Solid-state emission enhancement in vaulted trans-bis(salicylaldiminato) platinum(ii) crystals with halogen functionality

Article abstract of DOI:10.1039/c4dt00560k

The synthesis, structure, and solid-state emission of vaulted trans-bis(salicylaldiminato)platinum(ii) complexes 1-3 with halogen functionalities are described and compared with the non-substituted analogues. Chloro-substitution provided an improvement of the low emission properties of short-vaulted, non-substituted complexes 1 and 2 in the crystalline state at ambient temperature, while the intense emission of long-vaulted analogues 3 remained unchanged. Bromo-substituted crystals also emit intensively, while the fluoro analogue is non-emissive under the same conditions. Temperature-dependent emission spectra indicate that all chloro- and bromo-substituted crystals with enhanced emission properties at ambient temperature exhibit improved heat resistance properties towards emission decay with the halogen functionalities. X-ray diffraction studies revealed that such a positive effect of halogenation for the enhancement of solid-state emission is due to significant molecular constraints in the crystals by a combination of the vaulted structure and three-dimensional H...X hydrogen bonding interactions.

Full text of DOI:10.1039/c4dt00560k

Dalton
Transactions
View Article Online
View Journal | View Issue
PAPER
Solid-state emission enhancement in vaulted
trans-bis(salicylaldiminato)platinum(II) crystals with
halogen functionality†
Cite this: Dalton Trans., 2014, 43,
10074
Naruyoshi Komiya, Minoru Okada, Kanako Fukumoto, Shotaro Iwata and
Takeshi Naota*
The synthesis, structure, and solid-state emission of vaulted trans-bis(salicylaldiminato)platinum(II) com-
plexes 1–3 with halogen functionalities are described and compared with the non-substituted analogues.
Chloro-substitution provided an improvement of the low emission properties of short-vaulted, non-sub-
stituted complexes 1 and 2 in the crystalline state at ambient temperature, while the intense emission of
long-vaulted analogues 3 remained unchanged. Bromo-substituted crystals also emit intensively, while
the fluoro analogue is non-emissive under the same conditions. Temperature-dependent emission
spectra indicate that all chloro- and bromo-substituted crystals with enhanced emission properties at
ambient temperature exhibit improved heat resistance properties towards emission decay with the
halogen functionalities. X-ray diffraction studies revealed that such a positive effect of halogenation for
the enhancement of solid-state emission is due to significant molecular constraints in the crystals by a
combination of the vaulted structure and three-dimensional H⋯X hydrogen bonding interactions.
Received 22nd February 2014,
Accepted 7th May 2014
DOI: 10.1039/c4dt00560k
www.rsc.org/dalton
contacts such as π–π stacking5,6 and the construction of metal–
Introduction
metal interactions.2,3,5–8
Studies on the solid-state emission of transition-metal com-
plexes are important for the development of new functional solid-state emission and the molecular array of polymethylene-
materials that exhibit various stimuli-responsive emission pro- and polyoxyethylene-vaulted trans-bis(salicylaldiminato)-
Recently, we have investigated the correlation between the
perties, such as electroluminescence,1 vapochromism,2 and platinum(II) complexes in the crystalline state,5a,b where the
mechanochromism.3 Phosphorescent crystals of transition- specific heat resistance towards emission decay with increasing
metal complexes are extensively studied,2,3 due to their poten- temperature was found to be essential for intense phosphor-
tial for high-density integration, with the aim to realize escence at ambient temperature. Single-crystal X-ray diffraction
intense solid-state emission, although the emission of tran- (XRD) studies strongly suggest that the higher-ordered mole-
sition-metal complexes in the crystalline state is typically cular constraint by intermolecular interactions is an important
weaker than that in the solution state, due to the negative factor for solid-state emission and the heat resistance pro-
intermolecular effects in d–π conjugation systems.4 Two con- perties of the crystals. To gain further insight into the inter-
trasting strategies have been employed in molecular and molecular factors for the enhancement of solid-state emission,
crystal design to enhance the solid-state emission of tran- the effect of halogen functionalization of polymethylene-
sition-metal complex crystals: the functionalization of bulky vaulted trans-bis(salicylaldiminato)platinum(II) complexes 1–3
groups on each phosphor unit to avoid significant molecular (n = 10–12) was investigated. The introduction of chloro- and
bromo-substituents into the aromatic rings of vaulted plati-
num complexes enhances the emission properties in the crys-
Department of Chemistry, Graduate School of Engineering Science, Osaka University,
talline state by decreasing the structural dependence of the
Machikaneyama, Toyonaka, Osaka 560-8531, Japan.
heat resistance properties,5a,b while the fluoro analogues
E-mail: naota@chem.es.osaka-u.ac.jp
are entirely non-emissive. The XRD results revealed that the
present enhancement of emission by halogen functionali-
zation is due to an increase in the dimensionality of the mole-
cular constraint in the crystal units by a synergistic effect of
the vaulted structure and the hydrogen bonding network with
chlorine/bromine atoms.9 The platform also exhibits a wide
†Electronic supplementary information (ESI) available: Photophysical data of
1–4 in 2-MeTHF; Photophysical data of 1g, 2g, and 3g in crystalline state; Fron-
tier orbitals and their eigenvalues for 3a–d; excitation energy, oscillator strength
and major electronic configuration of 3a–d; relationship between the T1–S0
energy gap and λmax for 3a–d in 2-MeTHF at 77 K. CCDC 985138–985144. For
ESI and crystallographic data in CIF or other electronic format see DOI:
10.1039/c4dt00560k
10074 | Dalton Trans., 2014, 43, 10074–10085
This journal is © The Royal Society of Chemistry 2014

View Article Online
Dalton Transactions
Paper
chromogenic change over 41 nm for solid-state emission, obtained by recrystallization from EtOH. The trans-coordi-
simply by chloro-substitution at different positions on the aro- nation and vaulted structures of 2b and 3b–f have been
matic rings. Here, we describe the synthesis, structure, and unequivocally established by singe-crystal XRD at 113 K
solid-state emission of a series of polymethylene-vaulted trans- (Table 1). ORTEP10 drawings of these crystals are shown in
bis(salicylaldiminato)platinum(II) complex crystals bearing Fig. 1, where the angles of C(5)–Pt(1)–C(11) and dihedral
halogen functionalities, with a focus on the mechanistic angles of C(13)–N(1)–Pt(1)–O(1)/C(14)–N(2)–Pt(1)–O(2) are
rationale for the heat resistance properties based on the mole- listed to express a macroscopic view of the coordination pla-
cular arrays of the crystal unit.
narity for the trans-bis(salicylaldiminato)platinum moieties.
The C(5)–Pt(1)–C(11) angles in short-bridged 2b (unit 1: 154°;
unit 2: 155°) are significantly smaller than those in long-
bridged 3b (178°; 179°), 3c (168°), 3d (155°), 3e (173°), 3f
(174°; 178°), and the dihedral angles of C(13)–N(1)–Pt(1)–O(1)/
C(14)–N(2)–Pt(1)–O(2) in 2b (unit 1: 10.9°, 14.0°; unit 2: 10.2°,
18.5°) are much larger than those in 3b (2.6°, 6.3°; 0.4°, 6.5°),
3c (8.9°, 10.7°), 3d (6.0°, 19.9°), 3e (0.8°, 14.5°) and 3f (5.0°,
5.1°, 0.3°, 9.2°). A correlation between the coordination planar-
ity and the chain length in 4-Cl crystals 2b and 3b was also
observed in the non-substituted complexes, as indicated in the
C(5)–Pt(1)–C(11) angles of 162° for 1g, 172° for 2g, and 174°
for 3g.5b The specific bent structure of 3d is due to stabiliz-
ation by intermolecular stacking interactions as shown in
Fig. 14b, discussed in the following section.
Results and discussion
Synthesis and structure of vaulted complexes
A series of trans-bis(salicylaldiminato)platinum(II) complexes
bearing polymethylene bridges with and without a halogen
functionality 1–3 [1: n = 10; 2: n = 11; 3: n = 12; a: 3-Cl (ortho-
position of the phenol moiety); b: 4-Cl (meta-position); c: 5-Cl
(para-position); d: 6-Cl (ortho-position of the imine moiety);
e: 4-F; f: 4-Br; g: H] was prepared by reaction of PtCl2(CH3CN)2
Effect of halogen substituents on the emission properties in
the crystalline state
with the corresponding N,N′-bis(salicylidene)-1,ω-alkanedi- Complexes 1–3 bearing chloro- and bromo-substituents on the
amines in boiling dimethyl sulfoxide (DMSO) and toluene. A aromatic rings generally exhibit intense solid state emission
non-vaulted, 4,4′-dichloro-N,N′-dimethyl complex 4b was simi- properties in the crystalline state under excitation at 420 nm,
larly prepared from N-(4-chlorosalicylidene)-methylamine. although 2 × 10−4 M solutions of these complexes in 2-methyl-
Racemic crystals employed for single-crystal XRD studies were tetrahydrofuran (2-MeTHF) are non-emissive at 298 K under
Table 1 Crystallographic data for 2b, 3b, 3c, 3d, 3e and 3f
( )-2b
( )-3b
( )-3c
( )-3d
( )-3e
( )-3f
Formula
Mr
C25H30Cl2N2O2Pt
656.52
C26H32Cl2N2O2Pt
670.55
C26H32Cl2N2O2Pt
670.55
C26H32Cl2N2O2Pt
670.55
C26H32F2N2O2Pt
637.64
C26H32Br2N2O2Pt
759.45
T/K
113
113
113
113
113
113
Crystal colour, habit
Crystal size/mm
Crystal system
Space group
a/Å
b/Å
c/Å
Yellow, platelet
0.30 × 0.20 × 0.10
Orthorhombic
Pbca (#61)
14.0659(3)
24.2531(5)
28.6200(7)
90
90
90
9763.4(3)
16
1.786
Orange, block
0.30 × 0.30 × 0.20
Triclinic
Orange, block
0.50 × 0.40 × 0.30
Monoclinic
P21/c (#14)
18.462(1)
11.4626(6)
12.2654(6)
90
99.383(1)
90
2560.9(3)
4
Orange, block
0.60 × 0.20 × 0.20
Monoclinic
P21/c (#14)
10.5969(5)
10.0106(5)
24.093(1)
90
100.154(2)
90
2515.8(2)
4
Yellow, block
0.40 × 0.30 × 0.30
Monoclinic
C2/c (#15)
23.8726(8)
10.2735(4)
20.2881(6)
90
98.850(1)
90
4916.5(3)
8
Yellow, block
0.10 × 0.06 × 0.06
Triclinic
ˉ
ˉ
P1 (#2)
P1 (#2)
10.5711(5)
11.6286(6)
20.5715(10)
87.5780(10)
87.8350(19)
84.4990(18)
2513.5(2)
4
1.772
57.987
1320.00
54.9
10.6479(8)
11.7560(9)
20.876(2)
92.207(2)
93.481(2)
98.670(2)
2575.5(4)
4
α/°
β/°
γ/°
V/Å3
Z
ρcalcd/g cm−3
μ(MoKα)/cm−1
F(000)
1.739
56.914
1320.00
55.0
1.770
57.933
1320.00
54.9
1.723
57.254
2512.00
54.9
1.958
59.691
5152.00
55.0
85.642
1464.00
55.0
2θmax/°
No. of reflns measd
No. of obsd reflns
No. variables
R1 (I > 2σ(I))a
wR2 (all reflns)b
Goodness of fit
192 498
11 136
557
0.039
0.099
49 919
11 434
595
0.022
0.055
1.09
49 653
5843
298
0.044
0.117
1.13
48 829
5723
298
0.039
0.106
1.07
47 837
5609
298
0.027
0.060
1.07
51 925
11 709
595
0.069
0.18
1.05
1.09
a R1 = ∑(|Fo| − |Fc|)/∑(|Fo|). b wR2 = [∑(w(Fo2 − Fc2)2]/∑w(Fo2)2]1/2
.
This journal is © The Royal Society of Chemistry 2014
Dalton Trans., 2014, 43, 10074–10085 | 10075

View Article Online
Paper
Dalton Transactions
Fig. 1 ORTEP representation of halo-substituted trans-bis(salicylaldiminato)platinum (a) (S)-2b, (b) (S)-3b, (c) (S)-3c, (d) (S)-3d, (e) (S)-3e and (f) (S)-
3f as their racemic crystals. Thermal ellipsoids are shown at the 50% probability level. The angle of C(5)–Pt(1)–C(11) and dihedral angles of C(13)–N
(1)–Pt(1)–O(1)/C(14)–N(2)–Pt(1)–O(2) (in parentheses) are given under each structure.
Table 2 Photophysical data for 1–4 in the crystalline statea
Complex λabs (nm)
λem (nm) Φb
τ (μs)c CIE (x, y)
1bd
2bd
3ad
3bd
3cd
3dd
3ed
3fd
325, 436, 511 572
321, 433, 509 580
326, 444, 515 570
327, 447, 511 544, 569 0.29 (0.41) 1.01
333, 464, 535 598
0.05 (0.35) 0.06
0.12 (0.30) 1.36
0.01 (0.24) 0.11
0.49, 0.50
0.52, 0.48
0.49, 0.51
0.46, 0.54
0.56, 0.44
0.62, 0.38
0.10 (0.36) 0.74
324, 458, 538 605
0.08 (0.17) 0.51
e
e
e
305, 424, 500
—
—e (0.49)
—
—
326, 440, 511 541, 568 0.20 (0.47) 0.60
326, 420, 504 594 0.01 (0.12) 0.08
0.46, 0.53
0.55, 0.44
4b
a Data obtained at 298 K under excitation at 420 nm. All crystals were
obtained by recrystallization from EtOH or AcOEt. b Determined by the
absolute method using an integrating sphere. Values in parentheses
are those measured at 77 K. c λex = 415 nm. d Racemic crystal. e No emission.
the same conditions (Φ298K < 0.01).5,7 Crystals employed for
photophysical analyses were obtained by recrystallization from
EtOH for 1–3 and EtOAc for non-vaulted analogue 4b. Photo-
physical data of 1–3 and 4b in the crystalline state and in
2-MeTHF are given in Table 2 and Table S1, ESI,† respectively.
Quantum efficiencies (Φ) were determined using the absolute
method with an integrating sphere accessory.11 The lifetimes
(τ) of the crystals indicate that their emissions are phosphorescent.
Crystal 3b bearing 4-Cl and a dodecamethylene bridge exhi-
bits intense yellow emission at 298 K under excitation at
420 nm (Φ298K = 0.29), while non-vaulted, 4-Cl analogue 4b
emits a very weak red-orange phosphorescence under the same
conditions (Φ298K = 0.01). The ratio of quantum efficiencies at
298 and 77 K (Φ298K/Φ77K) is 0.71 for 3b and 0.08 for 4b, which
indicates that vaulted 3b has high heat resistance towards
emission decay with increasing temperature, and non-vaulted
4b is heat quenchable. The contrasting temperature-dependent
emission profiles for 3b and 4b in the range of 77–298 K are
shown in Fig. 2. The positive effect of vaulting on 4-chloro
complexes is much greater than that on non-substituted ana-
Fig. 2 Temperature-dependence of emissions for (a) heat resistant 3b
and (b) heat quenchable 4b crystals at 77 K–298 K (λex = 420 nm).
logues, as shown by the heat resistance properties (Φ298K/Φ77K
)
of non-substituted, vaulted complex 3g (0.63) and non-vaulted
analogue 4g (0.39).5a,b Fig. 3 shows normalised emission
spectra for 3b, 4b, 3g and 4g crystals at 298 K. Note that the
emission maxima of the 4b crystal (λmax = 594 nm) are signifi-
cantly red-shifted with respect to those of the 3b crystal
(544 nm) (Fig. 3a), while the emission spectra of the 3g crystal
are very similar to that of the 4g crystal (Fig. 3b).5a,b
Dependence of the emission intensities on the linker
length of 4-Cl-substituted crystals 1b–3b is significantly
10076 | Dalton Trans., 2014, 43, 10074–10085
This journal is © The Royal Society of Chemistry 2014

View Article Online
Dalton Transactions
Paper
cantly high quantum efficiencies at 77 K (Φ77K = 0.17–0.49,
Fig. 4a), a clear chain-length dependence is observed at 298 K
(Fig. 4b). Chloro-substituted crystals 1b–3b emit weakly
[Φ298K = 0.05 for 1b (n = 10)], moderately [0.12 for 2b (n = 11)]
and more intensively [0.29 for 3b (n = 12)] at 298 K as the
chain lengths of the polymethylene bridges increase. In con-
trast, only the 3g crystal exhibits a significant emission at
298 K (Φ298K = 0.32) among the non-substituted crystals, while
the 1g and 2g analogues with shorter linkers are almost non-
emissive under the same conditions (<0.01).5a,b The Φ298K
/
Φ77K ratios for Cl-substituted crystals 1b–3b are higher (1b:
0.14; 2b: 0.40; 3b: 0.71) than those of non-substituted crystals
1g–3g (1g: <0.01; 2g: <0.01; 3g: 0.63), which indicates that the
original heat resistance properties of 1g–3g crystals towards
emission decay increases by substitution with the 4-Cl group
on the aromatic rings. In addition, the extraordinarily high
linker dependence of the heat resistance properties for the
1g–3g crystals decreases significantly with halogen functionali-
zation. Such a contrasting linker-dependence of the heat resist-
ance of chloro- and non-substituted crystals can be visualized
by the temperature dependence of the emission spectra from
77 to 298 K, as shown in Fig. 5.
The strong halogen effect on the heat resistance properties
of the vaulted crystals is also observed for 4-Br-substituted
complex crystal 3f, which exhibits intense yellow emission
under UV excitation at ambient temperature. The quantum
efficiencies of the 3f crystal at 298 and 77 K are 0.20 and 0.47,
respectively. In contrast to the 4-Cl and 4-Br complexes, 4-F
complex crystal 3e is non-emissive at ambient temperature,
and the quantum efficiencies at 298 and 77 K are <0.01 and
0.49 respectively. The high heat resistance of 4-Cl and 4-Br
crystals 3b, 3f, and contrasting heat quenchable properties of
4-F crystal 3e are visualized by the temperature dependent
emission spectra (Fig. 2a, 6a and 6b) and the relationship
between the normalised intensity of the emission maxima and
temperature (Fig. 6c) for these crystals.
Fig. 3 Normalised emission spectra for (a) 4-chloro crystals, 3b, 4b and
(b) non-substituted crystals, 3g, 4g at 298 K (λex = 420 nm).
Chromatic controllability with chloro functionality
Chromogenic control can be achieved simply by the introduc-
tion of a Cl-substitution at different positions on the aromatic
rings. Yellow, orange and red emissions can be generated from
the crystals by substitution with a chloro group at the 3-, 4-, 5-,
and 6-positions, respectively, whereas the emission colour of
the non-substituted crystals 1g–3g is yellow. Emission spectra
of Cl-substituted crystals 3a–d with dodecamethylene bridges
are shown in Fig. 7, where the emission maxima (λmax) are sig-
nificantly varied and dependent on the position of the chloro
group [570 (3a), 569 (3b), 598 (3c) and 605 nm (3d) at 298 K
(Fig. 7a); 544 (3a), 543 (3b), 557 (3c) and 584 nm (3d) at 77 K
(Fig. 7b)]. The emission maxima of complexes 3a–d in the
2-MeTHF glass state at 77 K are 519 (3a), 521 (3b), 538 (3c) and
538 nm (3d) (Table S1, ESI†), which indicates an extraordinary
red-shift of the 3d crystal due to intermolecular interaction in
Fig. 4 Correlation between chain length and quantum efficiency of
1–3 crystals at (a) 77 and (b) 298 K (λex = 420 nm).
different from those of non-substituted crystals 1g–3g. Fig. 4 the condensed state. The CIE colour coordinates plotted on
shows the correlation between chain length and quantum the CIE1930 chromaticity chart in Fig. 7a indicate that the crys-
efficiency for the 1–3 crystals. Although all crystals have signifi- talline-state emissions are brilliantly coloured with high chro-
This journal is © The Royal Society of Chemistry 2014
Dalton Trans., 2014, 43, 10074–10085 | 10077

View Article Online
Paper
Dalton Transactions
Fig. 5 Temperature-dependence of emission for (a–c) 4-chloro (1b–3b) and (d–e) non-substituted (1g–3g) platinum complexes in the crystalline
state at 77–298 K (λex = 420 nm). Data in c (from Fig. 2a) and d–e (ref. 5a and b) are presented for comparison.
Fig. 6 Temperature-dependence of emission for (a) heat resistant 3f and (b) heat quenchable 3e crystals at 77–298 K (λex = 420 nm). (c) Decays in
normalised intensity of emission maxima (λmax) at 298 K for 3b, 3e and 3f crystals as a function of temperature.
matic purity. UV-vis diffuse reflectance spectra of 3a–d have a (H-bonding) interactions between Cl and imine H atoms
broad absorption band that is attributable to a mixture of (bonding A), and that between Cl and the linker H (bonding
1MLCT (metal-to-ligand charge transfer) and 1ILCT (intra- B). The c-axis projection (ab-plane) of crystal 3b shows that the
ligand charge transfer) at approximately 440–460 nm in the ac-plane is consecutively stacked with neighbouring ac-planes
crystalline state (Fig. 8). The significant hypsochromic shift in consisting of the (S)-form of unit 1 and (R)-form of unit 2,
the absorbance of 3a,b and the bathochromic shift in 3c,d are where H-bonding between Cl (unit 2) and linker H (unit 1)
rationally synchronized to these changes in emission colour.
atoms are observed in a homochiral manner (bonding C in
Fig. 9b). Heterochiral H-bonding between O (unit 1) and linker
H (unit 1) atoms is also observed on the bc-plane (bonding D,
Fig. 9c). The a-axis projection and the overhead view of non-
vaulted crystal 4b show that the aromatic moiety of each mole-
cular unit is stacked consecutively with a typical π-stacking dis-
tance [the distance between C(1)–C(6)–C(5) and C(2′)–C(3′)–
C(4′) planes] of 3.36 Å to give a highly regulated multilayered
structure (bonding A in Fig. 10a and b). H-bonding between Cl
Mechanistic rationale for solid-state emission enhancement
The contrasting difference in the emission intensities and
colours for vaulted 3b and non-vaulted 4b crystals (Fig. 2 and
3) can be explained by molecular alignment and intermole-
cular interactions in the crystals. Crystal 3b has an alternating
alignment of the (R)-form of unit 1 and (S)-form of unit 2 on
the ac-plane (Fig. 9a) by heterochiral hydrogen-bonding
10078 | Dalton Trans., 2014, 43, 10074–10085
This journal is © The Royal Society of Chemistry 2014

View Article Online
Dalton Transactions
Paper
Fig. 7 Normalised emission spectra for the 3a–d crystals at (a) 298 and
(b) 77 K (λex = 420 nm). The inset in (a) shows the CIE colour coordinates
of the emissions.
Fig. 8 Normalised diffuse reflectance UV-vis spectra for the 3a–d crys-
tals at 298 K (λex = 420 nm).
and imine H atoms is observed on the ac-plane as the sole sig-
nificant H-bonding interaction in crystal 4b (bonding B in
Fig. 10b). These results indicate that vaulted complex 3b has a
three-dimensional (3D) molecular constraint in the crystalline
state, while non-vaulted crystal 4b is less bound with stacking
Fig. 9 Packing and significant interactions in the 3b crystal. (a) b-,
(b) c- and (c) a-axis projections.
and H-bonding interactions in a 2D manner. Thus, the con- state has been discussed for non-vaulted trans-bis(salicyl-
trasting heat resistance properties of crystals 3b (Φ298K/Φ77K
aldiminato)platinum complexes bearing long alkyl chains.5c
=
0.71) and 4b (<0.01) are attributable to the degree of dimen- The specific red-shifted emission of the 4b crystal (Fig. 3) can
sionality in molecular constraint of the crystal unit, which be also attributed to highly regulated π-stacking,11 as shown in
would significantly inhibit the dispersion of photoenergy from Fig. 10a.
the excited state at higher temperature.5 The low quantum
Low structural dependence on the heat resistance pro-
efficiency of crystal 4b observed even at 77 K (Φ77K = 0.12, perties of 4-Cl-substituted crystals 1b–3b (Fig. 4) can also be
Table 2) can be rationalized by the energy dispersion through rationalized by their higher dimensionality of molecular con-
consecutive intermolecular π-stacking interactions of aromatic straint in the crystal unit. As shown by the packing of the
rings. The correlation between the low emission properties short-vaulted 2b crystal (n = 11, Fig. 11a), cofacial pairs of
and consecutive stacking molecular array in the crystalline (R)-unit 1 and (S)-unit 2, bound with Pt⋯Pt interaction
This journal is © The Royal Society of Chemistry 2014
Dalton Trans., 2014, 43, 10074–10085 | 10079

View Article Online
Paper
Dalton Transactions
Fig. 11 Packing and significant interactions in the 2b crystal. (a) c- and
(b) b-axis projections.
difference in the packing of non-substituted crystals, where
the long-vaulted 3g unit has 3D self-constraint with various
O⋯H and Pt⋯Pt interactions due to its highly planar struc-
ture, while the short-vaulted units 1g and 2g have low dimen-
sionality in self-constraint arising from their bent structures.5a,b
Thus, the enhancement of such self-constraint by Cl-substi-
tution leads to a decrease in the clear structure-dependence of
the heat resistance/quenchable properties of 1g–3g crystals
(Fig. 4b). The comparably high heat resistance of 4-Br-substi-
tuted crystal 3f (Fig. 6a) is also ascribed to a high dimensional-
ity of molecular constraint in the crystal unit, similar to that of
4-Cl analogue 3b (Fig. 9 and 12). Heat quenchable 4-F crystal
3e (Fig. 6b and c) has an alternating alignment of (R)- and
(S)-units, which are bound to each other with H-bonding inter-
actions between F and imine H atoms (Fig. 13). This singular
interaction on the ac-plane is the sole significant intermole-
cular interaction in crystal 3e. Such a low dimensionality of
molecular constraint in the crystal unit would induce the heat
quenchable properties of the 3e crystal.
Fig. 10 Packing and significant interactions in the 4b crystal. (a) a- and
(b) b-axis projections. (c) Overhead view of a stacked dimer.
(bonding A) are aligned alternatively with their enantiomeric
pairs of (S)-unit 1 and (R)-unit 2, with H-bonding interactions
between Cl and linker H atoms (bonding B). Heterochiral
H-bonding interactions between Cl and imine H atoms of
identical units are also observed on the ac-plane of the crystal
(bonding C in Fig. 11b). These results indicate that even short-
vaulted crystal 2b has a similar high dimensionality of self-
constraint in the molecular unit, as with long-vaulted crystal
3b, due to the significant contribution of Cl substituents to
the self-constraint of the crystal unit. This is in contrast to the
The molecular orbitals of 3a–d were estimated from density
functional theory (DFT; B3LYP/6-31*G, LanL2DZ) calculations
on the basis of the optimized structures. The highest-occupied
molecular orbitals (HOMO) of all complexes are principally
Pt(5d)–O(2p) hybrids, while the lowest-unoccupied molecular
10080 | Dalton Trans., 2014, 43, 10074–10085
This journal is © The Royal Society of Chemistry 2014

View Article Online
Dalton Transactions
Paper
Fig. 12 Packing and significant interactions in the 3f crystal. (a) b- and
(b) a-axis projections.
Fig. 14 Packing and significant interactions in the 3d crystal. (a) a-Axis
projection. (b) Overhead view of heterochiral stacked dimer.
maximum emission wavelengths of 3a–d, observed in a diluted
2-MeTHF glass state at 77 K, are strongly correlated to the
T1–S0 gaps [2.35 (3a), 2.38 (3b), 2.25 (3c), 2.30 eV (3d)] esti-
mated from TD-DFT calculations (Fig. S2, ESI†). Given the con-
clusion that the major electronic configuration of the S1(T1)
states are HOMO-to-LUMO, this correlation indicates that the
present chromatic changeability in the diluted glass state can
be explained simply based on the frontier orbitals of an iso-
lated system. The significant red-shift of the emission from
6-Cl crystal 3d (Fig. 7b) is ascribed to its specific π-stacking
interaction between crystal units. The a-axis projection of
the 3d crystal shows that cofacial dimeric pairs of (R)- and
(S)-units bound with π-stacking interaction (bonding A) are
aligned in an alternatively overturned packing manner with
the assistance of H-bonding interactions (bondings B and C)
(Fig. 14a). The overhead view of the heterochiral dimer unit
clearly shows the deep stacking situation where electron-rich
sites around O(1)/O′(1) atoms are bound with electron-
deficient sites around C(6)/C′(6) atoms in a head-to-tail
manner. Such strong donor–acceptor interactions would
induce a significant red-shift of the emission in the crystalline
state (Fig. 3a).12
Fig. 13 Packing and significant interactions in the 3e crystal. b-Axis
projection.
orbitals (LUMO) are CvN (π*) (Fig. S1, ESI†). The energy levels
and electronic configurations of the singlet and triplet states
of 3a–d were estimated from time-dependent DFT (TD-DFT)
calculations (Table S3, ESI†). The major electronic configur-
ation of the S1(T1) states are determined to be HOMO-to-
LUMO, which implies that the present phosphorescent emis-
sion is principally attributable to 3MLCT. Chromatic control by
chloro functionalization was rationalized on the basis of these
calculations and the molecular packing in the crystals. The
Fig. 15 shows schematic representations for the effect of Cl-
substitution on the packing and emission properties of long-
This journal is © The Royal Society of Chemistry 2014
Dalton Trans., 2014, 43, 10074–10085 | 10081

View Article Online
Paper
Dalton Transactions
Fig. 15 Schematic representation of the Cl-substitution effect on (a) long- and (b) short-vaulted crystals.
and short-vaulted crystals 2 and 3. The high coordination pla- emission decay (Φ298K/Φ77K: 0.53 for 4g5a,b and 0.08 for 4b).
narity and strong Pt⋯Pt interactions provide the long-vaulted This contrasting phenomenon can also be rationalized by the
(n = 12), non-substituted crystal 3g with high emission pro- Cl⋯H bonding, which acts as an important supporting factor
perties at 77 K and heat resistance towards emission decay at for the construction of a low dimensional stacking architec-
higher temperature (Fig. 15a, left).5a,b The Cl⋯H bonding ture, as shown in Fig. 10b. These results suggest that the emis-
network in the 4-Cl-substituted, long-vaulted (n = 12) 3b crystal sion enhancement with halogen functionalization is the result
takes precedence with the sacrifice of the advantageous Pt⋯Pt of a synergistic effect caused by the strong H-bonding ability
interactions to maximize the total stabilization of the crystal of halogen atoms and the specific 3D superstructure of the
unit. Thus, the emission and heat resistance properties of vaulted crystal unit.
crystal 3b remain high after Cl-substitution, due to the high
coordination planarity and high dimensionality of molecular
constraint (Fig. 15a, right). The short-vaulted (n = 11), non-sub-
stituted 2g crystal has no significant intermolecular inter-
Conclusions
actions such as H-bonding or Pt⋯Pt contact, which affords A series of polymethylene-vaulted trans-bis(salicylaldiminato)-
extraordinarily low heat resistance properties (Fig. 15b, left).5a,b platinum(II) complexes bearing halogen functionalities was
Cl-substitution of the short-vaulted complex (n
= 11) synthesized which exhibits intense emissions in the crystalline
increases self-constraint in the crystal unit by the addition of state. Chloro-substitution has proven to significantly increase
two-dimensional Cl⋯H bonding and Pt⋯Pt interactions with the lower heat resistance of short-vaulted, non-substituted
a decrease in the coordination planarity of the crystal unit crystals, and maintain the intense emission of long-vaulted
(Fig. 15b, right). This change in the structure and environment analogues, which leads to intense solid-state emission of the
of the crystal unit induces not only a decrease in quantum vaulted crystals with low structural dependence. XRD studies
efficiency at 77 K (Φ77K: 0.60 for 2g5a,b 0.30 for 2b), but also an have revealed that the emission enhancement with halogen
increase in the heat resistance properties (Φ298K/Φ77K: <0.01 functionalization is due to an increase in the dimensionality
for 2g5a,b and 0.40 for 2b).
of molecular constraint in the crystal unit due to a synergistic
It should be noted that Cl-substitution of non-vaulted effect of the vaulted structure and highly dimensional
crystal 4 significantly decreases the heat resistance towards H-bonding network interactions.
10082 | Dalton Trans., 2014, 43, 10074–10085
This journal is © The Royal Society of Chemistry 2014

View Article Online
Dalton Transactions
Paper
Complex 3a. Yellow block (5.9%); mp 229–230 °C. IR (KBr)
Experimental section
General
2924, 2849, 1619, 1594, 1441, 1404, 1325, 1228, 1187, 1142,
1079, 866, 734 cm−1 1H NMR (CDCl3, 500 MHz) δ 1.10–1.50
;
N,N′-Bis(salicylidene)-1,ω-alkanediamines were prepared by (m, 18 H), 2.22–2.33 (m, 2 H), 2.99 (ddd, J = 11.2, 10.4, 3.0 Hz,
reaction of substituted salicylaldehyde (3-Cl,13 4-Cl,14 5-Cl, 2 H), 5.24 (ddd, J = 11.2, 4.3, 4.3 Hz, 2 H), 6.55 (dd, J = 7.8,
6-Cl,14 4-Br and 4-F) with 1,ω-alkanediamine (ω = 10–12) in 7.8 Hz, 2 H), 7.19 (dd, J = 7.8, 1.6 Hz, 2 H), 7.48 (dd, J = 7.8,
boiling ethanol. Melting points were measured in a glass capil- 1.6 Hz, 2 H), 7.87 (s, 2 H); 13C NMR (CDCl3, 125 MHz) δ 23.2,
lary on a Büchi B-545 melting point apparatus. IR spectra were 27.0, 27.4, 27.5, 29.9, 59.7, 115.3, 121.6, 124.6, 132.4, 133.1,
1
recorded on a Bruker Equinox 55/S spectrometer. H and 13C 158.2, 158.4; HRMS (FAB+) m/z calcd for C26H32N2O235Cl2196Pt
NMR spectra were recorded on a Varian Unity-Inova 500 (M+): 670.1490; found: 670.1473.
spectrometer. Mass spectra were obtained on a Jeol JMS-DX
Complex 3b. Yellow block (23%); mp 200–201 °C. IR (KBr)
303 spectrometer. Elemental analyses were performed with a 2926, 2850, 1617, 1524, 1429, 1301, 1208, 1074, 932, 777 cm−1
;
Perkin-Elmer 2400II CHN elemental analyser. Diffuse reflec- 1H NMR (CDCl3, 500 MHz) δ 1.08–1.18 (m, 2 H), 1.26–1.53 (m,
tance UV-vis spectra were obtained on a Jasco V-570 spectro- 16 H), 2.10–2.21 (m, 2 H), 2.92 (ddd, J = 11.2, 10.3, 3.1 Hz,
meter equipped with an integrating sphere. Emission spectra 2 H), 4.86 (ddd, J = 11.2, 4.5, 4.5 Hz, 2 H), 6.57 (dd, J = 8.5,
were obtained using a Jasco FP-6500 spectrometer. Quantum 1.8 Hz, 2 H), 6.90 (d, J = 1.8 Hz, 2 H), 7.15 (d, J = 8.5 Hz, 2 H),
efficiencies were measured by the absolute method11 using a 7.77 (s, 2 H); 13C NMR (CDCl3, 125 MHz) δ 23.4, 27.1, 27.4,
Jasco FP-6500 spectrometer equipped with an integrating 27.5, 29.9, 58.8, 116.5, 119.4, 119.9, 134.3, 139.1, 158.1, 163.9.
sphere. Emission lifetime measurements were conducted Anal. calcd for C26H32Cl2N2O2Pt: C, 46.58; H, 4.81; N, 4.18.
using an Optical Building Blocks Easylife V instrument with a Found: C, 46.64; H, 4.68; N, 4.15.
415 nm LED for excitation.
Complex 3c. Orange block (25%); mp 235–236 °C; IR (KBr)
2923, 2852, 1619, 1530, 1461, 1391, 1315, 1178, 1135, 818,
705 cm−1 1H NMR (CDCl3, 500 MHz) δ 1.07–1.18 (m, 2 H),
;
1.25–1.54 (m, 16 H), 2.11–2.21 (m, 2 H), 2.92 (ddd, J = 11.2,
Synthesis of platinum complexes 1–3
A mixture of PtCl2(CH3CN)2 15 (0.423 g, 1.00 mmol), the corres- 10.2, 3.2 Hz, 2 H), 4.88 (ddd, J = 11.2, 4.1, 4.1 Hz, 2 H), 6.82 (d,
ponding N,N′-bis(salicylidene)-1,ω-alkanediamine (1.00 mmol), J = 8.9 Hz, 2 H), 7.20 (d, J = 2.7 Hz, 2 H), 7.24 (dd, J = 8.9,
and K2CO3 (0.900 g, 6.51 mmol) in DMSO (60 mL) was refluxed 2.7 Hz, 2 H), 7.75 (s, 2 H); 13C NMR (CDCl3, 125 MHz) δ 23.4,
with toluene (240 mL) at 140 °C for 24 h. After evaporation of 27.1, 27.3, 27.5, 29.9, 58.9, 119.8, 121.1, 121.9, 131.6, 133.5,
the solvent under reduced pressure, the residue was poured 157.8, 162.3; HRMS (FAB+) m/z calcd for C26H3235Cl2N2O2196Pt
into a mixture of EtOAc (20 mL) and water (200 mL). The (M+): 670.1490; found: 670.1473.
resulting organic layer was washed with water, dried over
MgSO4, and concentrated under reduced pressure to give a (KBr) 2926, 2854, 1612, 1594, 1527, 1438, 1397, 1350, 1315,
crude orange solid. Column chromatography (Fuji Silysia 1192, 950, 919, 781, 722 cm−1 1H NMR (CDCl3, 500 MHz) δ
Complex 3d. Orange solid (3.2%); mp 187.0–188.0 °C; IR
;
Chromatorex NH-DM1020, n-hexane–EtOAc) afforded 1–3 as a 1.12–1.64 (m, 18 H), 2.15–2.25 (m, 2 H), 3.08 (ddd, J = 11.2,
yellow or orange solid. The complexes were recrystallized from 10.3, 3.9 Hz, 2 H), 4.88 (ddd, J = 11.2, 5.0, 5.0 Hz, 2 H), 6.64
EtOH for photophysical studies (Table 2, Fig. 2–8).
(dd, J = 7.6, 1.1 Hz, 2 H), 6.80 (dd, J = 8.6, 1.1 Hz, 2 H), 7.15
Complex 1b. Yellow block (1.1%); mp 214–215 °C. IR (KBr) (dd, J = 8.6, 7.6 Hz, 2 H), 8.41 (s, 2 H); 13C NMR (CDCl3,
2928, 2854, 1622, 1593, 1524, 1458, 1423, 1392, 1293, 1201, 125 MHz) δ 23.9, 27.2, 27.3, 27.7, 30.4, 59.4, 117.0, 118.5,
1075, 937, 857, 782 cm−1
;
1H NMR (CDCl3, 500 MHz) 119.8, 132.4, 135.4, 155.9, 165.6; HRMS (FAB+) m/z calcd for
δ 1.20–1.83 (m, 14 H), 2.37–2.47 (m, 2 H), 2.97 (ddd, J = 11.4, C26H32N2O235Cl37Cl195Pt (M+): 671.1459; found: 671.1461.
10.8, 3.4 Hz, 2 H), 4.84 (ddd, J = 11.4, 3.9, 3.9 Hz, 2 H), 6.56 Complex 3e. Yellow block (34%); mp 172–173 °C; IR (KBr)
(dd, J = 8.5, 2.0 Hz, 2 H), 6.90 (d, J = 2.0 Hz, 2 H), 7.14 (d, J = 2930, 2854, 1623, 1544, 1434, 1301, 1216, 1155, 1114, 989,
8.5 Hz, 2 H), 7.74 (s, 2 H); 13C NMR (CDCl3, 125 MHz) δ 22.9, 850 cm−1 1H NMR (CDCl3, 500 MHz) δ 1.08–1.18 (m, 2 H),
;
25.7, 27.3, 28.7, 59.6, 116.4, 119.8, 119.9, 134.2, 139.0, 157.6, 1.27–1.54 (m, 16 H), 2.12–2.22 (m, 2 H), 2.91 (ddd, J = 11.3,
164.1; HRMS (FAB+) m/z calcd for C24H28N2O235Cl37Cl194Pt 10.4, 3.4 Hz, 2 H), 4.84 (ddd, J = 11.3, 4.4, 4.4 Hz, 2 H), 6.35
(M+): 642.1125; found: 642.1099.
(ddd, J = 8.7, 7.8, 2.5 Hz, 2 H), 6.55 (dd, J = 11.7, 2.5 Hz, 2 H),
Complex 2b. Yellow platelets (35%); mp 210–211 °C. IR 7.20 (dd, J = 8.7, 7.1 Hz, 2 H), 7.75 (s, 2 H); 13C NMR (CDCl3,
2
(KBr) 2924, 2853, 1621, 1593, 1524, 1425, 1393, 1295, 1200, 125 MHz) δ 23.4, 27.1, 27.4, 27.5, 29.9, 58.7, 104.8 (d, JC–F
=
1074, 932, 854, 780 cm−1
;
1H NMR (CDCl3, 500 MHz) 24 Hz), 105.5 (d, JC–F = 20 Hz), 135.3 (d, JC–F = 12 Hz), 117.9,
2
3
3
1
δ 1.20–1.64 (m, 16 H), 2.20–2.30 (m, 2 H), 2.85 (ddd, J = 11.4, 158.0, 165.3 (d, JC–F = 14 Hz), 166.2 (d, JC–F = 252 Hz); HRMS
10.0, 2.7 Hz, 2 H), 4.84 (ddd, J = 11.4, 3.9, 3.9 Hz, 2 H), 6.56 (FAB+) m/z calcd for C26H32F2N2O2195Pt (M+): 637.2080; found:
(dd, J = 8.5, 2.0 Hz, 2 H), 6.88 (d, J = 2.0 Hz, 2 H), 7.13 (d, J = 637.2063.
8.5 Hz, 2 H), 7.70 (s, 2 H); 13C NMR (CDCl3, 125 MHz) δ 23.8,
Complex 3f. Yellow block (27%); mp 220–221 °C. IR (KBr)
26.2, 27.2, 27.9, 30.4, 58.9, 116.5, 119.8, 119.9, 134.2, 139.1, 2925, 2850, 1618, 1587, 1523, 1429, 1398, 1340, 1299, 1208,
158.0, 164.3; HRMS (FAB+) m/z calcd for C25H3035Cl2N2O2196Pt: 1063, 917, 777 cm−1 1H NMR (CDCl3, 500 MHz) δ 1.07–1.19
;
656.1334 (M+); found: 656.1337.
(m, 2 H), 1.26–1.52 (m, 16 H), 2.10–2.22 (m, 2 H), 2.91 (ddd, J =
This journal is © The Royal Society of Chemistry 2014
Dalton Trans., 2014, 43, 10074–10085 | 10083

View Article Online
Paper
Dalton Transactions
11.2, 10.7, 3.1 Hz, 2 H), 4.83 (ddd, J = 11.2, 4.5, 4.5 Hz, 2 H),
6.71 (dd, J = 8.3, 2.0 Hz, 2 H), 7.08 (d, J = 8.3 Hz, 2 H), 7.08 (d,
J = 2.0 Hz, 2 H), 7.76 (s, 2 H); 13C NMR (CDCl3, 125 MHz)
δ 23.4, 27.1, 27.4, 27.5, 29.8, 58.9, 119.2, 119.7, 123.0, 127.8,
134.3, 158.2, 163.8; HRMS (FAB+) m/z calcd for
C26H32N2O279Br81Br195Pt (M+): 759.0458; found: 759.0446.
Complex 4b. A similar treatment of PtCl2(CH3CN)2 with
N-(4-chlorosalicylidene)methylamine (2 equiv.) gave an orange
block (12%); mp >290 °C; IR (KBr) 2916, 1624, 1590, 1523,
Notes and references
1 (a) R. C. Evans, P. Douglas and C. J. Winscom, Coord.
Chem. Rev., 2006, 250, 2093–2126; (b) Highly Efficient OLEDs
with Phosphorescent Materials, ed. H. Yersin, Wiley-VCH,
Weinheim, 2008; (c) H. Yersin, A. F. Rausch,
R. Czerwieniec, T. Hofbeck and T. Fischer, Coord. Chem.
Rev., 2011, 255, 2622–2652; (d) L. Xiao, Z. Chen, B. Qu,
J. Luo, S. Kong, Q. Gong and J. Kido, Adv. Mater., 2011, 23,
926–952.
1
1426, 1298, 1203, 1146, 1073, 938, 773 cm−1; H NMR (DMSO-
d6, 500 MHz) δ 3.52 (s, 6 H), 6.68 (dd, J = 8.7, 1.8 Hz, 2 H), 6.96
(d, J = 1.8 Hz, 2 H), 7.47 (d, J = 8.7 Hz, 2 H), 8.37 (s, 2 H); 13C
NMR (CDCl3/CD3OD, 125 MHz) δ 70.0, 116.7, 119.2, 119.8,
134.2, 139.2, 159.0, 163.3; HRMS (FAB+) m/z calcd for
C16H1435Cl2N2O2194Pt (M+): 530.0059; found: 530.0074.
2 Pt: (a) C. E. Buss and K. R. Mann, J. Am. Chem. Soc., 2002,
124, 1031–1039; (b) M. Kato, A. Omura, A. Toshikawa,
S. Kishi and Y. Sugimoto, Angew. Chem., Int. Ed., 2002, 41,
3183–3185; (c) L. J. Grove, J. M. Rennekamp, H. Jude and
W. B. Connick, J. Am. Chem. Soc., 2004, 126, 1594–1595;
(d) T. J. Wadas, Q.-M. Wang, Y. Kim, C. Flaschenreim,
T. N. Blanton and R. Eisenberg, J. Am. Chem. Soc., 2004,
126, 16841–16849; (e) Y. Sun, K. Ye, H. Zhang, J. Zhang,
L. Zhao, B. Li, G. Yang, B. Yang, Y. Wang, S.-W. Lai and
C.-M. Che, Angew. Chem., Int. Ed., 2006, 45, 5610–5613; Au:
(f) M. A. Rawashdeh-Omary, M. A. Omary, J. P. Fackler Jr.,
R. Galassi, B. R. Pietroni and A. Burini, J. Am. Chem. Soc.,
2001, 123, 9689–9691; (g) S. H. Lim, M. M. Olmstead and
A. L. Balch, J. Am. Chem. Soc., 2011, 133, 10229–10238;
(h) M. A. Malwitz, S. H. Lim, R. L. White-Morris,
D. M. Pham, M. M. Olmstead and A. L. Balch, J. Am. Chem.
Soc., 2012, 134, 10885–10893; Au–Ag: (i) A. Laguna,
T. Lasanta, J. M. López-de-Luzuriaga, M. Monge,
P. Naumov and M. E. Olmos, J. Am. Chem. Soc., 2010, 132,
456–457; ( j) T. Lasanta, M. E. Olmos, A. Laguna,
J. M. López-de-Luzuriaga and P. Naumov, J. Am. Chem. Soc.,
2011, 133, 16358–16361; Au–Tl: (k) E. J. Fernández,
J. M. López-de-Luzuriaga, M. Monge, M. E. Olmos, J. Pérez,
A. Laguna, A. A. Mohamed and J. P. Fackler Jr., J. Am. Chem.
Soc., 2003, 125, 2022–2023; Au–Cu: (l) I. O. Koshevoy,
Y.-C. Chang, A. J. Karttunen, M. Haukka, T. Pakkanen and
P.-T. Chou, J. Am. Chem. Soc., 2012, 134, 6564–6567;
(m) G. F. Manbeck, W. W. Brennessel, R. A. Stockland Jr.
and R. Eisenberg, J. Am. Chem. Soc., 2010, 132, 12307–
12318.
X-ray structure determination
Crystals suitable for XRD studies were analyzed using a Rigaku
R-AXIS RAPID imaging plate diffractometer with graphite-
monochromated Mo Kα radiation (λ = 0.71075 Å). The struc-
tures of ( )-2b, ( )-3b, ( )-3c, ( )-3d, ( )-3e, ( )-3f, and 4b were
solved using direct methods and refined with the full-matrix
least-squares method. In subsequent refinement, the function
2
2 2
Σω(Fo − Fc ) was minimized, where Fo and Fc are the
observed and calculated structure factor amplitudes, respecti-
vely. The positions of non-hydrogen atoms were determined
from difference Fourier electron density maps and refined ani-
sotropically. All calculations were performed using the Crystal
Structure crystallographic software package, and illustrations
were drawn using ORTEP.10 Details of the structure determi-
nations are given in Fig. 1 and Table 1. CCDC 985138 (2b),
985139 (3b), 985140 (3c), 985141 (3d), 985142 (3e), 985143 (3f),
and 985144 (4b) contain the supplementary crystallographic
data for this paper.
Computational methods
All calculations were conducted on the basis of DFT with
the B3LYP exchange-correlation functional16 and using the
Gaussian 09W program package.17 The basis set used was the
effective core potential (LanL2DZ) for a platinum atom18 and
6-31G* for the remaining atoms.19 Molecular orbitals and their
eigenvalues for complexes 3a–d were calculated using the opti-
mized molecular structures. The singlet–singlet (E(Sn)) and
singlet–triplet (E(Tn)) transition energies were estimated by
TD-DFT calculation (B3LYP/6-31G*, LanL2DZ).20 The results
are shown in Fig. S1 and Table S3, ESI.†
3 Review (a) A. L. Balch, Angew. Chem., Int. Ed., 2009, 48,
2641–2644; Au: (b) Y. Lee and R. Eisenberg, J. Am. Chem.
Soc., 2003, 125, 7778–7779; (c) H. Ito, T. Saito, N. Oshima,
N. Kitamura, S. Ishizaka, Y. Hinatsu, M. Wakeshima,
M. Kato, K. Tsuge and M. Sawamura, J. Am. Chem. Soc.,
2008, 130, 10044–10045; Au–Ag: (d) Ref. 2i; Cu:
(e) S. Perruchas, X. F. Le Goff, S. Maron, I. Maurin,
F. Guillen, A. Garcia, T. Gacoin and J.-P. Boilot, J. Am.
Chem. Soc., 2010, 132, 10967–10969.
4 P. J. Wagner and G. S. Hammond, Advances in Photochemis-
try, ed. W. A. Noyes Jr., G. S. Hammond and J. N. Pitts Jr.,
Interscience Publishers, New York, 1968, vol. 5, pp. 21–156.
5 (a) N. Komiya, M. Okada, K. Fukumoto, D. Jomori and
T. Naota, J. Am. Chem. Soc., 2011, 133, 6493–6496;
(b) N. Komiya, M. Okada, K. Fukumoto, K. Kaneta,
A. Yoshida and T. Naota, Chem. – Eur. J., 2013, 19, 4798–
Acknowledgements
This work was supported by a Grant-in-Aid for Scientific
Research, from the Ministry of Education, Culture, Sports,
Science and Technology, Japan. We gratefully acknowledge Mr
Masahiko Bando (Otsuka Pharmaceutical Co. Ltd, Japan) for
assistance with the X-ray crystallographic analysis of 4b.
10084 | Dalton Trans., 2014, 43, 10074–10085
This journal is © The Royal Society of Chemistry 2014

View Article Online
Dalton Transactions
Paper
4811; (c) N. Komiya, N. Itami and T. Naota, Chem. – Eur. J.,
2013, 19, 9497–9505.
6 (a) J. C. Ostrowski, M. R. Robinson, A. J. Heeger and
K. Soltys, A. Tulewicz, A. Kornowicz, R. Moszyński,
J. Lipkowski and J. Lewiński, Chem. – Eur. J., 2012, 18,
5637–5645.
G. C. Bazan, Chem. Commun., 2002, 784–785; 13 C. Postmus Jr., I. A. Kaye, C. A. Craig and R. S. Matthews,
(b) E. Q. Procopio, M. Mauro, M. Panigati, D. Donghi, J. Org. Chem., 1964, 29, 2693–2698.
P. Mercandelli, A. Sironi, G. D’Alfonso and L. De Cola, 14 N. U. Hofsløkken and L. Skattebøl, Acta Chem. Scand.,
J. Am. Chem. Soc., 2010, 132, 14397–14399; (c) A. Raimondi, 1999, 53, 258–262.
M. Panigati, D. Maggioni, L. D’Alfonso, P. Mercandelli, 15 F. P. Fanizzi, F. P. Intini, L. Maresca and G. Natile, J. Chem.
P. Mussini and G. D’Alfonso, Inorg. Chem., 2012, 51, 2966– Soc., Dalton Trans., 1990, 199–202.
2975; (d) V. A. Krylova, P. I. Djurovich, J. W. Aronson, 16 A. D. Becke, Modern Electronic Structure Theory, Part II, ed.
R. Haiges, M. T. Whited and M. E. Thompson, Organo- D. R. Yarkony, World Scientific, Singapore, 1995.
metallics, 2012, 31, 7983–7993; (e) D. M. Zink, M. Bächle, 17 M. J. Frisch, G. W. Trucks, H. B. Schlegel, G. E. Scuseria,
T. Baumann, M. Nieger, M. Kühn, C. Wang, W. Klopper,
U. Monkowius, T. Hofbeck, H. Yersin and S. Bräse, Inorg.
Chem., 2013, 52, 2292–2305.
7 N. Komiya, T. Muraoka, M. Iida, M. Miyanaga,
K. Takahashi and T. Naota, J. Am. Chem. Soc., 2011, 133,
16054–16061.
8 C. A. Strassert, C.-H. Chien, M. D. Galvez Lopez,
D. Kourkoulos, D. Hertel, K. Meerholz and L. De Cola,
Angew. Chem., Int. Ed., 2011, 50, 946–950.
9 Recent reports on H–X interactions in crystals:
(a) R. H. Jones, K. S. Knight, W. G. Marshall, J. Clews,
R. J. Darton, D. Pyatt, S. J. Coles and P. N. Horton, CrystEng-
Comm, 2014, 16, 237–243; (b) L. Barloy, E. Féghali,
M. Henry, L. Karmazin-Brelot, C. Bailly and M. Pfeffer,
Organometallics, 2013, 32, 6195–6200; (c) C. Ma, J. Wang,
L. Zhao, Y. Shi, W. Luo, Y. Yan, M. Fang, X. Wang and
H.-K. Liu, CrystEngComm, 2013, 15, 10311–10315;
(d) M. Karanam and A. R. Choudhury, Cryst. Growth Des.,
2013, 13, 4803–4814.
M. A. Robb, J. R. Cheeseman, G. Scalmani, V. Barone,
B. Mennucci, G. A. Petersson, H. Nakatsuji, M. Caricato,
X. Li, H. P. Hratchian, A. F. Izmaylov, J. Bloino, G. Zheng,
J. L. Sonnenberg, M. Hada, M. Ehara, K. Toyota, R. Fukuda,
J. Hasegawa, M. Ishida, T. Nakajima, Y. Honda, O. Kitao,
H. Nakai, T. Vreven, J. A. Montgomery Jr., J. E. Peralta,
F. Ogliaro, M. Bearpark, J. J. Heyd, E. Brothers,
K. N. Kudin, V. N. Staroverov, R. Kobayashi, J. Normand,
K. Raghavachari, A. Rendell, J. C. Burant, S. S. Iyengar,
J. Tomasi, M. Cossi, N. Rega, J. M. Millam, M. Klene,
J. E. Knox, J. B. Cross, V. Bakken, C. Adamo, J. Jaramillo,
R. Gomperts, R. E. Stratmann, O. Yazyev, A. J. Austin,
R. Cammi, C. Pomelli, J. W. Ochterski, R. L. Martin,
K. Morokuma, V. G. Zakrzewski, G. A. Voth, P. Salvador,
J. J. Dannenberg, S. Dapprich, A. D. Daniels, Ö. Farkas,
J. B. Foresman, J. V. Ortiz, J. Cioslowski and D. J. Fox,
GAUSSIAN 09 (Revision A.02), Gaussian, Inc., Wallingford,
CT, 2009.
18 (a) P. J. Hay and W. R. Wadt, J. Chem. Phys., 1985, 82, 270–
283; (b) P. J. Hay and W. R. Wadt, J. Chem. Phys., 1985, 82,
299–310.
10 M. N. Burnett and C. K. Johnson, ORTEP-III: Oak Ridge
Thermal Ellipsoid PlotProgram for Crystal Structure
Illustrations, Report ORNL-6895, Oak Ridge National 19 (a) M. M. Francl, W. J. Pietro, W. J. Hehre, J. S. Binkley,
Laboratory, Oak Ridge, 1996.
11 Y. Kawamura, H. Sasabe and C. Adachi, Jpn. J. Appl. Phys.,
2004, 43, 7729–7730.
M. S. Gordon, D. J. DeFrees and J. A. Pople, J. Chem. Phys.,
1982, 77, 3654–3665; (b) P. C. Hariharan and J. A. Pople,
Theor. Chim. Acta, 1973, 28, 213–222.
12 Red-shift in solid-state emission by π-stacking interactions: 20 (a) M. E. Casida, C. Jamorski, K. C. Casida and
(a) M. Brinkmann, G. Gadret, M. Muccini, C. Taliani,
N. Masciocchi and A. Sironi, J. Am. Chem. Soc., 2000, 122,
5147–5157; (b) K. Sokolowski, I. Justyniak, W. Śliwiński,
D. R. Salahub, J. Chem. Phys., 1998, 108, 4439–4449;
(b) R. E. Stratmann and G. E. Scuseria, J. Chem. Phys., 1998,
109, 8218–8224.
This journal is © The Royal Society of Chemistry 2014
Dalton Trans., 2014, 43, 10074–10085 | 10085