A crystallographic, spectroscopic, thermal, and DFT investigation of mixed ligand Cu(II) complexes of 2-benzoylbenzoate

Article abstract of DOI:10.1080/15533174.2012.684263

Two mixed ligand complexes of copper(II)-2-benzoylbenzoate (bba) with pyridazine and 4-picoline, namely bis(2-benzoylbenzoate) di(pyridazine) copper(II) 1 and bis(2-benzoylbenzoate)bis(4- picoline)copper(II) 2, have been synthesized and characterized by X-ray crystallography. Complexes 1 and 2 crystallize in the monoclinic P2₁/c space groups. The calculated frequency shifts have shown that the participation of carboxylate groups in coordination to themetal centers in monodentate fashion (δ(OCO)>200 cm^-1). The structural features of the complexes have been further studied by DFT/X3LYP extended hybrid functional. The thermal behavior of the complexes was studied by means of simultaneous thermogravimetry, differental thermogravimetry, and differential thermal analysis methods in a static air atmosphere. Copyright Taylor & Francis Group, LLC.

Full text of DOI:10.1080/15533174.2012.684263

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A Crystallographic, Spectroscopic, Thermal, and DFT
Investigation of Mixed Ligand Cu(II) Complexes of 2-
benzoylbenzoate
Caglar Sema a & Demir Serkan b
a Department of Chemistry , Faculty of Arts and Sciences, Erzincan University , Erzincan ,
Turkey
b Department of Chemistry , Faculty of Arts and Sciences, Ondokuz Mayis University ,
Atakum , Samsun , Turkey
Accepted author version posted online: 30 Jul 2012.Published online: 05 Oct 2012.
To cite this article: Caglar Sema & Demir Serkan (2012) A Crystallographic, Spectroscopic, Thermal, and DFT Investigation of
Mixed Ligand Cu(II) Complexes of 2-benzoylbenzoate, Synthesis and Reactivity in Inorganic, Metal-Organic, and Nano-Metal
Chemistry, 42:10, 1449-1458, DOI: 10.1080/15533174.2012.684263
To link to this article: http://dx.doi.org/10.1080/15533174.2012.684263
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Synthesis and Reactivity in Inorganic, Metal-Organic, and Nano-Metal Chemistry, 42:1449–1458, 2012
Copyright ꢀ Taylor & Francis Group, LLC
C
ISSN: 1553-3174 print / 1553-3182 online
DOI: 10.1080/15533174.2012.684263
A Crystallographic, Spectroscopic, Thermal, and DFT
Investigation of Mixed Ligand Cu(II) Complexes
of 2-benzoylbenzoate
Caglar Sema1 and Demir Serkan2
1Department of Chemistry, Faculty of Arts and Sciences, Erzincan University, Erzincan, Turkey
2Department of Chemistry, Faculty of Arts and Sciences, Ondokuz Mayis University, Atakum, Samsun,
Turkey
terials, and many fields of industry. They also have been utilized
by their high surface area, porosity, and attractive adsorptive
Two mixed ligand complexes of copper(II)-2-benzoylbenzoate
(bba) with pyridazine and 4-picoline, namely bis(2-benzoylben-
zoate)di(pyridazine)copper(II) 1 and bis(2-benzoylbenzoate)bis(4-
picoline)copper(II) 2, have been synthesized and characterized by
X-ray crystallography. Complexes 1 and 2 crystallize in the mon-
oclinic P21/c space groups. The calculated frequency shifts have
shown that the participation of carboxylate groups in coordination
to the metal centers in monodentate fashion (ꢀ(OCO) > 200 cm−1).
The structural features of the complexes have been further studied
by DFT/X3LYP extended hybrid functional. The thermal behavior
of the complexes was studied by means of simultaneous thermo-
gravimetry, differental thermogravimetry, and differential thermal
analysis methods in a static air atmosphere.
properties.[7–9]
2-benzoylbenzoic acid (Hbba) and its derivatives are used in
the synthesis of supramolecular coordination compounds,[10] in
the preparation of electron-transport materials,[10] and in sweet-
eners.[11] But the number of studies with the metal complexes
of 2-benzoylbenzoato [bba = (C14H9O3)−] is rare in the litera-
ture.[10–19]
Pyridazine (pdz) as an important heterocycle has two po-
tential N-donor coordination sites and can behave as a mono-
or bidentate ligand. Pyridazine and derivatives are widely used
in pharmaceutical and agrochemical areas.[20,21] Their synthesis
and applications have been comprehensively reviewed.[22,23]
Hbba, pdz, and 4-picoline (4-pic) ligands are shown in
Figure 1. In our previous work, we reported the synthesis and
structural characterization of transition metal complexes of bba
with the coligand 1,10-phenanthroline.[24,25]
Keywords 2-benzoylbenzoate, copper(II) complex, crystal structure,
DFT, X3LYP
INTRODUCTION
Definite organic compounds containing carboxylates as func-
In the present study, the synthesis, spectral, thermal charac-
tional group and/or supramolecular synthon are among the most terization, DFT/X3LYP analysis, and crystal structures of two
widely studied ligand classes at present because of providing new complexes, [Cu(bba)2(pdz)2] 1 and [Cu(bba)2(4-pic)2] 2,
a good facility for the synthesis of coordination compounds have been represented.
with interesting topologies. Versatile coordination modes are
available with carboxylato groups such as monodentate and
EXPERIMENTAL
chelate, different types of CO2 bridges, and O monoatomic
bridges.[1] In addition, stable complexes of low coordination
numbers are available with flexible and sterically bulk ligands.
Metal-carboxylate complexes have diverse structural, physical,
and chemical properties, giving rise to versatile practices such as
their use in dyes, extractants, drugs, pesticides, catalysts, mag-
netism, host–guest chemistry,[2–6] metal-organic framework ma-
Methods of Sample Characterization
All reactions were performed with commercially available
reagents and they were used without further purification. The
solvents were distilled and dried by standard procedures. IR
spectra were recorded on a Bruker Vertex 80V FT-IR spec-
trophotometer in the range 4000–450 cm−1 at a resolution of
4 cm−1 using KBr pellet. The C, H, and N content of the com-
plexes were determined with an Elementar Micro Vario CHNS
(Germany). Thermal analysis curves (thermogravimetry [TG],
differential thermal analysis [DTA], differential thermogravime-
try [DTG]) were simultaneously obtained on a Perkin-Elmer Di-
amond thermal analyzer (USA) in a static air atmosphere with
a sample of 5–10 mg.
Received 23 December 2011; accepted 1 April 2012.
The authors thank Professor Dr. Orhan Bu¨yu¨kgu¨ngo¨r for this help
with the data collection.
Address correspondence to Caglar Sema, Department of Chemistry,
Faculty of Arts and Sciences, Erzincan University, 24100, Erzincan,
Turkey. E-mail: semacaglar2002@hotmail.com
1449

1450
C. SEMA AND D. SERKAN
C, 64.14; H, 3.86; N, 8.31. Found (%): C, 64.01; H, 3.90; N,
8.25.
Synthesis of [Cu(bba)2(4-pic)2] (2)
2-Hbba ligand (0.136 g, 0.6 mmol) and Cu(CH3COO)2.H2O
(0.006 g, 0.3 mmol) were dissolved in 40 mL of methanol-
ethanol (1:1) mixture with continuous stirring at 50◦C. Then
a 4-pic ligand (100 µL, 1 mmol) was dropwise added to the
solution. Dark blue crystals of [Cu(bba)2(4-pic)2] were obtained
by slow evaporation of the solvent at room temperature after
one day. Yield: 90%. Anal. Calcd. for C40H32N2O6Cu (%):
FIG. 1. Structures of (a) 2-benzoylbenzoic acid, (b) pyridazine, and (c) 4-
picoline ligands.
Intensity data for the title compounds were collected using a C, 68.57; H, 4.57; N, 4.0. Found (%): C, 68.51; H, 4.41; N,
STOE IPDS-II area detector diffractometer (Germany, MoKα 3.91.
radiation, λ = 0.71073Å) at 293 K. The structures were solved
by direct methods and refined on F2 with the SHELX-97 pro-
RESULTS AND DISCUSSION
gram (University of Go¨ttingen, Germany).[26] All non-hydrogen
atoms were refined with anisotropic parameters. All hydrogen
atoms were included using a riding model.
Crystal Structure of 1
The molecular structure of complex 1 together with the atom
numbering scheme is shown in Figure 2 and the crystal pack-
ing determined by C-H. . .π interactions along b-axis is given in
Synthesis of [Cu(bba)2(pdz)2] (1)
Cu(CH3COO)2.H2O (0.006 g, 0.3 mmol) and 2-Hbba (2- Figure 3. The detail of data collection, refinement, and crystal-
benzoylbenzoic acid) ligand (0.136 g, 0.6 mmol) were dissolved lographic data for 1 and 2 are summarized in Table 1.
in 40 mL of ethanol with continuous stirring at 50◦C. Then pdz
Complex 1 crystallizes in the monoclinic P21/c space group.
ligand (75 µL, 1 mmol) was dropwise added to the solution. The monomer complex consists of two bidentate bba and two
X-ray quality blue crystals of [Cu(bba)2(pdz)2] were obtained monodentate pdz ligands. The copper(II) ion is located at the
by slow evaporation of the solvent at room temperature after center of inversion and the coordination around the metal ion is
one day. Yield: 85%. Anal. Calcd. for C36H26N4O6Cu (%): distorted octahedral.
FIG. 2. Molecular structure of 1 with ellipsoid probabilities of 50% for Cu and 35% for other atoms (color figure available online).

COPPER(II) COMPLEX, DFT; X3LYP
1451
TABLE 1
Crystal data and structure refinement parameters for 1 and 2
(1)
(2)
Empirical formula
Formula weight
Temperature (K)
Wavelength (Å)
Crystal system
Space group
Unit cell dimensions
a (Å)
C36H26N4O6Cu
674.15
296
0.71073
monoclinic
P 21/c
C40H32N2O6Cu
700.22
296
0.71073
monoclinic
P 21/c
13.7177(9)
8.3372(4)
14.1719(9)
90
103.462(5)
90
1576.27(16)
2
0.747
8.2903(7)
20.4904(12)
11.3213(9)
90
113.697(6)
90
1761.0(2)
2
0.669
b (Å)
c (Å)
α ◦
◦
β
◦
γ
V (Å)3
Z
A. coefficient (mm−1
)
Dcalc (mg m−3
)
1.420
1.320
Crystal size (mm)
Theta range for data
collection (◦)
0.150; 0.317; 0.610
1.86; 27.99
0.270; 0.467; 0.650
1.99; 26.00
Measured reflections
Indepen. reflections
Absorpt. correctiona
Refinement method
18409
3552
Integration
16421
3449
Integration
Full-matrix least-squares
Full-matrix least-squares
on F2
on F2
Final R indices [F2 > 2σ
(F2)]
R1 = 0.0342, wR2 = 0.0844
R (all data) = 0.0539,
wR2 = 0.0905
1.022
R1 = 0.0349, wR2 = 0.0974
R (all data) = 0.0431,
wR2 = 0.1014
Goodness-of-fit on F2
Largest difference peak
and hole (e/Å3)
1.042
–0.354; 0.245
–0.535; 0.230
CCDC number
831085
831086
aStoe and Cie (2002).[26]
weak coordination of O2 atom to the metal ion and hereby, a
pseudodistorted octahedral geometry around copper(II) center is
provoked rather than a square-planar geometry in contrast to that
IR results suggest. Selected hydrogen bonds are given in Table 2.
As shown in Table 3, there are intermolecular hydrogen bonds
between bba ligand and carbonyl O atom of the bba ligand (C3-
H3. . .O3; 2.437 Å) and between pdz and carboxylato O atom
of the bba ligands (C18-H18. . .O2; 2.407 Å). The chains are
cross-linked by C-H. . .π and π. . .π stacking interactions (C11-
H11. . .Cg2 (C2-C7) 2.908 Å, C15-H15. . .Cg3 (C9-C14) 2.793 Å,
and Cg1-Cg1 4.2788(13) Å) arranged by free rotation of benzoyl
synthons of flexible bba ligands, and these weak interactions
together with partially effective aforementioned H-bonds are
primarily responsible for self-assembling of 1 leading to the
lattice formation.
Cu-Obba bond distance is 1.9611(1) Å, which is similar to
that reported in [Cu(bba)2(benzimidazole)2] (1.95(13) Å)[19] and
in [Cu(bba)2(phen)] (1.92(2) and 1.96(2) Å),[24] where phen is
1,10-phenanthroline. Relatively long Cu-O2 distance (2.5387(1)
Å) and the small C1-O2-Cu1 angle (77.718◦(3)) denotes the
TABLE 2
Selected hydrogen bonds (◦) for 1
D—H H· · ·A D· · ·A D—H· · · A
D—H· · ·A
D—H (Å) (Å)
(Å)
(◦)
(1)
C3—H3···O3
0.93
0.93
2.44 3.180 (3)
2.41 3.309 (3)
137
163
C18—H18···O2

1452
C. SEMA AND D. SERKAN
FIG. 3. Crystal packing of 1 along b-axis, C-H···π interactions (dotted lines), and coordination polyhedra around central atoms (color figure available online).
(2.001(4) Å),[29] [Cu2(3-ClC2H4COO)4(4-pic)] (2.170(2)
Å),[30] and [CuBr(C9H16N2Si)]4 (2.013 Å)[31] where
(H2dipic), pmpa, PEPA, (3-ClC2H4COO), and (C9H16N2Si)
are Pyridine-2,6-dicarboxylic acid, N-(2-picolyl)picolinamide,
N-(2-pyridylethyl)picolinamide, 3-chloropropionato, and
Crystal Structure of 2
Structure analysis of 2 shows that complex crystallizes in
monoclinic P21/c space group. The symmetric unit consists of
two bba and two 4-pic ligands. As depicted in Figure 4, each
Cu(II) is coordinated by four oxygen each from two bba lig-
ands and by two nitrogen from two 4-pic ligands, resulting in a
distorted octahedral geometry analogous to 1. Crystal packing
determined by C17-H17. . .Cg2 interactions along a-axis is given
in Figure 5.
trimethylsilyl-(4-methylpyridine-2-yl)amine,
respectively.
The longer Cu-O2 distance (2.5857(1) Å) and the smaller
C1-O2-Cu1 angle (76.435◦(1)) more weakly provokes the
pseudo-octahedral geometry.
The intermolecular C17-H17. . .Cg2 (C8-C13) (2.9077 Å) and
C5-H5. . .Cg3 (C15-C20) (3.0134 Å) interactions between bba
ligands are only responsible for self-assembling of 2 and leads
to the crystal packing because none of intra- or intermolecular
H-bonds were detected from Platon analysis of the structure.
In previously reported Co(II) and Ni(II) counterparts of 1
and 2 with coligand 3-picoline, bba acted as monodentate and
two aqua ligands participated to the coordination in coplanar
Cu-Obba bond distance is 1.956(12) Å similar with the
corresponding one in [Cu(bba)2(benzimidazole)2] (1.95(13)
Å)[19] and [Cu(bba)2(phen)] (1.92(2) and 1.96(2).[24] Cu-N4-pic
bond distance is 1.997(15) Å, which is slightly longer than
the corresponding one in [Cu(dipic)(4-picoline)]n (1.920(15)
and 1.890(11) Å),[27] [Cu(pmpa)(4-methylpyridine)(H2O)]-
(H2O)(ClO4) (1.986(4) Å).[28] But Cu-N4-pic bond distance is
slightly shorter than in (PEPA)(4-methylpyridine)(H2O)](ClO4)
TABLE 3
Selected calculated and experimental vibrational frequencies of 1 and 2 in cm−1 and calculated intensities in km/mol
1
2
Assignment
Calc.
Exp.
Int.
Calc.
Exp.
Int.
υ(CH)4-pic
υ(CH)pdz
—
—
3067w
3020w
—
1673s
1586s
1379vs
—
—
15.82
11.59
—
292.59
292.36
1155.84
—
3114
—
3062w
—
38.92
—
3124
3087
—
1704
1622
1350
—
υ(CH)phenyl
υ(CH)aliph.
υ(C=O)
3080
2929
1688
1635
1336
1610
3017w
2918w
1668s
1591s
1372vs
1557w
54.12
30.14
363.63
323.58
1050.84
189.26
υ(OCO)asym
υ(OCO)sym
υ(C=N)
Note. s = strong; w = weak; vs = very strong.

COPPER(II) COMPLEX, DFT; X3LYP
1453
are listed in Table 3. The experimental and calculated IR spectra
of 1 and 2 are given in Figure 6. Even with scaling, the over-
estimation of calculated vibrations is caused by the negligence
of anharmonic effects, appears in the solid state, by DFT. How-
ever, for qualitative assignment of observed frequencies, it is
very practical and useful that the comparison of experimental
values with calculated vibration modes. In the observed spectra,
the characteristic υ(OCO)asym values are 1586 and 1590 cm−1
,
υ(OCO)sym values are 1379 and 1372 cm−1, and the calculated
ꢀ(OCO) values {υ(OCO)asym – υ(OCO)sym} are 207 cm−1 and
218 cm−1 for 1 and 2, respectively. These ꢀ(OCO) values are
in accordance with monodentate (ꢀ > 200 cm−1) coordina-
tion modes of carboxylate ligands.[34] Besides medium intensity
bands around 1604–1614 cm−1 may be assigned to υ(C–N) of
the aromatic ring of the Lewis base, confirming their presence
in adducts.[35]
FIG. 4. Molecular structure of 2 with ellipsoid probabilities of 50% for Cu
and 30% for other atoms (color figure available online).
Thermal Analysis
Thermal analysis plots of 1 and 2 are given in Figures 7
and 8, respectively. The thermal behavior of 1 was followed
up to 900◦C in a static air atmosphere. 1 decomposes in two
stages. The first stage between 161 and 258◦C corresponds to
the endothermic removal of the two pdz and one bba ligand with
position with bba ligands, and more ordered octahedral com-
plexes were resulted than 1 and 2.[32] This is because Co(II) and
Ni(II) are not as prone as Cu(II) to form highly distorted octa-
hedral complexes as 1 and 2. Therefore, the difference on the
coordination behaviors of bba ligands in corresponding Cu(II)
complexes here not only comes from versatility of bba ligands
but also from tendency of Cu(II) ion. This is because copper(II)
forms a larger variety of complexes with different coordination
geometries as compared with other transition metal(II) ions.
a mass loss of 57.16% (calcd. mass loss 57.50%; DTGmax
=
235◦C). Decomposition of the one bba ligand occurs in the
second stage (258–490◦C) with a mass loss of 34.36% (calcd.
mass loss 33.40%). The last decomposition step of the complex
seems vigorously exothermic (DTA at 449◦C) and is related
to the burning of organic residue. The total mass loss of all
decomposition process is 91.52% (calcd. 90.90%) and suggests
that CuO is the end product.
IR Spectra
Some characteristic experimental and calculated gas-phase
vibrational stretching frequencies scaled with 0.96, previously
obtained value in the literature for B3LYP/6–31g(d,p) level,[33]
Complex 2 shows a three-stage decomposition process. In
the first stage, endothermic degradation of one 4-pic occurs
between 134–188◦C with an experimental mass loss of 12.93%
FIG. 5. Crystal packing of 2 along b-axis, C-H···π interactions (dotted lines), and coordination polyhedra around central atoms (color figure available online).

1454
C. SEMA AND D. SERKAN
FIG. 6. Experimental (top) and calculated (bottom) IR spectra of 1 (a) and 2 (b).
FIG. 7. Simultaneous thermal analysis plots of 1. TG = thermogravimetry; DTG = differential thermogravimetry; DTA = differential thermal analysis (color
figure available online).

COPPER(II) COMPLEX, DFT; X3LYP
1455
FIG. 8. Simultaneous thermal analysis plots of 2. TG = thermogravimetry; DTG = differential thermogravimetry; DTA = differential thermal analysis (color
figure available online).
(calcd. mass loss 13.28%; DTGmax = 175◦C). The second stage
Computational Procedure
(188–310◦C) is related to degradation of one 4-pic and one bba
All computations in this study were executed by using the
Gaussian 03W Revision E.01[36] program suite and applying
ligand, giving an exothermic peak (found = 44.58, calcd. =
45.42%). In the last stage, which is extremely exothermic in the
310–535◦C range, one bba ligand abruptly burned (DTA = 410,
455, and 471◦C). The total mass loss of complete decomposition
process is 90.95% (calcd. 90.84%) and suggests that CuO is the
end product.
unrestricted formalism for all complexes. The extended den-
sity hybrid functional X3LYP was used throughout the calcula-
tions. The basis sets LANL2DZ, in geometry optimizations,
and 6–311 + G(d,p), in single-point energy (SPE) calcula-
tions, were applied for the Cu atom, while only 6–31g(d,p) was
FIG. 9. Superimpositions of optimized (blue) and X-ray (orange) geometries of 1 (a) and 2 (b) (color figure available online).

1456
C. SEMA AND D. SERKAN
TABLE 4
Selected distances and angles of the optimized and X-ray geometries of 1 and 2
Bond lengths (Å)
Bond angles (◦)
Calc.
Calc.
Bond
(1)
Cu1-N1
Cu1-O1
Cu1-O2
Exp.
X3LYP
B3LYP
Angle
Exp.
X3LYP
B3LYP
2.0133(16)
1.9611(13)
2.5387(1)
2.061
1.976
2.593
1.983
2.049
2.552
O1i-Cu1-N1i
O1-Cu1-N1i
O1-Cu-O2
91.11(6)
88.89(6)
56.849(2)
90.866
89.134
56.546
91.021
88.981
57.174
(2)
Cu1-O1
Cu1-N1
Cu1-O2
1.9560(12)
1.9970(15)
2.5857(1)
1.978
2.066
2.657
1.984
2.054
2.618
O1-Cu1-N1
O1-Cu1-N1i
O1-Cu-O2
89.39(6)
90.61(6)
55.961(2)
89.510
90.492
55.374
89.546
90.453
56.045
applied for non-metal atoms. The initial guess structures for ge- for the calculative procedure in this study, owing to the fact
ometry optimizations were taken from experimental X-ray ge- that optimized geometries are essential for all other calcula-
ometries and the succeeding calculations were carried out based tions in theoretical insight. In both functional, the calculated
on the optimized geometries. Harmonic vibrational frequency Cu1-O2 distances in both 1 and 2 more deviated from exper-
analyses of the optimized structures were performed to check imental values compared with the Cu1-N1 and Cu1-O1 dis-
whether they are the true global minima with no imaginary fre- tances. Therefore, the calculated structures of 1 and 2 favor the
quency. Calculated spectra were simulated by using the Swizard square-planar geometry. The Natural Bond Orbital (NBO) anal-
Program.[37]
ysis of intraunits of 1 fairly manifests electron populations of
d-orbitals within octahedral copper(II) center whereas electron
population between dz2 and dx2-y2 orbitals seems to be inter-
fused to some extent in 2. Second-order perturbation theory
analysis of Fock matrix in 1 and 2 specifies the strongest non-
covalent intramolecular interactions take place between donor
atoms and central copper(II) ions. Selected, considerably high,
second-order energies in Table 5 point out that tremendoulsy
weak covalent character of the related interactions. As seen, the
interactions between O2 and central atoms in 1 (3.03 kcal/mol)
and 2 (2.31 kcal/mol) are not as significant as these between O1
and central atoms. Accordingly, the weak interactions of these
donors to the metal centers are not to be considered as a co-
ordination bond by theoretical insight. Besides none of natural
bond orbitals was detected between donor atoms and central
ions.
Geometry Optimizations and NBO Analysis
The main geometrical parameters related to X-ray and op-
timized geometries of 1 and 2 are given in Table 4 and super-
impositions of X-ray and optimized structures of 1 and 2 are
presented in Figure 9. Also the results obtained by the most
popular all-purpose B3LYP functional are additionally given
for comparison in the Table 4. Though the results obtained both
from X3LYP and B3LYP calculations are in perfect agreement
with the experiment, X3LYP values are slightly better agree-
ment with the X-ray geometries than B3LYP ones. In addition,
the root mean square error values of overall X3LYP-optimized
structures of 1 and 2 are 0.333 Å and 0.466 Å while those
of B3LYP ones are 0.333 Å and 0.476 Å, respectively. Based
on the results, The X3LYP method was essentially preferred
TABLE 5
CONCLUSIONS
Major second order energies from NBO analysis
The newly synthesized Cu(II) complexes have been charac-
terized by elemental analyses, FT-IR, thermal analysis, and X-
ray single-crystal diffractometry. The crystal structure analysis
showed that compounds 1 and 2 consist of neutral monomeric
units and all complexes exhibit pseudo-octahedral geometry.
Conversely, both experimental IR spectroscopic and calculated
data present the monodentate coordination behavior of the bba
ligands to the metal centers and suggest square-planar geome-
try. Consequently, combining the whole findings we have con-
cluded that the geometry around metal ions distorted from
1
2
E2 (kcal/
mol)
E2 (kcal/
mol)
Donor Acceptor
Donor Acceptor
O1(LP) Cu1(LP∗) 16.01 O1(LP) Cu1(LP∗) 15.26
O2(LP) Cu1(LP∗)
N1LP) Cu1(LP∗)
3.03
14.9
O2(LP) Cu1(LP∗)
N1LP) Cu1(LP∗) 15.19
2.31
Note. LP = a lone pair valence orbital; LP∗ = empty valence orbital.

COPPER(II) COMPLEX, DFT; X3LYP
1457
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