 1, the iso-
lated form 1+ was identified structurally (see above) whilst
compound 1ꢀ was formulated with a fully reduced set of li-
ꢀ
II
Cꢀ
gands (pap , L ) and metal (Ru ).
Similarly, the neutral form of compound 2 is undoubtedly
a ruthenium(II) complex with the conventional pap and Lꢀ
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Fractional Non-Innocence of a b-Diketonate Ligand
FULL PAPER
Starting from the EPR-active RuIII species (3),
reduction clearly leads to a ruthenium(II) form
(3ꢀ). Oxidation to form compound 3+ could either
Table 5. EPR parameters, from measurements at 110 K in MeCN and 0.1m Bu4NPF6.
Complex
g1
g2
g3
1.869
1.990
giso
Dg
Reference
[Ru
[Ru
[Ru
[Ru
[Ru
[Ru
[Ru
[Ru
G
)
2.243
2.003
2.044
1.997
0.374
this work
this work
this work
this work
this work
[5]
R
2.012
2.202
1.997
2.303
2.539
1.990
2.155
1.985
2.17
0.022
0.2913
0.023
0.753
0.860
involve the metal (RuIII!RuIV) or the oxidizable
ꢀ
E
1.9107 2.093
C
b-diketonato ligand (L !L ). Neither the absence
R
1.974
1.55
1.68
1.985
2.035
2.141
2.0060 <0.01
2.108
2.26
of EPR signals nor the appearance of a long-wave-
length absorption at 710 nm are unambiguously in-
dicative; therefore, we resorted to DFT calcula-
tions (see the Supporting Information, Tables S2–
S13). Although the frontier orbitals of compound
3+ are obviously mixed, the predominantly ligand
character of the HOMO and
ACHTUNGTRENNUNG
G
)
2.204
[a]
[a]
[a]
A
–
–
–
[5]
[5]
[5]
E
2.323
3.00
2.156
2.142
1.846
1.64
0.477
1.36
[Ru(Lꢀ)3] (6)
[a] Not resolved.
the more-metal character of
the LUMO suggest that
a
RuIV(Lꢀ) configuration is the
most appropriate for 3+.
Spectroelectrochemistry in
the UV/Vis/NIR regions was
used in comparison with previ-
ously reported data for com-
pounds 4n, 5n, and 6n (Figure 6,
Figure 7, Figure 8, and Table 7)
to characterize the electronic
structures of the complexes,
supported by TD-DFT calcula-
tions (Table 8, Table 9, and
Table 10).
Intense absorptions at low
energies are of particular inter-
est in conjunction with the
frontier-orbital situation and
the oxidation-state description.
Remarkably, such features
were observed and confirmed
by TD-DFT calculations, espe-
Figure 5. Mulliken spin-density plots of a) 12+ (S=1/2), b) 1 (S=1/2), c) 2+ (S=1/2), d) 22+ (S=1), e) 2ꢀ (S=1/
2), f) 22ꢀ (S=1), and g) 3 (S=1/2).
cially for compound 12+ (lmax
=
1080 nm), which was attributed
to
a
LMCT process (Lꢀ!
RuIII), for compound 1ꢀ (lmax
=
Table 6. DFT-calculated Mulliken spin densities for paramagnetic complexes.
1000 nm), which was assigned to a LL/CT transi-
Ru
0.559
L
acac bpy pap
Reference
ꢀ
2+
Cꢀ
tion (pap !L ), and for compound 2 (lmax
=
[Ru
G
0.492
–
–
ꢀ0.032/ꢀ0.020 this work
1150 nm). This band, with e=14350mꢀ1 cmꢀ1, was
(12+
[Ru
[Ru
[Ru
[Ru
[Ru
N
ꢀ0.188 ꢀ0.016
–
–
–
–
–
–
0.611/0.594
this work
this work
this work
this work
[5]
identified with the help of TD-DFT calculations as
an LLCT transition between Lꢀ and L , thus re-
0.736
0.103
0.824
0.703
0.154/0.141
ꢀ0.031
C
0.012/0.011
0.077
0.253
0.875
flecting the partial oxidation of Lꢀ. The oxidation
of Lꢀ instead of RuIII at +1.35 V is due to stabiliza-
tion of the lower oxidation state of the metal by
0.099
–
–
–
–
0.050
the strong p-acceptor pap.[6] A related LLCT tran-
[Ru
[Ru
[Ru(L)3] (6)
ꢀ0.034 ꢀ0.001
–
–
–
1.036
0.005
–
–
–
–
[5]
[5]
[5]
ꢀ
0.749
0.806
0.246
0.193
C
sition (L !L ) has been observed for compound
53+,
which
was
formulated
as
[RuIV-
ꢀ
3+ [5]
C
(bpy)(L )(L )] . However, in contrast to the
bpy-containing compounds, the pap species report-
ligands, in which the low oxidation state of the metal is sta-
bilized by the strongly p-accepting 2-phenylazopyridine. The
identity of the highest-oxidized form, 22+, will be discussed
below in connection with UV/Vis/NIR spectroelectrochem-
istry.
ed herein are distinguished by their higher absorptivity.[6b]
Combining all of this information (Scheme 1) allows us to
compare the potentials of the RuIII/II waves in the electro-
chemical experiments (Table 4). The values of ꢀ0.74 (3),
0.50 (4+), and 1.22 V (1+) show a very strong anodic shift on
Chem. Eur. J. 2012, 00, 0 – 0
ꢂ 2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
&
5
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W. Kaim and G. K. Lahiri et al.
Scheme 1. Most-appropriate oxidation states of compounds 1n, 2n, and 3n.
Figure 7. UV/Vis/NIR spectroelectrochemistry of compound 2n in MeCN
and 0.1m Bu4NPF6.
Figure 6. UV/Vis/NIR spectroelectrochemistry of compound 1n in MeCN
and 0.1m Bu4NPF6.
going from the s-donating acacꢀ ligand, through the moder-
ately p-accepting bpy ligand, to the strongly p-accepting pap
ligand.
Relying on information from DFT spin-density calcula-
tions (Figure 5, Table 6), the g anisotropy values (Dg) in
Table 5 show some significant variation between the
Figure 8. UV/Vis/NIR spectroelectrochemistry of compound 3n in MeCN
and 0.1m Bu4NPF6.
rutheniumACHTUNGTRENNUNG(III) complexes. At one extreme, complexes with-
2þ
II
0
2þ
½RuIIIðpap0Þ2ðLꢀÞꢁ $ ½Ru ðpap Þ2ðL Þꢁ
out acceptor ligands (such as 6) exhibit a large Dg value
(1.36). The introduction of bpy or pap co-ligands decreases
this value, thus suggesting a notable participation of these li-
gands, with their lighter atoms, and much-smaller spin-orbit
coupling constants at the singly occupied MO. Two remarka-
ble examples with small Dg values stand out: compounds 12+
(0.374) and 2+ (0.2913). These results, which were confirmed
by relatively well-mixed DFT spin densities on the rutheni-
um center and the L ligands (Table 6), are indicative of the
resonance forms, shown in Equations (1) and (2). These
C
ð1Þ
ð2Þ
½RuIIIðpap0ÞðLꢀÞ2ꢁþ $ ½Ru ðpap ÞðL ÞðL Þꢁ
II
0
ꢀ
þ
C
These Equations [Eqs. (1) and (2)], as well as the DFT re-
sults, illustrate that the indirect effect of the strongly p-ac-
cepting pap co-ligands causes a fractional non-innocence on
the side of the oxidizable b-diketonate (Lꢀ).
Whilst the paramagnetic complex with ligand-centered
spin only exhibits minor g anisotropy, in accordance with the
predominant location of the unpaired electron on the lighter
atoms of the ligands, DFT analysis (Table 6) revealed that
system 1, which contains mixed-valent pap ligands, has a
C
forms involve oxidized L (i.e., L ), owing to the presence of
non-oxidized ruthenium(II), which, in turn, is stabilized by
the strongly p-accepting pap ligand.
&
6
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ꢂ 2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Eur. J. 0000, 00, 0 – 0
ÝÝ
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Fractional Non-Innocence of a b-Diketonate Ligand
FULL PAPER
Table 7. UV/Vis/NIR spectroelectrochemical data in MeCN and 0.1m Bu4NPF6.
charge-transfer
(LLIVCT)
l [nm] (e [mꢀ1 cmꢀ1])
Reference
band is observed with moder-
ate intensity at about 2000 nm
(Figure 6, Table 7).
Compounds
(pap)2(L)]2+ (12+
(pap)2(L)]+ (1+)
(pap)2(L)] (1)
(pap)2(L)]ꢀ (1ꢀ)
(pap)(L)2]2+ (22+
(pap)(L)2]+ (2+)
(pap)(L)2] (2)
(pap)(L)2]ꢀ (2ꢀ)
(acac)2(L)]+ (3+)
(acac)2(L)] (3)
(acac)2(L)]ꢀ (3ꢀ)
[Ru
[Ru
[Ru
[Ru
[Ru
[Ru
[Ru
[Ru
[Ru
[Ru
[Ru
[Ru
[Ru
[Ru
[Ru
[Ru
[Ru
[Ru
[Ru
N
)
)
1080
(16050), 460
(13550), 490
(10420), 543(sh), 350
1150(14350), 670
740(sh), 520(10700), 430(sh), 360
550 (17950), 490 (sh), 350 (36400)
(1450), 790(sh), 650(17250), 390(29900)
710(7400), 415(13690), 360(18740)
440(13680), 345(15820)
(22620), 470(sh), 410(9790)
(2950), 500(sh), 425(28600), 400(sh)
(21700), 390(14450), 370(14950), 345(17900)
(17650), 385(11850), 370(12400), 345(14650)
1510(390), 585(sh), 440(21300), 380(sh)
(3800), 425(23350), 370(31100), 300(24550)
(450), 650(2500), 450(sh), 425(27200), 350(21950)
655(sh), 530(sh), 450(25050), 425(23850), 350(21950)
640(19100), 590(sh), 400(17600), 385(sh), 345(sh)
780(6800), 450(21800), 425(sh), 365(31400)
590(sh), 490(24200), 420(sh), 350(21900)
1000(sh), 790(24300), 490(sh), 390(sh)
N
T
this work
this work
this work
this work
this work
this work
this work
this work
this work
this work
this work
[5]
670
(1110), 846
1000
N
G
T
ACHTUNGTRENNUNG
1968
E
R
ACHTUNGTRENNUNG
N
ACHTUNGTRENNUNG
E
A
ACHTUNGTRENNUNG
Conclusion
T
ACHTUNGTRENNUNG
1270
G
ACHTUNGTRENNUNG
A combination of structure-de-
termination, EPR spectrosco-
py, and UV/Vis/NIR spectroe-
lectrochemistry, in conjunction
with DFT calculations, has al-
lowed us to obtain a complete
picture of the proper oxida-
tion-state descriptions of new
redox systems 1n, 2n, and 3n.
The remarkable features of
these systems include full or
fractional oxidation of the po-
tentially redox-active b-diketo-
E
ACHTUNGTRENNUNG
ACHTUNGTRENNUNG
1010(sh), 760
780
E
ACHTUNGTRENNUNG
)
G
ACHTUNGTRENNUNG
520
520
U
N
N
T
[5]
[5]
[5]
[5]
[5]
[5]
[5]
[5]
N
N
A
)
)
1090
G
R
N
N
N
N
N
A
U
E
G
E
A
[5]
[5]
[Ru(L)3]ꢀ (6ꢀ)
E
nate, Lꢀ to L which has devel-
C
oped due to the strong p-ac-
rather negative spin density of ꢀ0.188 at the bridging and
ceptor effect of the pap ligand on the metal ion. Thus, the
results described herein are complementary to previous re-
ports about the Lꢀ ligand, which have been found[4c] to
electron-transfer-mediating ruthenium center.
A
corre-
Cꢀ
sponding (pap )!
ACHTUNGTRENNUNG
Table 8. TD-DFT (B3LYP/CPCM/MeCN)-calculated electronic transitions for 1n.
State Energy [eV] l [nm] (exptl) f (DFT)/e (exptl)
l [nmꢀ1] (DFT)
[RuIII(pap0)2(Lꢀ)]2+ (pap )2(L )] (12+) [doublet (S=1/2)]
Transition
Character
0
2+
[RuII
1078
ACHTUNGTRENNUNG
C
G
N
$
3
21
1.150
2.540
1080
490
0.158/9720
0.011/sh
HOMOꢀ1(b)!LUMO(b) (0.67)
HOMOꢀ1(b)!LUMO+2(b) (0.46)
HOMOꢀ1(b)!LUMO+3(b) (0.26)
HOMOꢀ6(a)!LUMO+1(a) (0.40)
HOMOꢀ4(a)!LUMO+1(a) (0.33)
HOMOꢀ3(a)!LUMO+1(a) (0.25)
L(p)/Ru(dp)!Ru(dp)/L(p*)
L(p)/Ru(dp)!pap(p*)/L(p*)
488
50
3.158
392
380
0.180/32920
pap(p)/Ru(dp)!pap(p*)
ACHTUNGTRENNUNG ACHTUNGTRENNUNG
[RuII(pap0)2(Lꢀ)]+ (1+) [singlet (S=0)]
1
5
7
1.781
2.305
2.766
696
540
450
670
570
460
0.013/3870
0.118/16050
0.055/14210
HOMO!LUMO (0.63)
L(p)!pap(p*)
Ru(dp)!pap(p*)
Ru(dp)!pap(p*)
L(p)!L(p*)
HOMOꢀ2!LUMO (0.64)
HOMOꢀ3!LUMO+1 (0.46)
HOMO!LUMO+2 (0.44)
HOMOꢀ6!LUMO+1 (0.32)
HOMOꢀ5!LUMO+1 (0.30)
18
3.318
373
370
0.398/29930
pap(p)!pap(p*)
Cꢀ
ACHTUNGTRENNUNG ACHTUNGTRENNUNG(pap )ACHTUNGTRENNUNG
[RuII (pap0)(Lꢀ)] (1) [doublet (S=1/2)]
1
4
8
14
46
0.621
1.514
2.087
2.501
3.488
1995
820
594
495
355
1968
846
590
490
345
0.032/1110
0.010/1370
0.032/13550
0.083/14400
0.286/33570
HOMO(a)!LUMO(a) (0.63)
HOMOꢀ1(a)!LUMO(a) (0.75)
HOMOꢀ1(b)!LUMO(b) (0.90)
HOMOꢀ2(b)!LUMO(b) (0.82)
HOMOꢀ4(b)!LUMO+1(b) (0.44)
HOMO(a)!LUMO+11(a) (0.30)
pap(p)!pap(p*)
Ru(dp)/pap(p)!pap(p*)
Ru(dp)!pap(p*)
Ru(dp)/pap(p)!pap(p*)
pap(p)!pap(p)
L(p)!L(p)
Cꢀ
A
(pap )2(Lꢀ)]ꢀ (1ꢀ) [singlet (S=0)]
2
5
23
1.875
2.273
3.486
1178
545
355
1000
543
360
0.099/10420
0.045/sh
0.225/33460
HOMO!LUMO+1 (0.66)
HOMOꢀ1!LUMO (058)
HOMO!LUMO+11 (0.39)
HOMO!LUMO+12 (0.27)
HOMO!LUMO+11 (0.37)
HOMO!LUMO+10 (0.19)
pap(p)!pap(p*)
Ru(dp)!L(p*)
pap(p)!pap(p*)
25
3.559
348
350
0.277/41100
pap(p)!pap(p*)
Chem. Eur. J. 2012, 00, 0 – 0
ꢂ 2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
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7
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W. Kaim and G. K. Lahiri et al.
Table 9. TD-DFT (B3LYP/CPCM/MeCN)-calculated electronic transitions for compound 2n.
State
l [nmꢀ1] (DFT)
ACHTUNGTRENNUNG
[RuIII(pap )(L )(L )]2+ (22+) [triplet (S=1)]
Energy [eV]
l [nm] (exptl)
f (DFT)/e (exptl)
Transition
Character
0
ꢀ
C
U
6
1.137
1091
1150
0.223/14350
HOMOꢀ1(b)!LUMO+1(b) (0.55)
HOMO(b)!LUMO(b) (0.16)
L(p)!L(p*)//Ru(dp)
15
60
1.882
3.326
659
372
670
370
0.008/sh
0.058/45500
HOMOꢀ8(b)!LUMO+1(b) (0.53)
HOMOꢀ9(a)!LUM1(a) (0.42)
HOMOꢀ8(b)!LUMO+2(b) (0.36)
HOMOꢀ3(a)!LUMO+1(a) (0.25)
L(p)!Ru(dp)
L(p)!pap(p*)
ACHTUNGTRENNUNG ACHTUNGTRENNUNG
[RuIII(pap0)(Lꢀ)2]+ (2+) [doublet (S=1/2)]
3
18
27
1.692
2.513
2.895
733
495
428
740
520
430
0.095/sh
0.050/10700
0.044/sh
HOMOꢀ2(b)!LUMO(b) (0.58)
HOMOꢀ3(a)!LUMO(a) (0.64)
HOMOꢀ5(a)!LUMO(a) (0.58)
HOMOꢀ4(b)!LUMO+1(b) (0.27)
HOMOꢀ3(b)!LUMO+2(b) (0.53)
HOMOꢀ3(b)!LUMO+3(b) (0.37)
L(p)!Ru(dp)
L(p)!pap(p*)
Ru(dp)!pap(p*)/L(p*)
53
3.400
364
360
0.046/37900
L(p)!L(p*)
ACHTUNGTRENNUNG ACHTUNGTRENNUNG
[RuII(pap0)(Lꢀ)2] (2) [singlet (S=0)]
5
2.208
2.598
3.457
561
478
358
550
490
350
0.127/17950
0.038/sh
HOMOꢀ1!LUMO (0.49)
HOMOꢀ2!LUMO (0.36)
HOMOꢀ1!LUMO+2 (0.51)
HOMOꢀ1!LUMO+1 (0.40)
HOMOꢀ7!LUMO (0.49)
HOMOꢀ8!LUMO (0.30)
Ru(dp)!pap(p*)
Ru(dp)!L(p*)
6
19
0.213/36400
pap(p)/L(p)!pap(p*)
Cꢀ
A
(pap )(Lꢀ)2]ꢀ (2ꢀ) [doublet (S=1/2)]
1
6
11
39
0.984
1.630
1.803
3.214
1260
760
687
386
1270
790
650
390
0.011/1450
0.010/sh
0.025/17250
0.108/29900
HOMO(a)!LUMO(a) (0.94)
HOMOꢀ1(a)!LUMO(a) (0.74)
HOMOꢀ2(b)!LUMO(b) (0.68)
pap(p)!L(p*)
Ru(dp)!L(p*)
Ru(dp)!L(p*)
HOMOꢀ1(a)!LUMO+10(a) (0.45)
pap(p)!pap(p*)
Table 10. TD-DFT (B3LYP/CPCM/MeCN)-calculated electronic transitions for compound 3n.
State Energy [eV]
ACHTUNGTRENNUNG
[RuIV(acac)2(Lꢀ)]+ (3+) [singlet (S=0)]
l [nmꢀ1] (DFT)
l [nm] (exptl)
f (DFT)/e (exptl)
Transition
Character
U
5
1.807
686
710
0.147/7400
HOMOꢀ4!LUMO (0.45)
HOMOꢀ2!LUMO (0.26)
HOMOꢀ9!LUMO (0.51)
HOMOꢀ10!LUMO (0.51)
HOMO!LUMO+4 (0.22)
acac(p)!Ru(dp)
10
14
2.820
3.329
439
373
415
360
0.045/13690
0.040/18740
acac(p)/L(p)!Ru(dp)
L(p)!Ru(dp)
ACHTUNGTRENNUNG ACHTUNGTRENNUNG
[RuIII(acac)2(Lꢀ)] (3) [doublet (S=1/2)]
14
2.871
431
440
380
0.120/13680
0.020/15820
HOMOꢀ1(a)!LUMO+1(a) (0.50)
HOMOꢀ1(b)!LUMO+6(b) (0.24)
HOMOꢀ3(a)!LUMO+1(a) (0.45)
HOMOꢀ1(b)!LUMO+5(b) (0.34)
Ru(dp)!L(p*)
19
3.129
396
acac(p)/Ru(dp)!L(p*)
ACHTUNGTRENNUNG ACHTUNGTRENNUNG
[RuII(acac)2(Lꢀ)2]ꢀ (3ꢀ) [singlet (S=0)]
1
3
4
1.426
2.058
2.67
869
602
462
1010
760
470
0.002/sh
0.337/22620
0.011/sh
HOMOꢀ1!LUMO (0.52)
HOMOꢀ2!LUMO (0.55)
HOMO!LUMO+1 (0.63)
HOMO!LUMO+12 (0.27)
HOMOꢀ2!LUMO+1 (0.58)
HOMOꢀ6!LUMO (0.42)
HOMOꢀ2!LUMO+5 (025)
Ru(dp)!L(p*)
Ru(dp)!L(p*)
Ru(dp)!acac(p*)
9
27
3.085
4.025
401
309
410
325
0.105/9790
0.314/16570
Ru(dp)!acac(p*)
L(p)/Ru(dp)!L(p*)
1H-phenalen-1-one (HL),[15] were prepared according to literature proce-
dures. Other chemicals and solvents were of reagent grade and used as
received. For spectroscopic and electrochemical studies, HPLC-grade sol-
vents were used. Caution: Perchlorate salts are potentially explosive and
should be handled with care and in very small amounts.
become reduced when bonded to strongly electrophilic
higher-valent elements.
Experimental Section
Instrumentation: UV/Vis/NIR studies were performed in MeCN and
0.1m Bu4NPF6 at 298 K by using an optically transparent thin-layer elec-
trode (OTTLE) cell that was mounted in the sample compartment of a
J&M Tidas spectrophotometer.[16] 1H NMR spectroscopy was performed
Materials: The starting metal complexes, ct-[Ru
(PPh3)2Cl2],[13] and [Ru (MeCN)2],[14] and the ligand, 9-hydroxy-
(acac)2A
(pap)2Cl2],[12] [Ru
ACHUTGTNRNEUNG AHCUTNGTREN(NUGN pap)-
G
A
CHTUNGTRENNUNG
&
8
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ꢂ 2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Eur. J. 0000, 00, 0 – 0
ÝÝ
These are not the final page numbers!

Fractional Non-Innocence of a b-Diketonate Ligand
FULL PAPER
on a Bruker Avance III 400 spectrometer. EPR spectroscopy was per-
formed in a two-electrode capillary tube[17] on an X-band Bruker system
ESP300 that was equipped with a Bruker ER035M gaussmeter and a HP
5350B microwave counter. Cyclic voltammetry (CV), differential pulse
voltammetry (DPV), and coulometric measurements were performed on
a PAR model 273A electrochemistry system with platinum wire as the
working- and auxiliary electrodes and an aqueous saturated-calomel ref-
erence electrode (SCE) in a three-electrode configuration. The support-
ing electrolyte was Et4NClO4 and the solute concentration was about
was heated at reflux under a nitrogen atmosphere for 1.5 h. The precipi-
tated AgCl was removed by filtration and HL (83 mg, 0.43 mmol) and
NEt3 (43 mg, 0.43 mmol, freshly distilled over KOH) were added to the
filtrate. The mixture was heated at reflux under a nitrogen atmosphere
for 24 h. The initial red–violet solution gradually changed to dark-red–
violet. The reaction mixture was evaporated to dryness and purified by
column chromatography on neutral alumina. Dark-red–violet complex 2
was eluted with a mixture of CH2Cl2/MeCN (5:2). Evaporation of the sol-
vent under reduced pressure yielded the pure complex as a solid. Yield:
70 mg (61%). 1H NMR (400 MHz, [D6]DMSO, 298 K): d=8.57 (d, 8.1,
1H), 8.31 (d, 6.2, 1H), 8.11 (d, 9.1, 2H), 8.07 (d, 7.7, 1H), 8.02 (d, 7.1,
1H), 7.97 (d, 7.4, 1H), 7.78–7.95 (m, 5H), 7.26–7.55 (m, 8H), 7.01 (d, 9.3,
1H), 6.85 ppm (dd, 9.3, 2H); MS (ESI+, MeCN): m/z calcd for 2+:
10ꢀ3 m. The half-wave potential (Eo298) was equal to 0.5
ACHTNUTRGNEG(UN Epa+Epc), where
Epa and Epc are the anodic- and cathodic CV peak potentials, respectively.
Elemental analysis was performed on a Perkin–Elmer 240C elemental
analyzer. MS (ESI) were recorded on a Micromass Q-ToF mass spec-
trometer.
675.07; found: 674.36; molar conductivity (MeCN): LM =20 Wꢀ1 cm2 mꢀ1
;
elemental analysis calcd (%) for C37H23N3O4Ru: C 65.77, H 3.43, N 6.22;
found: C 65.74, H 3.41, N 6.20.
Synthesis of [RuIII
ACHTNUGRTEN(NUNG acac)2(L)] (3): A mixture of [RuACHTNUTRGEG(NUNN acac)2ACHTUNGTRENNUNG(MeCN)2]
Crystallography: Single crystals of compounds [1]ClO4 and 3 were grown
by the slow evaporation of a solution of [1]ClO4 in CH2Cl2/n-hexane
(1:1) and a solution of compound 3 in MeCN/n-hexane (1:2), respectively.
The crystal data were collected on an Oxford X-CALIBUR-S CCD dif-
fractometer. Selected data-collection parameters and other crystallo-
graphic results are summarized in Table 1. All data were corrected for
Lorentz polarization and absorption effects. The program package
SHELX-97[18] was used for structure-solution and full-matrix least-
squares refinement on F2. Hydrogen atoms were included in the refine-
ment by using the riding model.
(100 mg, 0.26 mmol), HL (51 mg, 0.26 mmol) and NEt3 (27 mg,
0.26 mmol, freshly distilled over KOH) in EtOH (30 mL) was heated at
reflux under a nitrogen atmosphere for 10 h. The initial orange solution
gradually changed to dark-red–brown. The reaction mixture was evapo-
rated to dryness under reduced pressure and purified by column chroma-
tography on silica gel (60–120 mesh). Dark-red–brown complex 3 was
eluted with a mixture of CH2Cl2/MeCN (10:1). Evaporation of the sol-
vent under reduced pressure yielded the pure complex as a solid. Yield:
90 mg (69%). 1H NMR (400 MHz, CDCl3, 298 K): d=14.13, 13.46, 4.7,
1.25, ꢀ3.08, ꢀ3.42, ꢀ4.79, ꢀ27.73 ppm; MS (ESI+, MeCN): m/z calcd for
CCDC-882875 ([1]ACHTUNGTRENNUNG(ClO4)2) and CCDC-882874 (3) contain the supple-
mentary crystallographic data for this paper. These data can be obtained
free of charge from The Cambridge Crystallographic Data Centre via
www.ccdc.cam.ac.uk/data_request/cif.
3+: 495.04; molar conductivity (MeCN): LM =10 Wꢀ1 cm2 mꢀ1
; found:
494.86; elemental analysis calcd (%) for C23H21O6Ru: C 55.75, H 4.28;
found: C 55.74, H 4.27.
Computational details: Full geometry-optimizations were carried out by
using density functional theory at the (R)B3LYP level for compounds 1+,
1ꢀ, 2, 3+, 3ꢀ and the (U)B3LYP level for compounds 12+, 1, 2+, 22+, 2ꢀ,
3.[19] All elements except for ruthenium were assigned with the 6–31G*
basis set. The LANL2DZ basis set with effective core potential was em-
ployed to assign the ruthenium atom.[20] Vibrational-frequency calcula-
tions were performed to ensure that the optimized geometries represent-
ed the local minima and only positive Eigen values were obtained. All
calculations were performed with the Gaussian09 program package.[21]
Vertical electronic excitations based on (U)B3LYP/(R)B3LYP-optimized
geometries were computed for compounds 1n (n=+2, +1, 0, ꢀ1), 2n (n=
+2, +1, 0, ꢀ1) and 3n (n=+1, 0, ꢀ1) by using time-dependent density
functional theory (TD-DFT)[22] in MeCN with a conductor-like polariza-
ble continuum model (CPCM).[23] Chemissian 1.7[24] was used to calculate
the fractional contributions of various groups to each molecular orbital.
All of these calculated structures were visualized with ChemCraft.[25]
Acknowledgements
Financial support from the Department of Science and Technology and
the Council of Scientific and Industrial Research (fellowships to A.D.
and P.M.), New Delhi (India), the DAAD, the FCI, and the DFG (Ger-
many), is gratefully acknowledged. X-ray structural analysis of com-
pounds [1]ClO4 and 3 were performed at the National Single-Crystal Dif-
fractometer Facility of the Indian Institute of Technology, Bombay. We
acknowledge the IITB Computer Center for providing the computing fa-
cilities.
Synthesis of [RuII
ACHTUNGTRENNUNG(pap)2Cl2] (100 mg, 0.19 mmol) and AgNO3 (62 mg, 0.38 mmol) in EtOH
ACHTUNGTRENNUNG(pap)2(L)]ClO4 ([1]ClO4): A mixture of ct-[Ru-
[1] a) R. C. Mehrotra, R. Bohra, D. P. Gaur, Metal b-Diketonates and
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2009, 253, 1099; g) R. C. Fay, Coord. Chem. Rev. 1996, 154, 99.
[2] a) A. Das, T. Scherer, S. Maji, T. K. Mondal, S. M. Mobin, F. A. Ur-
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2011, 50, 7040; b) A. Das, T. M. Scherer, A. Dutta Chowdhury, S. M.
Mobin, W. Kaim, G. K. Lahiri, Inorg. Chem. 2012, 51, 1675; c) A.
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Mondal, S. M. Mobin, J. Fiedler, F. A. Urbanos, R. Jimꢅnez-Apari-
cio, W. Kaim, G. K. Lahiri, Chem. Eur. J. 2012, 18, 5667; e) D. Das,
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(30 mL) was heated at reflux under a nitrogen atmosphere for 1 h. The
precipitated AgCl was filtered off and HL (36 mg, 0.19 mmol) and NEt3
(20 mg, 0.2 mmol, freshly distilled over KOH) were added to the filtrate.
The mixture was heated at reflux under a nitrogen atmosphere for 6 h.
The initial blue–violet color of the solution gradually changed to dark-
red–violet. The reaction mixture was evaporated to dryness, the crude
product was dissolved in a minimum volume of MeCN, and a saturated
solution of NaClO4 (10 mL) was added. The resulting dark-brown precip-
itate was filtered off and washed twice with ice-cold distilled water and
dried under vacuum. The crude product was purified by column chroma-
tography on neutral alumina. Red–violet complex [1]ClO4 was eluted
with a mixture of CH2Cl2/MeCN (5:2). Evaporation of the solvent under
reduced pressure yielded the pure complex as a solid. Yield: 90 mg
(64%); 1H NMR (400 MHz, [D6]DMSO, 298 K): d=8.95 (d, 8.07, 2H),
8.31 (t, 7.7, 2H), 8.10–8.20 (m, 4H), 8.06 (d, 6.2, 2H), 7.40–7.61 (m, 5H),
7.33 (d, 7.7, 4H), 7.15 (m, 2H), 6.93 ppm (d, 8.1, 4H); MS (ESI+,
MeCN): m/z calcd for 1+: 663.11; found: 662.92; molar conductivity
(MeCN): LM =110 Wꢀ1 cm2 mꢀ1; IR (KBr): n˜ =1089, 625 cmꢀ1 (ClO4ꢀ); el-
emental analysis calcd (%) for C35H25ClN6O2Ru: C 55.11, H 3.35,
N 11.03; found: C 55.09, H 3.32, N 11.01.
ˇ
Das, B. Sarkar, T. K. Mondal, S. M. Mobin, J. Fiedler, S. Zꢆlis, F. A.
Synthesis of [RuII
N
A
mixture of [Ru
G
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(150 mg, 0.17 mmol) and AgClO4 (71 mg, 0.34 mmol) in EtOH (30 mL)
Chem. Eur. J. 2012, 00, 0 – 0
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www.chemeurj.org
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Received: May 21, 2012
Published online: && &&, 0000
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Fractional Non-Innocence of a b-Diketonate Ligand
FULL PAPER
Mixed ligation: The p-acceptor effect
of 2-phenylazopyridine (pap) on ruthe-
nium is indirectly responsible for the
Non-Innocent Ligands
A. Das, T. M. Scherer, P. Mondal,
S. M. Mobin, W. Kaim,*
G. K. Lahiri* ................. &&&& — &&&&
partial oxidation of 9-oxidophenale-
ꢀ
C
none (L !L ) in mixed-ligand com-
plexes [Ru
N
Experimental- and DFT Evidence for
the Fractional Non-Innocence of a
Diketonate Ligand
ACHTUNGTRENNUNGb-
Chem. Eur. J. 2012, 00, 0 – 0
ꢂ 2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
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These are not the final page numbers!