Supramolecular host-guest coordination systems: [(G+)(Me3E)3MII(CN) 6]∞ as ion exchangers, where (G+=Me3E, Et4N or stp), (E=Sn or Pb) and (M=Fe or Ru)

Article abstract of DOI:10.1016/S0277-5387(99)00176-X

A number of 3D-coordination polymers, constructed via [^dM(CN)₆] building blocks and (Me₃E) connecting units, have been prepared and characterized by X-ray powder diffraction and different spectroscopic methods. 1-Methyl-4-(4′-R-styryl) or (2′-R-styryl) pyridinium cations (stp) have been successfully encapsulated within the expandable wide channels of the 3D-coordination polymers by tribochemical or ion exchange reactions producing novel molecular composites. Apart from 6, [(4′-OCH₃-stp)(Me₃Sn)₃Fe ^II(CN)₆-MeOH]_∞ which exhibits thermochromic behaviour, the molecular composites [(stp)_x(Me₃E)₃Fe^III _1-xFe^II_x(CN)₆]_∞, 1-12 are mixed valence materials exhibiting localized interaction between the mixed valence iron. The results indicated an ion charge transfer interaction between the guest stp-cations and the host matrix. The molecular composites [(stp)(Me₃E)₃ M^II(CN)₆]_∞, 13-18 are due to the facile readiness of the coordination polymers [(Me₃E)₄M(CN)₆]_∞ and [(Et₄N)(Me₃Sn)₃Fe(CN₆)] _∞ to ion exchange. Elsevier Science Ltd.

Full text of DOI:10.1016/S0277-5387(99)00176-X

Polyhedron 18 (1999) 2711–2721
www.elsevier.nl/locate/poly
Supramolecular host–guest coordination systems:
1
II
1
[
(G )(Me E) M (CN) ] as ion exchangers, where (G 5Me E, Et N or
3
3
6 `
3
4
stp), (E5Sn or Pb) and (M5Fe or Ru)
*
Amany M.A. Ibrahim
Department of Chemistry, Faculty of Science, Ain Shams University, Cairo, Egypt
Received 5 February 1999; accepted 26 May 1999
Abstract
d
A number of 3D-coordination polymers, constructed via [ M(CN) ] building blocks and (Me E) connecting units, have been prepared
6
3
and characterized by X-ray powder diffraction and different spectroscopic methods. 1-Methyl-4-(49-R-styryl) or (29-R-styryl) pyridinium
cations (stp) have been successfully encapsulated within the expandable wide channels of the 3D-coordination polymers by tribochemical
II
or ion exchange reactions producing novel molecular composites. Apart from 6, [(49-OCH -stp)(Me Sn) Fe (CN) –MeOH] which
3
3
3
6
`
III
II
exhibits thermochromic behaviour, the molecular composites [(stp) (Me E) Fe Fe (CN) ] , 1–12 are mixed valence materials
x
3
3
1–x
x
6 `
exhibiting localized interaction between the mixed valence iron. The results indicated an ion charge transfer interaction between the guest
II
stp-cations and the host matrix. The molecular composites [(stp)(Me E) M (CN) ] , 13–18 are due to the facile readiness of the
3
3
6 `
coordination polymers [(Me E) M(CN) ] and [(Et N)(Me Sn) Fe(CN )] to ion exchange.
 1999 Elsevier Science Ltd. All rights
3
4
6
`
4
3
3
6
`
reserved.
Keywords: Coordination polymers; Molecular composites; Styryl pyridinium salts; Hexacyanometalate; Sn; Pb
1
. Introduction
dizing materials [16], they show a quite analogous interca-
lation chemistry exhibiting a variety of interesting chemi-
cal properties, such as magnetic, conductive and optical
characteristics. Thus, a considerable number of different
Lewis bases [17–19] have been successfully encapsulated
under comparatively mild reaction conditions. Also, the
encapsulation of several organometallic guest molecules
have been demonstrated [20,21]. On the other hand, the
most outstanding chemical property of [(Me E) M(CN) ]
While the metal dichalcogenide [1,2] and FeOCl [3–8]
materials have been extensively studied for many years as
layered compounds, the 3D-supramolecular coordination
polymers [(R E) M(CN) ] (R5alkyl or phenyl, E5Sn or
Pb, n53 or 4, M5Fe, Co, Ru or Os) have recently
attracted much interest [9–15]. The polymers containing
Fe and Co were successfully subjected to single-crystal
X-ray studies leading to initial reinspection of the structure
of the other polymeric homologues [12–15]. The non-
superimposable 3D-networks of [(Me E) M(CN) ] in-
3
n
6 `
3
4
6 `
polymers are their facile readiness to ion exchange [20–
23].
The present study has been developed to synthesize and
characterize novel host guest systems by encapsulating
1-methyl 4-(49-R-styryl) or (29-R-styryl) pyridinium cat-
ions (stp) within the channels of the 3D-coordination
3
3
6 `
volve distorted octahedral [M(CN) ] building blocks and
Me E (NC) connecting units of trigonal-bipyramidal
6
3
2
(
tbp) configuration. These polymers contain remarkably
III
wide, practically parallel, channels whose walls are inter-
polymers [(Me E) Fe (CN) ] or by ion exchange re-
3
3
6 `
nally coated by constituents of the lipophilic Me E groups
actions where the stp-cation can be introduced quantita-
tively into the channels of the negatively charged host-
3
[12,13].
II
2
Although chemically very different from the dichal-
network [(Me E) M (CN) ] .
3 3 6 `
III
cogenides, [(R E) Fe (CN) ] systems are strong oxi-
The choice of stp-compounds (Scheme 1) is based on
the wide applications of the stilbazolium salts in several
areas. They are used as electrochromic compounds for
3
3
6 `
*
Tel.: 120-2-260-1379; fax: 120-2-261-6474.
0
277-5387/99/$ – see front matter
 1999 Elsevier Science Ltd. All rights reserved.
PII: S0277-5387(99)00176-X

2
712
A.M.A. Ibrahim / Polyhedron 18 (1999) 2711–2721
atmosphere in the molar ratio 3:1. The polymers
(Me E) M(CN) ] were obtained as white precipitates
[
3
4
6 `
upon the addition of an aqueous solution of Me SnCl or
3
Me PbCl to K [M(CN) ] in the molar ratio 4:1.
3
4
6
H O
2
II
K [M(CN) ] 1 4Me ECl →[(Me E) M (CN) ] 1 4KCl
4
6
3
3
4
6 `
M 5 Fe or Ru E 5 Sn or Pb E 5 Pb, M 5 Fe (III)
E 5 Sn, M 5 Fe (IV), Ru (V)
Scheme 1.
(1)
their membrane potentials and high voltage sensitivity
24], as fluorescence probes to follow the fast change of
electrical membrane potential during an action potential in
neurons [25] and in nonlinear optical laser frequency
doublers and liquid crystals devices [25].
1
The polymer IV exchanges at most one (Me Sn )
[
3
1
cation for (Et N ) cation when exposed to an aqueous
4
solution of Et NCl to give the polymer VI.
4
H O
2
[
Me Sn) Fe(CN) ] 1 Et NCl →
3 4 6 ` 4
IV
[
(Et N)(Me Sn) Fe(CN) ] 1 Me SnCl
(2)
2
. Experimental
-Methyl-4-(49-R-styryl) or (29-R-styryl pyridinium
4
3
VI
3
6
`
3
The purity and identity of these coordination polymers
1
were checked by elemental analysis and vibrational spec-
tra.
iodides (stpi) were prepared by the base-catalysed aldol
condensation of picolinium iodide with different aldehydes
[26,27]. The purity and identity of (stpi), (Scheme 1) were
checked by thin layer chromatography, elemental analysis
and IR spectra. The stpi are in the trans form as long as
the condensation reaction is carried out in the dark.
The 3D-coordination polymers [(Me Sn) Fe(CN) ] , I,
2.1. Preparation of the molecular composites
stp-Cations can be encapsulated within the channels of
the coordination polymers I and II by mixing equimolar
quantities of both, the stpi-salt and I or II. The mixture
was wetted with few drops of water and ground smoothly
for a long time to avoid the effect of heat on the
3
3
6 `
and [(Me Pb) Fe(CN) ] , II, were obtained when aqueous
3
3
6 `
solutions of trimethyltin chloride or trimethyllead chloride
and K [Fe(CN) ] are mixed in the dark under nitrogen
3
6
Table 1
Elemental analysis and colours of the molecular composites 1–12
No.
Molecular compositions
Colour
Elemental analysis, % Calc./(Found)
C
H
N
Fe
6.10
III
0.1
II
0.9
1
2
3
4
5
6
7
8
9
[(49-H-stp)0.9(Me Sn) Fe Fe (CN) –2H O]
Buff
36.19
4.80
10.55
3
3
6
2
`
`
(
(
(
(
(
(
(
(
(
(
(
(
36.00)
27.08
26.91)
36.37
36.51)
36.48
36.54)
27.35
27.23)
38.72
38.69)
37.88
37.81)
35.44
35.38)
31.96
31.83)
33.94
33.82)
37.74
37.80)
36.37
36.33)
(4.83)
3.66
(3.60)
4.64
(4.56)
4.70
(4.62)
3.72
(3.69)
4.93
(4.91)
4.80
(4.90)
4.25
(4.28)
4.34
(4.38)
4.33
(4.35)
4.60
(4.62)
4.64
(4.60)
(10.31)
8.20
(7.96)
10.80
(10.70)
10.50
(10.32)
8.03
(7.87)
10.19
(9.89)
11.89
(11.72)
10.73
(10.59)
10.07
(10.00)
11.64
(11.58)
10.65
(10.51)
10.80
(10.71)
(5.92)
4.81
(4.76)
6.29
(6.23)
6.11
(6.06)
4.71
(4.62)
5.81
(5.78)
6.16
(6.10)
6.29
(6.18)
5.99
(5.81)
6.19
(6.12)
6.16
(6.12)
6.29
(6.16)
III
0.2
II
0.8
[(49-H-stp)0.8(Me Pb) Fe Fe (CN) –2H O]
Yellow
3
3
6
2
III
0.15
II
[(49-OH-stp)0.85(Me Sn) Fe Fe (CN) –2H O]
Orange
3
3
0.85
6
2
`
III
0.15
II
[(49-OCH -stp) (Me Sn) Fe Fe (CN) –2H O]
Yellow
3
0.85
3
3
0.85
6
2
`
III
0.2
II
[(49-OCH -stp) (Me Pb) Fe Fe (CN) –2H O]
Reddish brown
Orange
3
0.8
3
3
0.8
6
2
`
II
[(49-OCH -stp)(Me Sn) Fe (CN) –MeOH]
`
3
3
3
6
III
0.15
II
[(49-NMe -stp) (Me Sn) Fe Fe (CN)6]`
Brown
2
0.85
3
3
0.85
III
0.2
II
0.8
[(49-Cl-stp)0.8(Me Sn) Fe Fe (CN)6]`
Brown
3
3
III
0.3
II
0.7
[(49-Br-stp)0.7(Me Sn) Fe Fe (CN) –2H O]
Grey
3
3
6
2
`
III
0.25
II
0.75
1
1
1
0
1
2
[(49-NO -stp) (Me Sn) Fe Fe (CN) –H O]
Green
2
0.75
3
3
6
2
`
III
0.15
II
0.85
[(29-OH-stp)0.85(Me Sn) Fe Fe (CN) –H O]
Yellow
3
3
6
2
`
III
0.1
II
0.9
[(29-OCH -stp) (Me Sn) Fe Fe (CN)6]`
Yellowish brown
3
0.9
3
3

A.M.A. Ibrahim / Polyhedron 18 (1999) 2711–2721
2713
Table 2
Elemental analysis and colours of the molecular composites 13–18
No.
Molecular compositions
Colour
Elemental analysis, % Calc./(Found)
C
H
N
Fe
13
14
15
16
17
18
[(49-H-stp)(Me Sn) Fe(CN )]
`
Yellowish brown
Yellow
38.72
4.59
(4.51)
4.66
(4.76)
3.55
(3.38)
3.63
(3.80)
4.37
(4.26)
4.45
10.88
6.21
(6.15)
6.01
(5.92)
4.79
(4.61)
4.67
(4.61)
–
3
3
6
(
(
(
(
(
(
38.68)
38.76
38.36)
29.90
29.70)
30.15
30.00)
36.86
36.74)
36.96
36.87)
(10.62)
10.55
(10.47)
8.42
(8.32)
8.20
(8.03)
10.38
(10.12)
10.06
(9.72)
[(49-OCH -stp)(Me Sn) Fe(CN )]
`
3
3
3
6
[(49-H-stp)(Me Pb) Fe(CN) ]
6 `
Brown
3
3
[(49-OCH -stp)(Me Pb) Fe(CN) ]
6 `
Reddish brown
Canary green
Pale green
3
3
3
[(49-H-stp)(Me Sn) Ru(CN) ]
6 `
3
3
[(49-OCH -stp)(Me Sn) Ru(CN) ]
6 `
–
3
3
3
(4.40)
coordination polymers [28]. The products 1–12 (Table 1)
are finally washed with chloroform to remove the un-
reacted materials and dried under vacuum at 308C.
higher solubility in polar solvents than the tin derivatives
(decompose above 2208C). The white coordination poly-
mers III–VI are diamagnetic and thermally stable up to
3
008C.
III
III
1–x
stpi 1 [(Me E) Fe (CN) ] → [(stp) (Me E) Fe
3
3
6
`
x
3
3
The coordination polymers I, II, IV and VI are isostruc-
II
x
tural samples as indicated by the X-ray powder diagrams
Fig. 1). Their structural features are established by
Fe (CN )–nH O]
`
6
2
(
E 5 Sn or Pd 1–12
(3)
studying the single crystal X-ray diffractions of the coordi-
nation polymers [(Me E) Co(CN) ] (E5Sn or Pb)
3
3
6 `
[
9,10,12] which are the homologues of and isostructural
The encapsulated polymer 6 was also prepared by
mixing equimolar amounts of methanolic solutions of 1-
with I and II as they belong to the fundamental type
d
III
[(R E) M (CN) ] . Also, the coordination polymers III–
methyl-4-(49-OCH -styryl) pyridinium iodide and I. The
3 3 6 `
3
VI can be considered as members of the family of the
reaction mixture was left for 2 h in the dark under nitrogen
with continuous stirring at room temperature. The orange
precipitate was filtered off and washed several times with
methanol and then dried in vacuo at 308C.
The molecular species 13–18 were prepared by ion
exchange reactions. Addition of equimolar quantities of
each of the coordination polymers III–VI suspended in an
aqueous methanolic solution to the stpi-salt (1) or (3)
dissolved in methanol gave 13–18 (Table 2) after 3 h
stirring at room temperature and leaving the reaction
mixture overnight. The coloured solid precipitates were
filtered off, washed with water and then with methanol and
dried under vacuum at 408C.
IV
organotin
H O] ,
coordination polymers [(Me Sn) Fe(CN) –
3
4
6
4
[(Me Sn) Fe(CN) 2H O–C H O ]
and
2
`
3
4
6
2
4
8
2 `
[(Me Pb) Fe(CN) –2H O] studied by single crystal X-
3 4 6 2 `
ray diffractions as well as solid-state NMR spectra [13–
5,29,30]. These studies indicated the presence of two- or
three-dimensional network due to the presence of trigonal-
bipyramidal (tbp) (E5Sn or Pb) bridges
1
d
between the single d-transition metal ion M. The most
significant structural features of the 3D-network are the
presence of two different chains with each M atom as a
joint member of three intersecting chains; while one-third
of all chains are strictly linear, the other two-thirds display
alternately two different E–N–C angles that are both
smaller than 1808C. These chains display ample, straight
d
All the analytical and spectroscopic methods as well as
the instruments are described elsewhere [28].
˚
channels with a cross-section of about 10310 A capable
of encapsulating voluminous guest cations.
1
19
13
The solid-state
Sn and C NMR spectra of the
3
. Results and discussion
coordination polymers III–VI (Table 3) confirm the
presence of two chemically different (Me E) groups where
3
3
.1. Structure, chemical properties and thermal stability
at most one of the four (Me E) groups undergoes quantita-
3
of the coordination polymers
tive ion exchange [9,10,12,31–33]. These groups have six
crystallographically different methyl carbon setwise equiv-
alent around room temperature owing to rapid rotation
about their individual trigonal axes [9,10,12]. The network
involves also three equally abundant nonequivalent CN
ligands.
The coordination polymers I and II are obtained as
paramagnetic yellowish orange precipitates (m ; ca. 2.18
and 2.11 BM, respectively). The lead derivatives have
lower thermal stability (decompose above 1808C) and
eff

2
714
A.M.A. Ibrahim / Polyhedron 18 (1999) 2711–2721
Fig. 1. X-ray powder diffraction of the coordination polymers I, II, IV and VI.

A.M.A. Ibrahim / Polyhedron 18 (1999) 2711–2721
2715
Table 3
Solid-state NMR data [9,12,30–33] C and Sn, for III–VI
1
3
119
1
3
119
13
No.
Coordination polymer
d
C/ppm (methyl)
d
Sn
d
C/ppm
2
608C
20, 408C
ppm
–
(cyanide)
167–188
III
IV
V
[(Me Pb) Fe(CN) –2H O]
`
17.8, 18.1
3
4
6
2
1
9.24
[(Me Sn) Fe(CN) ]
6 `
18.9, 13.8, 12.8
1.5, 22.5
19.2, 14.4, 12.8
2.4, 1.4, 22.1
14.4
11.2
14.3
11.4
–
2108
146
297
132
2157.6
2181.3
178, 175,
169
166, 163
159
170.5
174.6
3
4
1
[(Me Sn) Ru(CN) ]
6 `
3
4
1
a
VI
a
[(Et N)(Me Sn) Fe(CN) ]
153.6 , 19.17, 16.6
2.9, 11.0
4
3
3
6
`
1
13
d
C/ppm (Ethyl).
The IR and Raman spectra of the coordination polymers
they occur usually at higher wave numbers than the n
CN
21
d
I–VI reveal the presence of [ M(CN) ] building blocks
bands of the corresponding salts [ca. n 52116 cm and
CN
21
6
and the different (Me E) units (Figs. 2 and 3). The IR
2072, 2043, 2025 cm ) for K Fe(CN) and K Fe(CN) ].
3
3 6 4 6
spectra display, mainly, two strong bands in the nCN
region. However, one of these bands tends, in some cases,
to split into two bands. The positions of these bands reflect
the covalent nature of the M–C;N→E bridging unit since
On the other hand, the Raman spectra show three absorp-
tion bands indicating the presence of three nonequivalent
CN ligands. In the n
region, two IR bands for I appear
E–C
2
1
21
at 527 cm (n(Sn–C)sy. ) and 552 cm (n(Sn–C)asy. ). The IR
band due to n of II appears as a broad one at 497
Pb–C
2
1
cm . On the other hand, the (n(E–C)asy. ) band of III–V
2
1
splits into two bands with no more than 9 cm difference
while the Raman (n(E–C)sy. ) and (n(E–C)asy. ) bands of III–VI
Fig. 2. IR spectra of the coordination polymers I–VI.
Fig. 3. Raman spectra of the coordination polymers I–VI.

2
716
A.M.A. Ibrahim / Polyhedron 18 (1999) 2711–2721
Table 4
low intensity of the Raman (n(Sn–C)asy. ) band advocate the
2
1
Vibrational frequencies (cm ) of I–VI
presence of trigonal planar (Me E) units which are axially
3
Compound nCN
nE–C
nMC
Raman IR
anchoring to two cyanide N atoms [34]. The broad
appearance of the nM–C band (IR spectra of I, II and VI)
and the presence of two split bands in the IR spectra of
III–V support the presence of two different [–NC–M–
CN–E–NC–] chains with M surrounded octahedrally by
six cyanide ligands as gathered from the X-ray and NMR
results.
IR
Raman
IR
a
wb
527 , 552
b
b
I
2145, 2155
2166, 2120
410
412
446
451
437
454
433
472
448
a
b
II
497
d
b
b
b
b
b
b
b
b
III
IV
V
2011, 2057, 2037, 2077 491, 499
471
501
520
555
517
551
520
553
w
2
071
2114
2067, 2091 518 , 547
133 552w
2076, 2102 519 , 546
518
w
2050, 2074
2049, 2084
2052, 2065
w
2
s
2
147
2075, 2082 518 , 550
124
553
w
b
VI
3.2. The electronic absorption spectra of the
coordination polymers
2
a
b
s
Nujol mull; weak; broad; strong.
The electronic absorption spectra of the metal ion with
5
2
appear at the expected positions (Table 4). These results
reveal the presence of tbp-configured Me E(NC) units as
d configuration in the ( T g) coordination polymers I and
2
II as Nujol mull matrix reveal five intense bands at 220,
260, 300, 320 and 440 nm (Table 5 and Fig. 4). These
bands are also observed at similar positions in the diffuse
3
2
well as the (Me E) cations. Also, the absence of the
3
symmetric vibrations in the IR spectra of II–VI and the
Table 5
The electronic absorption spectra of the coordination polymers I–VI as Nujol mull matrices and diffuse reflectance
Coordination
polymer
2M→L
L→M
2CT1
T1u(s)
L→M
2CT2
T2u
2d–d
A2g → T
L→M
2CT3
T1u(p)
4
2
T2g(p)→ t1u(p*)
1g
I
II
225, (220)
220, (222)
260, (258)
258, (258)
300, (300)
300, (305)
320, (320)
320, (322)
440, (450)
445, (460)
1
3
1CT
1d–d
1d–d
A1g → T
1g
1
1
1
A1g → T
A1g → T
A1g → T
1u
2g
1g
b
b
III
IV
V
220, (220)
225, (222)
220, (220)
220, (222)
250 , (258)
300 , (305)
b b
w
250, (260)
240, (255)
325 , (330 )
440
440
b
300 , (310)
b
b
w
VI
245 , (260)
320 , (320)
b
w
broad; weak.
Fig. 4. Electronic spectra of the coordination polymers I–VI as: (a) Nujol mull matrix; and (b) diffuse reflectance.

A.M.A. Ibrahim / Polyhedron 18 (1999) 2711–2721
2717
reflectance spectra. They resemble the bands observed in
the absorption spectrum of K [Fe (CN) ] at 219, 258, 300,
H O
2
stpi 1 3Me SnCl 1 K M(CN) →
3
6
3
4
6
3
18, 333 and 419 nm [35]. The first band at 220 nm is due
to p–p* transitions from the metal to the cyanide ligand
M→L band). The three bands at 260, 300 and 440 nm
1
d
3
II
[
(stp )(Me Sn) M (CN) ] 1 3KCl 1 KI
3
6
`
M 5 Fe or Ru
(4)
(5)
(
have been identified as charge transfer transitions from the
filled bonding orbitals; mainly of the cyanide ligand, to the
hole in the shell of the central metal ion. They have been
H O–MeOH
2
1
d
3
II
stpi 1 V or VI
→
[(stp )(Me
E)
M (CN)
]
3
6
`
2
2
2
2
2
assigned as T u(s)→ T g, T u(p)→ T g and T1u
The results of chemical analysis reveal in addition, that
several samples contain solvent molecules amounting to
one or two. This is further supported by DTA thermograms
which show an endothermic peak at 180–2208C and TGA
analysis which indicate that one or two solvent molecules
release out the network of the encapsulated polymers at
160–2108C. Although, the significance of presence of the
solvent molecules in the network of these encapsulated
compounds, rather than considering it as adsorbed solvent,
is not quite clear at the present time, it is worth noting that
the presence of a few drops of water enhance significantly
the rate of encapsulation, the case which has been previ-
ously observed for some other encapsulated polymers [19].
Also, the X-ray study of the supramolecular host–guest
system [(n-Bu N)(Me Sn) Fe(CN) –H O] indicated that
1
2
2
2
2
(
p)→ T g, respectively [35]. Apart from these intense
2
charge transfer bands, one band of low intensity is
observed at 320 nm due to ligand field (d–d) transitions
2
2
(
A g→ T g). The other bands due to (d–d) transitions
2 1
(ca. 285 and 370 nm) [35,36] are obscured by the more
intense broad bands due to L→M transitions.
The electronic absorption spectra of the Fe(II) ions with
6
1
d configuration ( A g) in the coordination polymers III–
1
VI as Nujol mull matrix exhibit mainly three absorption
bands at 220–225, 240–250 and 300–325 nm which have
the same features of the spectra of K Fe(CN) and
4
6
K Ru(CN) [36,37], Table 5 and Fig. 4. The second and
4
6
the third bands display slight red shift (ca. 255–260 and
05–330 nm) in the diffuse reflectance spectra. The last
two bands at 250 and 320 nm are assigned to (d–d)
3
4
3
2
6
2
the H O molecules belong at least in part, to the 3D-host
2
1
1
1
1
transitions A g→ T g and A g→ T g, respectively
framework [38].
1
2
1
1
[
36]. The intense band at 220 nm is due to charge transfer
The molecular composites are thermally stable, and
photo-stable compared to the corresponding polymers [28].
The host polymers became thermally stable and photo-
1
1
transition of the type A g→ T u (M→ L band).
The very weak band was supposed to appear at 422 nm,
as observed in the spectrum of K [Fe(CN) ] [36] due to
1
1
stable when the stp are present as guest cations in the
4
6
1
3
1
the first spin-forbidden transition; A g→ T g, appears at
cavities rather than the (Me
3
E ) cations. The encapsulated
1
1
4
40 nm in the diffuse reflectance spectra of IV and VI
polymer 6 exhibits thermochromic behavior since the
colour changes reversibly from orange to red on heating at
608C (Fig. 5). The DTA thermograms indicate the de-
composition of these encapsulating polymers by two
exothermic peaks within the temperature range 350–
5408C. The X-ray powder diffraction of the encapsulated
coordination polymers 13–18 indicate that they are iso-
structural compounds to the corresponding coordination
polymers.
while it is obscured in the spectra of III and V under the
more intense broad band at 320 nm.
3
.3. Analytical data and thermal stability of the
molecular composites
The results of chemical analysis (Table 1) reveal that the
stp-cations are encapsulated within the cavities of the
polymers I and II in molar ratios ,1 exhibiting zeolite
3.4. The IR spectra of the molecular composites
III
II
like host–guest systems [(stp) (Me E) Fe Fe (CN) ]
x
3
3
1–x
x
6 `
(
0,x,1). These encapsulating polymers are formed by
The IR spectra of the molecular composites reveal that
the bands are due to the 3D-host matrices and the stp-guest
cations (Tables 6 and 7). The presence of the solvent
molecules in the lattice of the encapsulated polymers was
further supported by the appearance of the broad band at
tribochemical reactions at room temperature. In this case,
the iodide anion functions as an electron donor and
partially reduces the host matrix, hence facilitating accom-
modation of the stp-cation. However, complete reduction
of Fe
III
21
could not be achieved even with continuous
3410–3446 cm due to nOH. The presence of the weak
2
1
grinding and leaving the reaction mixture for several days.
On 1the other hand, the molecular composites
band at 2119–2135 cm and the strong broad band below
21
2100 cm
indicates partial transformation of the
II
d
II
III
[(stp )(Me E) M (CN) ] ; 13–18, can be prepared by
[Fe (CN) ] building blocks to [Fe (CN) ] to give zeolite
3
3
6
`
6
6
following two different preparative routes; coprecipitation
like 3D-host–guest polymers. Under high resolution in the
from solution Eq. (4) and by ion exchange. At most one
nCN range, the IR spectra of 2, 3, 5, 7, 8 and 10 display two
bands below 2100 cm reflecting the significantly per-
1
21
(
Me E ) cation from the network of the polymers III–V
3
1
or the (Et N ) cation of VI was replaced by one stp-
turbed surroundings of the Me E-interlinked [Fe(CN) ]
4
3
6
cation, Eq. (5).
octahedra. However, the absence of the bands due to, nCN

2
718
A.M.A. Ibrahim / Polyhedron 18 (1999) 2711–2721
Fig. 5. Electronic spectra of the encapsulated polymer 6: (a) absorption spectra in Nujol mull; and (b) diffuse reflectance spectra: (i) orange; (ii) red.
Table 6
2
1
The IR spectra (cm ) of the molecular composites 1–12
1
Compound
nH2O
nC≡N
(stp ) cation
nE–C
nFe–C
a
nOH
nC≡N
nC5C
nC–N
gCH
w
b
w
w
w
w
w
1
2
3
4
5
6
7
8
9
3437
3420
3433, 3226
3446
3430
3420
3433
3439
3438
2123 , 2051
1634
1638
1641
1642
1640
1640
1639
1643
1639
1680
1640
1640
1617–1513
1615–1510
1622–1517
1617–1514
1618–1510
1616–1515
1620–1530
1622–1518
1617–1513
1620–1525
1614–1510
1618–1531
1207
1210
1208
1208
1210
1208
1210
1212
1218
1220
1230
1214
967
960
968
987
972
985
953
962
965
960
978
965
549, 535
498, 490
548, 538
460, 448, 410
456, 450, 418
462, 450, 412
470, 451, 410
446, 430, 414
470, 452
w
2130 , 2065, 2018
w
2119 , 2062, 2022
w
b
b
2128 , 2054
551
w
2132 , 2070, 2040
500, 489
b
b
2055
550
w
b
w
w
w
w
w
w
2120 , 2071, 2048
560, 553
558, 551
453 , 410
w
b
2130 , 2074, 2050
450 , 410
w
b
b
b
2130 , 2048
552
449 , 408
w
b
1
1
1
0
1
2
3410
3435, 3230
3430
2135 , 2076, 2055
550, 540
450 , 410
w
b
b
b
2120 , 2058
552
550
448 , 412
w
b
b
2125 , 2060
450 , 410
a
Overlapped with dH O.
broad; weak.
2
b
w
III
21
of the [Fe (CN) ] building blocks in the IR spectrum of 6
2104 cm
in the spectra of 16 and 17, supports the
6
indicates that the stp-cation is introduced quantitatively
within the channels of the host polymer producing ther-
mochromic encapsulated polymer. On the other hand, the
appearance of two or three IR active bands in the spectra
of 15–18 (Fig. 6), apart from one additional shoulder at
presence of three nonequivalent CN ligands of distorted
octahedral structure. The nCN bands of 13–18 occur at
higher wave numbers than the bands of the corresponding
host polymers reflecting more covalent interaction between
the cyanide N atoms and the (Me E) connecting units
3
under the effect of the nature of the guest cation. The
wavenumber of the n band increases along the sequence
CN
1
1
1
1
Me pb ,Me Sn ,49-OCH -stp ,49-H-stp .
Table 7
3
3
3
2
1
The IR spectra (cm ) of the molecular species 13–18
The characteristic bands of the stp-guest cations (Table
) exhibit shifts to higher wave numbers relative to the
6
Compound
nC≡N
nE–C
nM–C
bands of the stpi, indicating the presence of charge transfer
from the negative host framework to the stp-cations as
indicated by the diffuse reflectance spectra.
b
1
1
1
1
1
1
3
4
5
6
7
8
2090, 2055
2055
2104, 2067, 2060, 2016
2104, 2070, 2038
2104, 2094, 2061
2100, 2090, 2057
560, 551 , 537
460, 447
476, 447
456
445, 431
482, 412
480, 420
b
b
549 , 540, 519
508, 495, 485
499 , 491
560, 551, 535
b
b
b
b
The nFe–C vibrations, of 1–12, except 6, reflect clearly
III
II
the presence of both the [Fe (CN) ] and [Fe (CN) ]
6 6
b
550 , 540
building blocks while the broad appearance of both nE–C
and nFe–C bands or their splitting into two bands reflect the
b
broad.

A.M.A. Ibrahim / Polyhedron 18 (1999) 2711–2721
2719
Fig. 6. High-resolution IR spectra of 13–18 in the nCN and nMC stretching regions.
presence of two nonequivalent Me E(NC) units (Table
3.5. The electronic absorption spectra of the molecular
3
2
6
). This is further supported by the splitting of the band
composites
due to (n(E–C)asy. ) of 13–18 into two bands, and th2e
1
presence of the band due to (n(
) at around 537 cm
The spectra of 1–12 as Nujol mull matrices reveal that
the bands are due to both the stp-cations and the coordina-
tion polymers (Table 8). The broad bands at 216–225,
240–256 and 340–410 nm are attributed to p–p* transi-
tions of the stp-guest cations in addition to transitions due
Sn–C)sy.
2
1
and that of (n(Pb–C)sy. ) at 485 cm (Fig. 6 and Table 7).
Thus, from these IR spectroscopic features, it is evident
1
that the exchange of (Me E ) cations by the stp-cations
3
does not affect the local symmetries of the [M(CN)6]
building blocks.
1
1
1
1
to A g→ T u and A g→ T g of the polymers, respec-
1
1
1
2
Table 8
The electronic absorption spectra of 1–12 as Nujol mull matrices and diffuse reflectance as well as the magnetic moments
Compound
stpi
Molecular species
meff
1
1
a
p–p* transitions
p–p* transitions of stp and
A1g → T
CT3
CT
BM
1g
1
1
1
1
A1g → T
A1g → T
CT2
1u
2g
1
2
3
4
5
6
7
8
9
225
240
347
225
225
220
220
222
222
220
220
220
218
218
216
240
242
256
253
255
254
240
247
248
–
340
342
410
390
345
390
340
352
350
340
385
380
290
295
290
288
295
290
300
290
295
–
440
437
442
440
442
–
445
440
435
435
442
440
525
522
564
655
657
658
725
565
560
678
500
510
0.30
0.70
0.35
0.36
0.70
–
0.33
0.40
0.51
0.47
0.32
0.31
218
220
220
220
–
218
220
218
215
215
260
260
260
260
240
240
260
240
255
258
410
345
345
345
340, 430
350
355
340
340, 390
336, 380
1
1
1
0
1
2
252
255
295
290
a
Diffuse reflectance.

2
720
A.M.A. Ibrahim / Polyhedron 18 (1999) 2711–2721
2
tively. The bands due to p–p* transitions of the stp-guest
cations appear at more or less the same positions of the
stp-salts (Fig. 7). The composite band around 300 nm
of 1-methyl-4-(4 -methoxy-styryl) pyridinium cation as
well as those of the host coordination polymer (Fig. 5).
The band due to CT disappears while the diffuse reflect-
3
1
1
corresponds to d–d transitions, A g→ T g of the
ance spectrum reveals a broad band at 658 nm corre-
sponding to the ion pair CT. On the other hand, the
spectrum of the red sample displays an additional band at
620 nm which disappears on cooling the sample where the
colour changes from red to orange. This band appears at
745 nm in the diffuse reflectance spectrum exhibiting blue
shift on cooling.
The electronic absorption spectra of 13–16 exhibit the
same bands of 1–12 except those of [Fe (CN) ] building
blocks while the ion-pair CT band appears at longer
wavelengths. The absence of the [Fe (CN) ] building
1
1
II
[
Fe (CN) ] building blocks [37] and to charge transfer
6
2 2 III
transition (CT2, T → T ) within the [Fe (CN) )]
2u
2g
6
building blocks. The weak band at 435–445 nm can be
2
2
III
attributed to CT3, T (p)→ T g of the [Fe (CN) ]
1u
2
6
building blocks. These bands support the presence of
mixed valence iron hexacyano building blocks as also
indicated by the weak paramagnetic behavior of these
composites (Table 8). On the other hand, the diffuse
reflectance spectra exhibit an additional broad band at
III
6
III
5
00–725 nm (Fig. 7), corresponding to ion-pair charge
6
transfer (CT) between the negatively charged cavity of the
host polymer and the stp-cations [39,40]. Thus, the en-
capsulation of the guest stp-cations within the 3D-host
channels can be explained in terms of an ionic charge
transfer model. On the other hand, the electronic absorp-
tion spectra do not show any bands in the near-IR region
corresponding to an inter valence transition, indicating
localized interaction between the mixed valence iron [41].
The electronic absorption spectra of orange 6 exhibit the
absorption bands characteristic to the different transitions
blocks is further supported by the diamagnetic behavior of
these encapsulated polymers. Some bands due to d–d
transitions and the L→M charge transfer bands are ob-
scured by the more intense bands of the stp-guest cations
located at the same positions. The electronic absorption
spectra of 17 and 18 (Table 9) indicate that at most one of
1
the (Me Sn ) cations is exchanged quantitatively by the
3
stp-cation which encapsulates within the channels of the
negatively
charged
coordination
polymer
2
[(Me Sn) Ru(CN) ] .
3
3
6 `
Fig. 7. (a) Electronic absorption spectra of stpi (1), (2) and (3) and the corresponding encapsulated polymers 1, 3 and 4. (b) Diffuse reflectance spectra of
1), (7), 1 and 10.
(

A.M.A. Ibrahim / Polyhedron 18 (1999) 2711–2721
2721
Table 9
[15] P. Schwarz, S. Eller, E. Siebel, T.M. Soliman, R.D. Fischer, D.C.
Apperely, N.A. Davis, R.K. Harris, Angew. Chem., Intl. Ed. Engl.
35 (1996) 1525.
The electronic absorption spectra of 13–18 as Nujol mull matrices and
diffuse reflectance
1
1
a
[16] M. Hassanen, S.H. Etaiw, Eur. Polim. J. 29 (1993) 47.
[17] A.M.A. Ibrahim, S.H. Etaiw, T.M. Soliman, J. Organomet. Chem.
Compound
p–p* transition of stp and
A1g → T
CT
1g
1
1
1
1
A1g → T
A1g → T
1u
2g
4
30 (1992) 87.
1
1
1
1
1
1
3
4
5
6
7
8
222
225
220
220
222
220
245
250
244
252
240
244
340
390
338
392
340
385
320
315
295
300
300
295
530
670
532
675
526
569
[18] S.H. Etaiw, A.M.A. Ibrahim, J. Organomet. Chem. 456 (1993) 229,
and references therein.
[19] A.M.A. Ibrahim, T.M. Soliman, S.H. Etaiw, R.D. Fischer, J.
Organomet. Chem. 468 (1994) 93, and references therein.
[20] S. Eller, M. Adam, R.D. Fischer, Angew. Chem. 102 (1990) 1157.
[21] S. Eller, M. Adam, R.D. Fischer, Angew. Chem., Intl. Ed. Engl. 29
(1990) 1126.
a
Diffuse reflectance.
[22] S. Eller, P. Brandt, A.K. Brimah, P. Schwarz, R.D. Fischer, Angew.
Chem. 101 (1989) 1274.
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