Synthesis, crystal structure, electronic structure, bonding, photoluminescence and spectroscopic property investigations of a mononuclear 1,10-phenanthroline and 5-bromo-salicylate ternary indium(III) complex

Article abstract of DOI:10.1016/j.ica.2009.07.005

The synthesis, X-ray structure, electronic structure, bonding, photoluminescence, spectroscopic property and characterization of an indium(III) complex, [In(Hbsac)₃(phen)] (1) (H₂bsac = 5-bromo-salicylic acid, and phen = 1,10-phenant

Full text of DOI:10.1016/j.ica.2009.07.005

Inorganica Chimica Acta 362 (2009) 4791–4796
Contents lists available at ScienceDirect
Inorganica Chimica Acta
journal homepage: www.elsevier.com/locate/ica
Synthesis, crystal structure, electronic structure, bonding, photoluminescence
and spectroscopic property investigations of a mononuclear
1,10-phenanthroline and 5-bromo-salicylate ternary indium(III) complex
c
Yi-Ping Tong a,b, , Yan-Wen Lin
*
a Institute of Inorganic Chemistry, Hanshan Normal University, Chaozhou 521041, China
b Department of Chemistry, Hanshan Normal University, Chaozhou 521041, China
c Department of Biology, Hanshan Normal University, Chaozhou 521041, China
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 7 April 2009
Received in revised form 30 June 2009
Accepted 2 July 2009
Available online 9 July 2009
The synthesis, X-ray structure, electronic structure, bonding, photoluminescence, spectroscopic property
and characterization of an indium(III) complex, [In(Hbsac)3(phen)] (1) (H2bsac = 5-bromo-salicylic acid,
and phen = 1,10-phenanthroline) are presented. Complex 1 is octacoordinate and carboxylate chelating,
being novel and rarely reported for main group complexes. The electronic structure, bonding and the
charge transfer properties of light excitation and light emission are discussed in detail using first-princi-
ples theory, including partial density of states (PDOSs), crystal orbital overlap population (COOP), the
Keywords:
density functional theory (DFT/TDDFT) analysis schemes. The charge transfer is mainly
p ? p
* intraligand
Indium complex
5-Bromo-salicylic acid
Crystal structure
TDDFT level
charge transfer transition (ILCT) for excitation, and
p
?
p* ligand-to-ligand charge transfer transition
(LL0CT) for emission in nature.
Ó 2009 Elsevier B.V. All rights reserved.
Mixed-ligand
Partial density of states (PDOSs)
1. Introduction
new class of materials, such as behavior in photophysics and pho-
tochemistry, and properties in spectroscopy [1,5,14].
Indium complexes with chelating ligands are an important class
of coordination complex, finding interesting coordination struc-
tures in coordination chemistry, such as unusual coordination
modes [1–5], and potential applications in material sciences, such
as light emitters in photoluminescence and/or electrolumines-
cence [6–11].
Though the strong propensity of group 13 metals, in general, to
form stable six-coordinative complexes is well-known [8,12,13],
some octacoordinate indium(III) complexes with chelating ligands
have been found and characterized structurally over the past years
[1,5]. To the best of our knowledge, such octacoordinate metal
complexes are rarely reported for other main group metals, thus,
such indium(III) compounds offer potential opportunities either
for studies of rare bonding modes (octacoordinate number or high-
er) between main group metal center and chelating ligands in
coordination chemistry [1,5] or for seeking for new functional
organometal materials, such as light-emitting materials, and for
interesting aspects of physical and chemical properties for these
Salicylic acid and its derivatives are a class of heterodifunctional
chelating ligands capable of bonding to a range of metal centers as
either a monoanion or a dianion [15–20], and are capable of coor-
dinating in a range of bonding modes [21–25]. Scheme 1 repre-
sents two possible chelating coordination modes for salicylic
acid-derivated ligands, i.e. the carboxylate chelating mode and
the carboxylate–phenolate chelating mode; in general, the former
is favoured for the formation of complexes with higher coordina-
tive number owing to relatively less steric hindrance and con-
trarily, the latter is favoured for the formation of complexes with
lower coordinative number owing to the relatively larger steric ef-
fect. Therefore, octacoordinate, and carboxylate chelating organo-
metallic complexes with salicylic acid-derivated ligands may be
reasonably possible, and indeed, some octacoordinate, and carbox-
ylate chelating indium(III) analogues with other carboxylic acid li-
gands have been crystallographically verified recently [1,5].
However, up to now, no such complexes with salicylic acid deriv-
atives have been found. In this paper, we report the synthesis, crys-
tal structure, electronic structure, bonding, photoluminescence
and spectroscopic property investigations on a ternary mononu-
clear indium(III) complex with 5-bromo-salicylic acids (H2bsac =
5-bromo-salicylic acid) and 1,10-phenanthroline (phen = 1,10-
phenanthroline), namely, [In(Hbsac)3(phen)]3 (1), together with
* Corresponding author. Address: Institute of Inorganic Chemistry, Hanshan
Normal University, Chaozhou 521041, China. Tel.: +86 768 3692891; fax: +86 768
2525151.
E-mail address: typ2469@163.com (Y.-P. Tong).
0020-1693/$ - see front matter Ó 2009 Elsevier B.V. All rights reserved.
doi:10.1016/j.ica.2009.07.005

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Y.-P. Tong, Y.-W. Lin / Inorganica Chimica Acta 362 (2009) 4791–4796
H, N and O atoms, and effective core potentials basis set LanL2DZ
for In and Br atoms. The optimized calculation was confirmed to
be local minima by performing harmonic vibration frequency anal-
yses (no imaginary frequency found). No symmetry constraints
were applied and only the default convergence criteria were
undertaken during optimization.
Based on the optimized geometries, TDDFT calculations were
performed at the same B3LYP level, and with the same basis sets
as in DFT calculation for C, H, N, O, Br and In atoms to calculate
the vertical electron transition energies. The electron density dia-
grams of molecular orbitals were obtained with the MOLDEN 3.5
graphics program [29].
Scheme 1. Two types of chelating coordination modes: (a) carboxylate chelating
and (b) carboxylate–phenolate chelating.
2.4. Crystal structure determination and refinements
density functional theory (DFT) and time-dependent density func-
tional theory (TDDFT) studies of this compound.
Diffraction intensities for 1 were collected at 293 K on a Bruker
Smart Apex CCD diffractometer (Mo Ka, k = 0.71073 Å). Absorp-
tion corrections were applied by using SADABS [30]. The structures
were solved with direct methods and refined with full-matrix
least-squares technique using SHELXTL program package [31]. The
organic hydrogen atoms were generated in ideal positions. Aniso-
tropic thermal parameters were applied to all non-hydrogen
atoms. Experimental details of the X-ray analyses are provided in
Table 1. Selected bond lengths and angles are listed in Table 2.
2. Experimental
2.1. General
All the reagents and solvents employed were commercially
available and used as received without further purification. The
C, H and N micro-analyses were carried out on an Elementar Vario
El elemental analyzer. The FT-IR spectra were recorded using a
Nicolet magna-550(II) spectrometer in the KBr pellets in the range
4000–400 cmꢀ1. 1H NMR spectra were recorded with a Bruker Bio-
spin AVANCE 400 MHz spectrometer. The UV–Vis spectra were re-
corded on a Varian Cary-100 spectrometer. The steady-state
fluorescent spectra were determined with a SHIMADZU Instru-
ment RF5301 fluorescence spectrophotometer. The fluorescence
lifetime was determined with an Edinburgh Instrument FLS920
fluorescence spectrophotometer using a H2 gas lamp as the light
source. The ESI-MS was carried out on a high-resolution Finnigan
MAT LCQ mass spectrometer.
3. Results and discussion
3.1. Crystal structure of 1
Fig. 1 shows the molecular structure of 1 together with the
labeling scheme used. Selected geometric parameters are listed
in Table 2. Complex 1 is a monomer with InN2O6 core in which
the six chelating carboxylate oxygen atoms from three Hbsacꢀ li-
gands and two nitrogen atoms from one phen ligand, overall yield-
ing an octacoordinate geometry. A pair of Hbsacꢀ ligands (L1 and
L3) are located at approximately opposite sites to each other
2.2. Preparation of 1
Table 1
Crystal data and structure refinement for 1.
The complex was prepared by an electrochemical method. The
cell consisted of indium wire as the anode and a platinum wire
as the cathode. H2bsac (0.042 g, 0.2 mmol) and coligand phen
(0.020 g, 0.1 mmol) were dissolved in ethanol (60 mL) and a small
amount of tetra-n-butylammonium perchlorate was added to the
solution as a supporting electrolyte. A 30 V voltage was applied
to the cell for 6 h to allowed sufficient current flow for smooth dis-
solution of the indium metal. The cell can be summarized as In(+)/
ethanol + H2bsac + phen/Pt(ꢀ). The resultant solution was allowed
to stand for ca. four months, a colourless crystal of 1 was obtained
in approximate 70% yield based on H2bsac. Anal. Calc. for
C33H20Br3InN2O9 (943.05): C, 42.03; H, 2.14; N, 2.97. Found: C,
42.09; H, 2.21; N, 3.10%. m/z (ESI) 942 {[In(Hbsac)3(phen)]-1}ꢀ.
1H NMR (DMSO-d6, 400 MHz): 12.75 (s, 3 H), 9.18 (d, J = 7.63 Hz,
1 H), 8.47 (m, 2 H), 8.40 (m, 2 H), 7.86 (m, 4 H), 7.54 (d,
J = 5.2 Hz, 3 H), 6.84 (d, J = 5.6 Hz, 3 H). FT-IR (KBr, cmꢀ1): 3130
m, 1589 m, 1466 m, 1433 w, 1385 s, 1248 w, 1146 w, 1106 w,
871 w, 851 w, 825 m, 723 m, 628 w, 532 w, 472 w, 457 w.
Compound
1
Empirical formula
Formula weight
T (K)
Crystal system
Space group
a (Å)
C33H20Br3InN2O9
943.06
293(2)
triclinic
ꢀ
P1 (no. 2)
12.0012(8)
12.6354(8)
12.9974(8)
74.1990(10)
85.1150(10)
61.9000(10)
1670.75(18)
2
b (Å)
c (Å)
a
(°)
b (°)
c
(°)
V (Å3)
Z
l
(mmꢀ1
)
4.352
Crystal size (mm)
h Range for data collection (°)
Index ranges
0.45 ꢁ 0.29 ꢁ 0.25
1.89–27.00
ꢀ15 6 h 6 15, ꢀ16 6 k 6 16,
ꢀ15 6 l 6 16
14 056
Total reflections
Unique reflections (Rint
)
7153 [0.0281]
97.9
7153/3/436
1.019
0.0483
0.1286
Completeness to hmax
2.3. DFT and TDDFT calculations
Observed data/restraints/parameters
S on F2
a
The geometric optimization for 1 was performed on a Dell pre-
cision 490 computer using experimental geometry as input,
employing the GAUSSIAN98 suite of programs [26], at spin restricted
DFT wavefunctions (B3LYP) level [27,28], i.e. the Becke three-
parameter exchange functional in combination with the LYP corre-
lation functional of Lee, Yang and Parr with 6-311G** basis set for C,
R1 (I > 2
r
(I))
b
wR2 (all data)
Largest difference in peak and hole
1.383 and ꢀ1.063
(e Åꢀ3
)
P
P
a
R1
=
||Fo|ꢀ|Fc||/ |Fo|.
P
P
wR2 = [ w(Fo2 ꢀ Fc2)2/ w(F2o)2]1/2
.
b

Y.-P. Tong, Y.-W. Lin / Inorganica Chimica Acta 362 (2009) 4791–4796
4793
Table 2
Selected experimental/calculated bond lengths and angles (Å, °) for 1.
In(1)–O(1)
In(1)–O(2)
In(1)–O(4)
In(1)–O(5)
In(1)–O(7)
In(1)–O(8)
2.437(5)/2.201
2.230(5)/2.325
2.380(4)/2.373
2.214(4)/2.185
2.430(4)/2.374
2.201(4)/2.185
In(1)–N(1)
In(1)–N(2)
Br(1)–C(16)
Br(2)–C(23)
Br(2’)–C(23’)
Br(3)–C(30)
2.301(4)/2.361
2.303(4)/2.392
1.897(6)/1.959
1.886(4)/1.959
1.885(7)/1.959
1.885(6)/1.959
O(8)–In(1)–O(5)
O(8)–In(1)–O(2)
O(5)–In(1)–O(2)
O(8)–In(1)–N(1)
O(5)–In(1)–N(1)
O(2)–In(1)–N(1)
O(8)–In(1)–N(2)
O(5)–In(1)–N(2)
O(2)–In(1)–N(2)
O(8)–In(1)–O(4)
O(5)–In(1)–O(4)
O(2)–In(1)–O(4)
O(8)–In(1)–O(7)
O(5)–In(1)–O(7)
168.18(13)/163.7
84.67(16)/86.9
86.13(15)/87.0
91.74(15)/88.6
93.22(14)/88.7
153.73(17)/148.3
84.63(14)/82.0
86.71(14)/82.0
81.72(17)/78.7
134.98(13)/137.5
56.65(13)/57.1
120.98(15)/124.1
55.63(13)/57.1
135.64(12)/137.5
O(8)–In(1)–O(1)
O(4)–In(1)–O(7)
O(2)–In(1)–O(7)
O(5)–In(1)–O(1)
O(2)–In(1)–O(1)
O(4)–In(1)–O(1)
O(7)–In(1)–O(1)
N(1)–In(1)–O(7)
N(2)–In(1)–O(7)
N(1)–In(1)–O(1)
N(2)–In(1)–O(1)
N(1)–In(1)–N(2)
N(1)–In(1)–O(4)
N(2)–In(1)–O(4)
94.71(15)/94.7
79.48(12)/80.6
114.50(16)/124.1
86.02(15)/94.7
54.84(16)/57.5
76.53(15)/82.2
76.93(14)/82.2
83.93(14)/78.1
132.89(14)/128.1
151.38(15)/154.2
136.32(16)/136.2
72.03(15)/69.7
79.22(14)/78.1
131.67(14)/128.1
Fig. 1. ORTEP drawing of 1 with 50% probability thermal ellipsoids. The dash lines
represent intramolecular hydrogen bonding (O–HꢂꢂꢂO) interactions.
around the central indium(III), as reflected by a large angle of O(5)–
In(1)–O(8) of 168.18(13)°, and similarly, the other pair of ligands
(L2: another one Hbsacꢀ and L4: phen ligand) surround In(III) cen-
ter on approximately opposite vertices as both the O(1)–In(1)–N(1)
and O(2)–In(1)–N(1) angles are as large as 151.38(15) and
153.73(17)°, respectively. Furthermore, in InN2O6 core, both the
In1, O4, O5, O7 and O8 atoms and the In1, O1, O2, N1 and N2 atoms
are approximately coplanar, as the mean deviation of these atoms
are as little as 0.06 and 0.04 Å, respectively. These planes are essen-
tially perpendicular with a corresponding dihedral angle of ca.
89.7°. Thus two pairs of chelating ligands (L1 and L3, L2 and L4)
may be considered to be approximately located on two mutual
perpendicular planes, furnishing two orthogonal square-planar
arrangements around the same In(III) center. Both square-planar
geometries are highly distorted as indicated by the smaller bite
angles of the Hbsacꢀ and phen ligands (Table 2). All the In–O and
In–N lengths are typical and similar to other octacoordinate indiu-
m(III) complexes [1], and the two In–N bond lengths are identical
within 0.002 Å for phen ligand, but for In–O dimensions, one In–O
bond length is ca. 0.17–0.23 Å shorter than another one for each
Hbsacꢀ ligand, indicating that one carboxylate oxygen atom is
obviously much more strongly bonded to the In(III) atom than
the other in each Hbsacꢀ ligand, while two In–N interactions are al-
most identical for phen ligand.
experimental values. The calculated molecular orbital energy level
diagrams are presented in Fig. 3.
For 1, the HOMO and LUMO orbitals are predominantly
p bond-
ing orbital of L2 ligand (Hbsacꢀ) and p* antibonding orbital of L4
ligand (phen), respectively with little contribution from In(III).
The high-lying occupied orbitals (HOMOꢀ1 to HOMOꢀ15) are all
mainly
p
bonding orbitals of L1 (Hbsacꢀ), L2 (Hbsacꢀ), L3 (Hbsacꢀ)
and L4 (phen) (Fig. 3), while the orbitals with In character are far
below these orbitals in energy.
The low-lying unoccupied orbitals just above the LUMO orbital
in energy (LUMO+1 to LUMO+9) are all ligand
tals in character (LUMO+1, LUMO+2, and LUMO+6:
p
* antibonding orbi-
p
* of L4 (phen);
LUMO+5: p* of L2 (Hbsacꢀ, 87%); other: p* of L1 (Hbsacꢀ) + L3
(Hbsacꢀ)). No orbitals with obvious In character can be found in
these orbitals, thus both occupied and unoccupied frontier orbitals
are ligand-centered, and these orbitals are responsible for the light
excitation process (mentioned below).
3.3. Metal–ligand bonding
Density of states (DOSs) or partial density of states (PDOSs), in
combination with molecular orbital, especially frontier molecular
For L3 moiety, the crystallographically determined structure
exhibits disorder owing to a rotation about the bond linking the
carboxylate and phenol ring. The final conformation occupancy
factor was refined to almost 0.93, indicating one conformation
(labeling O6ꢂꢂꢂBr2, Fig. 1) is predominant over another one (labeling
O60ꢂꢂꢂBr20) (Fig. 1).
Strong intermolecular p–p stacking interactions between phen
(L4) and Hbsacꢀ (L2) ligand rings of adjacent 1 molecules are ob-
served in a head-to-tail way in the lattice with an inter-plane dis-
tance of ca. 3.37 Å (Fig. 2). Moreover the intramolecular hydrogen
bonding between Hbsacꢀ O–H groups and carboxylate O atoms
(O3ꢂꢂꢂO1 2.617(7), O6ꢂꢂꢂO4 2.590(6), O60ꢂꢂꢂO5 2.62(6) and O9ꢂꢂꢂO7
2.616(6) Å) are also present (Fig. 1); Both the p–p stacking interac-
tions and the hydrogen bonding interactions contribute critically
to the stability of the real solid.
3.2. Ground state electronic structure
The optimized geometry parameters for 1 are given in Table 2.
The optimized bond distances and angles agree well with the
Fig. 2. Perspective view of p–p stacking interactions in 1.

4794
Y.-P. Tong, Y.-W. Lin / Inorganica Chimica Acta 362 (2009) 4791–4796
5.0
L2
In
L4
L1 and L3
2.5
0.0
-15
-12
-9
-6
-3
0
Energy / eV
Fig. 4. Partial density of states (PDOSs) for 1.
Fig. 3. The frontier molecular orbital energy level diagram of 1.
0.04
In and L2
orbital, gives the overall electronic structure of a system. Crystal
orbital overlap population (COOP) analysis helps in studying the
detailed bonding between a group of atoms and the other atoms
in a system. The PDOSs and COOP of 1 are plotted in Figs. 4 and
5, respectively. The bonding in 1 was analyzed qualitatively using
these first-principles methods. The analysis revealed the clear band
gap and the fact that the states in the region of energy (ꢀ15–0 eV)
are mainly constructed from the ligands (L1–L4) orbitals and the
contributions from In center are much less and somewhat negligi-
ble (Fig. 4). These ligand orbitals are not fully localized but rather
mixed with one another, which is in agreement with the analyses
of molecular orbital (above). Slight metal–ligand antibonding
interactions are observed just near the HOMO level, and clear anti-
bonding interactions are also present between In center and L1 and
L3 ligands near the LUMO level, however the In–L2 metal–ligand
interaction is non-bonding and the In–L4 interaction is bonding
in vicinity of LUMO level (Fig. 5). All the metal–ligand interactions
above LUMO level in energy are antibonding in nature and are un-
filled. Contrarily, all the metal–ligand interaction below HOMO le-
vel in energy (ꢀ15–7 eV) are all basically bonding in nature and are
filled, though two distinct regions of the In–L4 antibonding inter-
action and one distinct region of the In–(L1,L3) antibonding inter-
actions are seen at this energy region, respectively (Fig. 5).
The PDOSs plot therefore suggests a small degree of covalency
of the metal–ligand bonds. This is in agreement with the electronic
population on the In atom, the net charges calculated by Mulliken
population analysis scheme (MPA) being 1.5 positive charge for 1.
This electron transfer is mainly into the 5s orbital on the In atom.
Taking the analysis of the orbital interactions and the atomic
charges together it is plausible to propose the qualitative bonding
picture, which includes the mainly ionic interaction between the
central In atom and the ligands.
In and (L1, L3)
In and L4
0.02
0.00
-0.02
-0.04
-15
-12
-9
-6
-3
0
Energy / eV
Fig. 5. The crystal orbital overlap population (COOP) for the bandstructure of 1.
The primary feature of the TDDFT calculated absorption bands
of 1 (Table 3) shows two moderately-to-strongly intense low-en-
ergy absorptions at 303 and 314 nm with oscillator strength
0.0883 and 0.0113, respectively. The oscillator strength varia-
tions for the two bands are in very agreement with those of
the molar absorptivity of the two experimental bands, thus the
two low-energy absorption bands (303 and 314 nm) can be read-
ily associated with the experimental low-lying absorption bands
in UV–Vis spectrum (289 and 310 nm), with the difference
between the calculated peaks compared to the experimental
ones likely due to solvent effects. In fact, our TDDFT calculation
has also predicted the lowest energy excited state and ground
state (ES-GS) separation and this lowest energy absorption band
is 448 nm in a lower energy range, and has a much weaker oscil-
lator strength predicted (0.0003) than for those mentioned above
(Table 3). This absorption may be very weak in absorption inten-
sity, and was not observed in the experimental UV–Vis spectrum
for 1.
3.4. Electronic spectrum and properties
The absorption spectrum of 1 in chloroform is recorded for
comparison with the calculated spectrum based on singlet excited
states. Only the excited states that arise from singlet–singlet tran-
sitions were correlated with the UV–Vis spectrum. The experimen-
tal UV–Vis spectrum of 1 shows two low-lying absorption bands at
Only the most significant transitions associated with each
absorption band are listed in Table 3. For example, for 448 nm
absorption band, many transitions are calculated. One transition
is listed in Table 3 (HOMO ? LUMO (98%)) as only its percentage
orbital transition composition is over 5%. If multiple transitions
289 and 310 nm with
respectively (Table 3).
e ,
roughly 12 359 and 1748 Mꢀ1 cmꢀ1

Y.-P. Tong, Y.-W. Lin / Inorganica Chimica Acta 362 (2009) 4791–4796
4795
Table 3
Experimental and calculated UV–Vis absorption bands, oscillator strengths, transition configurations and transition properties of 1.
Calculated/experimental (nm)
f/
e
(Mꢀ1 cmꢀ1
)
Transition configuration
Character
448
314/310
0.0003
0.0113/1748
HOMO ? LUMO (98%)
p
p
p
p
p
p
p
p
p
?
?
?
?
?
?
?
?
?
p* (LL0CT)
p* (ILCT)
p* (LL0CT)
p* (LL0CT)
p* (ILCT)
p* (ILCT)
p* (LL0CT)
p* (ILCT)
p* (LL0CT)
HOMOꢀ6 ? LUMO (44%)
HOMOꢀ4 ? LUMO (22%)
HOMOꢀ3 ? LUMO (18%)
HOMOꢀ15 ? LUMO+1 (9%)
HOMOꢀ2 ? LUMO+3 (37%)
HOMO ? LUMO+2 (23%)
HOMOꢀ1 ? LUMO+4 (19%)
HOMOꢀ1 ? LUMO+2 (7%)
303/289
0.0883/12 359
have percentage orbital transition composition with absolute
values over 5%, they are all listed, for example, the 314 nm absorp-
tion band in Table 2 (HOMOꢀ6 ? LUMO (44%), HOMOꢀ4 ? LUMO
(22%), HOMOꢀ3 ? LUMO (18%) and HOMOꢀ15 ? LUMO+1 (9%))
and the 303 nm absorption band (HOMOꢀ2 ? LUMO+3 (37%),
HOMO ? LUMO+2 (23%), HOMOꢀ1 ? LUMO+4 (19%) and HOMO-
1 ? LUMO+2 (7%)).
According to our TDDFT calculations, the low-energy 314 nm
absorption band (oscillator strength 0.0113) mainly arises from
four transitions with percentage orbital transition composition
HOMOꢀ3, respectively, and the
p
* antibonding orbital of L4 (phen)
for LUMO and LUMO+1 in character (Figs. 3 and 6), thus the
314 nm absorption band is mainly labeled as a phen(L4)-centered
intraligand charge transfer (ILCT) [32,33], but mixed with
Hbsacꢀ(L1L3 and L2)-to-phen(L4) ligand-to-ligand charge transfer
(LL0CT) transition with
p ?
p* nature (Table 3). Similarly, the
303 nm absorption band (oscillator strength 0.0883) can mainly
ascribed as a Hbsacꢀ(L1L3)-centered intraligand charge transfer
(ILCT) [32,33], but mixed with Hbsacꢀ(L2)-to-phen(L4) ligand-to-
ligand charge transfer (LL0CT) transition with
3).
p ? p
* nature (Table
over 5% (Table 3). Owing to being the
p bonding orbital of ligand
L4 (phen) for HOMOꢀ6 and HOMOꢀ15, the
p bonding orbitals of
ligand L1L3 (Hbsacꢀ) and of ligand L2 (Hbsacꢀ) for HOMOꢀ4 and
3.5. Luminescent spectrum and properties
Complex 1 is photoluminescent in chloroform. The emission
maximum for 1 is 457 nm with corresponding excitation wave-
length 324 nm in chloroform (Fig. 7). Similar to those of other
In(III) metal complexes [8], the lifetime of 1 is ca. 2.58 ns in trichlo-
romethane at room temperature.
According to the TDDFT calculation and molecular orbital anal-
yses, the transitions in lowest excited state ground state (ES-GS)
separation of 1 is mainly associated with the transitions from the
corresponding HOMO to LUMO (percentage orbital transition com-
position up to 98%), in which the HOMO is mainly the
p bonding
orbital of Hbsacꢀ(L2), while the LUMO is the * antibonding orbital
p
of phen(L4); thus, according to the energy-gap law for radiationless
deactivation [34–42], the photoluminescence here should be de-
scribed as
a ligand-to-ligand charge transfer transition with
p
?
p* nature (LL0CT) [43].
1.2
Excitation
Emission
0.9
0.6
0.3
0.0
250
300
350
400
450
500
550
600
Wavelength / nm
Fig. 6. Contour surfaces of the frontier molecular orbitals most involved in the
calculated excitations of UV–Vis spectra of 1.
Fig. 7. The excitation and emission spectra for 1 in chloroform.

4796
Y.-P. Tong, Y.-W. Lin / Inorganica Chimica Acta 362 (2009) 4791–4796
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A mononuclear, octacoordinate, carboxylate chelating ternary
indium(III) complex with 5-bromo-salicylic acid and 1,10-phenan-
throline, [In(Hbsac)3(phen)] (1) has been synthesized and charac-
terized crystallographically. Complex 1 crystallizes in the triclinic
ꢀ
´
[13] J. Romero, M.L. Durán, A. Rodriguez, J.A. Garcia-Vázquez, A. Sousa, D.J. Rose, J.
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12.0012(8) Å, b = 12.6354(8) Å, c = 12.9974(8) Å,
a = 74.1990(10)°,
b = 85.1150(10)°, = 61.9000(10)° and Z = 2. Such octacoordinate
c
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Millam, A.D. Daniels, K.N. Kudin, M.C. Strain, O. Farkas, J. Tomasi, V. Barone, M.
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M.A. Al-Laham, C.Y. Peng, A. Nanayakkara, C. Gonzalez, M. Challacombe,
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geometry in 1 is novel and rarely reported so far for main group
metal complexes. The electronic structure and bonding property
of metal–ligand interactions are discussed in detail using first-
principles theory with partial density of states (PDOSs) and crystal
orbital overlap population (COOP) analysis schemes. DFT- and
TDDFT-based theoretical calculation results show considerable
agreement with experimental ones. 1 exhibits typical
p ?
p* li-
gand-centered, intraligand charge transfer nature (ILCT), but mixed
with ligand-to-ligand charge transfer transitions (LL0CT) for the
low-lying UV–Vis absorption bands. The emissive state of 1 is as-
signed as a singlet
p ?
p* ligand-to-ligand charge transfer transi-
tion (LL0CT).
Acknowledgments
This work was supported by the Natural Science Foundation of
Department of Education of Guangdong Province of China and the
Natural Science Foundation of Guangdong Province of China (Grant
No. 06301028).
Appendix A. Supplementary material
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CCDC 641727 contains the supplementary crystallographic data
for 1. These data can be obtained free of charge from The Cam-
bridge Crystallographic Data Centre via www.ccdc.cam.ac.uk/da-
ta_request/cif. Supplementary data associated with this article
can be found, in the online version, at doi:10.1016/
j.ica.2009.07.005.
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