The inclusion behavior of benzo-15-crown-5 with hydrated transition metal picrates

Article abstract of DOI:10.1016/S0277-5387(98)00193-4

Six kinds of benzo-15-crown-5 (L) adducts having the stoichiometric formula M(Pic)₂ · L · xH₂O (M=Mn, Cu, x=2; M=Co, Ni, Zn, Cd, x=4; Pic means picrate anion) have been synthesized and characterized by EA, IR, UV and molar conductance. The X-ray crystal structural analysis of the benzo-15-crown-5 adduct with hydrated copper(II) picrate revealed that the benzo-15-crown-5 molecule virtually acts as a second-sphere ligand, which associates with the copper(II) ion by hydrogen bonding of the coordinating water molecule. By the comparison of the IR, UV spectra and molar conductance of the new adducts prepared, it can be deduced that the other adducts exhibit the similar coordination environment to that of the copper adduct.

Full text of DOI:10.1016/S0277-5387(98)00193-4

Polyhedron Vol[ 06\ Nos[ 14\ 15\ pp[ 3216Ð3229\ 0887
Þ 0887 Elsevier Science Ltd
Pergamon
All rights reserved[ Printed in Great Britain
9166Ð4276:87 ,08[99¦9[99
\
PII] S9166Ð4276"87#99082Ð3
The inclusion behavior of benzo!04!crown!4 with
hydrated transition metal picrates
Baoming Ji\aꢀ Zhixian Zhou\b Kuiling Dingb and Yanzhong Lib
aDepartment of Chemistry\ Luoyang Teacher|s College\ Luoyang 360911\ People|s Republic of China
bDepartment of Chemistry\ Zhengzhou University\ Zhengzhou 349941\ People|s Republic of China
"Received 00 March 0887^ accepted 6 May 0887#
Abstract*Six kinds of benzo!04!crown!4 "L# adducts having the stoichiometric formula M"Pic#1 = L = xH1O
"MꢁMn\ Cu\ xꢁ1^ MꢁCo\ Ni\ Zn\ Cd\ xꢁ3^ Pic means picrate anion# have been synthesized and char!
acterized by EA\ IR\ UV and molar conductance[ The X!ray crystal structural analysis of the benzo!04!crown!
4 adduct with hydrated copper"II# picrate revealed that the benzo!04!crown!4 molecule virtually acts as a
second!sphere ligand\ which associates with the copper"II# ion by hydrogen bonding of the coordinating water
molecule[ By the comparison of the IR\ UV spectra and molar conductance of the new adducts prepared\ it
can be deduced that the other adducts exhibit the similar coordination environment to that of the copper
adduct[ Þ 0887 Elsevier Science Ltd[ All rights reserved
Keywords] copper"II#^ picrate^ crown ether^ X!ray^ hydrogen bond^ crystal structure[
———————————————————————————————————————————————
INTRODUCTION
of crystalline extracted complexes of hydrated lan!
thanide picrates with B04C4 have been obtained[ X!
ray crystal structural analysis revealed that the B04C4
molecules do not coordinate directly with lanthanide
ions\ but act as a second!sphere ligand which is associ!
ated with lanthanide picrates by hydrogen bonding of
coordinating water molecules ð3\ 4\ 5Ł[ These inter!
esting results motivated us to extend our study of
the second!sphere coordination of metal crown ether
chemistry[ In the present paper\ we report the syn!
thesis and the characterization of the B04C4 adducts
with hydrated transition metal "Mn\ Co\ Ni\ Cu\ Zn
and Cd# picrates and the crystal structure of the
B04C4 adduct with hydrated copper"II# picrate[
In the process of the chemical extraction of metal ions
with crown ether species\ picrate is usually used as a
hydrophobic counter!anion to carry the hostÐguest
complexes into the organic phase[ The extraction
mechanism is closely related to the interaction pattern
of the picrate complexes of the metal ions with crown
ethers[ The establishment of the crystal and molecular
structures of these complexes indicated that the alkali
and alkaline earth metal ions coordinate directly with
the crown ether molecules[ Nakagawa et al[ dem!
onstrated that the solvent extract abilities of aqueous
lanthanide picrates with common crown ethers\ such
as 04!crown!4\ 07!crown!5 and their benzo or
cyclohexano derivatives\ are much lower than those
of aqueous alkali! and alkaline!earthÐmetal picraes\
in spite of the apparent matching of the host cavity
size and the diameter of the naked lanthanide cation[
The low extract abilities are attributed to incomplete
dehydration of trivalent lanthanide ions upon extrac!
tion ð0\ 1\ 2Ł[ Recently\ in the course of our study
on the extraction mechanism of hydrated lanthanide
picrates with benzo!04!crown!4 "B04C4#\ a new series
EXPERIMENTAL
Rea`ents
All the chemicals used were of reagent grade[ B04C4
was recrystallized from n!heptane "m[p 68Ð79>C#[
Hydrated transition metal "MꢁMn\ Co\ Ni\ Cu\ Zn
and Cd# picrates were prepared by the reaction of
picric acid and the corresponding metal carbonates in
good yields[ Their general formula was determined to
be M"Pic#1 = 5H1O by elemental analysis[
ꢀAuthor to whom correspondence should be addressed[
3216

3217
Baoming Ji et al[
Table 0[ The crystallographic data and re_nement par!
Chemical and physical measurements
ameters
Melting points were measured on a WC!0 apparatus
and are uncorrected[ Transition metal ion contents
were determined by EDTA complexometric titration
method[ Microanalyses "C\ H and N# of the adducts
were carried out on a Carlo!Erba 0095 elemental ana!
lyzer[ The IR spectra were recorded on a Shimadzu
324 spectrometer in KBr pellets[ UVÐVIS spectra were
Empirical formula
Formula weight
Crystal color\ habit
Crystal dimensions "mm#
C15H17N5O10Cu
713[97
green\ prismatic
9[19×9[19×9[29 mm
9[21
Omega scan peak width at
half!height ">#
Ä
a "A#
02[431"2#
06[923"6#
6[461"0#
Ä
measured with a Shimadzu UV!1099 spectrometer[ b "A#
Ä
c "A#
Conductivity measurements were performed with a
DDS!00A conductometer with acetone as solvent at
14>C[
a ">#
b ">#
g ">#
89[30"1#
099[43"0#
097[20"1#
0515[3"7#
−2
Ä
V "A
#
¹
Space group
Z
p0 "(1#
1
General procedure for the preparation of the adducts
Dcalc "g cm−2
F"999#
#
0[572
735[99
6[63
34[9
The adducts were prepared by dissolving a 0]1
molar ratio of hydrated metal picrate and B04C4 in a
1]1]0 "v:v:v# mixed solvent of MeCN\ EtOH and H1O\
and the resulting solutions were _ltered and allowed
to stand over several days until the crystalline prod!
ucts of the adducts were separated[ A green single
crystal of copper"II# adduct suitable for X!ray struc!
tural analysis was obtained by recrystallization using
the same mixed solvent[
m "MoKa# "cm−0
1umax ">#
#
Total No[ of re~ections measured 3059
No[ observations ðI×2[99 s "I#Ł
R
Rw
Maximum peak "e A
Minimum peak "e A
2501
9[921
9[938
9[49
−
−2
Ä
Ä
#
−
−2
#
−9[30
X!ray crystal structure determination of Cu adduct
All measurements were made on a Rigaku AFC6R
di}ractometer with graphite monochromated MoKa
radiation and a 01 kW rotating anode generator[ Cell
constants and orientation matrix for data collection
were obtained from a least!squares re_nement using
the setting angles of 08 carefully centered re~ections
in the range of 12[12³1u³15[62>[ The data were cor!
rected for Lorentz and polarization e}ects and empiri!
cal absorption[
The structure was solved by direct methods and
expanded using Fourier techniques[ The nonhydrogen
atoms were re_ned anisotropically[ Hydrogen atoms
were included but not re_ned[ All calculations were
performed on a Micro VAX2099 computer using
teXsan crystallographic software package of Molec!
ular Structure Corporation "0874 and 0881#[ Neutral
atom scattering factors were taken from Cromer and
Waber[ Atomic coordinates and anisotropic tem!
perature factors for all nonhydrogen atoms were
re_ned by full!matrix least!squares[
sition metal picrate and ligand in a molar ratio of 0]1
was used[
All the adducts possess similar IR spectra\ indi!
cating that they have similar coordination pattern[
The IR spectra of the adducts revealed that the molec!
ular symmetric vibration absorption of the ligand at
ca[ 879 cm−0 disappears and that the nARÐOÐC absorp!
tion at 0149 cm−0 does not undergo any changes in
the adducts[ The intensity of the nas"CÐOÐC# absorption
at 0019 cm−0 for the adducts decreases obviously in
comparison with that of the free ligand[ These results
implied that some interaction between hydrated tran!
sition metal picrates and aliphatic ether oxygen atoms
rather than the phenolic ether oxygen atoms occurs in
the adducts[ This conclusion will be further con_rmed
by the X!ray crystal structure analysis of the copper"II#
adduct[ The strong absorption bands at 2199Ð2499
cm−0 in the adducts show the presence of the water
molecules\ which is consistent with that of micro!
analysis[
The crystallographic data and re_nement par!
ameters are listed in Table 0[ The selected bond dis!
tances and angles are given in Table 1
The measurements of the UVÐVIS spectra of the
adducts show that all the adducts possess the similar
absorption pattern[ The absorption for the picrate
anion at 219Ð229 nm does not show much di}erence
before and after the formation of the adducts[ This
RESULTS AND DISCUSSION
The elemental analysis data as shown in Table 2 implies that the coordination pattern of the hydrated
indicate that all the adducts prepared have a 0]0 metal transition metal picrates does not undergo a pro!
picrateÐligand stoichiometry with two or four water nounced conformational change after the adducts
molecules\ although a mixture of the hydrated tran! were formed and as a result the central transition

Behavior of benzo!04!crown!4
3218
Table 1[ Selected bond lengths and angles for the Cu adduct "estimated stan!
dard deviations in parentheses#
Ä
Bond length "A#
O3ÐC00
CuÐO5
CuÐO6
CuÐO7
CuÐO8
O0ÐC0
O0ÐC03
O3ÐC09
0[830"1#
0[805"1#
0[837"1#
0[826"1#
0[314"3#
0[300"3#
0[315"3#
0[322"3#
9[81
9[84
9[70
9[74
O7ÐH10
O7ÐH11
O8ÐH12
O8ÐH13
O3ÐH10
O0ÐH11
0[648
0[810
Bond angle ">#
O5ÐCuÐO6
O5ÐCuÐO7
O5ÐCuÐO8
O6ÐCuÐO7
048[73"7#
O6ÐCuÐO8
O7ÐCuÐO8
H10ÐO7ÐH11
H12ÐO8ÐH13
83[93"7#
059[00"8#
001[6
80[02"7#
76[39"7#
83[02"7#
095[0
Table 2[ Synthesis\ analytical and molar conductivity data of the adducts
Anal[ Found "calcd# ")#
Conductivityb
Yield
")#
M[p[
">C#
"V−0 cm1 mol−0
#
Adducta
C
H
N
M
Mn"Pic#1 = L = 1H1O
Co"Pic#1 = L = 3H19
Ni"Pic#1 = L = 3H19
Cu"Pic#1 = L = 1H1O
Zn"Pic#1 = L = 3H19
Cd"Pic#1 = L = 3H1O
64
57
60
62
53
54
075Ð077
053Ð055
031Ð033
065Ð067
057Ð069
011Ð013
27[16 "27[18# 2[33 "2[33# 09[27 "09[20# 5[38 "5[63#
24[01 "26[70#
23[33 "25[37#
23[29 "25[51#
04[29 "08[49#
19[08 "14[47#
22[32 "25[90#
25[34 "25[38# 2[64 "2[63#
25[42 "25[49# 2[61 "2[63#
8[68 "8[72#
8[78 "8[72#
5[38 "5[78#
6[90 "5[76#
26[76 "26[75# 2[31 "2[39# 09[07 "09[08# 6[64 "6[61#
25[30 "25[11# 2[58 "2[60#
23[39 "23[23# 2[40 "2[41#
8[72 "8[64#
8[20 "8[14# 01[92 "01[26#
6[57 "6[48#
aPic is picrate anion\ L is benzo!04!crown!4[
bMeasured in 09−2M acetone solutions at 14>C^ the conductivity values of corresponding hydrated transition metal picrates
are shown in parentheses[
metal ions may not take part in the direct interaction angles of 048[73"7# and 059[00"8#> for O5ÐCuÐO6 and
with the oxygen atoms of crown ether[
O7ÐCuÐO8 are less than 079>[ Therefore\ the coor!
The molar conductivity values "as shown in Table dination about the Cu atom can be considered as a
2# for these adducts in acetone are in the range of distorted square planar[ It is obvious that the latter
04[2Ð24[1 V−0 cm1 mol−0\ which is the indication of part\ B04C4\ does not take part in the coordination
nonelectrolytes for the adducts ð6Ł[ Therefore\ the with the Cu cation directly[ However\ it was included
transition metal ions in the adducts do not coordinate in the adduct by hydrogen bonding between one of
with the B04C4 molecule directly and no free picrate the coordinating water molecules and two aliphabic
anion was released\ which further supports the results ether oxygen atoms "O0 and O3#[ Two phenolic oxy!
obtained by UVÐVIS spectral measurements[
gen atoms in B04C4 do not participate in the for!
The molecular structure of the Cu adduct is shown mation of hydrogen bond\ which is consistent with
in Fig[ 0[ The adduct consists of two parts\ Cu"P! the result obtained by IR determination[ The distance
Ä
ic#1 = 1H1O and B04C4[ In the former part\ two phe! for O0ÐH11 and O3ÐH10 are 0[810 and 0[648 A\
nolic oxygen atoms "O5 and O6# in picrate anions and respectively\ which is the indication of the formation
two oxygen atoms "O7 and O8# in water molecules of typical hydrogen bonds ð7Ł[ Therefore\ the water
coordinate with central Cu cation\ and as result\ the molecule in the adduct virtually acts as a bridge to
coordination number for Cu"II# is 3[ The bond lengths associate the copper"II# picrate with B04C4 molecule
for CuÐO5\ CuÐO6\ CuÐO7 and CuÐO8 are 0[830"1#\ through hydrogen bonding[ This kind of inclusion
Ä
0[805"1#\ 0[837"1# and 0[826"1# A\ respectively[ The phenomenon of B04C4 is similar to the results of
bond angles of 80[02"7#\ 83[02"7#\ 83[93"7# and our previous studies on the complexation of hydrated
76[39"7#> for O5ÐCuÐO7\ O7ÐCuÐO6\ O6ÐCuÐO8 and lanthanide picrates with B04C4 ð3\ 4\ 5Ł[ However\ it
O8ÐCuÐO5\ respectively\ are near to 89> and the bond is completely di}erent from the complexation patterns

3229
Baoming Ji et al[
Fig[ 0[ Molecular structure of Cu"Pic#1 = B04C04 = 1H1O[
REFERENCES
of CuCl1 and hydrated Cu"ClO3#1 = 5H1O with B04C4\
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On the basis of the crystal structure analysis of the
copper adduct and the investigation of IR\ UVÐVIS
spectra and molar conductance of the title adducts\ it
can be concluded that the coordination ability of the
water molecules and picrate anion with transition
metal ions are stronger than that of B04C4 molecule\
and as a result the hydrated transition metal picrate
rather than the transition metal crown ether cationic
complex is formed predominately[ Due in part to the
steric hindrance of the bulky picrate anion and coor!
dinating water molecules around the transition metal
ion\ the cavity of B04C4 molecule can not accom!
modate the copper"II# or other transition metal ions
directly\ although the cavity size of the B04C4 mol!
ecule is close to the size of these transition metal ions
ð8\ 09Ł[ Consequently\ the B04C4 molecule adopts a
special association mode in order to combine with
them\ i[e[ the B04C4 molecule virtually acts as a
second!sphere ligand which associates with the
hydrated transition metal picrates by hydrogen bond!
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