Synthesis and spectroscopic studies of metal complexes of N,N′-p-phenylenedimethylenebis(pyridin-4-one) with d- and f-block metal ions

Article abstract of DOI:10.1081/SIM-120039269

The preparations are reported for a range of complexes of the ligand N,N′-p-phenylenedimethy]enebis(pyridin-4-one) (XBP) with the d-block ions Mn(II) to Zn(II) and also with Cd(II), Y(III), and the lanthanide ions. Relevant solid state EPR, electronic and far-IR spectra are reported and interpreted in terms of the metal ion coordination geometries and, where appropriate, the likely long-range polymeric structures of the compounds. The value of the zero-field splitting (zfs) parameter, D = 0.069 cm^-1, obtained from the S = 1 type EPR spectrum of the compound {[Cu₂(XBP) ₃(NO₃)₂](NO₃)₂· 2H₂O}_n is compared with those of other compounds involving discrete Cu ... Cu dimer interaction. The results of luminescence measurements on the complexes of Sm(III), Eu(III), Tb(III), and Dy(III) are also given.

Full text of DOI:10.1081/SIM-120039269

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Synthesis and Spectroscopic
Studies of Metal Complexes of
N,N′‐p‐Phenylenedimethylenebis(pyridin‐4‐one) with
d‐ and f‐Block Metal Ions
David M. L. Goodgame a & Amanda M. Menzer a
a Chemistry Department , Imperial College London , London, SW7 2AZ, UK
Published online: 16 Nov 2010.
To cite this article: David M. L. Goodgame & Amanda M. Menzer (2004) Synthesis and Spectroscopic Studies of Metal
Complexes of N,N′‐p‐Phenylenedimethylenebis(pyridin‐4‐one) with d‐ and f‐Block Metal Ions, Synthesis and Reactivity in
Inorganic and Metal-Organic Chemistry, 34:7, 1237-1257, DOI: 10.1081/SIM-120039269
To link to this article: http://dx.doi.org/10.1081/SIM-120039269
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SYNTHESIS AND REACTIVITY IN INORGANIC AND METAL-ORGANIC CHEMISTRY
Vol. 34, No. 7, pp. 1237–1257, 2004
Synthesis and Spectroscopic Studies of
Metal Complexes of N,N0-p-
Phenylenedimethylenebis(pyridin-4-one)
with d- and f-Block Metal Ions
*
David M. L. Goodgame and Amanda M. Menzer
Chemistry Department, Imperial College London, London, UK
ABSTRACT
The preparations are reported for a range of complexes of the ligand
N,N0-p-phenylenedimethylenebis(pyridin-4-one) (XBP) with the d-block
ions Mn(II) to Zn(II) and also with Cd(II), Y(III), and the lanthanide
ions. Relevant solid state EPR, electronic and far-IR spectra are reported
and interpreted in terms of the metal ion coordination geometries
and, where appropriate, the likely long-range polymeric structures of
the compounds. The value of the zero-field splitting (zfs) parameter,
D ¼ 0.069 cm21, obtained from the S ¼ 1 type EPR spectrum of the com-
.
pound f[Cu2(XBP)3(NO3)2](NO3)2 2H2Ogn is compared with those of
other compounds involving discrete Cu ꢀ ꢀ ꢀ Cu dimer interaction. The results
*
Correspondence: David M. L. Goodgame, Chemistry Department, Imperial College
London, London SW7 2AZ, UK; E-mail: d.goodgame@imperial.ac.uk.
1237
DOI: 10.1081/SIM-120039269
0094-5714 (Print); 1532-2440 (Online)
www.dekker.com
Copyright # 2004 by Marcel Dekker, Inc.

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of luminescence measurements on the complexes of Sm(III), Eu(III),
Tb(III), and Dy(III) are also given.
Key Words: Polymeric complexes; Transition metals; Lanthanides;
EPR; Electronic spectra; Luminescence spectra.
INTRODUCTION
The synthesis of new polymeric metal complexes forming either sheet
structures involving contiguous arrays of large metallacyclic rings or three-
dimensional networks continues to attract attention because of their potential
as metal-organic analogues of zeolites. Several variables can be employed in
design strategies for materials of this type. A wide range of metal ions can be
used as “node” points in such compounds, often with attendant variations in
metal ion coordination geometry. Additionally, the types of donor groups
coordinated to the metal centres by the organic bridging ligands can be varied,
as can the lengths and geometries of the “spacer” unit connecting those
donor groups. In such solid state materials further factors such as hydrogen
bonding and p–p stacking interactions may often play an appreciable role
in influencing the type of structure that results.[1,2]
The great majority of the organic bridging ligands used in this area of
research contains nitrogen donor groups, such as pyridine units, and many diffe-
rent structural types have been reported.[1,3–12] Those with O-donor groups have
received rather less attention,[1] although work involving carboxylate anions as
bridging ligands is producing an increasing range of interesting structures.[13–19]
We have previously shown that neutral O-donor “extended reach” ligands
containing pyridone units as donor end-groups readily form coordination
polymers with both transition metal[20] and lanthanide[21] ions. As x-ray
studies showed that the ligand N,N0-p-phenylenedimethylenebis(pyridin-
4-one) (XBP) (Fig. 1) formed several polymeric complexes with particularly
complex, interwoven structures[22–24] we have explored the synthesis and
spectroscopic properties of a wider range of compounds formed by XBP
and we report here the results of that work.
Figure 1. Formula of XBP.

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1239
RESULTS AND DISCUSSION
The complexes of XBP we have obtained are listed in Tables 1 and 2 for
some d- and f-block metal ions, respectively.
Complexes of Mn(II) to Zn(II) and Cd(II)
All the cobalt(II) complexes are of the type Co(XBP)X2, where X ¼ NO3,
Cl, Br, I, or NCS, but their solid state electronic spectra clearly show that the
coordination geometry at the cobalt centre is anion-dependent. The bright blue
complexes formed by cobalt(II) halides and cobalt(II) isothiocyanate all show
the characteristic, strong, three-component d–d bands (Fig. 2, band energies
4
listed in Table 3) arising from the transitions n2 [4A2(F) ! T1(F) in the
4
near-IR region] and n3 [4A2(F) ! T1(P) centred on ca 16,000 cm21],
expected for an essentially tetrahedral CoO2X2 chromophore of C2v
symmetry.[25] In the case of the cobalt(II) chloride complex additional evidence
for the pseudotetrahedral geometry at the cobalt centre[26] is provided by
the presence of nas(Co–Cl) and nsym(Co–Cl) bands at 318 and 289 cm21
,
respectively, in its far-IR vibrational spectrum. The analogous complex of
zinc(II) chloride has a similar pair of n(Zn–Cl) vibrational bands at 316
and 281 cm21 respectively, again consistent with a distorted tetrahedral,
C2v, coordination geometry. Although crystals of sufficient quality for single
crystal x-ray study were not obtained for these compounds, it seems likely
that their long-range structures take the form of polymeric chains in which
the tetrahedrally coordinated metal centres are linked by the XBP ligands.
In contrast, the electronic spectrum (Table 3) of the purple complex
formed by cobalt(II) nitrate is characteristic of an essentially octahedral
CoO6 chromophore.[27] In view of the 1 : 1 XBP : Co stoichiometry, the six-
coordination would be achieved either by the presence of bidentate anions
at each cobalt centre in a [Co(XBP)(NO3)2]n chain or a more complex array
structure involving both XBP and nitrate bridges between the metal atoms.
.
The electronic spectra of the nickel(II) complexes Ni(XBP)Cl2 H2O and
.
Ni(XBP)2(ClO4)2 2H2O (Table 3) also show the presence of essentially
octahedral coordination geometry at the metal centres as the d–d bands are
of relatively low intensity and at energies expected[28] for the transitions n1
3
3
[3A2g(F) ! T2g(F)] and n2 [3A2g(F) ! T1g(F)]. In each case, the band
arising from n3[3A2g(F) ! T1g(P)] is obscured by a very intense charge-
3
transfer band at ca. 25,000 cm21. In view of the very poor coordinating ability
of the perchlorate anion, the octahedral coordination observed for the
nickel(II) perchlorate complex suggests that a possible long-range solid state
structure is a sheet polymer formed by XBP bridges between the nickel

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Figure 2. Electronic spectra of the solid complexes Co(XBP)2X2 (X ¼ Cl, Br, I,
and NCS).
centres, with pairs of aqua ligands in trans-positions. The compound may thus
be formulated as f[Ni(XBP)2(H2O)2](ClO4)2gn. The long-range structure of
the nickel(II) chloride complex is less clear but the stoichiometry suggests
that the six-coordination is achieved by a combination of both XBP and
chloride bridges, with possible aqua ligand bonding.
All the manganese(II) complexes have very simple X-band EPR spectra
consisting of a single band at geff ¼ 2.0, with no evidence of any significant
zero-field splitting (zfs). Spectra of this type are consistent with either a coordi-
nation geometry of very high symmetry at the manganese(II) centres or the
presence of sufficiently strong dipolar coupling between those centres to cause
the loss of the zfs.[29] The considerable distance between the pair of donor
oxygen atoms in the XBP ligand renders it most unlikely that the linking of
manganese(II) centres by such XBP bridges would result in sufficient magnetic
interaction to cause the collapse of the multi-band structure indicative of zfs.
It is, however, a well-established feature of coordination chemistry that
chloro- and bromo complexes of the type ML2X2 (where L ¼ a unidentate
donor ligand) frequently achieve six-coordination at the metal ion by the
bridging action of the halide ions, and such bridges result in an efficient

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1245
Table 3. Electronic band energies (in cm21) for the cobalt(II), nickel(II), and copper(II)
complexes of XBP in the solid state.
Compound
Electronic band energiesa
[Co(XBP)(NO3)2]
.
[Co(XBP)Cl2] H2O
8,000, 13,325, 17,200 sh, 18,500, 20,200 sh
5,800, 7,100, 8,125 sh, 15,625 sh, 16,125, 17,400
5,575 sh, 6,325, 7,400 sh, 15,150 sh, 15,875, 17,100 sh
5,400 sh, 6,175, 7,300, 14,400 sh, 15,275, 17,125
8,250 br, 15,500 sh, 16,400, 17,800 sh
8,200, 15,400
[Co(XBP)Br2]
[Co(XBP)I2]
[Co(XBP)(NCS)2] 0.5H2O
.
.
Ni(XBP)Cl2 H2O
.
Ni(XBP)2(ClO4)2 2H2O
.
Cu2(XBP)3(NO3)4 2H2O
8,850, 14,800
11,000 sh, 14,500
.
Cu(XBP)Cl2 2.5H2O
5,700 sh, 12,050
5,550 sh, 11,350
.
Cu(XBP)Br2 1.5H2O
ash, shoulder and br, broad.
cause of the loss of zfs in the EPR spectrum when M ¼ Mn(II).[29] Accordingly,
the loss of the expected zfs in the manganese(II) chloride and bromide
complexes of XBP is consistent with the presence of halide bridges between
the metal centres. Further evidence for that is provided by their far-IR
vibrational spectra, which have no n(Mn–X) bands above 220 cm21. A decision
as to whether, in each case, all the halide ions act as bridges between Mn centres
or whether combinations of bridging and unidentate binding are present, as in
the compound [Mn(m-XBP)Cl2]n formed by the related ligand N,N0-m-phenyl-
enedimethylenebis(pyridin-2-one),[30] would require a single-crystal x-ray
study. An x-ray study would also elucidate the role of the water molecules in
these compounds but crystals of sufficient quality were not obtained.
The single band EPR spectrum observed for the compound Mn(XBP)2
.
(ClO4)2 3H2O suggests that it has the same type of long-range polymeric
structure advanced for the nickel(II) perchlorate complex discussed previously
.
and that it can be formulated as f[Mn(XBP)2(H2O)2](ClO4)2 H2Ogn.
The X-band EPR spectra of the copper(II) chloride and bromide complexes
exhibit a single, very broad band at ca. g ¼ 2, again indicating the presence of
halide bridges resulting in extensive dipolar coupling between the copper(II)
centres and loss of the resolution of g anisotropy.
The copper(II) nitrate complex of the stoichiometry Cu2(XBP)3
[23]
to have the formulation
.
(NO3)4 2H2O has been previously shown
.
f[Cu2(XBP)3(NO3)2](NO3)2 2H2Ogn and a structure in which pairs of copper
atoms are linked by two m–O(pyridone) bridges to form Cu2O2 units with a
˚
. . .
Cu Cu separation of 3.34 A and an S ¼ 1 type EPR spectrum. That close
. . .
Cu Cu separation is depicted in Fig. 3 as a schematic drawing of the

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Goodgame and Menzer
Figure 3. Schematic representation of the dinuclear [Cu2O2] unit in the structure of
.
f[Cu2(XBP)3(NO3)2](NO3)2 2H2Ogn.
x-ray determined structure.[23] There is further extensive bridging action by the
XBP ligands resulting in the formation of a complex, large-ring (68-mem-
bered), interwoven network of such units and a long-range structure which
is best viewed by accessing it on the Cambridge Crystallographic
Data Centre (compound ref. ZIGTAK).
Use of the equations given by Wasserman, Snyder, and Yager for the
derivation of the g values and zfs parameters from the EPR spectra of randomly
oriented S ¼ 1 molecules[31] yields the values: gxy ¼ 2.08, gz ¼ 2.21, and
D ¼ 0.069 cm21. The zfs parameter, D, observed for this XBP complex of
copper(II) nitrate is smaller than those found for some other antiferro-
magnetically coupled dimeric Cu(II) systems, such as copper(II) carboxylate
dimers (D in range 0.3–0.45cm21 [32]
bridges (e.g., adenine, hypoxanthine, 4-azabenzimidazole or 7-azaindole; D
)
or dimers formed by nitrogen donor
0.1–0.18cm21 [33,34]
or those employing both N- and O-donor ligands such
)
as 3-ethyl-2-pyridone (for which D ¼ 0.29cm21).[35] A smaller D value would
˚
...
be expected from the larger Cu Cu separation (3.34 A) in f[Cu2(XBP)3(NO3)2]
.
(NO3)2 2H2Ogn as compared with those in the dimers referred to above,
˚
for which Cu Cu is in the range ca. 2.6–3.0 A. Interestingly, an X-band
. . .
.
EPR spectrum very similar to that of f[Cu2(XBP)3(NO3)2](NO3)2 2H2Ogn
has been reported[36] for the 1-methyluracil (1-MeU) complex cis-[(NH3)2
.
Pt(1-MeU)2Cu(H2O)2]SO4 4.5H2O in which pairs of cis-[(NH3)2Pt(1-MeU)2
Cu(H2O)2]2þ cations pack in a centrosymmetric head–head arrangement

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1247
˚
. . .
with a Cu Cu separation of 3.48 A, but without any bridges between the two
copper centres.[37]
Reaction of zinc(II) perchlorate with XBP gave the compound
.
Zn(XBP)2(ClO4)2 2H2O, whereas with zinc(II) nitrate the resulting complex
.
was Zn2(XBP)3(NO3)4 4H2O. The 3 : 2 XBP : Zn stoichiometry observed for
the latter compound suggests that it may have a structure similar to that found
previously for the copper(II) nitrate complex.[23] The compound f[Zn2(XBP)4]
[23]
.
(BF4)4 4H2Ogn is known
to contain closely similar M2O2 units (drawn
schematically in Fig. 4; access Cambridge Crystallographic Data Centre,
compound ref. ZIGSUD, to view full structure) but in which the coordinated
nitrate groups present in the copper nitrate complex are each replaced by a
coordinated pyridin-4-one unit in the zinc compound. It seems likely, there-
fore, that the zinc perchlorate complex is more appropriately formulated
.
as f[Zn2(XBP)4](ClO4)4 4H2Ogn, with a structure in which XBP bridges
generate a complex array of metallacyclic rings, with a combination of
34- and 38-membered rings, and with XBP “through-ring” threading,
The x-ray powder diffraction pattern of the complex of stiochiometry
.
Cd(XBP)3(ClO4)2 2MeCN 2H2O shows that it is isostructural with the
.
[22]
.
compound Mn(XBP)3(ClO4)2 2MeCN
and it has, therefore, the same
polymeric structure involving polycatenated sheets of 34- and 68-membered
rings with octahedral CdO6 node points. It is appropriately formulated as
.
.
f[Cd(XBP)3](ClO4)2 2MeCN 2H2Ogn.
Figure 4. Schematic representation of the dinuclear [Zn2O2] unit in the structure of
.
f[Zn2(XBP)4](BF4)4 4H2Ogn.

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Goodgame and Menzer
Lanthanide Complexes
The stoichiometries of the complexes of XBP formed by the lanthanide(III)
nitrates fall into two groups: those in the series La to Eu (Pm not studied)
.
are of the type M4(XBP)7(NO3)12 4H2O, whereas those from Gd to Yb have
.
the stoichiometry M2(XBP)3(NO3)6 2H2O. A change in stoichiometry and/or
structure in analogous complexes is frequently observed as one progresses
across the lanthanide series (a manifestation of the discontinuity feature
that is often found at gadolinium and which has been termed the “gadolinium
break”[38]). It may be noted that reactions were also carried out with a repre-
sentative member of each series (Nd and Er, respectively) varying the
XBP : metal mole ratio (5 : 1, 2 : 1, and 1 : 5) and also the solvent medium
employed (MeOH, EtOH, MeCN, and MeNO2) but without any change in
the stoichiometry or crystallinity of the resulting products. Unfortunately,
we have been unable to obtain any member of either of the two series of
lanthanide nitrate complexes in the form of x-ray-quality crystals for definitive
structural analysis.
It also proved very difficult to obtain good quality crystals of members of the
more limited ranges of lanthanide(III) chloride and perchlorate complexes listed
.
in Table 2. The structure of one of them, Nd2(XBP)7(ClO4)6 7H2O, has been
shown[24] to have the formula f[Nd2(XBP)6(H2O)4](XBP)(H2O)3(ClO4)6gn
and to form a very complex array of chains of interpenetrating “cages”
of 34-membered metallacycles with adjacent chains cross-linked by non-
coordinated XBP molecules hydrogen-bonded to aqua ligands.
We have, however, taken the opportunity to explore the photoluminescence
properties of a representative range of the Sm, Eu, Tb, and Dy complexes in the
.
solid state (Table 4). The samarium complex Sm4(XBP)7(NO3)12 4H2O and
the dysprosium complexes phosphoresce relatively weakly. The samarium
Table 4. Luminescence data for some lanthanide(III) complexes of XBP.
Excitation
(nm)
Emission
(nm)
Lifetime
(msec)
Compound
.
Sm4(XBP)7(NO3)12 4H2O
377
396
346
366
395
346
366
563, 598, 643a
593, 616a
58
613
741
59
.
Eu4(XBP)7(NO3)12 4H2O
Tb2(XBP)3(NO3)6 2H2O
.
Dy2(XBP)3(NO3)6 2H2O
490, 545a, 583, 621
482, 575a
.
593, 613a
490, 547a, 585, 621
484, 576a
359
624
49
.
Eu2(XBP)3Cl6 2H2O
Tb2(XBP)3Cl6 2H2O
.
Dy(XBP)3(ClO4)3 2H2O
.
aBand used for lifetime measurements.

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1249
6
complex exhibits low-intensity emission bands at 563 nm (4G5/2 ! H5/2),
6
6
598 nm (4G5/2 ! H7/2), and 643nm (4G5/2 ! H9/2), whereas those for the
dysprosium complexes are at ca. 483 nm (4F9/2 ! H15/2) and ca. 576 nm
6
(4F9/2 ! H13/2). The europium complexes show strong phosphorescent
6
emission, with bands at 593nm (5D0 ! F1) and ca. 615 nm (5D0 ! F2). The
7
7
terbium complexes luminesce very strongly and four dominant bands appear
in their phosphorescence emission spectra at 490 nm (5D4 ! F6), ca. 546nm
7
(5D4 ! F5), ca. 584 nm (5D4 ! F4), and 621 nm (5D4 ! F3). The phosphor-
escence lifetimes (Table 4) are in the order Tb3þ . Eu3þ ꢁ Sm3þ ꢂ Dy3þ and
are similar in magnitude to those observed previously for polymeric complexes
of these metal ions with N,N0-ethylenebis(pyrrolidin-2-one).[39] In view of
the paucity of comparative data for such compounds with complex, interwoven,
network structures further work on related compounds with well-documented
structures is needed before further comments about these data are warranted.
7
7
7
EXPERIMENTAL
Synthesis
XBP
This was prepared as described previously.[22] The ligand crystallises as
a tetrahydrate but is denoted below simply as XBP.
Metal Complexes of XBP
Caution! Although we did not observe any explosive behaviour with any
of the perchlorate complexes described below, all metal perchlorates must be
regarded as potentially explosive and appropriate safety measures must be taken.
The complexes showed only ill-defined decomposition points on heating.
.
[Mn(XBP)(NO3)2] 2H2O
.
A solution of Mn(NO3)2 4H2O (0.1 mmol, 0.025 g) and XBP (0.1 mmol,
0.036 g) in methanol (6 mL) was allowed to evaporate slowly over concen-
trated H2SO4 in a desiccator. Yellow “sea-urchin-like” clusters of microcrys-
tals were formed within 2 weeks; these were collected and dried under reduced
pressure.
.
[Mn(XBP)Cl2] 2.5H2O
.
Solutions of MnCl2 4H2O (0.1 mmol, 0.020 g) and XBP (0.1 mmol,
0.036 g) each dissolved in a 1 : 1 mixture of methanol (2 mL) and 2,2-

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dimethoxypropane (2 mL) were mixed and stirred for 30 min, resulting in the
formation of a white suspension. Addition of methanol (3 mL) gave a clear
solution. This was allowed to concentrate as above and yellow microcrystal-
line globules formed over a period of several days.
.
[Mn(XBP)Br2] H2O and [Co(XBP)Br2]
.
.
Warm solutions of MnBr2 4H2O (0.1 mmol, 0.029 g) or CoBr2 6H2O
(0.1 mmol, 0.033 g), respectively, each in ethanol (3 mL), were added slowly,
with stirring, to a similar ethanolic solution of XBP (0.2 mmol, 0.072 g, in
3 mL) followed by stirring at 50 8C for 1 hr. The cream-coloured (Mn) or
dark blue (Co) powders which formed were filtered off, washed with ethanol,
and dried over silica gel under reduced pressure.
.
Mn(XBP)2(ClO4)2 3H2O
A solution of manganese(II) perchlorate hexahydrate (0.033 mmol,
0.012 g) and XBP (0.1 mmol, 0.036 g) in methanol (6 mL) was allowed to con-
centrate overnight over concentrated H2SO4 in a desiccator. The yellow
“feathery” crystals which formed were collected and air-dried.
[Co(XBP)(NO3)2]
A solution of Co(NO3)2 6H2O (0.1 mmol, 0.029 g) and XBP (0.1 mmol,
.
0.036 g) in a mixture of methanol (2 mL) and acetonitrile (4 mL) was allowed
to evaporate slowly over concentrated H2SO4 in a desiccator. The purple,
microcrystalline globules which separated over 1 week were collected and
dried under reduced pressure.
.
[Co(XBP)Cl2] H2O
.
A solution of CoCl2 6H2O (0.1 mmol, 0.024 g) in acetonitrile (3 mL) was
mixed with one of XBP (0.1 mmol, 0.036 g) in a mixture of methanol (1 mL)
and acetonitrile (3 mL). The resulting blue suspension was stirred for ca. 1 hr
and then centrifuged to remove the blue solid which was dried under reduced
pressure.
[M(XBP)I2] (M ¼ Co, Zn)
A 0.1 M solution of the respective metal iodide in ethanol was prepared in
situ from sodium iodide and the hydrated Co or Zn nitrate. An aliquot (1 mL)
containing 0.1 mmol of the respective metal iodide (0.031 g for Co, 0.032 g for
Zn) was added dropwise to a warm solution of XBP (0.2 mmol, 0.072 g) in
ethanol (4 mL). The dark blue (Co) or yellow (Zn) powders which separated
within several hours were filtered off, washed with ethanol, and dried over
silica gel under reduced pressure.

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.
[Co(XBP)(NCS)2] 0.5H2O
The mixing of solutions of cobalt(II) thiocyanate (0.1 mmol, 0.018 g) and
XBP (0.2 mmol, 0.072 g) in warm ethanol (4.2 mL) resulted in the formation
of a dark blue precipitate which was collected as for [M(XBP)I2] (M ¼ Co,
Zn).
.
Ni(XBP)Cl2 H2O
.
A hot solution of NiCl2 6H2O (0.1 mmol, 0.024 g) in butan-1-ol (3 mL)
was added dropwise to a similar solution of XBP (0.2 mmol, 0.072 g, in 3 mL).
A blue-green precipitate formed instantly. Stirring was maintained under
gentle reflux for ca. 3 hr and the mixture was then centrifuged to separate
the solid. The complex was washed with diethyl ether and dried under reduced
pressure.
.
M(XBP)2(ClO4)2 2H2O (M ¼ Ni, Zn)
A solution of the respective metal perchlorate hexahydrate (0.033 mmol,
0.012 g) in acetonitrile (4 mL) was added dropwise to a solution of XBP
(0.1 mmol, 0.036 g) in a mixture of methanol (1 mL) and acetonitrile
(3 mL). The nickel complex separated as a fine, green powder over a period
of 3–4 days. The solution of the zinc complex was filtered after 3 days and
the resulting solution deposited colourless crystals during the following 36 hr.
.
Cu(XBP)Cl2 2.5H2O
.
Methanolic solutions of CuCl2 2H2O (0.1 mmol, 0.017 g, in 3 mL) and
XBP (0.1 mmol, 0.036 g, in 3 mL) were mixed and stirred for ca. 1 hr. The
resultant greeny-yellow powder was collected by centrifuging and dried
under reduced pressure.
.
Cu(XBP)Br2 1.5H2O
This was obtained by essentially the same method as for the bromide
complexes of Mn(II) and Co(II) but with cold methanol as the solvent.
.
[Cu2(XBP)3(NO3)2](NO3)2 2H2O
.
A solution of Cu(NO3)2 3H2O (0.1 mmol, 0.024 g) in a mixture of
methanol (1 mL) and acetonitrile (3 mL) was added slowly to a similar sol-
ution of XBP (0.1 mmol, 0.036 g, in 4 mL of solvent mixture). A green cloudi-
ness may be produced by too rapid addition of the metal salt solution and this
can be cleared by dropwise addition of methanol. The clear solution was
allowed to concentrate slowly over concentrated H2SO4 in a desiccator and
green crystals formed over 4–5 days.

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1252
Zn2(XBP)3(NO3)4 4H2O
Goodgame and Menzer
.
.
A hot solution of Zn(NO3) 6H2O (0.1 mmol, 0.030 g) in ethanol (3 mL)
was added dropwise with stirring to one of XBP (0.2 mmol, 0.072 g) also in
ethanol (3 mL). A cream-coloured solid formed instantly. Stirring was main-
tained under gentle reflux for a further 3 hr after which the solid was collected
by centrifuging. It was washed with diethyl ether and dried under reduced
pressure.
.
Zn(XBP)Cl2 H2O
An aqueous solution of zinc(II) chloride (0.1 mmol, 0.014 g, in 3 mL) was
added dropwise to a solution of XBP (0.1 mmol, 0.036 g) in a mixture of water
(5 mL) and methanol (2 mL). The clear solution was left to evaporate slowly
over concentrated H2SO4. Florets of small crystals formed over a period of
several days and these were air-dried.
.
Cd(XBP)3(ClO4)2 2MeCN 2H2O
.
.
Dropwise addition of a solution of Cd(ClO4)2 6H2O (0.033 mmol,
0.014 g) in acetonitrile (4 mL) to a solution of XBP (0.1 mmol, 0.036 g) in a
mixture of methanol (1 mL) and acetonitrile (3 mL) gave an immediate
cream-coloured precipitate. Methanol (ca. 1 mL) was added dropwise until
the precipitate redissolved. The resulting clear solution was allowed to con-
centrate in a desiccator over concentrated H2SO4; pale yellow crystals formed
overnight.
.
M4(XBP)7(NO3)12 4H2O (M ¼ La, Ce, Pr, Nd, Sm, Eu) and
.
M2(XBP)3(NO3)6 2H2O (M ¼ Gd, Tb, Dy, Ho, Er, Yb)
A methanolic solution of the hydrated lanthanide(III) nitrate (0.1 mmol in
3 mL) was added slowly to one of XBP (0.2 mmol, 0.072 g) also in methanol
(3 mL) and the resulting milky suspension stirred for 2 hr. The fine powders
which formed were filtered off, washed with cold methanol, and dried under
reduced pressure.
.
M2(XBP)3Cl6 8H2O (M ¼ Pr, Nd)
.
.
A solution of PrCl3 7H2O (0.067 mmol, 0.025 g) or NdCl3 6H2O
(0.067 mmol, 0.024 g), respectively, each in a mixture of methanol (1 mL)
and acetonitrile (2 mL), was added to a similar solution of XBP (0.2 mmol,
0.072 g) resulting in the immediate formation of a cloudy suspension. Metha-
nol was added dropwise until complete dissolution was achieved (ca. 2 mL
required). The resulting clear solution was allowed to evaporate slowly over
concentrated H2SO4 in a desiccator. After 1–2 days a small quantity of fine
powder had reformed and this was filtered off and the filtrates were left to con-
centrate as before. Clusters of “canoe-shaped” crystals formed over a further

ORDER
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Long-Range Polymeric Complexes
1253
3–4 day period. These were collected, washed with cooled acetonitrile, and
air-dried.
.
Eu2(XBP)3Cl6 2H2O
The synthetic route was essentially the same as for the previous two com-
pounds but microcrystalline globules of the cream-coloured Eu complex
formed overnight from the initial reaction mixture. These were collected,
washed with acetonitrile, and dried under suction.
.
M2(XBP)3Cl6 nH2O (M ¼ Tb, n ¼ 2; M ¼ Dy, Yb, n ¼ 0)
These were also obtained by the same method as for the europium chlor-
ide complex but in these cases the reaction mixture which turned cloudy
immediately was stirred for approximately two and a half hours and then cen-
trifuged to separate the solid complex. The resulting fine powders were
washed with diethyl ether and dried over silica gel under reduced pressure.
.
.
M(XBP)3(ClO4)3 2H2O (M ¼ Y, Dy); M2(XBP)7(ClO4)6 nH2O
(M ¼ La, Gd, n ¼ 7; M ¼ Sm, n ¼ 4)
A methanolic solution of the hydrated lanthanide(III) perchlorate
(0.04 mmol in 3 mL) was added slowly to one of XBP (0.2 mmol, 0.072 g)
also in methanol (3 mL) and the resulting milky suspension stirred for 2 hr.
The fine powders which formed were filtered off, washed with cold methanol,
and dried under reduced pressure.
.
Nd2(XBP)7(ClO4)6 7H2O
.
A solution of Nd(ClO4)3 6H2O (0.04 mmol, 0.022 g) in a mixture of
methanol (1 mL) and acetonitrile (2 mL) was added to a similar solution of
XBP (0.2 mmol, 0.072 g, in 3 mL). The white precipitate which formed
instantly was redissolved by addition of methanol (4 mL) and water (1 mL).
The resulting clear solution was allowed to evaporate at room temperature, fil-
tered after ca. 1 week to remove a small amount of mauve powder and then left
to concentrate further. After a further week the florets of pale mauve crystals
which had formed were collected and air-dried.
Analyses and Physical Measurements
Microanalyses were by the Microanalytical Service, Department of
Chemistry, Imperial College. EPR spectra were measured on powdered
solid state samples at room temperature using a Varian E12 X-band (ca.
9.5 GHz) spectrometer. Infrared spectra were measured on a Research Series
Fourier Transform spectrometer as Nujol mulls between CsI plates. Solid state

ORDER
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1254
Goodgame and Menzer
electronic spectra were measured by the reflectance method over the range
4000–30,000 cm21 using a Beckman DK2 spectrometer and the standard
reflectance accessory. Luminescence spectra were recorded on powdered
solid state samples using a Perkin–Elmer LS50 luminescence spectrometer
fitted with the standard solid state sample accessory. The phosphorescence
lifetimes were obtained by recording the decay of the emission band inten-
sities (as designated in Table 4) over twenty 0.1 msec intervals for the terbium
complexes and at 0.01 msec intervals for the other complexes. In each case,
a plot of the natural logarithm of the phosphorescence intensity against
time gave a straight line, the gradient of which is equal to the reciprocal
of the phosphorescence lifetime. The x-ray powder diffraction pattern of
.
.
Cd(XBP)3(ClO4)2 2MeCN 2H2O was obtained with a Siemens D-500
powder diffractometer.
ACKNOWLEDGMENT
We thank the Engineering and Physical Sciences Research Council for a
Research Studentship to A.M.M. and for equipment.
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Received August 12, 2003
Accepted March 22, 2004
Referee I: C. H. Winter
Referee II: M. E. Hagerman

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