Quantum chemical and spectroscopic study of the structure of 2-acetylindan-1,3-dione complexes with metal(II) ions

Article abstract of DOI:10.1016/S0022-2860(01)00522-1

A series of M(II) (M = Cu, Zn, Cd, Pb) complexes with the physiologically active 1-acetylindan-1,3-dione were synthezed. All complexes were obtained with the metal to ligand ratio 1:2. The presence of two water molecules in the inner coordination sphere of the Zn(II) and Cd(II) complexes was proven. The structure and coordination mode of the newly synthesized Cd(II) and Pb(II) complexes were investigated using NMR (13C CPMAS and 13C NMR in DMF-d₇ solution) method. Semi-empirical (PM3) and ab initio (ECP-312G) calculations of the structure and IR spectra of the free ligand and corresponding metal(II) complexes were performed. It is shown that the structure of the Pp(II) complex differs significantly from the distorted tetrahedral structure of the Cu(II), Zn(II), and Cd(II) complexes.

Full text of DOI:10.1016/S0022-2860(01)00522-1

Journal of Molecular Structure 595 ꢀ2001) 67±76
www.elsevier.com/locate/molstruc
Quantum chemical and spectroscopic study of the structure of
2-acetylindan-1,3-dione complexes with metalꢀII) ions
a,
b
a
c
*
Venelin Enchev , Anife Ahmedova , Galya Ivanova , Iwona Wawer ,
Neyko Stoyanovd, Mariana Mitewab
aInstitute of Organic Chemistry, Bulgarian Academy of Sciences, 1113 So®a, Bulgaria
bDepartment of Chemistry, University of So®a, 1, J. Bourchier Av., 1126 So®a, Bulgaria
cFaculty of Pharmacy, Medical University of Warsaw, Banacha 1, 02097 Warsaw, Poland
dCollege of Technology, University of Rousse, 7200 Razgrad, Bulgaria
Received 1 December 2000; accepted 15 January 2001
Abstract
A series of MꢀII) ꢀM ˆ Cu, Zn, Cd, Pb) complexes with the physiologically active 2-acetylindan-1,3-dione were synthesized.
All complexes were obtained with the metal to ligand ratio 1:2. The presence of two water molecules in the inner coordination
sphere of the ZnꢀII) and CdꢀII) complexes was proven. The structure and coordination mode of the newly synthesized CdꢀII)
and PbꢀII) complexes were investigated using NMR ꢀ13C CPMAS and 13C NMR in DMF-d7 solution) method. Semi-empirical
ꢀPM3) and ab initio ꢀECP-31G) calculations of the structure and IR spectra of the free ligand and corresponding metalꢀII)
complexes were performed. It is shown that the structure of the PbꢀII) complex differs signi®cantly from the distorted
tetrahedral structure of the CuꢀII), ZnꢀII) and CdꢀII) complexes. q 2001 Elsevier Science B.V. All rights reserved.
Keywords: 2-Acetylindan-1,3-dione±metal complexes; MO calculations; NMR
1. Introduction
its complexation properties are available up to now
[9±11].
The physiological activity of 2-acetylindan-1,3-
dione ꢀ2AID) and its derivatives is well documented
[1±3]. Its structure has also been studied by X-ray, IR
and NMR spectroscopy [4±7]. Recently, some of us
have investigated the ground and excited state proper-
ties of 2AID using spectroscopic ꢀNMR, UV and
¯uorescence) and quantum chemical ꢀAM1) methods
[8], and have shown evidence of proton transfer
occurring in the ®rst excited singlet state. On the
other hand, 2AID, being a b-diketone, shows good
complexation properties. However, only few data on
There is no X-ray structure of an 2AID±metal
complex in the Cambridge Structural Data Base.
The aim of the present paper is to study the composi-
tion and structure of a series of metalꢀII) complexes
with 2AID by a combined approach of experimental
and quantum-chemical methods.
2. Experimental and calculations
2.1. Synthetic procedures
2-Acetylindan-1,3-dione was obtained by mixing
of 0.05 M phthalic anhydride and 0.3 M acetic
*Corresponding author. Fax: 1359-2-700225.
E-mail address: venelin@orgchm.bas.bg ꢀV. Enchev).
0022-2860/01/$ - see front matter q 2001 Elsevier Science B.V. All rights reserved.
PII: S0022-2860ꢀ01)00522-1

68
V. Enchev et al. / Journal of Molecular Structure 595 82001) 67±76
1
anhydride with 0.05 M acetylacetone. The mixture
was heated under re¯ux until the phthalic anhydride
was completely dissolved. Then it was cooled to 808C
and 0.15 M triethylamine was added. After 12±14 h,
the reaction mixture was poured on 150 g ice with
50 ml concentrated HCl. The resulting precipitate
was ®ltered and washed with water until neutral
reaction. The precipitate was dissolved in 500 ml
3% solution of NaOH, and ®ltered again. The ®ltrate
was acidi®ed with HCl ꢀ1:1) resulting in the formation
of a precipitate of 2AID. The product was twice
recrystalized from ethanol; mp 109±1108C; yield
71%.
The complexes were obtained by mixing metha-
nolic solution of the corresponding metal acetate
with ethanolic solution of the ligand. The reaction
mixtures were re¯uxed for about 30 min at 908C
until precipitates were obtained. The latter were
washed with ethanol and dried for four weeks above
P4O10. The presence of two water molecules in the
ZnꢀII) and CdꢀII) complexes was proved using ther-
mogravimetric analysis. All chemicals were analy-
tical grade reagents.
performed. The 2D H±13C multiple bond connec-
tivity ꢀHMBC) spectra were recorded with a spectral
width of ca. 2000 Hz for H and 15 000 Hz for 13C,
relaxation delay 1.5 s, FT size 2K £ 256W.
1
2.3. Quantum-chemical calculations
The PM3 [12,13] calculations were performed for
2AID and its MꢀII) complexes with Zn, Cd and Pb
using the mopac 6.0 program [14]. Geometries were
optimized without any constrains. The analytic
gradient minimization method implemented within
an extrapolation procedure called eigenvector
following ꢀEF) was used. The mean gradient threshold
Ê 21
was 0.01 kcal mol21
A . The vibrational analysis of
the obtained structures was carried out. The calculated
wavenumbers of all normal modes were scaled by a
factor of 0.893.
The ab initio structure optimizations for 2AID and
its Zn, Cd and Pb complexes were performed at the
RHF level. The geometry optimization of the CuꢀII)
complex was performed at UHF level. Geometric
structures were optimized within C1 symmetry. The
calculations described herein were carried out with
the Stevens±Basch±Krauss±Jasien effective core
potentials ꢀECP) and their concomitant basis sets for
all the atoms ꢀECP-31G) [15,16]. The ab initio
calculations were performed using the gamess
program package [17]. The IR frequencies for the
metal complexes were not calculated because
numerical differentiation is a very time-consuming
procedure.
2.2. IR, EPR and NMR measurements
The IR spectra were recorded on a Perkin±Elmer
FTIR-1600 spectrophotometer ꢀKBr tablets). EPR
spectra were measured on a Bruker B-ER 420 X-
band spectrometer ꢀtemperature range 100±300 K).
The DTG data were obtained on a Perkin±Elmer
TGS-2 instrument.
Cross polarization ꢀCP) magic angle spinning
ꢀMAS) solid state 13C NMR spectra were recorded
on a Bruker MSL-300 instrument at 75.5 MHz.
Powder samples were spun at 8.4 kHz in 4 mm ZrO2
rotor, a contact time of 4 ms, a repetition time of 6 s
and a spectral width of 20 kHz were used for accumu-
lation of 300±600 scans. Chemical shifts were
calibrated indirectly through the glycine CyO signal
recorded at 176.0 ppm relative to TMS.
3. Results and discussion
The X-ray [4] determined and ab initio calculated
structure of 2AID is shown in Fig. 1. There is reason-
able agreement between the results obtained by PM3,
ab initio ꢀECP-31G) calculations and crystallographic
data ꢀTable 1). According to Antipin et al. [6], the
experimental O12´´´O17 distance in 2AID ꢀat
Ê
21208C) is 2.650 A indicating the presence of the
The NMR spectra for DMF-d7 solutions were
measured at ambient temperature on a Bruker DRX-
250 spectrometer, operating at 250.13 and 62.90 MHz
for 1H and 13C, respectively, using a dual 5 mm probe
head. Standard 1D experiments with 308 pulses, 1 s
relaxation delay, 16K time domain points, zero-®lled
to 64K for the protons and 32K for the carbons were
O±H´´´O intramolecular hydrogen bond. The PM3
and ECP-31G calculations predict this distance to be
2.683 and 2.730 A, respectively. The 13C NMR data
Ê
of the solid compound and in DMF-d7 solution at
room temperature are listed in Table 2. A signi®cant
down®eld shift of the resonance peak of the carbonyl

V. Enchev et al. / Journal of Molecular Structure 595 82001) 67±76
69
Fig. 1. Stereographic packing diagram, stereographic view and ab initio calculated structure for 2-acetylindan-1,3-dione.

Table 1
Ê
Ab initio ꢀECP-31G) and PM3 calculated structural parameters of 2AID and its compexes with CuꢀII), ZnꢀII), CdꢀII) and PbꢀII). Bond lengths are in A, angles in degrees, dipole
moments in D and IR frequencies in cm21. For the numbering of the atoms see Figs. 1 and 3. Available experimental data are also given
Parameter
2AID
CuꢀAID)2 ZnꢀAID)2
ZnꢀAID)2´2H2O
CdꢀAID)2
PM3
CdꢀAID)2´2H2O
PbꢀAID)2
PM3
Experimentala PM3
ECP ECP
PM3
ECP
PM3
ECP
ECP
PM3
ECP
ECP
Selected distances
C1±C2
1.386
1.396
1.363
1.394
1.393
1.358
1.475
1.479
1.488
1.448
1.342
1.475
1.352
1.140
1.560
1.239
1.214
1.400 1.412 1.416
1.401
1.387
1.402
1.379
1.410
1.381
1.499
1.494
1.487
1.432
1.412
1.505
1.281
1.987
2.024
1.266
1.216
1.415
1.412
1.416
1.396
1.409
1.398
1.513
1.495
1.487
1.443
1.423
1.515
1.292
1.955
1.988
1.275
1.236
1.401
1.387
1.402
1.379
1.410
1.381
1.500
1.497
1.483
1.430
1.415
1.505
1.275
2.025
2.062
1.263
1.217
2.552
2.552
1.414
1.413
1.415
1.395
1.409
1.398
1.509
1.491
1.490
1.448
1.415
1.514
1.305
1.966
1.969
1.274
1.235
3.835
3.838
1.401
1.387
1.402
1.379
1.411
1.380
1.503
1.494
1.476
1.434
1.414
1.501
1.268
2.179
2.242
1.253
1.218
1.415
1.413
1.416
1.397
1.408
1.399
1.512
1.497
1.488
1.447
1.426
1.518
1.291
2.172
2.213
1.273
1.237
1.401
1.387
1.402
1.379
1.411
1.380
1.501
1.492
1.479
1.437
1.408
1.502
1.275
2.224
2.225
1.252
1.217
4.259
4.259
1.415
1.413
1.415
1.398
1.408
1.399
1.512
1.504
1.483
1.453
1.424
1.521
1.287
2.317
2.279
1.263
1.240
2.369
2.378
1.400
1.388
1.401
1.380
1.409
1.381
1.499
1.497
1.478
1.455
1.394
1.502
1.285
2.083
2.754
1.235
1.218
1.414
1.413
1.416
1.397
1.409
1.399
1.512
1.498
1.486
1.450
1.415
1.516
1.299
2.222
2.361
1.267
1.237
C2±C3
C3±C4
1.388 1.415 1.412
1.401 1.413 1.416
1.381 1.400 1.396
1.411 1.411 1.410
1.381 1.401 1.399
1.500 1.508 1.513
1.486 1.496 1.495
1.480 1.490 1.485
1.480 1.480 1.441
1.367 1.378 1.423
1.487 1.507 1.515
1.343 1.352 1.291
0.968 0.976 1.950
1.839 1.927 1.978
1.224 1.246 1.274
1.213 1.235 1.237
C4±C5
C5±C6
C6±C1
C7±C5
C8±C6
C9±C7
C9±C8
C9±C10
C10±C11
O12±C10
O12±H22 ꢀM)
O17±H22 ꢀM)
O17±C8
O18±C7
M±O44
M±O47
Selected bond angles
C5±C7±O18
C6±C8±O17
C8±C9±C7
126.2
125.8
107.5
128.1
126.0
124.9
121.2
129.9
126.3 125.3 124.5
128.7 127.0 123.9
108.4 108.2 108.1
127.8 128.9 129.5
124.3 125.8 127.5
124.8 126.3 123.0
121.6 121.0 120.7
129.0 128.8 128.9
89.9
125.7
120.8
108.1
127.9
130.8
119.7
125.7
123.4
101.7
113.4
115.2
124.4
123.3
108.0
129.4
128.1
123.0
121.0
128.6
90.7
125.6
120.9
108.4
128.0
131.0
119.3
125.1
123.8
97.8
124.5
123.4
107.7
129.4
127.9
123.2
121.1
128.2
91.6
125.9
123.4
108.7
127.9
128.6
119.6
123.1
124.8
83.4
124.1
122.7
107.9
129.6
128.9
122.6
121.7
127.8
81.9
126.0
123.4
108.5
127.7
128.5
119.5
123.5
124.6
83.4
123.8
123.0
108.1
129.8
129.1
122.1
121.9
127.7
77.5
125.8
123.4
108.4
127.8
129.3
120.2
124.0
124.3
75.2
124.3
123.8
108.1
129.5
128.0
123.1
121.4
128.5
75.3
C9±C7±O18
C9±C8±O17
C9±C10±C11
C9±C10±O12
C10±C9±C7
O12±M±O17
O12±M±O35
O12±M±O23
130.1
112.0
119.5
121.7
109.5
134.1
121.2
113.1
123.7
127.8
124.4
128.9
123.7
127.7
121.1
151.8
85.0
96.7
81.3
91.4
Selected dihedral angles
C8±O17±M±O23
C8±O17±M±O35
C10±O12±M±O23
C10±O12±M±O35
2116.6
135.8
2124.0 2126.9 2150.2 2120.0 2131.7 2132.7 2129.6 2144.6 287.7 282.6
239.5 236.3
121.7
122.7
124.9
125.1
105.3
135.7
126.7
130.0
125.2
128.2
124.9
129.0
127.3
126.2
132.3
120.9
2120.7 2123.5 2101.4 2122.9 2121.9 2121.7 2123.9 2112.1 138.9
141.1
2109.2
64.5
70.9
145.8

Table 1 ꢀcontinued)
Parameter
2AID
CuꢀAID)2 ZnꢀAID)2
ZnꢀAID)2´2H2O
CdꢀAID)2
PM3
CdꢀAID)2´2H2O
PbꢀAID)2
PM3
Experimentala PM3
ECP ECP
PM3
3.30
ECP
PM3
1.02
ECP
7.87
ECP
3.78
PM3
4.46
ECP
0.84
ECP
3.68
Dipole moment
4.09
3.54b
4.09
4.69b
2.64
4.25
Selected infrared frequencies
O±H str.
3263
3357c
1740
C8yO17 str.
C7yO18 str.
CyC str.
1635
1617c
1773
1671c
1661
1619c
1775
1671c
1699
1680
1630c
1609c
1774
1680
1670c
1694c
1502
1566c
1653c
1795
1616c
1705c
1675c
1576c
1635
1592c
1445
1579c
1458
1581c
g factor
g'
2.077d
2.276d
gk
a
X-ray data at room temperature [4].
In dioxan 258C [10].
In KBr.
b
c
d
At 105 K.

72
V. Enchev et al. / Journal of Molecular Structure 595 82001) 67±76
Table 2
13C NMR chemical shifts ꢀppm) for 2AID and its CdꢀII) and PbꢀII) complexes in solid state and DMF-d7 solution. For numbering of the atoms,
see Figs. 1 and 3
Carbon
Solid state
2AID
Solution
2AID
Cdꢀ2AID)2´2H2O
Pbꢀ2AID)2
Cdꢀ2AID)2´2H2O
Pbꢀ2AID)2
C1
C2
C3
C4
C5
C6
C7
C8
C9
125.0
134.4
135.0
121.8
138.2
140.2
188.6
195.9
109.3
122.0
134.0
136.7
122.0
138.4
138.4
196.2
196.2
108.6
119.5
132.2
132.2
122.4
137.9
134.5
192.8
195.2
113.1
115.2
188.4
190.8
32.5
122.4
134.7
134.7
122.4
139.6
139.6
189.1
192.4
109.0
120.5
132.9
132.9
120.5
138.3
138.3
193.7
195.8
108.4
122.3
133.9
133.9
122.3
138.2
138.2
193.4
194.9
109.5
C10
C11
182.9
18.3
194.1
185.1
20.4
195.8
27.2
189.5
24.5
29.1
27.2
28.2
carbon C8 compared to solution ꢀD ˆ dsolution 2
dsolid ˆ 23:5 ppm†; and an up®eld shift of the
hydroxyl carbon C10 ꢀD ˆ 2:1 ppm† are informative
of the existence of a hydrogen-bonded cycle, in agree-
ment with X-ray diffraction results. In the solution
spectrum of 2AID, a single resonance appeared for
every pair of CH carbons ꢀC2, C3 and C1, C4) and
also for the quaternary carbons C5, C6. The formation
of the O12±H´´´O17 hydrogen bond stiffens the
molecule and increases its asymmetry. Therefore, in
the CPMAS spectrum of solid 2AID, separate
resonances for particular carbons are observed ꢀFig.
2); the signals of C1 and C4 are separated by 3.2 ppm,
the signals of C5 and C6 by 2.0 ppm and those of C2
and C3 by 0.6 ppm.
The complexes of 2AID with CuꢀII), ZnꢀII), CdꢀII)
and PbꢀII) were isolated as solid state species ꢀpreci-
pitates). The analytical data ꢀTable 3) showed the
formation of the complexes with metal to ligand
ratio 1:2. Thermogravimetric measurements indicated
the presence of two water molecules in the inner
coordination sphere of the ZnꢀII) and CdꢀII)
complexes. In both cases, mass losses were recorded
in the temperature ranges 107±1398C ꢀfound 7.83%,
calcd 7.75%) and 100±1278C ꢀfound 6.40%, calcd
6.89%) for Zn ꢀII) and Cd ꢀII), respectively.
changes in shielding of the carbons in the vicinity of
MꢀII). The most pronounced effect is observed for
C11 ꢀCH3), down®eld shift D0 ˆ dsolid complex 2
dsolid 2AID amounts to 10.8 or 8.9 ppm for CdꢀII) and
14.3 or 9.9 ppm for PbꢀII). Smaller differences are
observed for C10 [D0 ˆ 11:2 ppm for CdꢀII) and 5.5
or 2.2 ppm for PbꢀII)] and C3 [D0 ˆ 0:7 ppm for
CdꢀII) and 3.8 or 5.9 ppm for PbꢀII)].
Ab initio optimized structures of the CuꢀII), CdꢀII),
ZnꢀII) and PbꢀII) complexes of 2AID are shown in
Fig. 3. Selected structural parameters obtained by
PM3 and ECP-31G calculations are given in Table
1. There are no considerable differences between the
geometry of the free ligand ꢀ2AID) and that involved
in complexes, except for the fragment where the
coordination occurs. The distance C8±C9
Ê
Ê
ꢀ1.480 A) decreases to 1.441±1.453 A and C9±
Ê
Ê
C10 ꢀ1.378 A) increases to 1.415±1.426 A. The
C8±O17 bond becomes longer, in contrast to the
C10±O12 one, as a result of the coordination. The
Ê
C10±O12 ꢀ1.352 A) bond lengths decrease to
Ê
1.287±1.305 A and the C8±O17 ꢀ1.246 A)
Ê
Ê
increase to 1.263±1.275 A. The last two changes
explain the differences in the IR spectra of the
free ligand and the corresponding complexes. In
this way, the lengths of the double and single
bonds in the so formed chelate ring are averaged.
The coordination of the metal ion produces large

V. Enchev et al. / Journal of Molecular Structure 595 82001) 67±76
73
Fig. 2. 13C CPMAS NMR spectrum of solid 2-acetylindan-1,3-dione and Pbꢀ2AID)2 complexes.
The distances O17±M and O12±M depend on the
metal ion radii. The oxygen atoms coordinated to
MꢀII) are not coplanar with it ꢀsee the dihedral
angles in Table 1) and the complexes have a
distorted ꢀ¯attened) tetrahedral structure.
The CuꢀII) complex is paramagnetic and EPR
active. The EPR spectrum recorded at different
temperatures ꢀ100±300 K, a powder sample) is
typical for CuꢀII) ꢀd9) complexes with lower
symmetry, showing partially resolved two-component
anisotropy. No hyper®ne structure ꢀhfs) was observed
due to 63.65Cu ꢀI ˆ 3=2† ꢀTable 1). These data prove
the distorted tetrahedral structure for the CuꢀII)
complex. The latter is typical for CuꢀII) complexes
due to the Jahn±Teller effect.
According to the quantum-chemical calculations,
Table 3
Elemental analyses data of the complexes
Complex
Molecular formula
C ꢀ%)
H ꢀ%)
Calculated
Found
Calculated
Found
CuꢀAID)2
C22H14O6Cu ꢀ437.90)
C22H18O8Zn ꢀ475.77)
C22H18O8Cd ꢀ522.79)
C22H14O6Pb ꢀ581.55)
60.4
55.4
50.5
45.4
60.3
55.7
50.0
45.6
3.2
3.8
3.5
2.4
3.0
3.3
3.0
2.1
ZnꢀAID)2´2H2O
CdꢀAID)2´2H2O
PbꢀAID)2

Fig. 3. Ab initio ꢀECP-31G) calculated structures of the Znꢀ2AID)2´2H2O, Cdꢀ2AID)2´2H2O ꢀFig. 3a), Cuꢀ2AID)2 and Pbꢀ2AID)2 ꢀFig. 3b) complexes.

V. Enchev et al. / Journal of Molecular Structure 595 82001) 67±76
75
Fig. 4. PM3 calculated structures of the Znꢀ2AID)2´2H2O and Cdꢀ2AID)2´2H2O complexes.
the two ligands in the Pbꢀ2AID)2 complex lie in
approximately perpendicular planes ꢀsee the dihedral
angle C8±O17±M±O23, Table 1). This result could
explain the appearance of two signals for C9, C10 and
C11 ꢀTable 2) separated by 2.1, 2.4 and 4.3 ppm,
respectively, in the 13C CPMAS NMR spectrum.
Additional signals in the spectrum of solid
Cdꢀ2AID)2´2H2O, best seen for the C11 of methyl
group, indicate that in this case also, the two ligands
are not equivalent, most likely due to interaction with
the water molecule.
Ab initio and PM3 calculations were also
performed for Znꢀ2AID)2 and Cdꢀ2AID)2 in the
presence of two water molecules in the inner coordi-
nation sphere ꢀaccording to DTA data; Table 3). The
results are shown in Figs. 3 and 4, respectively. IR
evidence for the presence of water molecules in the
ZnꢀII) and CdꢀII) complexes is also available Ð a

76
V. Enchev et al. / Journal of Molecular Structure 595 82001) 67±76
very broad band at ,3500 cm21 corresponding to a
stretching vibration and a middle intensive band at
,1550 cm21 corresponding to a bending vibration
in water are observed.
The PM3 and ECP calculated geometries of the
ZnꢀII) and CdꢀII) complexes in presence of two
water molecules in the inner coordination sphere
leads to changes in the metal±oxygen bond lengths,
in comparison with Znꢀ2AID)2 and Cdꢀ2AID)2. PM3
results for Znꢀ2AID)2´2H2O show that both the bond
[2] L.W. Hazleton, W.H. Dolben, USA Patent 2 884 357,
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[3] J.T. Correll, L.L. Coleman, St. Long, R.F. Willy, Proc. Soc.
Exp. Biol. Med. 80 ꢀ1952) 139.
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[5] M.V. Petrova, E.E. Liepins, J.J. Paulins, I.Ya. Gudele, E.Yu.
Gudriniece, Izv. Acad. Nauk Latv. SSR, Ser. Khim. ꢀ1987) 601.
[6] M.Yu. Antipin, M.V. Petrova, Ya.Ya. Paulins, Yu.T.
Struchkov, E.Yu. Gudriniece, Izv. Acad. Nauk Latv. SSR,
Ser. Khim. ꢀ1989) 102.
[7] E. Liepins, M.V. Petrova, E. Gudriniece, J. Paulins, S.L.
Kuznetsov, Magn. Res. Chem. 27 ꢀ1989) 907.
[8] V. Enchev, S. Bakalova, G. Ivanova, N. Stoyanov, Chem.
Phys. Lett. 314 ꢀ1999) 234.
Ê
lengths M±O12 and M±O17 increase by 0.038 A.
However, in the case of the Cdꢀ2AID)2´2H2O,
Ê
M±O12 becomes longer ꢀby 0.045 A) and the
[9] D. Zacharova-Kalavska, A. Perjessy, I. Zelensky, Coll. Czech.
Chem. Commun. 35 ꢀ1970) 225.
Ê
M±O17 bond becomes shorter by 0.017 A. A similar
result is obtained for the ECP optimized
Znꢀ2AID)2´2H2O: a small increase in the M±O12
[10] T.L. Usova, O.A. Osipov, L.S. Minkina, V.G. Zaletov, Koord.
Khim. 9 ꢀ1983) 879.
Ê
bond length ꢀ0.011 A) and a decrease in the M±O17
Ê
bond length ꢀ0.019 A). In the case of the
Cdꢀ2AID)2´2H2O, ECP calculations show a strong
increase in both M±O12 and M±O17 bond lengths
Ê
by 0.135 and 0.066 A, respectively. The latter become
[11] K.P. Butin, R.D. Rakhimov, I.G. Il'ina, Izv. Acad. Nauk, Ser.
Khim. ꢀ1999) 71.
[12] J.J.P. Stewart, J. Comput. Chem. 10 ꢀ1989) 209.
[13] J.J.P. Stewart, J. Comput. Chem. 12 ꢀ1991) 320.
[14] J.J.P. Stewart, mopac 6.0, QCPE No. 455, Bloomington, IN,
1990.
[15] W.J. Stevens, H. Basch, M. Krauss, J. Chem. Phys. 81 ꢀ1984)
6026.
longer than the corresponding ones in Pbꢀ2AID)2,
even though the metal ion radius of the PbꢀII) is
greater.
[16] W.J. Stevens, H. Basch, M. Krauss, P. Jasien, Can. J. Chem.
70 ꢀ1992) 612.
[17] M.W. Schmidt, K.K. Baldridge, J.A. Boatz, S.T. Elbert,
M.S. Gordon, J.H. Jensen, S. Koseki, N. Matsunaga,
K.A. Nguen, S. Su, T.L. Windus, M. Dupuis,
J.A. Montgomery Jr., J. Comput. Chem. 14 ꢀ1993) 1347.
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