The copper(II) complex with two didentate schiff base ligands. The unique rearrangment that proceeds under alcohol vapor in the solid state to construct noninclusion structure

Article abstract of DOI:10.1246/cl.2008.78

The complexation reaction of copper(II) ion and N-(m-hydroxyphenylene) salicylideneaminate (mhsa) in EtOH yields EtOH-inclusion and noninclusion crystalline samples, [Cu(mhsa)₂]·2EtOH (1) and [Cu(mhsa) ₂] (2), respectively. The amorp

Full text of DOI:10.1246/cl.2008.78

78
Chemistry Letters Vol.37, No.1 (2008)
The Copper(II) Complex with Two Didentate Schiff Base Ligands. The Unique Rearrangment
that Proceeds under Alcohol Vapor in the Solid State to Construct Noninclusion Structure
Yuhki Shibuya,1 Keiko Nabari,1 Mitsuru Kondo,ꢀ1;2 Sachie Yasue,3 Kenji Maeda,3 Fumio Uchida,3 and Hiroyuki Kawaguchi4
1Department of Chemistry, Graduate School of Science, Shizuoka University, 836 Ohya, Suruga-ku, Shizuoka 422-8529
2Center for Instrumental Analysis, Shizuoka University, 836 Ohya, Suruga-ku, Shizuoka 422-8529
3Hautform Division, Fuji Chemical Co., Ltd., 1683-1880 Nakagaito, Nasubigawa, Nakatsugawa 509-9132
4Coordination Chemistry Laboratories, Institute for Molecular Science, Myodiaji, Okazaki 444-8787
(Received October 15, 2007; CL-071131; E-mail: scmkond@ipc.shizuoka.ac.jp)
The complexation reaction of copper(II) ion and N-(m-
hydroxyphenylene)salicylideneaminate (mhsa) in EtOH yields
EtOH-inclusion and noninclusion crystalline samples, [Cu-
.
(mhsa)2] 2EtOH (1) and [Cu(mhsa)2] (2), respectively. The
amorphous sample obtained by drying 1 rearranges to the nonin-
clusion complex 2 under alcohol vapor in the solid state.
Metal complex-assembled compounds that contain solvent
molecules in the structure have often shown unique structural
changes caused by removal and reinclusion of solvent mole-
Figure 1. Structures of the monomeric unit (a) and the one-dimensional
chain (b) of 1.
cules.1,2 Such structural changes generally reconstruct the initial
assembled inclusion structures (route a in Scheme 1).2 On the
other hand, transformation from the amorphous state to a new
noninclusion state by exposure of the removed vapor is unusual
(route b in Scheme 1).
C, 62.11; H, 5.56; N, 4.83%; Found: C, 62.56; H, 5.27;
N, 4.37%). The filtrate further afforded plate crystals of
[Cu(mhsa)2] (2) within a few days (Elemental analysis (%)
Calcd for C26H20N2CuO4: C, 63.99; H, 4.13; N, 5.74%; Found:
C, 63.69; H, 4.23; N, 5.74%).
We have studied the preparation and functions of new mon-
omeric metal complexes that assemble by intermolecular hydro-
gen bonds. For example, a new hydrogen-bonded network struc-
ture has been shown for a nickel complex with a tetradentate
Schiff base ligand that has two hydroxy groups.3 Recently, we
selected N-(m-hydroxyphenylene)salicylideneaminate (mhsa)
as a bidentate Schiff base ligand (Scheme 2) for construction
of metal complexes with new hydrogen-bonded assembled struc-
tures. We found that the resulting CuII–mhsa complexes show a
unique transformation, shown as route b in Scheme 1.
Their crystal structures were clarified by X-ray diffraction
studies. Figure 1 shows the monomeric units and the hydro-
gen-bonded chain structure of 1.5 The copper(II) center is
not based on a trans-arrangement but on a cis-structure. The
distortion around the copper(II) centers can be estimated by
the plane–plane angle ꢀ defined by the two chelate rings, as
illustrated in Scheme 2, in which ꢀ angles of 0, 90, and 180ꢁ cor-
respond to the trans-square planar, tetrahedral, and cis-square
planar geometries, respectively. It has been reported that in the
series of [Cu(sal-R)2] complexes, their ꢀ angles systematically
increase with increases in the steric hindrances of the R groups:
The two crystalline samples were obtained by refluxing an
EtOH solution of [Cu(salicylaldehyde)2]4 and m-aminophenol.
Standing of the solution for a few hours afforded columnar
i
ꢀ angles are 0, 39, 58, and 59ꢁ for R groups of Me, Et, Pr,
.
crystals of [Cu(mhsa)2] 2EtOH (1), which were collected by
filtration (Elemental analysis (%) Calcd for C30H32N2CuO6:
t
and Bu, respectively.6 On the other hand, [Cu(sal-Ph)2] shows
trans-square planar geometry (ꢀ ¼ 0ꢁ).7 The ꢀ angles of 1 are
about 126ꢁ, demonstrating that the copper(II) centers are based
on geometries between cis-square planar and tetrahedral.
As illustrated in Figure 1b, the hydroxy groups of mhsa
ligands form hydrogen bonds with the two EtOH molecules
˚
(OꢂꢂꢂO = 2.69(2) and 2.72(0) A), which further form hydrogen
Scheme 1.
HO
OH
R
N
N
N
N
-
-
-
-
O
O
O
O
Cl
α
-form
β-form
sal-R
5-Cl-sal-Ph
mhsa
Scheme 2. Structure of didentate Schiff base ligands and definition of the
ꢀ angle of copper(II) complexes with the chelate ligands.
Figure 2. Structures of the monomeric unit (a) and the two-dimensional
layer (b) of 2.
Copyright Ó 2008 The Chemical Society of Japan

Chemistry Letters Vol.37, No.1 (2008)
79
bonds to an adjacent [Cu(mhsa)2] unit (OꢂꢂꢂO = 2.76(5) and
trile and other alcohol vapor such as MeOH and PrOH,
while other solvents such as Et2O, hexane, CHCl3, CH2Cl2,
THF, and water do not cause this transformation. It is notewor-
thy that the transformation does not proceed under the vapor of
CHCl3, CH2Cl2, and THF, despite 1 is easily soluble in these
solvents, implying that hydrophilic property and enough solubil-
ity of solvents are required for the transformation. This transfor-
mation is new and unique in the field of hydrogen-bonded
assembled metal complexes.
In summary, we have prepared new copper(II) complexes, 1
and 2, with two mhsa ligands. An amorphous sample obtained
from 1 shows a unique transformation to 2 in the solid state
under alcohol vapor, even though the resulting sample is a non-
inclusion sample. Further studies of this unique transformation
are currently in progress.
˚
2.77(7) A). These hydrogen-bonding interactions create a
one-dimensional chain along the b axis.
Figure 2 shows the monomeric units and crystal structure of
2.8 Similarly to 1, the copper(II) center is based on the geometry
between cis-square planar and tetrahedral, in which the ꢀ angle
is also about 126ꢁ. In contrast to 1, two hydroxy groups of the
mhsa of 2 form direct hydrogen bonds with the coordinating
oxygen atoms of mhsa in the different adjacent [Cu(mhsa)2]
units, creating a two-dimensional layer in the ac plane.
In contrast to [Cu(sal-R)2], [Cu(5-Cl-sal-Ph)2] crystallizes
not only in the trans-square planar structure (ꢀ ¼ 0ꢁ) but also
in the cis-arranged structure (ꢀ ¼ 141ꢁ).9 The structures of the
monomeric units of 1 and 2 are close to the cis-formed struc-
ture.9,10 For the mhsa ligand, two structural isomers are defined
by orientations of the hydroxy groups as illustrated in Scheme 1,
and the two forms are designated ꢁ- and ꢂ-forms. For the
mhsa ligands in this Cu–mhsa system, 1 contains only ꢁ-forms
(Figure 1), while 2 involves both ꢁ- and ꢂ-forms (Figure 2).
As mentioned, one of the interesting aspects of hydrogen-
bonded complexes containing solvent molecule is the structural
rearrangements as they respond to the removal and reinclusion
of the solvent molecules in the solid state. Complex 1 contains
EtOH molecules. We have studied the structural changes of 1
by removal of the EtOH molecules, followed by exposure of it
to EtOH vapor by monitoring the X-ray powder diffraction
(XRPD) patterns (Figure 3).
Thermogravimetric (TG) measurements indicate that the
EtOH molecules are removed on heating at about 120 ꢁC (see
Supporting Information).11 Based on the TG data, the included
EtOH molecules of 1 were removed on heating at 120 ꢁC under
reduced pressure. No intense XRPD peaks were observed for the
dried sample (Figure 3c), indicating that the sample obtained is
amorphous. Exposure of the amorphous sample to EtOH vapor
overnight gave a new XRPD pattern (Figure 3d). Curiously,
the pattern obtained is not consistent with that of the initial crys-
tal structure of 1 but is consistent with the simulation pattern of
2 (Figure 3e), even though this complex contains no inclusion
molecules. This means that the amorphous sample obtained from
1 transforms to 2 in the solid state under EtOH vapor. Interest-
ingly, this transformation also proceeds by exposure to acetoni-
This work was supported by a Grant-in-Aid for Scientific
Research (C) from the Ministry of Education, Culture, Sports,
Science and Technology, Japan. The authors thank Mr. R. Ikeya
of the Center for Instrumental Analysis for support in obtaining
the X-ray diffraction data.
References and Notes
1
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3
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Crystallographic data for the complex: C30H32N2CuO6, Mr ¼ 580:14, monoclin-
˚
ic, space group P2/n (No. 13), a ¼ 14:50ð4Þ, b ¼ 11:36ð2Þ, c ¼ 18:43ð4Þ A, ꢂ ¼
3
107:93ð3Þꢁ, V ¼ 2889ð12Þ A , Z ¼ 4, Dcalcd 1.334 g cmꢃ3
, ꢃ(Mo Kꢁ) =
˚
0.800 mmꢃ1, T ¼ 293 K, ꢄ ¼ 0:7107 A, ! scan, 21272 reflections measured,
5870 unique, R ¼ 0:0869 (all data). The data collection was performed on a
Rigaku CCDC Mercury system. The structure was solved by a direct method
using SIR-92 and refined on F2. Geometrical hydrogen atoms were located on
the calculated positions. All non-hydrogen atoms were treated anisotropically.
Hydrogen atoms were included but not refined. Crystallographic data reported
in this paper has been deposited with Cambridge Crystallographic Data Centre
as supplementary publication no. CCDC-xxxx.
˚
6
a) H. Yokoi, Bull. Chem. Soc. Jpn. 1974, 47, 3037. b) E. C. Lingafelter, G. L.
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8
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Crystallographic data for the complex: C26H20N2CuO4, Mr ¼ 488:00, monoclin-
˚
ic, space group P2/n (No. 13), a ¼ 9:826ð6Þ, b ¼ 15:11ð3Þ, c ¼ 15:174ð9Þ A,
3
ꢂ ¼ 93:01ð2Þꢁ, V ¼ 2249ð5Þ A , Z ¼ 4, Dcalcd 1.441 g cmꢃ3, ꢃ(Mo Kꢁ) =
˚
1.007 mmꢃ1, T ¼ 293 K, ꢄ ¼ 0:7107 A, ! scan, 13826 reflection measured,
˚
5854 unique, R ¼ 0:0850 (all data). The data collection was performed on a
Rigaku CCDC Mercury system. The structure was solved by a direct method
using SIR-92 and refined on F2. Geometrical hydrogen atoms were located on
the calculated positions. All non-hydrogen atoms were treated anisotropically.
Hydrogen atoms were included but not refined. Crystallographic data reported
in this paper have been deposited with Cambridge Crystallographic Data Centre
as supplementary publication no. CCDC-xxxx.
9
A. Takeuchi, H. Kuma, S. Yamada, Synth. React. Inorg. Met.-Org. Chem. 1994,
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11 Supporting Information is available electronically on the CSJ-Journal web site;
http://www.csj.jp/journals/chem-lett/.
Figure 3. XRPD patterns of freshly prepared sample of 1 (a), the simula-
tion pattern of 1 (b), dried sample (c), sample obtained by exposure of
EtOH vapor (d), and the simulation pattern of 2 (e).
Published on the web (Advance View) December 15, 2007; doi:10.1246/cl.2008.78