Synthesis and X-ray crystal structure of a Cd(II) complex of Rhodamine B

Full text of DOI:10.1081/SIM-100107704

Synthesis and Reactivity in Inorganic and Metal-Organic
Chemistry
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SYNTHESIS AND X-RAY CRYSTAL STRUCTURE OF A
Cd(II) COMPLEX OF RHODAMINE B
Jian-Qiang Qu , Liu-Fang Wang , Yi-Zhi Li , Gang-Chun Sun , Qiao-Jun Zhu &
Chun-Gu Xia
To cite this article: Jian-Qiang Qu , Liu-Fang Wang , Yi-Zhi Li , Gang-Chun Sun , Qiao-Jun Zhu
& Chun-Gu Xia (2001) SYNTHESIS AND X-RAY CRYSTAL STRUCTURE OF A Cd(II) COMPLEX OF
RHODAMINE B, Synthesis and Reactivity in Inorganic and Metal-Organic Chemistry, 31:9,
1577-1585, DOI: 10.1081/SIM-100107704
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Date: 30 December 2016, At: 19:56

SYNTH. REACT. INORG. MET.-ORG. CHEM., 31(9), 1577±1585 (2001)
SYNTHESIS AND X-RAY CRYSTAL
STRUCTURE OF A Cd(II) COMPLEX
OF RHODAMINE B
Jian-Qiang Qu,1 Liu-Fang Wang,*,1 Yi-Zhi Li,1
Gang-Chun Sun,1 Qiao-Jun Zhu,2 and Chun-Gu Xia3
1State Key Laboratory of Applied Organic Chemistry,
Lanzhou University, Lanzhou 730000, P. R. China
2Department of Chemistry, Tianshui Teachers College,
Tianshui 741000, P. R. China
3State Key Laboratory of Oxo-Synthesis and Selective
Oxidation, Lanzhou Institute of Chemical Physics,
Chinese Academy of Sciences, Lanzhou 730000,
P. R. China
ABSTRACT
A new solid cadmium(II) complex of Rhodamine B (RB),
Cd[(RB)(OAc)2(H2O)], has been synthesized by the reaction
of Rhodamine B with Cd(OAc)2Á2H2O in the presence of
NaOC2H5. The crystal structure of the complex has been de-
termined by X-ray di€raction. The crystal belongs to the
monoclinic space group P21/n (No. 14), a ˆ 10.268(2), b ˆ
18.861(4), c ˆ 16.667(3), b ˆ 105.18(3), Z ˆ 4, V ˆ 3115.2(11),
*Corresponding author. E-mail: qujq@netease.com
1577
Copyright # 2001 by Marcel Dekker, Inc.
www.dekker.com

1578
QU ET AL.
F (000) ˆ 1424, R ˆ 0.0409, wR ˆ 0.1532. The structure ana-
lysis reveals that the geometry around Cd is a distorted tet-
rahedron (Cd(II) adopts a typical sp3 hybrid orbital).
INTRODUCTION
Rhodamine B (RB) and its derivatives are classic dyes with wide ap-
plications, such as coloring cells1, antitumour agents274, photosensitized cell
killing5,6, solar collectors7, quantum counters8, lasers9, and also as dye in
analytical chemistry. The applications make RB and its derivatives to be
subjects of considerably fundamental interest. The crystal structure of RB
has been reported10. Although the synthesis, characterization and ¯uores-
cence of the complexes of RB with metal ions have been discussed pre-
viously, the crystal structures of the complexes have been rarely reported.
The only report was the crystal structure of a Rh(I)7RB complex11. In this
paper, we report the synthesis and crystal structure of a new cadmium(II)
complex of RB, Cd[(RB)(OAc)2(H2O)]. The results of the structure analysis
reveal that the geometry around Cd is a distorted tetrahedron and Cd(II)
adopts a typical sp3 hybrid orbital.
EXPERIMENTAL
Materials
Rhodamine B was purchased from the Third Reagent Factory of
Shanghai, P. R. China. Cadmium acetate dihydrate was purchased from the
Reagent Factory of Shanghai, P. R. China. All other chemicals were com-
mercially available.
Physical Measurements
The Cd content of the complex was determined by titration with
EDTA. C, H and N were determined on a Vario EL elemental analyzer.
Molar conductance at room temperature was measured in 10À3 M DMSO
solution using a DDS-11A digital molar conductometer. IR spectra in the
range of 40007200 cmÀ1 were recorded on a Nicolet-170SX FT-IR spec-
trophotometer using KBr discs. 1H NMR spectra were recorded on a Varian
FT-80A spectrometer in DMSO-d6 with TMS as an internal reference.

Cd(II) COMPLEX OF RB
Preparation of the Complex
1579
To absolute ethanol (20 mL), was added RB (0.88 g, 0.002 mol) and
ꢀ
heated to 30740 C. When RB was dissolved, a NaOC2H5 solution (20 mL
of 0.1 M) was added dropwise. After 374 min, cadmium acetate dihydrate
(0.53 g, 0.002 mol) was added quickly and the reaction mixture was re¯uxed
with stirring for 4 h. Some undissolved material was ®ltered o€ from the hot
solution. When the ®ltrate was cooled to room temperature, small brown
crystals with green ¯uorescence were separated out, washed three times with
ethanol and methanol (1:1), and dried in vacuum for 48 h. The yield is 0.99 g
(72%). The brown crystals suitable for X-ray di€raction were formed from
the mother liquor through slow evaporation after three weeks. Anal. Calc.
for C32H38N2O8Cd (MW 691.05): C, 55.61; H, 5.54; N, 4.05; Cd, 16.26%.
Found: C, 55.31; H, 5.09; N, 4.19; Cd, 16.53%. IR (cmÀ1): 1637(s,
nas(COOÀ)); 1339 (s, ns(COOÀ)); 451 (s, n(Cd-O)). 1H NMR (ppm, DMSO-
d6): d 7.93 (m, 1H, H-24); 7.72 (m, 2H, H-26, H-27); 7.30 (m, 1H, H-25);
6.47(m, 6H, H-1, H-2, H-4, H-5, H,-7 H-8); 3.35 (m, 10H,
ÀCH2CH3‡H2O); 1.82 (s, 6H, CH3COOÀ); 1.10 (m, 12H, ÀCH2CH3). LM
(DMSO, 289K): 10.80 SÁcm2ÁmolÀ1
Data Collection and Re®nement of the Crystal Structure
A brown single crystal of the dimensions 0.2060.2560.30 mm was
mounted on a glass ®ber. The crystal data were collected on an Enraf-
Nonius CAD4 four-cycle di€ractometer with graphite-monochromated Mo-
Ka radiation (l ˆ 0.71069 A) using a o-2y scan mode with a o scan width of
0.60‡tany, and scan rate of 8.24 minÀ1. A total of 7126 independent re-
¯ections was collected, in the range 3ꢀ < 2y < 53ꢀ of which re¯ections with
I > 2.0s(I) were used in the structure determination and re®nement after c-
scan corrections.
The structure was solved by direct methods (Sheldrick, 1990) and
successive di€erence Fourier syntheses12. The hydrogen atoms in H2O were
located in di€erence Fourier maps, while the remaining hydrogen atoms
were ®xed geometrically and the distances to hydrogens were set by a pro-
gram. All hydrogen atoms were included in calculations but not re®ned. The
®nal least square cycle gave R ˆ 0.0409 and wR ˆ 0.1532 (w ˆ 1=s2(F0)). All
calculations were performed on a PIII-550 computer using programs con-
tained in the SHELX-97package 12. Crystal data are given in Table I. The
selected bond distances and angles are listed in Table II. Figure 1 presents a
perspective view of the molecular structure of the complex.

1580
QU ET AL.
Table I. Crystal Data and Details of the Structure Determination for the Complex
Formula
Formula weight
C32H38CdN2O8
691.05
Crystal system
Space group
Monoclinic
P21=n (No. 14)
a [A]
b [A]
10.268(2)
18.861(4)
c [A]
b [ꢀ]
16.667(3)
105.18(3)
3115.2(11)
V [A3]
Z
4
1.474
0.754
1424
Density (calculated) [g=cm3]
m(Mo-Ka) [mmÀ1
F(000)
]
Crystal size [mm]
Temperature (K)
Radiation [A]
y [ꢀ]
0.2060.2560.30
293
MoKa 0.71073
1.7to 27.5
Data set
Total data
Independent data
R(int)
Observed data [I > 2.0 s(I)]
Number of reference
Number of parameter
R, wR, S
À13 < h < 12; 0 < k < 24; 0 < l < 21
7126
7126
0.000
6601
7216
388
0.0409, 0.1532, 1.09
0.00, 0.00
À0.55, 0.74
Max. and Av. Shift=Error
Min. and Max. resd. dens. [e=A3]
RESULTS AND DICUSSION
The elemental analyses and synthetic condition suggested that Cd(II)
formed a 1 : 1 (metal : ligand) complex with RB. The complex is stable in air.
It is soluble in water, EtOH and MeOH and easily soluble in DMF and
DMSO. The molar conductance in DMSO (10.80 SÁcm2ÁmolÀ1) indicates
that it is essentially a non-electrolyte in DMSO13.
The reaction mechanisms of the complex are shown in Fig. 2.
In ethanol solution, there exists an equilibrium between the two forms of
RB: lactone and zwitterion.7 When NaOC2H5 was added, the balance was
disturbed, and then the zwitterion form of RB combined easily
with Cd(Ac)2Á2H2O. After a series of electron transfers, the complex is
formed.

Cd(II) COMPLEX OF RB
1581
Table II. Selected Bond Distances (A) and Angles (ꢀ) of the Complex
Cd1-O3
Cd1-O5
Cd1-O6
Cd1-O8W
O1-C11
O1-C12
O2-C28
O3-C28
O4-C29
O5-C29
O6-C31
O7-C31
N1-C3
1.9805(14)
1.9546(14)
2.223(3)
N2-C6
C1-C2
C1-C10
C2-C3
C4-C11
C5-C12
C6-C71.4166(14)
C7-C8
C8-C13
C9-C10
C9-C13
C10-C11
C12-C13
1.3361(13)
1.3937(17)
1.4104(16)
1.3930(16)
1.4355(16)
1.3914(16)
2.000(2)
1.3238(12)
1.3849(12)
1.2466(15)
1.2411(18)
1.2280(18)
1.2471(17)
1.228(6)
1.4052(14)
1.4242(14)
1.4098(14)
1.4097(14)
1.4022(14)
1.3810(14)
1.295(7)
1.3182(6)
O3-Cd1-O5
O3-Cd1-O6
O3-Cd1-O8W
O5-Cd1-O6
O5-Cd1-O8W
O6-Cd1-O8W
C11-O1-C12
Cd1-O3-C28
Cd1-O5-C29
Cd1-O6-C31
C2-C1-C10
C1-C2-C3
107.58(6)
N1-C3-C2
O2-C28-O3
O4-C29-O5
O6-C31-O7
N2-C6-C7
C6-C7-C8
C7-C8-C13
C10-C9-C13
C1-C10-C9
O1-C11-C4
O1-C12-C5
C8-C13-C9
124.53(12)
120.80(13)
124.53(13)
122.1(5)
120.72(9)
119.18(9)
122.40(9)
113.27(9)
121.43(10)
115.60(9)
113.00(9)
121.56(9)
107.18(6)
111.25(7)
109.47(9)
100.01(7)
120.59(9)
120.67(8)
123.63(10)
126.64(11)
122.4(3)
121.96(11)
122.54(12)
The structure of the complex can be described as approximately
orthogonal two planes and one of the planes linking up with a tetra-
hedron: (1) the Rhodamine chromophore (plane 1); (2) the ring carbon
atoms of a benzoate group (plane 2), which binds a tetrahedron through
its carboxylate group; (3) a tetrahedral coordination. The portion of the
tetrahedral coordination can be described as approximately and mutually
equiangular three planes: (10) the carboxylate atoms of the benzoate group
(plane 3), containing C(23), C(28), O(2), O(3), Cd and O(8); (20) the
acetate group (plane 4), containing O(4), O(5), C(29), C(30), Cd and O(8);
(30) the remaining acetate group (plane 5), containing O(6), O(7), C(31),
C(32), Cd and O(8). The angles between these planes are as follows: planes
172, 73.38ꢀ; planes 273, 18.1ꢀ; planes 374, 69.73(4)ꢀ; planes 375,
70.25(8)ꢀ; planes 475, 40.27(8)ꢀ. The geometry around Cd may be
described as a distorted tetrahedron, in which Cd(II) adopts a typical sp3

1582
QU ET AL.
Figure 1. A perspective view of the complex showing the labeling of non-H
atoms.
hybrid orbital. H-bonds can be found between coordination water, O(4)
and O(7). The bond lengths and angles of hydrogen bonds are listed in
Table III.
In IR spectra of the complex, a n(Cd-O) band appears at 451 cmÀ1
(including a Cd-O bond of an acetate group)14, while RB spectra do not
exhibit such a band. The strong bands at 1637and 1339 cm À1 in the complex
are assigned to nas(COOÀ) and ns(COOÀ) modes, respectively. The value of
Dn[Dn ˆ nas(COOÀ)À ns(COOÀ)] is 298 cmÀ1, indicating coordination of a
RB carboxylate group with Cd(II) in a monodentate chelating fashion15.
This is consistent with results of the X-ray di€raction. The characteristic
n(CˆO) (a lactone form of RB) frequency of a RB carboxyl group
(1709 cmÀ1) disappeared in the complex, suggesting that RB exists in a
zwitterion form in the complex16. This is also consistent with results of the
X-ray di€raction.

Cd(II) COMPLEX OF RB
1583
Figure 2. Reaction mechanisms of the complex.
In 1H NMR spectra of the complex, a new signal assigned to CH3COO
protons appears at 1.82 ppm, while RB spectra do not exhibit such a signal,
indicating that an acetate group participates in complexation. Due to the
existence of H2O in the complex, the number of protons at 3.35 ppm in-
creases to 10 from 8.
Table III. Bond Distances (A) and Angles (ꢀ) of Hydrogen Bonds
Bond
OˆH
H-O
Distance
Angle
Symmetry
O8W H8WA O4
O8W H8WB O70.85
0.93
1.972.625(2)
125.4
a
2.54
3.390(6) 9.9 17
a

1584
QU ET AL.
ACKNOWLEDGMENTS
This work was supported by the China Innovation Center for Life
Science (JB 00980462) and the Natural Science Foundation of Gansu Pro-
vince (ZS991-A23-059-Y). We are thankful to Professor George M. Shel-
drick of Gottingen University in Germany for providing the Shelx-97
program.
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Received April 3, 2001
Accepted July 28, 2001
Referee I: K. Sakata
Referee II: M. Mikuriya