Synthesis, crystal structure, spectroscopic and thermal properties of a novel mixed ligand copper(II) complex with 5,5-dimethylhydantoin and benzylamine

Article abstract of DOI:10.1515/znb-2006-0203

The crystal structure of the newly synthesized complex, trans-aqua-bis(benzylamino)-bis(5,5-dimethylhydantoinato) copper(II) was determined by X-Ray single crystal data. The thermal analyses, FT-IR and magnetic susceptibility data are also presented. The complex crystallizes in the monoclinic system, space group C2. The complex features a distorted square pyramidal [CuN₄O] coordination with 5,5-dimethylhydantoinato, benzylamine and water ligands. The 5,5-dimethylhydantoinato anion is bonded to the copper(II) ion via its deprotonated N atom in the 3-position.

Full text of DOI:10.1515/znb-2006-0203

Synthesis, Crystal Structure, Spectroscopic and Thermal Properties of a
Novel Mixed Ligand Copper(II) Complex with 5,5-Dimethylhydantoin
and Benzylamine
Murat Tas¸a, Serkan Soylub, and Hu¨meyra Batıc
a Karadeniz Technical University, Giresun Faculty of Arts and Sciences, Department of Chemistry,
Giresun, Turkey
b Karadeniz Technical University, Giresun Faculty of Arts and Sciences, Department of Physics,
Giresun, Turkey
c Ondokuz Mayıs University, Faculty of Arts and Sciences, Department of Chemistry, Kurupelit,
Samsun, Turkey
Reprint requests to Dr. M. Tas¸. Fax: +90 0454 2164518. E-mail: murattas@ktu.edu.tr
Z. Naturforsch. 61b, 133 – 138 (2006); received September 7, 2005
The crystal structure of the newly synthesized complex, trans-aqua-bis(benzylamino)-bis(5,5-di-
methylhydantoinato) copper(II) was determined by X-Ray single crystal data. The thermal analyses,
FT-IR and magnetic susceptibility data are also presented. The complex crystallizes in the monoclinic
system, space group C2. The complex features a distorted square pyramidal [CuN4O] coordination
with 5,5-dimethylhydantoinato, benzylamine and water ligands. The 5,5-dimethylhydantoinato anion
is bonded to the copper(II) ion via its deprotonated N atom in the 3-position.
Key words: Hydantoins, Hydantoinato, 5,5-Dimethylhydantoin, Mixed Ligand Complex,
Thermal Analyses
Introduction
atom, are of great interest in the chemistry of coordi-
nation compounds. The ligands can act either as neu-
tral molecules or deprotonated as monoanions [5]. As
ligands, hydantoins (Scheme 1 b, c, d) contain several
donor atoms and exhibit excellent coordination prop-
erties [6]. To date, various mixed ligand complexes of
copper(II) having succinimide (Scheme 1 a) or pheny-
toin (Scheme 1 c) ligands and alkylamine ligands were
prepared (Scheme 2) [7 – 10]. The X-ray data proved
that the coordination to Cu(II) is realized via the en-
docyclic nitrogen atom N3 in Scheme 1 b, c, d of the
monoanionic ligand (Scheme 2) [6 – 8]. The complexes
have square planar [CuN4] (reddish violet), distorted
square planar [CuN4] (blue-violet), and square pyra-
midal [CuN4O] (blue) coordination geometries in the
solid state and give deep blue or blue solutions accom-
panied by distinct spectral changes regardless of the
structures in the solid states. The electronic and struc-
Hydantoin (2,4-imidazoline) is a compound in
which an N-H replaced an CH2 group of succin-
imide (Scheme 1 a) According to Oh et al., the com-
pound (2,4-imidazoline) (Scheme 1 b) was first dis-
covered by Bayer in 1861 as a hydrogenation prod-
uct of allantoin [1]. Since then hydantoin derivatives
have been important intermediates in the synthesis of
several amino acids. Due to their antimicrobial and
anticonvulsant properties and their action against all
types of epileptic form seizures they have been used
with much clinical success [1 – 4]. Phenytoin (5,5-
diphenylhydantoin) (Scheme 1 c), is another well-
known hydantoin group of drug.
Complexes of transition metals with five-membered
heterocyclic ligands such as hydantoins or succin-
imides (Scheme 1 a), possessing more than one donor
Scheme 1. a: Succinimide, b: hydantoin,
c: 5,5-diphenylhydantoin, d: 5,5-dimethyl-
hydantoin.
c
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M. Tas¸ et al. · Mixed Ligand Copper(II) Complex with 5,5-Dimethylhydantoin and Benzylamine
Table 1. Crystal data and structure refinement for the
[Cu(C5H7N2O2)2(C7H9N)2H2O].
Empirical formula
Formula weight
Crystal dimensions /mm
Crystal shape
(C24H34N6O5)Cu
550.11
0.33×0.30×0.28
prism
Colour
Unit cell dimensions
blue-violet
a = 19.2120 (13) A
b = 5.6610 (3) A
R1 = H, X=CH2, succinimidate
˚
R1 = Phenyl, X=NH, 5,5-diphenylhydantoinate
˚
˚
R = Phanylalkyl
c = 24.5750 (15) A
β = 96.143 (5)◦
Scheme 2. Structure of the succinimide and 5,5-diphenyl-
hydantoin complexes.
3
˚
Volume
Z
2657.4 (3) A
4
Crystal system, space group
Density ρcalc
Absorption coefficient
Data collection
Temperature
monoclinic, C2
1.375 g/cm3
0.87 mm−1
STOE IPDS 2 diffractomer
293 (2) K
Theta range
Index ranges
1.67◦ < θ < 25◦
h = −22 → 22;
k = −6 → 6;
l = −29 → 29
14182
Reflections collected
Independent reflections
4682 (Rint = 0.071)
4369
0.28(1)
2
2
Reflections with |F| > 2σ(|F| )
Scheme 3. The structure of the aqua-trans-bis-(benzyl-
Flack parameter [20]
amino)-bis-(5,5-dimethylhydantoinato) copper(II) complex.
Absorption correction
integration
T
min, Tmax
Restraints; parameters
Largest diff. peak and hole [eA
0.763; 0.793
4; 342
0.36; −0.49
R1 = 0.033; wR2 = 0.078
R1 = 0.035; wR2 = 0.079
1.017
tural features of species in solutions have still not been
elucidated [7].
−3
˚
2
]
2
Final R indices |F| > 2σ(|F| )
In this work, we studied a mixed ligand copper(II)
complex with 5,5-dimethylhydantoin(Scheme 1 d) and
benzylamine (phenylmethylamine). Although, com-
plexes of 5,5-diphenylhydantoin have been studied ex-
tensively, this is the first example of complexes of 5,5-
dimethylhydantoin (Scheme 3).
R Indices (all data)
2
Goodness-of-fit on |F|
X-AREA [11]; for data reduction: X-RED32 [11]; to
solve structure: SHELXS97 [12]; to refinement structure:
SHELXL97 [13]; for molecular graphics: ORTEPIII [14]; to
prepare material for publication: WinGX [15].
Experimental Section
Preparation of the complex
Materials and measurements
5,5-Dimethylhydantoin, benzylamine, and copper(II) ac-
etate monohydrate were commercially available and were
reagent grade. FT-IR spectra (4000 – 200 cm−1) were
recorded on a Jasco-430 FT-IR spectrophotometer with sam-
ples prepared as KBr pellets. The magnetic susceptibility of
the complex was measured using a Sherwood scientific MX1
model Gouy magnetic susceptibility balance at room temper-
ature. A Rigaku TG8110 thermal analyzer was used to record
TG and DTA curves in static air atmosphere at a heating rate
of 10 Kmin−1 in the temperature range of 20 – 1000 ◦C using
platinum crucibles. Highly sintered α-Al2O3 was used as a
reference.
To a solution of copper(II) acetate monohydrate (0.50 g,
2.5 mmol) and 5,5-dimethylhydantoin (0.64 g, 5 mmol) in
water (20 ml), benzylamine (0.54 g, 5 mmol) was added
slowly and a blue solid was precipitated. The mixture was
◦
stirred for 1 h at 50 C. The solid was dissolved with the
addition of absolute ethanol to give a deep blue solution
at 50 ◦C. The solution was cooled to room temperature.
Blue-violet needles precipitated and were filtered and dried
˜
on air (Yield: 65.8%). FT-IR (KBr): ν = 3525 υ(N1-H),
1697 – 1646 υ(C=O), 1465 and 1452 υ(C-N), 1608 δ(H2O),
696 – 613 υ(Cu-N), 400 υ(Cu-O) cm−1. C24H34N6O5Cu
(550.11): calcd. C 52.40, H 6.23, N 15.28; found C 52.59,
The crystal data were collected using ω-2θ scan tech- H 6.37, N 15.35.
niques on a Stoe IPDS-2 diffractometer with a graphite-
filtered Mo-Kα radiation (λ = 0.71073 A). Software imental magnetic moment of 1.29 BM corresponding to one
programs used, for data collection and cell refinement: unpaired electron.
The complex is slightly antiferromagnetic with an exper-
˚
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M. Tas¸ et al. · Mixed Ligand Copper(II) Complex with 5,5-Dimethylhydantoin and Benzylamine
135
Fig. 1. ORTEP-III diagram with 40% probability ellipsoids of the aqua-trans-bis-(benzylamino)-bis-(5,5-dimethyl-
hydantoinato) copper(II) complex.
and angles are listed and compared with data of
5,5-diphenylhydantoin complex in Table 2. Molecu-
lar structure and hydrogen bonds are shown in Figs 1
and 2, respectively.
The coordination around the Cu(II) atom is distorted
square pyramidal [CuN4O]. 5,5-Dimethylhydantoinato
and benzylamine groups function as monodentate lig-
ands, similar to the situation in related complexes
having 5,5-diphenylhydantoinato and alkylamine lig-
ands [7 – 10, 16]. The five-membered ring of the 5,5-
dimethylhydantoinato group (A and B in Fig. 1) is
nearly planar and the carbonyl O atoms lie in the
plane. Maximum deviations were found for atom
˚
N(4) with 0.021(2) A for ring A and for atom N(2)
˚
with −0.071(2) A for ring B (Fig. 1). The 5,5-
dimethylhydantoinato and benzylamine ligands are in
trans positions at the basal plane of the pyramid, the
water molecule is bonded to the metal atom in the ax-
ial position (Fig. 1).
Fig. 2. Intra- and inter-molecular hydrogen bonds of the com-
plex.
Results and Discussion
In the basal coordination plane formed by the
N atoms, the Cu-N distances are not equivalent and
Molecular structure of the complex
˚
are in the range from 2.000(2) to 2.039(2) A. Accord-
Crystallographic data of the complex (Scheme 3) ing to CSD [17], the average Cu-Nhyd and Cu-Namine
˚
are summarized in Table 1. Selected bond lengths bond lengths are 1.99 and 2.03 A, respectively [7].
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M. Tas¸ et al. · Mixed Ligand Copper(II) Complex with 5,5-Dimethylhydantoin and Benzylamine
◦
˚
Table 2. Selected interatomic distances (A) and angles ( ) for Table 3. Hydrogen-bonding geometry for the complex.
the title and a related complex.
◦
˚
˚
˚
D–H···A
D–H (A) H···A (A) D···A (A) D–H···A ( )
∗
O(5)–H(1O)···O(2)i 0.817(10) 2.141(15) 2.945(3) 168(5)
Title complex
Related complex
O(5)–H(2O)···O(3)i 0.819(10) 2.29(2)
3.086(4) 163(6)
3.023(3) 174(3)
2.861(4) 168(3)
2.828(3) 145.9
2.802(3) 146.7
2.850(3) 148.7
2.878(3) 146.9
3.784(6) 124.96
3.655(4) 126.13
iv
Bonds:
N(1)–H(1)···O(3)ii
0.76(3)
2.26(3)
2.18(3)
2.04
2.01
2.04
Cu(1)-N(6)
Cu(1)-N(5)
Cu(1)-N(2)
Cu(1)-N(4)
N(2)-C(1)
N(2)-C(2)
N(1)-C(1)
N(1)-C(3)
N(3)-C(6)
N(3)-C(8)
N(4)-C(6)
N(4)-C(7)
O(1)-C(1)
O(2)-C(2)
O(3)-C(6)
O(4)-C(7)
Cu(1)-O(5)
2.037(2)
2.000(2)
2.039(2)
2.025(2)
1.400(3)
1.352(4)
1.332(4)
1.450(4)
1.321(4)
1.457(4)
1.387(4)
1.367(4)
1.236(3)
1.232(3)
1.252(3)
1.228(3)
2.371(2)
2.030(3)
2.032(4)
1.990(4)
2.026(4)
1.405(6)
1.345(7)
1.343(7)
1.459(7)
1.340(7)
1.457(7)
1.392(5)
1.374(7)
1.238(7)
1.232(6)
1.237(7)
1.232(6)
2.397(4)
N(3)–H(2)···O(1)iii 0.70(3)
N(5)–H(5A)···O(4) 0.90
N(5)–H(5B)···O(1) 0.90
N(6)–H(6A)···O(3) 0.90
N(6)–H(6B)···O(2) 0.90
C(16)–H(16)···Cg1iv 0.930
C(20)–H(20)···Cg2v 0.930
2.08
3.173
3.029
iii
i
ii
x,1 + y,z; 1/2 + x,1/2 + y,z; −1/2 + x,−1/2 + y,z; 1/2 −
x,−1/2 + y,−z; v 1/2 − x,1/2 + y,1 − z; Cg1: atoms [C(12)-C(17)]
and Cg2: atoms [C(19)-C(24)].
126.6(3)◦, respectively, also reflect electron delocaliza-
tion in the π-conjugatedsystem (Table 2) [10]. The Cu-
N
hyd distances of the 5,5-dimethylhydantoinare longer
than those of the 5,5-diphenylhydantoin in the com-
plexes.
Angles:
N(5)-Cu(1)-N(4)
N(5)-Cu(1)-N(6)
N(4)-Cu(1)-N(6)
N(5)-Cu(1)-N(2)
N(4)-Cu(1)-N(2)
N(6)-Cu(1)-N(2)
N(5)-Cu(1)-O(5)
N(4)-Cu(1)-O(5)
N(6)-Cu(1)-O(5)
N(2)-Cu(1)-O(5)
N(6)-Cu(1)-N(5)-C(11)
∗O(5)-Cu(1)-N(5)-C(11)
88.5(1)
176.4(1)
90.5(1)
89.5(1)
165.7(1)
90.6(1)
88.0(1)
95.7(1)
95.6(1)
98.3(1)
−8.1(2)
−178.5(2)
89.2(2)
175.0(2)
93.7(2)
89.1(2)
163.5(2)
86.9(2)
91.9(1)
86.7(1)
92.2(1)
109.8(1)
58.6(4)
−154.2(5)
Hydrogen bonds link the molecular units into a two-
dimensionally network (Table 3). In particular one may
notice that the coordinated water molecule O(5) of
unit x, y, z is bifurcated hydrogen bonded to carboxyl
oxygen atoms O(2) and O(3) in unit x, n + y, z (n
is an integer) (Fig. 2). These hydrogen bonds result
in the formation of polymeric chains along the (010)
axis. Additionally, the nitrogen atoms N(1), N(3) act
as donors for hydrogen bonds, giving rise to the for-
mation of N–H···O intermolecular hydrogen bonds
with carbonyl oxygen atoms O(3) in unit 1/2 + x,
1/2 + y, z and O(1) in unit −1/2 + x, −1/2 + y, z)
(Table 3, Fig. 2). All these intermolecular interactions
result in the formation of sheets of molecules lying
parallel to the [110] axis. There are also intramolec-
ular N–H···O hydrogen bonds formed between ben-
zylamine hydrogen atoms and carbonyl oxygen atoms
of the 5,5-dimethylhydantoinato ligands (Fig. 2). Sim-
ilar intramolecular hydrogen bonds are also found in
related distorted square planar [CuN4] complexes [7 –
10, 16]. Therefore, intramolecular hydrogen bonds ap-
pear to play a supplementary role in stabilizing dis-
torted square pyramidal [CuN4O] complexes in the
solid state (Fig. 2).
(5,5-Diphenylhydantoinato)2 (2,2-diphenyl-ethylamine)2 Cu [16].
The trans-Nhyd-Cu-Nhyd and trans-Namine-Cu-Namine
bond angles are 165.7(1) and 176.3(1)◦, respectively
(Table 2). Nhyd-Cu-Namine bond angles lie between
88.5(1) and 90.6(1)◦ (Table 2). O(5)-Cu-N(2)hyd, O(5)-
Cu-N(4)hyd, O(5)-Cu-N(5)amine and O(5)-Cu-N(6)amine
bond angles are 98.3(1), 95.7(1), 88.0(1) and 95.6(1) ◦,
respectively. While the dihedral angle between the two
phenyl rings is 3.7(2)◦, the dihedral angle between the
two 5,5-dimethylhydantoinato planes is 11.7(1)◦. It is
clear that these planes are nearly parallel to each an-
other. Owing to the steric interaction between the sub-
stituents the atoms N(2), N(5), N(4) and N(6) (Fig. 1)
are not coplanar and the Cu atom also slightly de-
˚
viates from this plane by −0.173(1) A. The amine
ligands are in the E-conformation (Fig. 1, Table 2).
The C(1)-N(2)-C(2) and C(6)-N(4)-C(7) angels are
106.9(2) and 107.0(2)◦ and indicate sp2 character of
the deprotonated N(2) and N(4) atoms; the angles of
O(1)-C(1)-N(2), O(2)-C(2)-N(2), O(3)-C(6)-N(4) and
O(4)-C(7)-N(4) of 124.3(3), 126.1(3), 123.9(3), and
As different from related complexes, there are also
weak C-H-π interactions in the molecular sheets. In-
termolecular C-H-π interactions between the C(16)-
H(16) group and the ring center of Cg1(C12-17) and
between the C(20)-H(20) group and the ring center of
Cg2(C19-24) are observed. These C-H-π interactions
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M. Tas¸ et al. · Mixed Ligand Copper(II) Complex with 5,5-Dimethylhydantoin and Benzylamine
137
link the sheets of molecules to each other (parameters
summarized in Table 3).
IR spectra of the complex
5,5-Dimethylhydantoin shows two bands at 3527
and 3467 cm−1 for N-H stretching vibrations. The
higher wave number band corresponds to the stretch-
ing vibration of the N(1)-H bond adjacent to a
carbonyl group and the lower band is attributed
to the N(3)-H bond surrounded by two carbonyl
groups (Scheme 3 d) [18]. C=O vibrations of 5,5-
dimethylhydantoin appear at 1770 and 1735 cm−1 as Fig. 3. TG and DTA curves of the complex.
sharp and strong bands.
heating the υ(NH2) peak of benzylamine occurred at
3260– 3150 cm−1. The δ(H2O) peak at 1608 cm−1 for
the complex suggests the presence of a coordinated
water molecule inside the coordination sphere [19].
Metal nitrogen bond vibrations were seen at 696 and
613 cm−1, and the metal oxygen bond vibrations
The distinction between O and N coordination of
imides (succinimide and hydantoins) is not readily
made by infrared spectra because shifts in υ(C=O)
may result either from coordination through carbonyl
oxygen or from the deprotonation and coordination
of the imide nitrogen atoms [19]. It is expected
that coordination will occur preferentially through the
deprotonated N(3) nitrogen atom [6, 19]. Coordina-
tion through the carbonyl oxygen and N(1) nitrogen
atoms (Scheme 1 b – d) is inhibited by steric hin-
at 400 cm−1
.
Thermal analyses of the complex
The title complex undergoes endothermic and
drance [19]. In the title complex υ(C=O) appears at exothermic decomposition in five stages (Fig. 3). The
◦
1697– 1646 cm−1 whereas it is seen at 1770 and first stage in the range 80– 138 C is related to the en-
◦
1735 cm−1 in free 5,5-dimethylhydantoin. The υ(C– dothermal removal (DTAmax 97 C) of 1 mole coor-
N(1)) mode at 1471 cm−1 for the 5,5-dimethylhyd- dinated water (calcd. 3.28%; found 3.36%). The sec-
◦
antoin shifts to lower wave numbers and appears at ond stage between 139 and 217 C is accompanied
1465 cm−1 indicating that the N(1) atom is non- by a mass loss of 32.42% (calcd. 33.13%) and corre-
coordinated, while the υ(C–N(3)) mode at 1440 cm−1 sponds to the removal of two benzyl (C6H5-CH2) rad-
for the 5,5-dimethylhydantoin shifts to higher wave icals. In this s◦tage, exothermic reactions take place at
number and appears at 1452 cm−1 in the complex in- 159 and 165 C, and endothermic reaction occurs at
dicating N− formation and coordination via the N(3) 162 ◦C, indicating the release of the benzyl radicals in
atom [19]. The υ(N(3)H) band (Scheme 1 d) appear- parallel with melting and decomposition. At th◦e third
ing at 3467 cm−1 in the free 5,5-dimethylhydantoin stage of decomposition between 217 and 269 C, the
should be absent in the spectrum of the complex, mass loss was found to be 5.53% (calcd. 5.82%), cor-
but this region is obscured by υ(O–H) from coordi- responding to endothermic removal of two NH2 radi-
◦
nated water. After heating for 2 h at 110 C, there cals. Immediately after this stage, in the region 269 –
is no band for N(3)H and H2O which indicates the 351 ◦C the fourth stage of pyrolysis was accompanied
removal of the proton of N(3) upon complex forma- by a mass loss of 35.67% and in the last stage, the or-
tion. The υ(N(1)H) band at 3527 cm−1 in the free 5,5- ganic residue was burned in a highly exothermic reac-
◦
dimethylhydantoin is seen at 3525 cm−1 as a shoul- tion between 351 and 470 C (DTAmax 460 ◦C; loss of
der next to the υ(O–H) vibration in the complex. Af- weight: 8.28%). Total loss of weight in the fourth and
ter heating for 2 h at 110 ◦C the shoulder sharp- fifth stages correspond to pyrolysing of 5,5-dimethyl-
ened as a peak. This result suggests that the proton of hydantoinato ligands (found 43.95%; calcd. 43,31%).
N(1) was not separated upon complex formation. The In the fourth and fifth stages 85.26% of the complex
υ(NH2) peaks of the benzylamine ligands are obscured are removed to leave CuO (calcd. 85.54%), identified
by υ(O–H) of coordinated water. As expected, after by IR spectroscopy.
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M. Tas¸ et al. · Mixed Ligand Copper(II) Complex with 5,5-Dimethylhydantoin and Benzylamine
Supplementary Data
cation to CCDC, 12 Union Road, Cambridge CB2 1EZ, UK
(fax: +44-1223-336033 or e-mail: deposit@ccdc.cam.ac.uk).
Crystallographic data (excluding structure factors) have
been deposited with the Cambridge Crystallographic Data
Centre as the supplementary publication No. CCDC 276037.
Copies of the data can be obtained, free of charge, on appli-
Acknowledgement
The authors are grateful for Prof. Dr. Orhan Bu¨yu¨kgu¨ngo¨r
for X-ray data collection.
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Unauthenticated
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