Spectroscopic studies of phosphazene polymers containing photoluminescent metal complexes

Article abstract of DOI:10.1002/ejic.201100341

A series of small phosphazene ligands with pendant 6-phenyl-2,2′- bipyridyl moieties, namely L¹ [N₃P₃(OPh) ₅(OPhbpyPh)], L² [N₃P₃(biph) ₂(OPhbpyPh)₂], L

Full text of DOI:10.1002/ejic.201100341

FULL PAPER
DOI: 10.1002/ejic.201100341
Spectroscopic Studies of Phosphazene Polymers Containing Photoluminescent
Metal Complexes
Eric W. Ainscough,*[a] Harry R. Allcock,[b] Andrew M. Brodie,*[a] Keith C. Gordon,*[c]
Mark D. Hindenlang,[b] Raphael Horvath,[c] and Carl A. Otter[a]
Keywords: Phosphazenes / Polymers / Rhenium / Palladium / Platinum
A series of small phosphazene ligands with pendant 6-
nor set confirming the cyclopalladation. The ligand pendant
phenyl-2,2Ј-bipyridyl moieties, namely L1 [N3P3(OPh)5- arms are involved in intermolecular stacking interactions
(OPhbpyPh)], L2 [N3P3(biph)2(OPhbpyPh)2], L3 [N3P3(tBu-
biph)2(OPhbpyPh)2], L4 [N3P3(biph)2(OPhbpyPh)Cl] and L5
[N3P3(biph)2(OPhbpyPh)(OPh)] [OPhbpyPh = 4-(4-phenoxy)-
6-phenyl-2,2Ј-bipyridine, OPh = phenoxy, biph = 2,2Ј-oxybi-
phenyl and tBubiph = 4,4Ј-di-tert-butyl-2,2Ј-oxybiphenyl],
have been used to synthesise the new cyclometallated palla-
dium(II) and platinum(II) complexes [(L1-H)PdCl], [(L1-H)-
PtCl], [(L1-H)(PdCl)2], [(L3-H)(PdCl)2], [(L4-H)PtCl], [(L5-H)-
PtCl] and the rhenium(I) complex [L5Re(CO)3Cl]. Single-
crystal X-ray diffraction analysis was performed on the free
ligand L2 and the palladium complexes [(L1-H)PdCl] and
[(L3-H)(PdCl)2]. In both PdII complexes, the metal centre lies
in a distorted square-planar geometry with an “N2CCl” do-
with adjacent molecules. A polyphosphazene (L6) with 4-tert-
butylphenoxy (OtBuPh) and the potential donor OPhbpyPh
as pendant groups was prepared and used to synthesise
metallopolymers with ReI and PtII. Spectroscopic and compu-
tational studies were conducted to compare the discrete com-
plexes with the polymers with similar metal pendants as well
as to model compounds in the literature. By using UV/Vis
and resonance Raman spectroscopic techniques it was found
that very few deviations from known metal chromophores
exist for both the triphosphazene- and polyphosphazene-
based complexes. The transient resonance Raman spectra of
the PtII complexes revealed a ligand radical anion signature
associated with the N2C unit.
design is the fact that the photophysical properties of the
chromophores can be tuned by using substituents on the
polymer support.[18–20]
Introduction
The synthesis of new polymers containing transition-
metal complexes is an area of research that is attracting
increasing interest[1–3] due to a diverse range of prospective
applications for polymer-based metal complexes, including
sensors,[4–7] biomedical applications[8–10] and catalysis.[11,12]
Owing to their well-understood emissive properties,[13]
metal complexes have attracted attention in the field of or-
ganic light-emitting diode (OLED) device construction[14]
and examples of electroluminescent polymers containing
metal ions as chromophores are also becoming more wide-
spread.[15–17] One aspect that is of significance for OLED
Phosphazene systems are good candidates for such appli-
cations as the polymer backbone can be easily derivatised,
allowing the development of a wide range of polymers con-
taining various ligands and metal complexes.[21] The influ-
ence of different substituents on the physical properties of
a polymer, such as the glass transition temperature (Tg), is
also well understood.[22] Hence, the systematic design of a
luminescent material with the desired properties for fabrica-
tion of a specific device should be achievable. Indeed, the
possibility of adapting cyclic and polymeric phosphazenes
to this end has been proposed in several earlier re-
ports.[23–28]
Recently we reported the preparation and excited-state
spectroscopic studies of a series of cyclic phosphazenes con-
taining RuII and ReI bipyridine complexes and found that
there is little interaction between the phosphazene core and
the chromophore.[29] We have now extended the study to
examine the photophysical properties of polymeric ReI and
PtII derivatives as well as related small-molecule com-
pounds. We report herein the synthesis and spectroscopy of
the new systems and also describe the crystallography of
two new PdII-containing cyclic analogues.
[a] Chemistry-Institute of Fundamental Sciences, Massey
University,
Private Bag 11 222, Palmerston North 4442, New Zealand
Fax: +64-6-3505602
E-mail: e.ainsoug@massey.ac.nz
a.brodie@massey.ac.nz
[b] Department of Chemistry, The Pennsylvania State University,
University Park, PA 16802, USA
[c] MacDiarmid Institute for Advanced Materials and
Nanotechnology, Department of Chemistry, University of
Otago,
Dunedin 9054, New Zealand
Fax: +64-3-4797906
E-mail: kgordon@chemistry.otago.ac.nz
Supporting information for this article is available on the
WWW under http://dx.doi.org/10.1002/ejic.201100341.
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[(L-H)PdCl] (L = HOPhbpyPh),[30] for example, [(L1-H)-
PdCl]. The disubstituted ligands L2 and L3 afforded the di-
metallic complexes [(L2-H){PdCl}2] and [(L3-H){PdCl}2],
which precipitated directly from the mother liquor.
Recrystallisation from dimethyl sulfoxide (DMSO) gave
compounds that retained solvated DMSO and showed neg-
ligible solubility in common organic solvents other than di-
methylformamide (DMF). The crystals of [(L2-H){PdCl}2]
that initially form gave microanalytical data consistent with
the presence of three DMSO solvate molecules after drying
under vacuum overnight. Drying under vacuum for another
48 h removed two of these molecules and the final DMSO
was removed by heating the complex under vacuum at
75 °C.
Results and Discussion
Small-Molecule Compounds: Synthesis of Ligands and
Complexes
The ligand L1 (Figure 1) was prepared by the reaction of
HOPhbpyPh with the phosphazene N3P3(OPh)5Cl as de-
scribed previously.[29] Similarly, the new phosphazenes L2,
L3 and L4 were prepared by the reaction of 1 or 2 equiv.
of the sodium salt of HOPhbpyPh with N3P3(biph)2Cl2 or
N3P3(tBubiph)2Cl2 in the presence of the catalyst, tetrabu-
tylammonium bromide (Scheme 1). The 31P NMR spectra
of L2 and L3 both contain the anticipated two-phosphorus
doublet and one-phosphorus triplet resonances (see the
Exp. Sect.). During the preparation of L2 we observed the
appearance of a singlet at δ = 22.70 ppm corresponding to
the monosubstituted species L4. This phosphazene can be
prepared from the reaction between 1 equiv. of the sodium
salt of HOPhbpyPh with a slight excess of N3P3(biph)2Cl2
and isolated by chromatography. It can then be used as a
starting material for further substitution reactions; hence
L5 was prepared from the subsequent reaction of L4 with
sodium phenolate.
The complex [(L3-H){PdCl}2] is only marginally more
soluble than [(L2-H){PdCl}2] in DMSO, which is surprising
because other tBubiph-substituted phosphazenes are highly
soluble. Crystals of [(L3-H){PdCl}2] suitable for X-ray
analysis were obtained by recrystallisation by vapour dif-
fusion of EtOH into a DMF solution of the complex. The
data only refined well when the contributions from disor-
dered solvent molecules (both DMF and EtOH, corre-
sponding to 1278 electrons per molecule of the complex)
were removed from the model. Complexes [(L1-H)PdCl]
and [(L4-H)PdCl] are readily soluble in CH2Cl2 or CHCl3,
which suggests that the lack of solubility of [(L2-H){PdCl}2]
and [(L3-H){PdCl}2] is due to extensive intermolecular
stacking networks, which are possible as a result of the two
flat, cyclometallated aromatic ligand arms (see the Crystal
Structures section). These motifs are common in planar
PdII and PtII complexes of polypyridine ligands.
Organoplatinum complexes of L1-H and L5-H were pre-
pared in a similar manner to the organopalladium com-
plexes starting from [Pt(PhCN)2Cl2]. However, the double
cycloplatination of L2 and L3 did not occur as readily as
the corresponding double cyclopalladination and we did
not obtain samples free of the monoplatinated product.
From the reaction between N3P3(biph)2Cl2 and 1 equiv. of
[(L-H)PtCl] (L = HOPhbpyPh)[7] in the presence of Cs2CO3
as base, we were able to obtain the complex [(L4-H)PtCl].
When 2 equiv. of [(L-H)PtCl] were used in a similar reac-
tion with N3P3(tBubiph)2Cl2, the product [(L3-H){PtCl}2]
was obtained but, as with the double cycloplatination reac-
tions, a satisfactory separation from the small amount of
monosubstituted material present in the reaction mixture
was not achieved. The reaction of L5 with [Re(CO)5Cl] pro-
duced the complex [L5Re(CO)3Cl] (Figure 1, c) in which the
phosphazene acts as a bidentate ligand through the nitro-
gen atoms of the bipyridyl unit.
Figure 1. (a) Ligand L1 (ref.[29]). (b,c) Representative examples of
metal complexes.
Crystal Structures
Representative examples of the metal complexes are de-
picted in Figure 1. Organopalladium complexes were pre-
pared from L1, L2 and L3 by reaction of the ligands with
L2·CH2Cl2
Crystals of the ligand L2 were grown from CH2Cl2/hex-
[Pd(PhCN)2Cl2] in methanol/benzene at reflux to give cy- ane solution and the structure (Figure 2 and Table 1) con-
clometallated 6-phenyl-2,2Ј-bipyridine complexes with the firms the double substitution of the biphenyl-derived pre-
same “N2CCl” coordination environment of the metal as in cursor phosphazene with ligand moieties. The phosphazene
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Phosphazene Polymers
Scheme 1. Synthesis of the cyclotriphosphazene ligands L2, L3, L4 and L5.
ring is essentially planar with the P–N bond lengths Table 1. Selected bond lengths [Å] and angles [°] for L2.
[1.576(3) to 1.582(3) Å] and angles (PNP average 121.6° and
P1–N1
P1–N3
P2–N1
1.581(3)
1.579(3)
1.579(3)
P2–N2
P3–N2
P3–N3
1.577(3)
1.582(3)
1.575(3)
NPN average 118.1°) being typical for cyclotriphosphaz-
enes.[22]
N1–P1–N3
N3–P3–N2
N2–P2–N1
117.79(17)
118.09(16)
118.40(16)
P1–N1–P2
P2–N2–P3
P3–N3–P1
121.40(19)
121.3(2)
121.9(2)
Both ligand arms in the structure are involved in offset
π-stacking interactions with the ligand arms of adjacent
molecules. These interactions and other H–π and π–π ar-
rays are prominent in the crystal packing and channels con-
taining disordered solvent molecules are formed in the lat-
tice in a way similar to that seen in other substituted cyclic
phosphazenes with a high aromatic content.[29,31–36]
[(L1-H)PdCl]
Yellow needles of the complex [(L1-H)PdCl] were grown
by the slow diffusion of CH3OH into a CH2Cl2 solution of
the complex. The crystal structure (Figure 3a and Table 2)
Figure 2. Crystal structure of L2.
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confirms the cyclopalladination of the phosphazene ligand. ring are similar [between 1.572(3) and 1.591(3) Å] and the
The PdII centre lies in a distorted square-planar geometry PNP (average 121.8°) and NPN (average 117.2°) angles are
with an “N2CCl” donor set.
also typical.[22] For comparison, selected calculated bond
lengths and angles are shown in Table S1.
The ligand plane is involved in offset π-stacking interac-
tions with the ligand planes of adjacent molecules in the
crystal giving rise to staggered layers of the complex
moieties running approximately along the a axis (Figure 3,
b). The molecules are arranged in a “pair-wise” manner so
that the origins of the stacking interactions differ on either
side of the coordinated ligand plane. On one face, the ligand
arms approach so that the PdII centre lies approximately
3.412 Å from C19 of the coordinated phenyl ligand of the
adjacent molecule and the chloride ligands hydrogen bond
to H5 of the 4-phenoxy spacer groups in a symmetrical ar-
ray (Figure 3, b). On the other side of the ligand plane, the
rings are offset so that the central pyridine ring lies close to
a terminal ligand ring on the adjacent molecule requiring
the Pd···Pd separation to be larger between these faces
(7.034 Å, cf. 5.037 Å).
[(L3-H)(PdCl)2]
Yellow plates of [(L3-H)(PdCl)2] were grown from the dif-
fusion of ethanol vapour into a DMF solution of the com-
plex. The crystal structure (Figure 4a) confirms the double
cyclometallation of L3 and selected bond lengths and angles
are given in Table 3.
Table 3. Selected bond lengths [Å] and angles [°] for [(L3-H)-
(PdCl)2].
Pd1–N4
Pd1–N5
Pd1–C18
Pd1–Cl1
1.958(4)
2.139(5)
1.988(6)
2.3093(15)
Pd2–N6
Pd2–N7
Pd2–C40
Pd2–Cl2
1.975(4)
2.092(5)
2.059(5)
2.3165(16)
Figure 3. (a) Crystal structure of [(L1-H)PdCl]. (b) Intermolecular
packing in the compound showing extended π-stacking.
P1–N1
P1–N3
P2–N1
1.575(5)
1.574(5)
1.570(5)
P2–N2
P3–N2
P3–N3
1.569(5)
1.582(5)
1.593(5)
Table 2. Selected bond lengths [Å] and angles [°] for [(L1-H)PdCl].
Pd1–C17
Pd1–N4
2.062(4)
1.963(3)
Pd1–N5
Pd1–Cl1
2.087(4)
2.3164(11)
N4–Pd1–C18
N4–Pd1–N5
N5–Pd1–Cl1
C18–Pd1–Cl1
C18–Pd1–N5
N4–Pd1–Cl1
80.8(2)
N6–Pd2–C40 80.2(2)
79.42(17)
100.58(12)
99.14(17)
160.2(2)
N6–Pd2–N7
N7–Pd2–Cl2
79.95(8)
98.25(14)
P1–N1
P1–N3
P2–N1
1.582(3)
1.575(3)
1.588(3)
P2–N2
P3–N2
P3–N3
1.572(3)
1.587(3)
1.591(3)
C40–Pd2–Cl2 101.67(16)
C40–Pd2–N7 160.1(2)
176.02(12)
N6–Pd2–Cl2
177.32(13)
N4–Pd1–C17
N4–Pd1–N5
C17–Pd1–Cl1
80.42(15)
79.90(14)
99.93(11)
N5–Pd1–Cl1
N4–Pd1–Cl1
C17–Pd1–N5 160.17(14)
99.82(10)
177.86(10)
N1–P2–N2
N1–P1–N3
N2–P3–N3
118.1(3)
116.9(3)
117.9(3)
P1–N1–P2
P1–N3–P3
P2–N2–P3
123.2(3)
121.7(3)
121.5(3)
N1–P1–N3
N1–P2–N2
N2–P3–N3
117.84(18)
117.37(18)
116.42(18)
P1–N1–P2
P1–N3–P3
P2–N2–P3
120.6(2)
121.7(2)
123.1(2)
The two PdII coordination environments are distorted
square planes and comparable to that in [(L1-H)PdCl].
However, the two sites are not identical: Pd2 has similar
The Pd–N and Pd–C bond lengths in the terminal aro- Pd–C and Pd–N bond lengths in the terminal bonding rings
matic rings of the ligand are similar at 2.087(4) and of the ligand arms [2.060(6) and 2.090(5) Å, respectively],
2.062(4) Å, respectively. The length of the Pd–N bond to whereas Pd1 has a long Pd–N [2.142(5) Å] and short Pd–C
the central pyridine ring is slightly shorter at 1.963(3) Å and [1.984(6) Å] distance.
the Pd–Cl distance is 2.3164(11) Å. The geometric param-
The ligand arms on the molecule are orientated such that
eters about the metal centre are very similar to those re- they extend in opposite directions above and below the
ported for the complex [Pd(Phbpy)Cl] (Phbpy = 6-phenyl- plane of the phosphazene ring. Both ligand arms are in-
2,2Ј-bipyridine).[37] The P–N distances in the phosphazene volved in intermolecular stacking interactions with adjacent
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Phosphazene Polymers
Figure 4. (a) Crystal structure of [(L3-H)(PdCl)2]. (b) Representation of the long-range packing motif in [(L3-H)(PdCl)2] showing the
formation of rectangular channels (2,2Ј-oxybiphenyl groups that occupy the channels have been excluded for clarity).
molecules, as observed with [(L1-H)PdCl] and similar com- of TFE was added and this had the unwanted side-effect of
plexes. However, the presence of two planar aromatic arms replacing some of the OPhbpyPh moieties with TFE (with
pointing in opposite directions gives rise to an interesting recurrence of the yellow colouration in the reaction mix-
long-range motif. The metal centres are stacked along the c ture). Hence we obtained polymers with lower OPhbpyPh
axis at the corners of an interlocking rectangular array in content than expected (around 7%). Furthermore, metal
which one molecule spans two corners to form one side of complexes of these polymers showed poor solubility after
the rectangle (Figure 4, b). The resulting grids contain large work-up so we examined a different system.
channels containing disordered solvent and the structure
only refined well when the contributions made by the sol-
vent molecules to the diffraction data were removed. A
large void comprising approximately 30% of the total crys-
tal volume was left after this treatment. This feature of the
solid-state structure could explain the poor solubility of the
complex and its retention of solvent.
When the sodium salt of 4-tert-butylphenol (tBuPhOH)
was added to the reaction mixture instead of TFE, substitu-
tion occurred without replacement of OPhbpyPh, but we
could not achieve complete substitution of the chloro
groups. Hence, by using a large excess of tBuPhOH in the
presence of the promoter tetrabutylammonium bromide
(TBAB) over extended reaction times and a higher boiling
solvent such as toluene, the best result was a polymer for-
mulated as {[NP(OtBuPh)2]0.5[NP(OPhbpyPh)(OtBuPh)]0.25
-
Synthesis and Characterisation of Polyphosphazenes
[NP(OtBuPh)Cl]0.25}n. The difficulties associated with this
process are consistent with reports in the literature,[22] al-
though fully substituted [NP(OtBuPh)2]n can be ob-
tained.[38] Interestingly, even though 25% of the polymeric
units contained unreacted P–Cl units, the polymer was sub-
jected to work-up under aqueous conditions and showed
no signs of hydrolysis or cross-linking.
We initially tried to produce phosphazene copolymers
containing OPhbpyPh and trifluoroethoxy (TFE) pendant
groups from sequential reactions of the corresponding so-
dium salts with (NPCl2)n. The substitution of Na-
OPhbpyPh on the polymer backbone is rapid [the sodium
salt of OPhbpyPh is yellow in solution and the colouration
disappears almost instantly when added to a solution of
The maximum replacement of P–Cl units was achieved
(NPCl2)n at room temperature]. However, complete substi- by first treating (NPCl2)n with 0.25 molequiv. of
tution of the TFE groups was only achieved when an excess HOPhbpyPh in the presence of Cs2CO3 in THF to produce
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Scheme 2. Syntheses of the polyphosphazene L6 and metallo-polymers.
{[NP(OPhbpyPh)Cl]0.25(NPCl2)0.75 n
]
(Scheme 2). Subse- yellow polymer [L6{Re(CO)3Cl}0.25]. This polymer is solu-
quent addition of an excess of tBuPhOH and reaction for ble in CHCl3 and CH2Cl2 after washing with EtOH and
7 days at reflux in the presence of TBAB resulted in poly- drying but does not redissolve in THF. The characterisation
mers containing between 4 and 8% [NP(OtBuPh)Cl] units, data of the new polymers are given in the Exptl. Sect. The
for example, {[NP(OtBuPh)2]0.75–x[NP(OtBuPh)(OPhbpy- increase in the polydispersity index (PDI) from 1.97 for the
Ph)]0.25[NP(OtBuPh)Cl]x}n (x = 0.06), designated as L6. metal-free polymer L6 to over 2 on addition of Pt or Re is
These polymers were also stable to aqueous work-up and consistent with some thermal degradation of the backbone
showed no signs of decomposition after several months chain. The increase in the glass transition temperature (Tg)
Stable polyphosphazenes that contain unreacted chlorine from 83 °C for L6 to 120 °C for [L6{Re(CO)3Cl}0.25] sug-
atoms have been reported previously in systems with steri- gests the carbonyl ligands bound to the Re interact with the
cally hindering side-groups.[38–40] That the residual P–Cl hydrogen atoms from the pendant OtBuPh groups. Similar
units fail to remain unsubstituted and resistant to hydrolysis weak C–H···O interactions involving CO ligands have been
is probably because they are so sterically protected by observed in small-molecule complexes.[41,42] Interactions
hydrophobic groups that neither aryl oxide ions nor water similar to the intermolecular π-stacking of the pendant
molecules can reach them.
arms seen in the small molecules L2 and [(L3-H)(PdCl)2]
The reaction of L6 with [Pt(PhCN)2Cl2] in a 1:1 mixture are unlikely in the polymers because the pendant arms are
of THF and toluene at reflux produced the orange, cyclo- probably spaced well apart from each other. The phospho-
platinated polymer [L6(PtCl)0.25]n, which, after washing rus NMR spectroscopic data for the polyphosphazenes all
with EtOH and drying under vacuum, remained soluble in show resonances at about –18 ppm, which can be assigned
THF and CHCl3 and partially soluble in CH2Cl2. The reac- to the phosphorus atoms bound to the OtBuPh and
tion of L6 with [Re(CO)5Cl] in THF at reflux yielded the OPhbpyPh groups and can be compared with the value of
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Phosphazene Polymers
–17.1 ppm observed for the fully substituted polymer 1174 cm–1, which corresponds to hydrogen bending modes
[NP(OtBuPh)2]n.[38] The metal-free polymer L6 also shows on the phenoxy or 2,2Ј-oxybiphenyl units. Furthermore, for
a broad, poorly resolved shoulder at around –19 ppm, in- complexes containing L4 and L5, large peaks are observed
dicative of the presence of chlorine atoms bound to the at 1488 and 950 cm–1, assigned to hydrogen stretching and
phosphorus backbone, as in P(OtBuPh)Cl units. The ReI delocalised 2,2Ј-oxybiphenyl vibrations, respectively. Com-
and PtII polymers exhibit a similar feature although it is plexes containing L1 show peaks at 1096 and 888 cm–1,
not as well resolved. The results of other spectroscopic which correspond to hydrogen stretching and delocalised
studies (see below) are consistent with [L6{Re(CO)3Cl}0.25
]
phenoxy vibrations. The spectra of the polymers are very
and [L6(PtCl)0.25]n having the same coordination environ- similar. Compared with the small-molecule spectra, the
ments as their small-molecule analogues.
dominant peak is shifted to 1214 cm–1 and many peaks ap-
pear broadened. Carbonyl stretches are observed as strong
peaks in the FTIR spectra of the rhenium compounds
[L5Re(CO)3Cl] and [L6Re(CO)3Cl]. Back-bonding from the
metal d orbitals to the carbonyl anti-bonding orbitals
causes a decrease in the CϵO stretching frequency, which
may give an insight into the electron density at the metal
centre. Both the small-molecule complex [L5Re(CO)3Cl]
and the polymer [L6Re(CO)3Cl] show identical peaks at
2023, 1922 and 1890 cm–1, which are themselves within
5 cm–1 of those observed for [Re(Ph2-bpy)(CO)3Cl].[52] The
discrepancy in frequencies is within experimental error.
This suggests a minimal electronic effect of the phosphaz-
ene on the chromophore, be it the polymeric or small-mole-
cule variants, and also gives some confidence in the use of
cyclotriphosphazenes as computationally and spectroscopi-
cally manageable analogues for the study of polymeric sys-
tems.
Spectroscopic Analysis
A variety of spectroscopic studies were performed on the
small-molecule complexes [(L1-H)PtCl], [(L1-H)PdCl], [(L4-
H)PtCl], [L5Re(CO)3Cl] and [(L5-H)PtCl] as well as on the
polymers [L6{Re(CO)3Cl}0.25] and [(L6-H)(PtCl)0.25]. Den-
sity functional theory (DFT) calculations were performed
on the small-molecule complexes as well as related model
chromophores to aid the description of experimental obser-
vations. The effectiveness of the computational calculations
was gauged by comparison of a number of calculated and
experimental properties.[43,44] A robust method used to de-
termine if the calculation is modelling the molecule effec-
tively is to compare experimental and simulated vibrational
spectra. The frequencies of the vibrations reflect the bond-
ing of the system of interest and even a qualitative analysis
of intensities can be informative as the IR band intensities
probe the effectiveness of the calculation in terms of model-
ling dipoles. The Raman intensities inform of how effec-
tively polarisability is modelled, which is biased to the fron-
tier molecular orbitals.[44–46]
Electronic Absorption, Emission and Lifetime Data
The electronic absorption, emission and lifetime data for
selected compounds are summarised in Table 5 and
Table S2. The absorption spectra of the platinum complexes
The FTIR and FT-Raman spectra of the small-molecule
complexes were compared with simulated data. The re-
sulting mean absolute deviations (MADs) of the fre-
quencies are shown in Table 4; the values are indicative of
satisfactory calculations.[29,43–45,47–51]
are comparable to that of [(4,6-diphenyl-bpy)PtCl].[53]
A
low-energy tail at around 500–520 nm is assigned as a d–d
transition, moderate-energy bands at around 400–450 nm
can be attributed to a metal-to-ligand charge-transfer
(MLCT) transition and higher-energy bands at around
330 nm are due to ligand-centred transitions. This is also
consistent with resonance Raman assignments (see below).
In addition, high-energy peaks observed at around 245 nm
for [(L4-H)PtCl] and [(L5-H)PtCl] can be assigned to transi-
tions in the 2,2Ј-oxybiphenyl units attached to the phosph-
azene. This peak is absent for compounds containing L1
in which phenoxy groups are present instead. For com-
pound [(L1-H)PdCl], the d–d and MLCT transitions are
blueshifted to 424 and 398 nm, respectively, which is similar
to [(4,6-diphenyl-bpy)PdCl].[54] An absorption blueshift for
analogous Pt and Pd complexes has previously been re-
ported and is attributed to a higher ionisation potential of
Table 4. Mean absolute deviations (MADs) between experimental
and calculated data.
MAD
Raman [cm–1]
IR [cm–1]
[(L1-H)PtCl]
[(L1-H)PdCl]
[(L4-H)PtCl]
[L5Re(CO)3Cl]
[(L5-H)PtCl]
6
6
7
8
4
10
9
10
9
10
Infrared Spectra
The infrared spectra of all the metal complexes are very the frontier d orbitals of the latter metal.[54,55] [L6Re-
dependent on the ligand. Complexes with the same ligand (CO)3Cl] is very similar to an analogous compound that
appear almost identical, for example, [(L5-H)PtCl] and lacks the phenyl substituent at the 6-position reported
[L5Re(CO)3Cl], with any differences arising solely from the earlier.[29] This suggests that the dihedral angle between the
variation of the phenoxy and 2,2Ј-oxybiphenyl attachments phenyl and bpy is great enough to disrupt conjugation
on the phosphazene units of L1 and L4/L5, respectively. All across this part of the ligand in the ground state. The ab-
the spectra are dominated by a broad peak at around sorption spectra of the phosphazene polymers are very sim-
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ilar to those of the corresponding small-molecule com-
plexes. The main difference lies in decreased molar absorp-
tivities, which is explained by their lower chromophore
densities. This is evidence that no electronic communication
exists across the polyphosphazene chain.
Table 5. Electronic absorption, emission and lifetime data for se-
lected compounds in dichloromethane at 298 K.
λabs [nm] (ε
λem
[nm]
τ [ns]
[103 Lmol–1 cm–1])
[(L1-H)PtCl]
512 sh (0.44), 437 (5.0), 419
sh (4.8), 365 (9.7), 332 (22),
292 (45)
424 sh (0.53), 398 sh (1.5),
347sh (16), 330 (24), 291 (49)
512 sh (0.49), 436 (4.5), 419
sh (4.2), 364 (8.9), 335 (19)
572
270Ϯ10
[(L1-H)PdCl]
[(L4-H)PtCl]
564
572
572
–
270Ϯ10
280Ϯ10
[(L5-H)PtCl][a] 506 sh (0.49), 437sh (3.3),
415 (3.4), 367 sh (7), 332
(14), 282 (32)
[L5Re(CO)3Cl] 394 (4.4), 301 (24)
[L6Re(CO)3Cl] 383 (1.2), 304 (5.8), 267 (7.6)
634
619
568
27Ϯ5
60Ϯ10
210Ϯ40
[(L6-H)PtCl]
516 sh (0.03), 428 (0.2), 368
(11)
[a] Emission of [(L1-H)PdCl] was too weak for lifetime acquisition.
Emission and lifetime properties are important for the
design of OLEDs. Comparisons with complexes that do not
contain phosphazenes are thus useful to ascertain whether
phosphazenes are suitable for these devices. Emission ap-
pears to be solely dependent on the metal centre, the plati-
num and rhenium compounds emitting most strongly at 572
and 634 nm, respectively, in dichloromethane. This is com-
parable to the data for similar complexes published in the
literature, for which emission is observed at 564 and
629 nm, respectively.[29,52,53] Lifetimes, however, are some-
what shorter, giving decay constants of around 270 ns for
the platinum complexes and 27 ns for the rhenium complex,
which compares with around 500 and 47 ns, respectively, for
similar compounds in the literature.[29,53] For [L6Re(CO)3-
Cl], this can be attributed to the extra phenyl group at the
6-position of bpy, however, no significant structural
changes exist for the platinum chromophores. For both the
emission and lifetimes, the polymers have values close to
their discrete small-molecule counterparts.
Resonance Raman Spectra
Resonance Raman spectroscopy may be used to identify
the absorbing chromophore for a specific electronic exci-
tation. Normal modes that mimic ground-to excited-state
geometry changes are preferentially enhanced in intensity
and this enables unambiguous assignments to be made of
chromophorically active regions in a molecule.[44,47,56,57]
Figure 5 shows the resonance Raman spectra of [(L1-H)-
PtCl] at a number of excitation wavelengths. These are
representative of the compounds [(L4-H)PtCl] and [(L5-H)-
PtCl] as the spectra are almost identical. Furthermore, for
all the compounds, the spectra acquired at 406.7 and
Figure 5. Resonance Raman spectra acquired in dichloromethane
at a number of excitation wavelengths. (a) Spectra of [(L1-H)PtCl],
which are also representative of [(L4-H)PtCl] and [(L5-H)PtCl].
(b) Apectra of [(L1-H)PdCl]. (c) Spectra of [L5Re(CO)3Cl].
(d) Spectra of the polymeric compound [L6Re(CO)3Cl]. Solvent
457.9 nm are very similar to those at 413.1 and 444.3 nm, peaks are marked by asterisks.
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Phosphazene Polymers
respectively, and have therefore been omitted for clarity. and 1548 cm–1 (comparable to the bands at 1042 and
The spectrum of [(L1-H)PtCl] acquired at 350.7 nm shows 1540 cm–1, respectively, for the platinum spectra) are ob-
resonance-enhancement at 1358, 1483 and around served at an excitation wavelength of 350.7 nm, however,
1610 cm–1, which are identified as modes delocalised over they diminish rapidly at higher wavelengths. This is consis-
the entire OPhbpyPh unit with significant contributions tent with a blueshift of the MLCT band until it overlaps
from both Ph units. In the spectra acquired at 444.3 nm and with the πǞπ* transition caused by lower metal d-orbital
higher wavelengths, the peaks at 1042 and 1540 cm–1 show energies.
strong relative enhancement. This is consistent with the
The spectra of the rhenium compound [L5Re(CO)3Cl]
probing of two different electronic states and these peaks are different to those of the platinum and palladium com-
are associated with an MLCT excited state due to their pounds due to two-coordinate binding of Re to L5 com-
localisation on the bpy portion of the ligand (an example pared with three-coordinate binding of L5, L4 or L1 to the
is shown in Figure 6, a). The spectra acquired at 406.7 and other metals. The resonance Raman spectra generated with
413.1 nm are intermediate between the higher- and lower- 350.7 nm excitation shows a number of bands similar to
energy spectra. The relative intensities of the solvent bands [Re(bpy)(CO)3Cl], but in addition new or significantly
are greater because this wavelength region corresponds to shifted features are observed at 1358, 1544 and 1609 cm–1.
a dip in the absorption spectrum between two peaks. The Analysis of these shows the involvement of 6-Ph or 4-PhO
spectrum of [(L1-H)PdCl] shows some similar peak fre- moieties in the normal modes, as shown in parts b and c of
quencies but different intensities compared with the plati- Figure 6. Also notable is the emergence of a peak at
num compounds. MLCT transition marker bands at 1051 1617 cm–1 at excitation wavelengths of 406.7 nm and longer,
which corresponds to somewhat more localised bpy vi-
brations. This, and the presence of a CϵO stretching-peak
at 2026 cm–1, which shows higher relative intensities in the
lower-energy spectra, supports the assignment of the ab-
sorption band at 394 nm as a MLCT transition.
The polymer spectra are very similar to their small-mole-
cule counterparts, showing peaks at the same wavenumbers
and with the same relative intensities, which suggests the
same state is probed in each case. Note that solvent peaks
appear more marked due to lower chromophore densities
compared with the monomers.
Transient Resonance Raman Spectroscopy
The use of transient resonance Raman spectroscopy en-
ables the direct observation of the excited state of a com-
pound. The sample is excited by using the leading edge of
a laser pulse and near-simultaneously probed by using the
trailing edge of the pulse. A number of excited-state species
have characteristic peaks, for example, bpy peaks can be
observed in the excited states of [Ru(bpy)3]2+ as well as
[Re(bpy)(CO)3Cl].[58] The spectra collected for compounds
[(L1-H)PtCl], [(L5-H)PtCl] and [(L4-H)PtCl] are very sim-
ilar and are represented by the spectrum of the latter in
Figure 7, which shows several excited-state features. Three
different pulse energies were used to monitor their growth
and a plot of the log of the peak intensity against the log
of power results in a line with a gradient of one. In a situa-
tion in which there is partial excited-state population, non-
linear behaviour is observed.[59] However, in this case, in
which the excited-state lifetime is long compared with the
laser pulse duration, saturation of the excited-state popula-
tion within the irradiated sample volume is observed. This
is consistent with the photon-to-molecule ratio, which is
around 30 for the highest pulse energy.[60] Excited-state fea-
Figure 6. Normal-mode diagrams depicting the vibrations of
(a) [(L1-H)PtCl] at 1540 cm–1, (b) [L5Re(CO)3Cl] at 1358 cm–1 and
tures are observed at 1042, 1465, 1547 and, after solvent-
subtraction, at 1171 cm–1. Some of these peaks appear at
frequencies similar to the stretching vibrations of the bpy·–
(c) [L5Re(CO)3Cl] at 1609 cm–1. The cyclotriphosphazene unit has
been omitted for clarity as no activity is observed in any other part
of the complex for this mode.
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E. W. Ainscough, A. M. Brodie, K. C. Gordon et al.
FULL PAPER
obtained from Merck and [Re(CO)5Cl] was obtained from the Pres-
sure Chemical Co. (Pittsburgh). (Pentaphenoxy)[4-(6-phenyl-2,2Ј-
bipyridin-4-yl)phenoxy]cyclotriphosphazene (L1),[29] 4-(4-hydroxy-
phenyl)-6-phenyl-2,2Ј-bipyridine (HOPhbpyPh),[61] [(L-H)PtCl] (L
radical anion observed in the excited-states of [Ru-
(bpy)3]2+ and [Re(bpy)(CO)3Cl].[58] However, assignment of
these peaks to bpy·– is precluded by the absence of several
characteristic bands, most notably a strong feature nor-
mally observed at 1283 cm–1. As a result of the tridentate
nature of the ligand this is not surprising and we assign the
excited-state features to a OPhbpyPh·– state.
=
HOPhbpyPh),[7]
[Pt(PhCN)2Cl2],[62]
[Pd(PhCN)2Cl2],[63]
N3P3(OPh)5Cl (OPh = phenoxy),[64] N3P3(biph)2Cl2 (biph = 2,2Ј-
oxybiphenyl),[65] N3P3(tBubiph)2Cl2 (tBubiph = 4,4Ј-di-tert-butyl-
2,2Ј-oxybiphenyl),[31] and (NPCl2)n
were prepared according to
[22]
literature procedures.
1H NMR spectra were recorded at 162 MHz and 31P{1H} NMR
spectra at 400 MHz with a Bruker Advance 400 spectrometer. Elec-
trospray mass spectra were obtained from CH3CN solutions with a
Micromass ZMD spectrometer run in the positive ion mode. Listed
peaks correspond to the most abundant isotopomer; assignments
were made by a comparison of observed and simulated spectra. IR
spectra were recorded as KBr discs with a Perkin–Elmer FT-IR
Paragon 1000 spectrometer and electronic absorption spectra were
recorded with a Shimadzu UV-160A spectrometer. Glass transition
temperatures were measured with a TA Instruments Q10 differen-
tial scanning calorimetry apparatus at a heating rate of 10 °C/min
and with a sample size of around 10 mg. Gel permeation chromato-
grams were obtained by using a Hewlett–Packard HP 1100 gel per-
meation chromatograph equipped with two Phenomenex Phenogel
linear 10 columns and a Hewlett–Packard 1047A refractive index
detector. The samples were eluted at 1.0 mL/min with a 10 mm
solution of tetra-n-butylammonium nitrate in THF and the elution
times were calibrated with polystyrene standards. Microanalyses
were performed by the Campbell Microanalytical Laboratory, Uni-
versity of Otago.
Figure 7. Transient resonance Raman spectra of [(L4-H)PtCl] at a
number of pulse energies. The inset shows the growth of the peak
at 1547 cm–1 with respect to pulse power.
FT-Raman spectra were acquired by using a Bruker Equinox 55
interferometer coupled with a FRA-106 Raman module and a
DT418T liquid-nitrogen cooled Germanium detector. A 1064 nm
Nd:YAG laser operating at 450 mW was used as the source. The
samples were pressed into KBr disks. Resonance Raman spectra
were recorded in 10–3 mol/L CH2Cl2 solutions using a set-up pre-
viously described.[48,66] In short, the excitation beam and collection
Conclusions
Ground- and excited-state studies have been carried out
on discrete and polymeric phosphazene compounds. UV/
Vis and resonance Raman analyses show high-energy πǞπ* lens are in a 135° backscattering arrangement. Scattered photons
were focused on the entrance slit of an Acton SpectraPro500i spec-
trograph with a 1200 grooves/mm grating, which disperses the radi-
ation in a horizontal plane on a Princeton Instruments Spec10 li-
quid-nitrogen-cooled CCD detector. A Coherent Innova I-302
krypton ion laser was used to provide excitation wavelengths (λex)
of 350.7, 406.7 and 413.1 nm, a solid-state CrystaLaser for
444.3 nm and a Melles Griot OmNihrome argon-ion laser for
457.9, 488.0 and 514.5 nm. Notch filters matched to these wave-
lengths were used to remove the laser excitation line. Transient reso-
nance Raman signals were acquired by using a single pulse of a
transitions at around 330 nm located in the bipyridyl-based
portion of the ligand and lower-energy MLCT transitions
for the platinum and rhenium complexes. There is little de-
viation from analogous compounds lacking the phosphaz-
ene substituents. Transient resonance Raman spectra of the
platinum complexes show excited-state features that are dis-
tinct from the radical anion of bipyridine. Furthermore, we
have shown that the cyclotriphosphazene complexes are ap-
propriate for modelling the behaviour of the polyphosphaz-
enes as there is little deviation in the photophysics between Brilliant (Quantel) Nd:YAG pulse laser operating at λex = 354.7 nm
to excite and probe the sample. A similar set-up but with a
300 grooves/mm grating was used to perform continuous-emission
spectroscopy at λex = 350.7 nm. Lifetime measurements were ob-
tained by excitation using the Brilliant laser described above. The
emission transients were recorded by a Hamamatsu H5783-04 pho-
tomultiplier at 580, 620, 660 and 700 nm and read out on a TDS
3032B (Tektronix) digital oscilloscope. The errors were estimated
by using the standard deviation between each wavelength. Typi-
cally, the natural logarithm of the data could be fit linearly with
R2 values greater than 0.95.
the two classes of compounds. The findings suggest that
material and photophysical properties of polyphosphazenes
can be effectively decoupled from one another; that is, inde-
pendent control is possible. By extension, it should be pos-
sible to incorporate other properties such as catalysis while
retaining control over parameters such as Tg, solubility and
chemical stability.
Experimental Section
Ligand Synthesis
General: Analytical-grade solvents were used as received with the
exception of tetrahydrofuran (THF), which was distilled from so-
dium/benzophenone. Tetrabutylammonium bromide (TBAB) was
N3P3(biph)2(OPhbpyPh)2 (L2): A mixture of HOPhbpyPh (325 mg,
1.0 mmol) and NaH (40 mg of a 60% dispersion in oil) in THF
(30 mL) was stirred at room temperature over 1 h. P3N3(biph)2Cl2
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Phosphazene Polymers
(288 mg, 0.5 mmol) and TBAB (30 mg) were added and the mixture
was heated at reflux overnight. The THF was removed in a rotary
evaporator, the residue extracted with CH2Cl2 and the extract fil-
tered through Celite. Chromatography on silica using MeOH (0–
2%) in CH2Cl2 as eluent yielded the product as a white powder,
which was recrystallised from CH2Cl2/hexane and dried under vac-
Complex Synthesis
[(L1-H)PdCl]: A solution of L1 (92 mg, 0.1 mmol) and [Pd(PhCN)2-
Cl2] (38 mg, 0.1 mmol) in MeOH/benzene (1:1, 15 mL) was heated
at reflux overnight. The solution was taken to dryness in a rotary
evaporator to give a yellow oil, which formed a yellow powder
when triturated with MeOH. The powder was recrystallised from
1
uum; yield 361 mg (63%). H NMR (CDCl3): δ = 8.74–8.64 (m, 6
1
CH2Cl2/hexane and dried under vacuum at 75 °C; yield 50 mg. H
H), 8.19–8.16 (m, 4 H), 7.99 (s, 2 H), 7.56–7.36 (m, 20 H), 7.13–
NMR (CDCl3): δ = 8.61 (m, 1 H), 7.99 (m, 1 H), 7.90 (m, 1 H),
7.66 (s, 1 H), 7.62 (m, 1 H), 7.55 (m, 2 H), 7.40 (s, 1 H), 7.35 (m,
1 H), 7.28–7.11 (m, 18 H), 7.01–7.03 (m, 4 H), 7.03–6.88 (m, 8
H) ppm. 31P{1H} NMR (CDCl3): δ = 9.6–9.0 (m, 3 P) ppm. IR:
7.11 (m, 4 H) ppm. 31P{1H} NMR (CDCl3): δ = 25.43 (d, JPP
=
93 Hz, 2 P), 9.66 (t, JPP = 91 Hz, 1 P) ppm. IR: ν
= 1230 (s),
˜
max
1173 (vs) cm–1. MS (ES): m/z = 1150 [L2 + H]+. C68H46N7O6P3
(1150.06): calcd. C 71.02, H 4.03, N 8.53; found C 70.79, H 4.22,
N 8.56.
ν
=
1242 (s), 1203 (vs), 1175 (vs), 1160 (vs) cm–1.
˜
max
C52H39ClN5O6P3Pd (1064.69): calcd. C 58.66, H 3.69, N 6.58;
found C 58.55, H 3.70, N 6.51.
N3P3(tBubiph)2(OPhbpyPh)2 (L3):
A mixture of HOPhbpyPh
(162 mg, 0.5 mmol) and NaH (20 mg of a 60% dispersion in oil,
0.5 mmol NaH) in THF (30 mL) was stirred at room temperature
over 1 h. P3N3(tBubiph)2Cl2 (198 mg, 0.25 mmol) and TBAB
(30 mg) were added and the mixture was heated at reflux overnight.
The THF was removed in a rotary evaporator, the residue extracted
with CH2Cl2 and the extract filtered through Celite. Chromatog-
raphy on silica using MeOH (0–2%) in CH2Cl2 as eluent yielded
the product as a white powder, which was recrystallised from
[(L1-H)PtCl]: A solution of L1 (125 mg, 1.4 mmol) and [Pt(PhCN)2-
Cl2] (64 mg, 1.4 mmol) in MeOH/benzene (1:1, 15 mL) was heated
at reflux overnight. The solution was taken to dryness in a rotary
evaporator to give a yellow oil. Vapour diffusion of pentane into a
solution of the oil in CHCl3 gave the complex as an orange precipi-
tate, which was dried under vacuum at 75 °C; yield 100 mg. 1H
NMR (CDCl3): δ = 8.79 (m, 1 H), 7.97–7.85 (m, 2 H), 7.64–7.47
(m, 4 H), 7.40 (m, 1 H), 7.31–7.10 (m, 19 H), 7.09–7.04 (m, 4 H),
7.03–6.95 (m, 4 H), 6.94–6.90 (m, 4 H) ppm. 31P{1H} NMR
1
CH2Cl2/hexane and dried under vacuum; yield 270 mg (79%). H
NMR (CDCl3): δ = 8.72–8.64 (m, 6 H), 8.19 (m, 4 H), 8.00 (m, 2
H), 7.90–7.82 (m, 6 H), 7.56 (m, 4 H), 7.51 (m, 4 H), 7.44 (m, 6
H), 7.38 (m, 4 H), 7.32 (m, 2 H), 7.03 (m, 4 H), 1.32 (s, 36 H) ppm.
31P{1H} NMR (CDCl3): δ = 25.4 (d, JPP = 92 Hz, 2 P), 10.0 (t, JPP
(CDCl ): δ = 8.9–8.4 (m, 3 P) ppm. IR: ν
= 1234 (s), 1202 (vs),
˜
3
max
1193 (vs), 1174 (vs), 1160 (vs) cm–1. C52H39ClN5O6P3Pt (1153.35):
calcd. C 54.15, H 3.41, N 6.07; found C 53.85, H 3.50, N 5.98.
= 1230 (s), 1201 (vs), 1184 (vs) cm–1.
[(L2-H)(PdCl)2]:
A
mixture of L2 (75 mg, 0.65 mmol) and
= 92 Hz, 1 P) ppm. IR: ν
˜
max
MS (ES): m/z = 1375 [L3 + H]+. C84H78N7O6P3 (1374.48): calcd.
[Pd(PhCN)2Cl2] (50 mg, 1.31 mmol) in MeOH/benzene (1:1,
15 mL) was heated at reflux overnight. A yellow precipitate formed
that was collected by filtration, washed with CH2Cl2 and Et2O,
recrystallised from DMSO and dried under vacuum at 75 °C; yield
C 73.40, H 5.72, N 7.13; found C 73.12, H 5.91, N 7.13.
N3P3(biph)2(OPhbpyPh)Cl (L4):
A mixture of HOPhbpyPh
(243 mg, 0.75 mmol) and NaH (20 mg of a 60% dispersion in oil,
0.5 mmol NaH) in THF (35 mL) was stirred at room temperature
over 1 h. P3N3(biph)2Cl2 (473 mg, 0.83 mmol) and TBAB (20 mg)
were added and the mixture was heated at reflux over 5 h. The
THF was removed in a rotary evaporator, the residue extracted
with CH2Cl2 and the extract filtered through Celite. Chromatog-
raphy on silica using MeOH (0–2%) in CH2Cl2 as eluent yielded
the product as a white solid, which was dried under vacuum at
1
60 mg. H NMR ([D6]DMSO): δ = 8.66 (m, 2 H), 8.57–8.51 (m, 4
H), 8.32–8.25 (m, 6 H), 8.24–8.17 (m, 2 H), 7.76 (m, 2 H), 7.71 (m,
2 H), 7.65 (m, 4 H), 7.57 (m, 4 H), 7.51 (m, 4 H), 7.43 (m, 6 H),
7.22 (m, 4 H), 7.01 (m, 4 H) ppm. 31P{1H} NMR ([D6]DMSO): δ
= 25.3 (d, JPP = 92 Hz, 2 P), 9.8 (t, JPP = 92 Hz, 1 P) ppm. IR:
ν
= 1230 (s), 1169 (vs) cm–1. C68H44Cl2N7O6P3Pd2 (1431.79):
˜
max
calcd. C 57.04, H 3.10, N 6.85; found C 56.77, H 3.30, N 6.63.
1
[(L3-H)(PdCl)2]·0.5DMSO: A mixture of L3 (69 mg, 0.05 mmol)
and [Pd(PhCN)2Cl2] (38 mg, 0.1 mmol) in MeOH/benzene (1:1,
15 mL) was heated at reflux overnight. A yellow precipitate formed
that was collected by filtration and washed with Et2O. Purification
was achieved by vapour diffusion of MeOH into a DMSO solution
75 °C; yield 580 mg (89%). H NMR (CDCl3): δ = 8.70–8.64 (m,
2 H), 8.61 (m, 1 H), 8.18 (m, 2 H), 7.93 (m, 1 H), 7.88–7.80 (m, 3
H), 7.55–7.48 (m, 8 H), 7.48–7.23 (m, 12 H), 7.24 (m, 2 H) ppm.
31P{1H} NMR (CDCl ): δ = 22.70 (s, 3 P) ppm. IR: ν
= 1232
˜
3
max
(s), 1176 (vs) cm–1. MS (ES): m/z = 862 [L + H]+. C46H31ClN5O5P3
(862.14): calcd. C 64.08, H 3.62, N 8.12; found C 64.18, H 3.87, N
7.95.
1
of the precipitate, which was dried under vacuum. H NMR ([D6]
DMSO): δ = 8.75 (m, 2 H), 8.68–8.62 (m, 4 H), 8.42–8.26 (m, 8
H), 7.86 (m, 2 H), 7.81 (m, 2 H), 7.65–7.60 (m, 8 H), 7.57–7.52 (m,
6 H), 7.18–7.07 (m, 8 H), 1.34 (s, 36 H) ppm. 31P{1H} NMR ([D6]-
DMSO): δ = 25.07 (d, JPP = 93 Hz, 2 P), 9.97 (t, JPP = 93 Hz, 1
N3P3(biph)2(OPhbpyPh)(OPh) (L5): To
a solution of phenol
(33 mg, 0.35 mmol) in THF (20 mL), NaH (15 mg of a 60% disper-
sion in oil, 0.35 mmol NaH) was added and the mixture was stirred
over 0.5 h. L4 (300 mg, 0.35 mmol) and TBAB (10 mg) were added
and the mixture was heated at reflux overnight. The THF was re-
moved in a rotary evaporator, the residue extracted with CH2Cl2
and the extract filtered through Celite. Chromatography on silica
using CH2Cl2/MeOH (0–2%) as eluent gave a white powder that
was recrystallised from CH2Cl2/hexane and dried under vacuum at
P) ppm. IR: ν
= 1230 (s), 1181 (vs) cm–1. C85H79Cl2N7-
˜
max
O7.5P3Pd2S0.5 (1734.34): calcd. C 60.17, H 4.66, N 5.78; found C
60.08, H 4.66, N 5.88.
[(L4-H)PtCl]: A mixture of [(L-H)PtCl] (L = HOPhbpyPh) (55 mg,
0.1 mmol), N3P3(biph)2Cl2 (57 mg, 0.1 mmol) and Cs2CO3
(300 mg, 0.9 mmol) in acetone was stirred at reflux overnight. The
reaction mixture was taken to dryness in a rotary evaporator, the
residue extracted with CH2Cl2 and then filtered through Celite. Ad-
dition of hexane to the filtrate caused an orange complex to pre-
1
75 °C; yield 248 mg (78%). H NMR (CDCl3): δ = 8.71–8.62 (m,
3 H), 8.18 (m, 2 H), 7.98–7.95 (m, 1 H), 7.89–7.82 (m, 3 H), 7.58–
7.23 (m, 24 H), 7.13–7.01 (m, 2 H), 7.03 (m, 2 H) ppm. 31P{1H}
NMR (CDCl ): δ = 25.5 (m, 2 P), 9.7 (m, 1 P) ppm. IR: ν
=
cipitate that was collected by filtration and dried under vacuum;
˜
3
max
1230 (s), 1175 (vs) cm–1. MS (ES): m/z = 920 [L5 + H]+. yield 55 mg. H NMR (CDCl3): δ = 8.80 (m, 1 H), 7.90 (m, 2 H),
1
C52H36N5O6P3 (919.79): calcd. C 67.90, H 3.94, N 7.61; found C
68.51, H 4.18, N 7.76.
7.72 (m, 2 H), 7.62–7.47 (m, 12 H), 7.45–7.32 (m, 10 H), 7.20 (m,
1 H), 7.02 (m, 1 H), 7.00 (m, 1 H) ppm. IR: ν
= 1231 (s), 1174
˜
max
Eur. J. Inorg. Chem. 2011, 3691–3704
© 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjic.org 3701

E. W. Ainscough, A. M. Brodie, K. C. Gordon et al.
(vs) cm–1. C46H30Cl2N5O5P3Pt (1091.67): calcd. C 50.61, H 2.77, N water (ϫ2) and EtOH (ϫ3) were performed with the THF solution
FULL PAPER
6.42; found C 50.26, H 2.84, N 6.31.
being filtered before the final EtOH precipitation. The recovered
polymer was dried under vacuum; yield 700 mg. Mw = 598000. PDI
= 1.97. Tg = 83 °C. 31P{1H} NMR (CDCl3): δ = –18.5 (s), –19 (br.
sh) ppm. C22.40H25.72Cl0.06N1.50O1.94P (380.12): calcd. C 70.78, H
6.82, N 5.53, Cl 0.56 (for x = 0.06); found C 68.94, H 6.93, N 5.53,
Cl 0.55.
[(L5-H)PtCl]: A mixture of L5 (92 mg, 0.1 mmol) and [Pt(PhCN)2-
Cl2] (47 mg, 0.1 mmol) in MeOH/benzene (1:1, 15 mL) was heated
at reflux overnight. An orange precipitate formed that was col-
lected by filtration, washed with Et2O and dried under vacuum at
75 °C; yield 47 mg. The filtrate was taken to dryness, redissolved
in MeOH/benzene (1:1, 15 mL) and heated for a further 2 d at re-
flux to yield a second crop of the complex (30 mg). 1H NMR
(CDCl3): δ = 8.74 (m, 1 H), 7.88–7.80 (m, 2 H), 7.71 (m, 2 H),
7.58–7.36 (m, 17 H), 7.36–7.26 (m, 7 H), 7.23 (m, 2 H), 7.15 (m, 1
H), 7.07 (m, 2 H), 7.03–7.68 (m, 2 H) ppm. 31P{1H} NMR
(CDCl3): δ = 25.60 (d, JPP = 92 Hz, 2 P), 9.76 (m, 1 P) ppm. IR:
[L6PtCl]: [Pt(PhCN)2Cl2] (31 mg, 0.66 mmol) was added to a solu-
tion containing L6 (100 mg, 0.26 mmol) in THF/toluene (1:1,
40 mL) and the solution was heated at reflux over 5 h, stirred at
room temperature overnight and then heated at reflux for a further
5 h. The solution was filtered and concentrated to dryness in a
rotary evaporator. The residue was washed thoroughly with ethanol
and dried under vacuum at 40 °C; yield 90 mg. Mw = 346000. PDI
= 2.42. Tg = 87 °C. 31P{1H} NMR (CDCl3): δ = –17.8 (s) ppm.
C22.40H25.47Cl0.31N1.50O1.94PPt0.25 (437.50): calcd. C 61.46, H 5.88,
N 4.80, Cl 2.52; found C 61.95, H 6.07, N 4.75, Cl 2.98.
ν
= 1230 (s), 1176 (vs). C52H35ClN5O6P3Pt (1149.32): calcd. C
˜
max
54.34, H 3.07, N 6.09; found C 54.46, H 3.17, N 6.14.
[L5Re(CO)3Cl]: A mixture of L5 (50 mg, 0.54 mmol) and [Re(CO)5-
Cl] (20 mg, 0.55 mmol) in toluene was heated at reflux over 5 h.
The solution was filtered while hot and after standing for 3 d a
yellow precipitate developed that was collected by filtration,
washed with Et2O and dried under vacuum; yield 60 mg. 1H NMR
(CDCl3): δ = 9.09 (m, 1 H), 8.68–8.61 (m, 2 H), 8.22 (m, 1 H), 8.13
(m, 2 H), 7.98 (m, 1 H), 7.74–7.68 (m, 2 H), 7.66–7.54 (m, 11 H),
7.53–7.36 (m, 10 H), 7.29 (m, 1 H), 7.24–7.15 (m, 3 H), 7.11 (m, 2
H) ppm. 31P{1H} NMR (CDCl3): δ = 25.38 (d, JPP = 97 Hz, 2 P),
[L6Re(CO)3Cl]: [Re(CO)5Cl] was added to a solution containing L6
(100 mg, 0.26 mmol) in THF (30 mL) and the solution was heated
at reflux over 5 h. The solution was filtered and concentrated to
dryness in a rotary evaporator. The residue was washed thoroughly
with ethanol and dried under vacuum; yield 80 mg. Mw = 691000.
PDI = 2.75. Tg = 120 °C. 31P{1H} NMR (CDCl3): δ = –18.6
(s) ppm. IR: ν
= 2023 (vs), 1922 (vs), 1890 (vs), 1509 (vs), 1214
˜
max
10.54 (m, 1 P) ppm. IR: νmax = 2023 (vs), 1922 (vs), 1890 (vs), 1231
(br. Vs), 1171 (vs) cm–1. C23.15H25.72Cl0.31N1.5O2.75PRe0.25 (456.54):
calcd. C 60.84, H 5.63, N 4.59, Cl 2.41; found C 61.34, H 5.98, N
4.63, Cl 1.99.
˜
(s), 1200 (s), 1171 (vs) cm–1. C55H36ClN5O9P3Re (1225.48): calcd.
C 53.90, H 2.96, N 5.71; found C 54.78, H 3.08, N 5.57.
Polymer Synthesis
Crystallography: The X-ray data were collected with a Siemens P4
four circle diffractometer using a Siemens SMART 1 K CCD area
detector. The crystals were mounted in an inert oil, transferred into
the cold gas stream of the detector and irradiated with graphite-
monochromated Mo-Kα (λ = 0.71073 Å) X-rays. The data were col-
lected by using the SMART program and processed with SAINT[67]
to apply Lorentzian and polarisation corrections to the diffraction
spots (three-dimensionally integrated). The crystal data are given
in Table 6. The structures were solved by direct methods and re-
fined by using the SHELXTL program.[68] For the solution of
L2·4H2O, the electron density (316 e– per cell) of the occupationally
{[NP(OtBuPh)2]0.75–x[NP(OtBuPh)(OPhbpyPh)]0.25[NP(OtBuPh)-
Cl]x}n (L6): Cs2CO3 (7 g, 20 mmol) and HOPhbpyPh (420 mg,
1.2 mmol) were added to a solution containing (NPCl2)n (580 mg,
5 mmol) in THF (150 mL) and the mixture was heated at reflux
over 24 h. tBuPhOH (1.7 g, 11.3 mmol) was added and the mixture
was heated at reflux for a further 24 h and then TBAB (0.1 g) was
added and the heating continued for 7 d. The mixture was concen-
trated in a rotary evaporator and the crude polymer precipitated
on addition of the concentrated mixture to water (1 L). Further
precipitation of concentrated THF solutions of the polymer in
Table 6. Selected crystallographic data for the compounds.
L2·4H2O
[(L1-H)PdCl]
[(L3-H)(PdCl)2]·3EtOH·6DMF
Empirical formula
M [g/mol]
Crystal system
Space group
a [Å]
b [Å]
c [Å]
α [°]
β [°]
γ [°]
Z
C68H54N7O10P3
1222.09
monoclinic
C2/c
38.2128(7)
11.4682(1)
30.5730(5)
90
C52H39ClN5O6P3Pd
1064.64
C108H136Cl2N13O15P3Pd2
2232.91
monoclinic
P21/c
14.5806(3)
23.7124(2)
28.5845(6)
90
98.004(1)
90
4
triclinic
¯
P1
9.5812(1)
11.8367(2)
22.0207(3)
81.585(1)
80.197(1)
68.383(1)
2
108.071(1)
90
8
T [K]
84(2)
12737.2(3)
1.275
1.58
51.5
84(2)
2278.27(5)
1.552
6.31
50.7
84(2)
9786.6(3)
1.515
5.47
51.36
Volume [Å3]
ρcalcd. [g/cm]
μ(Mo-Kα) [mm–1]
2θmax [°]
R(int)
0.0792
12065 / 333 / 867
0.0722
0.1969
0.960
0
0.0833
18455 / 312 / 1064
0.062
0.1664
0.911
Data / restraints / parameters
R1 [IϾ2σ(I)]
wR2 (all data)
GOF on F2
8274 / 48 / 613
0.0506
0.0970
1.102
3702
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© 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Inorg. Chem. 2011, 3691–3704

Phosphazene Polymers
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and positionally disordered water molecules was removed by using
PLATON/SQUEEZE[69] and 2481.6.0 Å3 was left accessible by the
void. Similar treatment was used for the solvent molecules in [(L3-
H)(PdCl)2]·3EtOH·6DMF for which 1278 e– per cell were removed
and 3160.7 Å3 was left accessible by the void.
CCDC-816708 (for L2·4H2O), -816709 (for [(L1-H)PdCl]) and
-816710 (for [(L3-H)(PdCl)2]·3EtOH·6DMF) contain the supple-
mentary crystallographic data for this paper. These data can be
obtained free of charge from The Cambridge Crystallographic
Data Centre via www.ccdc.cam.ac.uk/data_request/cif.
Supporting Information (see also the footnote on the first page of
this article): Calculated bond lengths and angles for [(L1-H)PdCl]
and TD-DFT data for selected complexes.
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Received: March 31, 2011
Published Online: August 2, 2011
3704
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Eur. J. Inorg. Chem. 2011, 3691–3704