Switchable cycloplatinated ferrocenylamine derivatives of acridone, naphthalimide and anthraquinone

Article abstract of DOI:10.1016/S0020-1693(03)00152-X

Acridone, naphthalimide and anthraquinone derivatives of the cycloplatinated ferrocenylamine {Pt[(η⁵-CpFe(σ,η⁵-C₅H ₃CH₂NMe₂)](dmso)C≡C-} have been prepared and the X-ray structure for the anthraquinone derivative has been determined. Spectroelectrochemistry has been used to probe the ground and excited states of these molecules. Irrespective of whether the fluorophore is bound to the ethynylPt(II) link via a nodal nitrogen (acridone) or to the aromatic ring (naphthalimide and anthraquinone) fluorophore emission is quenched in the ground state and partially restored in the oxidised species. Low energy donor-acceptor charge-transfer bands of the oxidised compounds are characteristic.

Full text of DOI:10.1016/S0020-1693(03)00152-X

Inorganica Chimica Acta 352 (2003) 129Á135
/
www.elsevier.com/locate/ica
Switchable cycloplatinated ferrocenylamine derivatives of acridone,
naphthalimide and anthraquinone
Elise M. McGale, R. Eva Murray, C. John McAdam, Joy L. Morgan,
Brian H. Robinson *, Jim Simpson
Department of Chemistry, University of Otago, PO Box 56, Dunedin, New Zealand
Received 6 August 2002; accepted 30 September 2002
Dedicated in honor of Professor Martin A. Bennett
Abstract
Acridone, naphthalimide and anthraquinone derivatives of the cycloplatinated ferrocenylamine {Pt[(h5-CpFe(s,h5-
C5H3CH2NMe2)](dmso)Cꢀ
/
CÁ} have been prepared and the X-ray structure for the anthraquinone derivative has been determined.
/
Spectroelectrochemistry has been used to probe the ground and excited states of these molecules. Irrespective of whether the
fluorophore is bound to the ethynylPt(II) link via a nodal nitrogen (acridone) or to the aromatic ring (naphthalimide and
anthraquinone) fluorophore emission is quenched in the ground state and partially restored in the oxidised species. Low energy
donor-acceptor charge-transfer bands of the oxidised compounds are characteristic.
# 2003 Elsevier Science B.V. All rights reserved.
Keywords: Cycloplatination; Ferrocenylamine; Spectroelectrochemistry; Acridone; Naphthalimide; Anthraquinone
1. Introduction
function in a similar fashion. Targeted fluorophores for
the dyads were acridone, where 1 could be attached at
the nitrogen atom, N-methylnaphthalimide and anthra-
quinone, where 1 could be attached to the p-system.
Cycloplatinated ferrocenylamines 1 offer a redox
center which undergoes a reversible one-electron oxida-
tion to a stable cation [1]. The HOMO is essentially
centered on the ferrocenyl moiety and lowered in energy
relative to a non-cycloplatinated ferrocenylamine by the
donor Pt(II) substituent. Furthermore, there are rigid
ligand preferences in the trans PtÁ
/
N and trans PtÁL
/
positions for p-acceptors and s-donors, respectively [1Á
/
3]. As a consequence, this redox centre can be tuned by a
judicious choice of ligands coordinated to the platinu-
m(II) giving a potential range of 0.01 to ꢀ0.50 volts
/
against decamethylferrocene. The archetypal redox
centre [Fc]ꢀ/0 has been found to induce molecular
2. Experimental
switching in ferrocenylÁ
[4Á6]. We were, therefore, interested to see if emissive
assemblages where 1 was the redox center would also
/
ethynylÁ
/
fluorophore dyads
/
The compounds 10-(2-propynyl)-9-acridone [7], 2-
iodoacridone [8], 4-trimethylsilylethynyl-N-methyl-1,8-
naphthalimide [9], 1a [1] and 1c [3] were prepared by
literature procedures. 4-Ethynyl-N-methyl-1,8-naphtha-
limide was prepared in an analogous way to the 4-
ethynyl-1,8-naphthalimides reported previously [10].
* Corresponding author. Tel.: ꢀ
906.
E-mail address: brobinson@alkali.otago.ac.nz (B.H. Robinson).
/
63-3-4797 907; fax: ꢀ63-3-4797
/
0020-1693/03/$ - see front matter # 2003 Elsevier Science B.V. All rights reserved.
doi:10.1016/S0020-1693(03)00152-X

130
E.M. McGale et al. / Inorganica Chimica Acta 352 (2003) 129Á135
/
Microanalyses were carried out by the Campbell Micro-
analytical Laboratory, University of Otago. 1H and
195Pt NMR spectra were recorded on Varian Unity
Inova 300 and 500 MHz spectrometers, respectively, in
CDCl3 at 25 8C; d195Pt data are referenced to K2PtCl6.
Table 1
Crystallographic data for 5
Empirical formula
Formula weight
Crystal system
C31H29NO3SFePt
746.55
triclinic
¯
P1
Space group
Unit cell dimensions
IR and UVÁVis spectra were recorded on a Perkin-
/
Elmer spectrum BX FT-IR and a Varian Cary 500
scanning spectrophotometer, respectively. Electron im-
pact mass spectra were recorded on a Kratos MS80RFA
and electrospray mass spectra on a Shimadzu LCMS-
QP 8000 spectrometer. Cyclic and square wave voltam-
metry in CH2Cl2 were performed using a three-electrode
cell with a polished disk, Pt (2.27mm2) as the working
˚
a (A)
10.050(2)
12.616(3)
20.999(4)
94.04(3)
99.87(3)
93.04(3)
2610.8(9)
4
˚
b (A)
˚
c (A)
a (8)
b (8)
g (8)
3
V (A )
˚
Z
electrode; solutions were ꢀ
10ꢁ3 M in electroactive
/
Dcalc (Mg mꢁ3
m(Mo Ka) (mmꢁ1
F(000)
)
1.899
6.023
material and 0.10 M in supporting electrolyte (triply
recrystallised TBAPF6). Data was recorded on a Power-
lab/4sp computer-controlled potentiostat. Scan rates of
)
1464
168(2)
Temperature (K)
Crystal size (mm3)
u Range (8)
Total reflections
Independent reflections
Rint
0.34ꢃ/0.20ꢃ0.04
/
0.05Á
voltammetry and for Osteryoung square-wave voltam-
metry, square-wave step heights of 1Á5 mV, a square
amplitude of 15Á25 mV with a frequency of 30Á240 Hz.
/
1 V sꢁ1 were typically employed for cyclic
1.97Á26.54
/
11613
9232
/
0.0750
343
1.043
/
/
No. parameters
GoF (F2)
All potentials are referenced to decamethylferrocene;
E1/2 for sublimed ferrocene was 0.55 V. Infrared and
R1 [I ꢁ
wR2 (all data)
˚
Residuals (e A
/2s(I)]
R1ꢂ
wR2ꢂ
8.004 and ꢁ
/
0.1071
0.3398
4.556
UVÁVis OTTLE data were obtained from standard cells
/
/
ꢁ3
with platinum grid electrodes. Fluorescence measure-
ments were conducted on optically dilute samples
)
/
(absorbance B0.05) in spectroscopic grade solvents on
/
a Perkin-Elmer luminescence spectrometer LS50B. The
quantum yield was calculated by comparing the inte-
grated fluorescence spectra with a comparable com-
H). 195Pt NMR (CDCl3, ppm): ꢁ
Vis
(CH2Cl2, lmax, nm, o l molꢁ1cmꢁ1): 399 (923), 255
(4173). Eꢀ/0 (CH2Cl2, V): 0.27.
/
3755. IR (CH2Cl2,
cmꢁ1): n(CꢁO, CꢁN) 1632, 1601. n(CꢀC) 2114. UVÁ
/
pound, 4-piperidino-N-methyl-1,8-naphthalimide (ffꢂ
/
0.91).
2.1. Preparation of {Pt[(h5-CpFe(s,h5-
C5H3CH2NMe2)](dmso)[10-(2-propynyl)-9(10H)-
acridinone]}
2.2. Preparation of {Pt[(h5-CpFe(s,h5-
C5H3CH2NMe2)](PPh3)[10-(2-propynyl)-9(10H)-
acridinone]}
Compound 1a (0.120 g, 0.2 mmol) and 10-(2-propy-
nyl)-9(10H)-acridone (0.047 g, 0.2 mmol) were stirred
for 3 h at room temperature (r.t.) with CuI (0.0038 g,
0.02 mmol) in degassed piperidine (10 ml). The solvent
was removed in vacuo and the residue taken up in
CH2Cl2 the organic layer washed with water, dried over
MgSO4 and the solvent removed in vacuo. The residue
separated using column chromatography on alumina;
the first band eluted with ethylacetate gave 2 which was
recrystallised in CH2Cl2 layered with EtOH (0.084 g,
28%). Anal. Calc. for C31H32N2O2SFePt: C, 49.70; H,
Triphenylphosphine (0.013 g, 0.05 mmol) was added
to 2 (50 mg, 0.05 mmol) in CH2Cl2 (20 ml) and the
solution was stirred for 3 h at r.t. The solvent was
removed in vacuo and 3 recrystallised in CH2Cl2 layered
with EtOH. (39 mg, 83%). Anal. Calc. for C47H41N2OP-
FePt: C, 60.58; H, 4.44; N, 3.00. Found: C, 60.30; H,
4.55; N, 2.81%. 1H NMR (CDCl3, ppm): 2.88, 2.95 {2ꢃ
[s, 1H, ÁCH Á]}, 3.11, 3.35 {2ꢃ[d, 3H, Jꢂ3 Hz,
3JPtÁH CH3]}, 3.78 (s, 5H, h5-C5H5Fe),
12 Hz, NÁ
3.78 (m, 3H, h5-C5H3Fe), 4.02 (m, 3H, h5-C5H3Fe),
4.66 (d, 2H, Jꢂ2 Hz, ÁCH2), 7.21Á7.40 (m, 13H, PhÁ
H), 7.52Á7.59 (m, 2H, acridoneÁH), 7.63Á7.70 (m, 6H,
4ꢃacridoneÁH, 2ꢃPhÁH) 8.50 (dd, 2H, Jꢂ8, 2 Hz,
acridoneÁ 4232. IR
H). 195Pt NMR (CDCl3, ppm): Á
(CH2Cl2, cmꢁ1): nCꢁO, CꢁN, 1632, 1601; n(CꢀC) 2114.
UVÁ
Vis (CH2Cl2, lmax, nm, o l molꢁ1cmꢁ1): 403 (712),
383 (569), 256 (2970). Eꢀ/0 (CH2Cl2, V): 0.23.
/
/
/
/
/
ꢂ
/
/
1
4.31; N, 3.75. Found: C, 49.53; H, 4.74; N, 3.69%. H
[s, 3H, 3JPtÁH
ꢂ
/
18
/
/
/
/
NMR (CDCl3, ppm): 2.82, 3.16 {2ꢃ
Hz, NÁCH3]}, 3.37, 3.44 {2ꢃ[s, 3H, Pt satellites Jꢂ
Hz, SÁCH3]}, 3.73 (d, 2H, Jꢂ14 Hz, Á
5H, h5-C5H5Fe), 4.10 (d, 2H, Jꢂ2 Hz, h5-C5H3Fe),
4.30 (t, 1H, Jꢂ CH2Á
2 Hz, h5-C5H3Fe), 5.08 (s, 2H, Á
N), 7.32 (m, 2H, acridone-H), 7.76 (dd, 4H, Jꢂ5.4, 1
Hz, acridoneÁH), 8.57 (dt, 2H, Jꢂ8, 1 Hz, acridoneÁ
/
/
/
/
/
/
/
12
/
/
/
/
/
/
/
/
CH2), 4.06 (s,
/
/
/
/
/
/
/
/
/
/
/

E.M. McGale et al. / Inorganica Chimica Acta 352 (2003) 129Á
/
135
131
2.3. Preparation of {Pt[(h5-CpFe(s,h5-C5H3CH2-
NMe2)](dmso)[4-ethynyl-N-methyl-1,8-
naphthalimide]}
2.5. X-ray data collection, reduction and structure
solution for 5
Crystal data for 5 are given in Table 1. Recrystallisa-
tion from dichloromethane/ethyl acetate layered with
hexane, yielded dark brown plates one of which was
used for data collection. Data was collected at 168 K on
a Bruker SMART CCD diffractometer, processed using
XSCANS [11].
Analysis of the reflection data revealed substantial
twinning in the crystal. A unique cell was subsequently
found and the associated reflections chosen using the
program RLAT [12], these were used in the subsequent
solution and refinement process. The structure was
4-Ethynyl-N-methyl-1,8-naphthalimide (0.055 g, 0.23
mmol) and 1a (0.119 g, 0.22 mmol) were stirred in 20 ml
dried, degassed triethylamine with 5% CuI at r.t. for 24
h. The solvent was removed from the deep redÁbrown
/
reaction mixture under reduced pressure, the resulting
solid dissolved in CH2Cl2 and washed six times with 20
ml H2O to remove any remaining triethylamine. The
solution was then treated with MgSO4, filtered and the
solvent removed in vacuo. Recrystallisation from hot
methanol gave 4 as a dark purpleÁbrown crystalline
/
¯
solved in the non-centric space group P1 by Patterson
methods using SHELXS [13]. Early stages of the refine-
¯
ment indicated that the non-centric alternative P1
solid (0.11 g, 67%). Anal. Calc. for C30H32PtFeN2O3S:
C, 47.94; H, 4.29; N, 3.73; S, 4.27. Found: C, 47.53; H,
4.33; N, 3.77; S, 4.08%. EI MS: m/z 749 [M]ꢀ. 1H
3
NMR (CDCl3, ppm): 3.08 (s, 3H, JPtÁH
¯
would be more appropriate; conversion P1 and full-
ꢂ36 Hz,
/
matrix least-squares refinement using SHELXL-97 [14]
and TITAN2000 [15] revealed all atoms of the two unique
molecules in the triclinic unit cell. Pt, Fe and S atoms
were assigned anisotropic temperature factors and the H
atoms were included in calculated positions with iso-
tropic temperature factors 1.2 times that of Uiso of the
atoms to which they are bound. A number of high peaks
were found in the final difference map close to the heavy
atoms reflecting the lack of absorption corrections on
the data.
NCH3), 3.46 (s, 3H, NCH3), 3.55 (s, 3H, naphthÁ
NCH3), 3.70 (s, 3H, SCH3), 3.76 (s, 3H, SCH3), 3.88
(AB, 2H, JAB
13.8 Hz, NCH2), 4.16 (m, 5H, h5-
C5H5Fe), 4.19 (m, 2H, two of h5-C5H3Fe), 4.42 (m, 1H,
one of h5-C5H3Fe), 7.74 (m, 2H, naphth.), 8.47 [d (Jꢂ
7.8Hz), 1H, naphth.], 8.60 [d (Jꢂ7.2 Hz), 1H, naphth.],
8.78 [d (Jꢂ
7.5 Hz), 1H, naphth.]. 195Pt NMR (CDCl3,
ppm): ꢁ
3717. IR (CH2Cl2, cmꢁ1): nCꢀC 2083, nCꢁO
/
ꢂ
/
/
/
/
/
1694, 1656, nSꢁO 1128. UVÁVis (CH2Cl2; lmax, nm, o l
/
molꢁ1cmꢁ1): 250 (30,300), 284 (17,400), 350 (810), 408
(25,500). Eꢀ/0 (CH2Cl2, V): 0.22.
3. Results and discussion
2.4. Preparation of {Pt[(h5-CpFe(s,h5-
C5H3CH2NMe2)](dmso)[2-ethynyl-anthraquinone]}
Synthetic strategies for the preparation of 2Á
/
5 are
shown in Schemes 1Á3. The synthesis of the ynamine 2
/
was achieved via a CuI-catalysed reaction between 10-
(2-propynyl)-9-acridone and 1a (Scheme 2). This route,
rather than one between 1b and acridone, avoids the
problem of b-adduct formation which are the principal
products with ferrocenyl analogues [6]. Replacement of
2-Ethynyl-anthraquinone (0.112 g, 0.48 mmol) and 1a
(0.266 g, 0.48 mmol) were refluxed in dried, degassed
piperidine (10 ml) with 5% CuI for 5 h. The solvent was
removed under reduced pressure, and the resulting solid
was purified using column chromatography on alumina;
the first band eluted with ethylacetate gave 5 which was
recrystallised in CH2Cl2 layered with hexane (0.145 g,
40%). Anal. Calc. for C31H29FeNO3PtS: C, 49.87; H,
3.92; N, 1.88; S, 4.29. Found: C, 49.86; H, 3.92; N, 2.01;
the dmso ligand in the trans PtÁN position by the
/
stronger p-acceptor PPh3 gave 3. Only ynamine com-
plexes of acridone were accessible as attempts to prepare
a 2-ethynylacridone derivative via coupling reactions of
1b with 2-iodoacridone were unsuccessful. However,
Sonogashira coupling reactions were a convenient, high-
S, 3.96%. ES MS: m/z 746 [M]ꢀ (74%) 745 [Mꢁ
/
H]ꢀ
(100%). H NMR (CDCl3, ppm): 2.89 (s, 3H, JPtÁH
18 Hz, NCH3), 3.22 (s, 3H, 3JPtÁH
18 Hz, NCH3), 3.42
1
3
ꢂ
/
ꢂ
/
(s, 3H, SCH3), 3.49 (s, 3H, SCH3), 3.53 (m, 2H, NCH2),
4.15 (s, 5H, C5H5), 4.18 (m, 2H, two of h5-C5H3Fe),
4.43 (m, 1H, one of h5-C5H3Fe), 7.67 (dd, 1H, Jꢂ
/
8, 2
8, 2
Hz, anth.), 8.31 (m, 2H, anth.). 195Pt NMR (CDCl3,
ppm): ꢁ
3699. IR (CH2Cl2, cmꢁ1): nCꢀC 2094, nCꢁO
Hz, anth.), 7.80 (m, 2H, anth.), 8.19 (dd, 2H, Jꢂ
/
/
1673, nSꢁO 1131. UVÁVis (CH2Cl2; lmax, nm, o l
/
molꢁ1cmꢁ1): 305 (25,200), 403 (7000). Eꢀ/0 (CH2Cl2,
V): 0.30.
Scheme 1.

132
E.M. McGale et al. / Inorganica Chimica Acta 352 (2003) 129Á
/
135
Scheme 2.
yield synthetic route to complexes of naphthalimide 4
and anthraquinone 5 (Scheme 3).
3.1. Spectroelectrochemistry
Compounds 2Á5 display chemically reversible one-
/
All compounds were stable in air and soluble in
chlorinated solvents, acetone and alcohols. They were
fully characterised by elemental analysis, EI MS, 1H
NMR, 195Pt NMR and IR spectroscopy. The nPtCꢀC
energies were typical of a s,h1-acetylide group although
electron oxidation processes in their cyclic and square
wave voltammetry. The potentials (Table 1) are similar
to other cycloplatinated ferrocenylamines and the ob-
served oxidation step is assigned to the [‘Fc’]ꢀ/0 couple
{hereafter ‘Fc’ꢂ
Pt[(h5-CpFe(s,h5-C5H3CH2NMe2)]}.
/
dependent on the PtÁ
strong acceptors, naphthalimide and anthraquinone,
nCꢀC(4,5)ꢂ
2083 cmꢁ1 shifting to higher energy
nCꢀC(2)ꢂ
2112 cmꢁ1 for the weaker acceptor, an N-
/
Cꢀ
/
C terminal substituent. For the
The cathodic shift in the [‘Fc’]ꢀ/0 potential from
[1a]ꢀ/0 to [1c]ꢀ/0 is due3 to the acetylide anion being a
more effective p-donor than Clꢁ. This p-donor ability is
apparently ameliorated by the electron-acceptor acety-
lide substituents acridone or anthraquinone such that
[2]ꢀ/0 and [5]ꢀ/0 lie between [1a]ꢀ/0 and [1c]ꢀ/0. As a
caveat, the p-donor capability appears to be unaffected
by attachment of the electron-acceptor directly to the
‘aromatic’ ring system or as an ynamine. Nonetheless,
/
/
bound acridone. As has been noted elsewhere [3], nPtCꢀC
is insensitive to the orthogonal p-acceptor ligand and
nCꢀC
ꢂ
2112 cmꢁ1 for both 2 and 3. The n(CꢁO, CꢁN)
/
bands for the acridone and naphthalimide unit were
typical of the parent molecules showing that there was
little perturbation of their electronic structure by the
cycloplatinated ethynyl group. There was a small upfield
[4]ꢀ/0ꢂ[1c]ꢀ/0, that is, cathodic of [1a]ꢀ/0 even though
/
shift from d195Pt(1) at ꢁ
stronger electron acceptor and p-donor in the trans PtÁ
C position; d195Pt(2) ꢁ
3725, 5 ꢁ3717 (cf. ꢁ3700 for 1c
[3]). Replacement of dmso in the trans-PtÁN position by
large downfield shift to
4232 as expected.
/
3763 ppm, because of the
a naphthalimide is a strong electron acceptor. B3LYP
calculations [16] indicate that the similarity between 2
and 5 and their weaker p-donor capability relative to 4 is
a reflection of the poor p-orbital extension of the
acetylide ligand to the Pt(II) coordination centre in 2
and 5. The acetylide orbital profile for 4 is very similar
/
/
/
/
/
a
p-acceptor causes
195Pt(3)ꢂ
a
d
/
ꢁ
/
Scheme 3.

E.M. McGale et al. / Inorganica Chimica Acta 352 (2003) 129Á
/
135
133
to that in 1c. Substitution of the trans PtÁ
/
N ligand,
Table 2
Eꢀ/0 and electronic spectral data
dmso, in 2 by a good p-acceptor decreases the electron
density on ‘Fc’ with an anodic shift to 0.27V from 2 to 3,
in agreement with other cycloplatinated systems [2].
Compound Eꢀ/0
(V)
lmax (o1) neutral lmax (o1) oxidised CT
band
Compounds 2Á
reduction processes ꢁ
/
5 also show one-electron irreversible
1.00 V at potentials compar-
1a
1c
0.33
0.22
449 (2.4)
465 (3.4)
/
ꢁ
/
395 (1320), 480
(540)
396, 475
able to the reduction potentials of the parent fluoro-
phores. Radical anions of 2 and 4 were obtained by in
situ electroreduction in the ESR cavity and in both cases
the ESR parameters were the same as those for the
parent fluorophore anions [17] under the same condi-
tions. This clearly demonstrates that the LUMO in the
ground state is a fluorophore-based orbital.
2
3
4
5
0.27
0.23
0.22
0.30
378 (108), 398
(4.3)
768
836
773
768
384 (130), 401
(4.9)
401
350 (81.4), 408
(255)
411, 592
297, 395
305 (252), 403
(70)
Electronic spectra of 2Á
/
5 are given in Table 2. The
p* bands in neutral 2Á5 are
energies of the pÁp* or nÁ
/
/
/
In CH2Cl2 at 20 8C; E8 (V) (referenced against decamethylferrocene,
Pt, CV data, 200 mV sꢁ1); l (nm), o ꢃ10ꢁ2 l molꢁ1 cmꢁ1
relatively unperturbed from the parent ethynylfluoro-
phore. This supports the conclusion from the electro-
chemistry and IR data that there is little communication
between the Pt(II) unit and the fluorophore. In the
ground state the HOMO is essentially a ‘Fc’ orbital. ‘Fc’
compounds characteristically [1,2] have two transitions
/
.
although there appeared to be a small red shift.
However, the most important feature of the spectra of
ꢀ Á5ꢀ was the appearance of a broad low energy band
2
/
in the NIR around 800Á900 nm (Table 2, Fig. 1). This
/
band is absent in non-polyaromatic complexes of ‘Fc’ꢀ
but a similar type of transition has been seen in other
at 450Á
/
470 and B350 nm and the energy of these is
/
relatively invariant with the ligands around the Pt(II)
coordination sphere. With the acridone compounds,
oxidised ferrocenylethynylÁ
donors. These low energy bands in the electronic spectra
of 2ꢀ Á5ꢀ show negative solvatochromism, typical
/
dyads with polyaromatics as
these transitions are subsumed by the strong nÁp*
/
/
transitions of the fluorophore; in 4 the ‘ferrocenyl’
band is only seen as an ill-defined shoulder.
behaviour of charge-transfer transitions in which the
excited state is less polar than the ground state [18].
Consequently, these bands in the oxidised species can be
assigned to a donor-acceptor transition ‘Fc’ꢀ 1
R) from the HOMO of the fluorophore to an orbital
largely on the ‘Fc’ moiety.
Fluorescence is totally quenched in the ground state
5. Upon oxidation to 2ꢀ Á5ꢀ there was a red-shift
of the emission wavelength relative to the parent
Spectroelectrochemical oxidation of each compound
in-situ in OTTLE cells, or by chemical oxidation, caused
significant changes in the electronic spectra (Fig. 1). The
spectra generated had well-defined isosbestic points and
were reversible, indicating that the oxidised species is
reasonably stable in this timeframe. Oxidation consis-
/
(Cꢀ
/
CÁ
/
of 2Á
/
/
tently caused a blue shift of the pÁ
Because of overlapping bands in the 400Á
it is difficult to comment on changes to the ‘Fc’ bands
/
p* and nÁ
/
p* bands.
/
500 nm region
fluorophore and a slight enhancement of fluorescence.
Fig. 1. UVÁ
/
Vis spectral changes in an OTTLE cell during the oxidation of 2 in CH2Cl2ꢀ
/
0.1 mol lꢁ1 TBAP, cꢂ
/
1.0ꢃ
10ꢁ3 mol lꢁ1, Pt, 20 8C.
/

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E.M. McGale et al. / Inorganica Chimica Acta 352 (2003) 129Á135
/
Fig. 2. Perspective views of the two unique molecules of 5 showing the atom numbering schemes with thermal ellipsoids drawn at the 50%
probability level. For clarity only the first two atoms of consecutively numbered cyclopentadienyl rings are labelled. Molecule 1 of 5. (b) Molecule 2
of 5.
3.2. X-ray structure determination of 5
Table 3
˚
Selected bond lengths (A) and bond angles (8) for 5
The crystal comprises two unique molecules of 5 in
the triclinic unit cell. A perspective view of both
molecules of 5 is shown in Fig. 2 and defines the atom
numbering schemes. Differences in bond lengths and
angles between the discrete molecular units can be
ascribed to crystal packing effects. The quality of the
data obtained from the heavily twinned crystal (see
experimental) precludes detailed comparison of the
metrical data with the related molecules [Pt{(s,h5-
Molecule 1
Molecule 2
Bond lengths
Pt(1)Á/C(13)
2.04(3)
2.05(3)
1.17(4)
1.43(4)
2.194(7)
2.14(2)
1.47(3)
1.46(4)
1.43(4)
Pt(2)Á/C(23)
2.00(2)
2.02(3)
1.19(3)
1.45(3)
2.182(6)
2.12(2)
1.45(4)
1.47(4)
1.46(3)
Pt(1)Á/C(116)
Pt(2)Á/C(216)
C(116)Á/C(117)
C(216)Á/C(217)
C(117)Á/C(118)
C(217)Á/C(218)
Pt(1)Á
Pt(1)Á
N(1)Á
C(11)Á
C(12)Á
/
S(1)
Pt(2)Á
Pt(2)Á
N(2)Á
C(21)Á
C(22)Á
/
S(2)
/N(1)
/N(2)
/C(11)
/
C(21)
C5H3CH2NMe2)Fe(h5-C5H5)}(dmso)X, (Xꢂ
SiMe3,
Cꢀ
/
Á
/
Cꢀ
/
CÁ
/
/
C(12)
C(13)
/C(22)
C-(h5-C5H4)Fe(h5-C5H5),3 but the structure
/
/C(23)
Á
/
/
proposed for 5 is clearly confirmed from the crystal-
lographic data. Selected bond length and angle data are
given in Table 3 with data from molecule 1 used in the
following discussion. The coordination sphere of the
platinum atom comprises the S(1) atom of the S-bound
DMSO ligand trans to the amine N(1) atom of the
orthometallated ferrocenylamine ligand. The Pt-bound
C(13) atom of the substituted cyclopentadiene ring is
trans to the C(116) atom of the terminally bound 2-
anthraquinoneacetylide, which occupies the fourth co-
Bond angles
C(13)ÁPt(1)Á
C(116)Á
C(13)ÁPt(1)Á
C(116)Á
C(13)ÁPt(1)Á
N(1)ÁPt(1)Á
C(117)ÁC(116)Á
Pt(1)
/
/
N(1)
82.5(9) C(23)Á
90.8(9) C(216)Á
96.7(8) C(23)ÁPt(2)Á
89.7(8) C(216)Á
170.8(10) C(23)ÁPt(2)Á
176.7(6) N(2)ÁPt(2)Á
C(217)ÁC(216)Á
Pt(2)
/
Pt(2)Á
/
N(2)
83.0(9)
91.4(9)
94.5(7)
/
Pt(1)Á
/N(1)
/Pt(2)Á
/N(2)
/
/
S(1)
/
/
S(2)
/
Pt(1)Á
/S(1)
/Pt(2)Á
/S(2)
91.1(7)
172.3(10)
177.5(6)
/
/
C(116)
/
/
C(216)
/
/
S(1)
/
/
S(2)
/
/
169(3)
177(3)
/
/
172(2)
C(116)Á
/
C(117)Á
/
C(216)Á
/
C(217)Á
/
172(3)
C(118)
C(218)

E.M. McGale et al. / Inorganica Chimica Acta 352 (2003) 129Á
/
135
135
ordination site. The N(1) and C(13) atoms are the
donors in a five-membered chelate ring formed by the
orthometallated ferrocenylamine ligand. Some deviation
from the idealised square planar geometry about Pt is
apparent with deviations from the PtL4 ring plane
References
[1] (a) C.E.L. Headford, R. Mason, P.R. Ranatunge-Bandarage,
B.H. Robinson, J. Simpson, J. Chem. Soc., Chem. Commun.
(1990) 601;
(b) P.R.R. Ranatunge-Bandarage, B.H. Robinson, J. Simpson,
Organometallics 13 (1994) 500.
˚ ˚
ranging from ꢁ0.071(9) A, Pt(1) to 0.04(1) A, C(13).
/
The PtL4 ring plane is inclined at an angle of 8.4(8)8
to the plane of the cyclometallated cyclopentadienyl
ring, while the anthraquinone ring plane is approxi-
mately orthogonal to both the coordination plane of the
Pt atom, 76.8(8)8, and the cyclopentadienyl rings of the
ferrocenyl moiety, 80(1)o to C(12)Á Á ÁC(16) and 81(1)8 to
C(17)Á Á ÁC(111). The cyclopentadiene rings in the ferro-
cenyl moiety adopt an approximately eclipsed confor-
mation with the dihedral angle 3.7(8)8 between the ring
planes.
[2] (a) P.R.R. Ranatunge-Bandarage, S.M. Johnston, N.W. Duffy, J.
McAdam, B.H. Robinson, J. Simpson, Inorg. Chem. 13 (1994)
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(b) N.W. Duffy, M. Spescha, B.H. Robinson, J. Simpson,
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4. Conclusion
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(2003) 931.
[7] A.R. Katritzky, W.H. Ramer, J. Org. Chem. 50 (1985)
855.
An analysis of the electrochemical and spectral data
has enabled the HOMO and LUMO in these neutral
cycloplatinated molecules with organic fluorophores to
be defined; the HOMO is ‘Fc’ based whereas the LUMO
is entirely fluorophore-centred. In principle, the cyclo-
platinated ferrocenylamine moiety offers an alternative
to other organometallic species like ferrocene as a
functional redox switch. In this case the on/off cap-
ability is related to the existence of charge-transfer states
in the oxidised ferrocenium molecule and we have
shown that low energy electronic CT transitions are a
signature for this capability. But whether the acceptor
orbital is largely ferrocenyl in character or has signifi-
cant Pt(II) component is yet to be determined. Never-
theless, in comparison to analogous ferrocenyl
compounds [6] there is only weak redox-switching
capability.
[8] M. Vlassa, I.A. Silberg, R. Custelceanu, M. Culea, Synth.
Commun. 25 (1995) 3493.
[9] P. Nguyen, S. Todd, D. van den Biggelaar, N. Taylor, T. Marder,
F. Wittmann, R. Friend, Synlett (1994) 299.
[10] C.J. McAdam, B.H. Robinson, J. Simpson, Organometallics 19
(2000) 3644.
[11] XSCANS, Area Detector Control and Integration Software, Bruker
AXS, Madison WI, 1997.
[12] RLAT, Bruker AXS, Madison WI, 1997.
[13] G.M. Sheldrick, SHELXS-96, A Program for the Solution of
Crystal Structures from Diffraction Data, University of Gottin-
¨
gen, Gottingen, Germany, 1996.
¨
[14] G.M. Sheldrick, SHELXL-97, A Program for the Refinement
Crystal Structures, University of Gottingen, Gottingen, Germany,
¨ ¨
1997.
[15] K.A. Hunter and J. Simpson, TITAN2000, A Molecular Graphics
Program to Aid Structure Solution and Refinement with the
SHELX Suite of Programs, University of Otago, New Zealand,
1999.
[16] E.M. McGale, C.J. McAdam, unpublished work.
[17] (a) S. Niizuma, H. Kawata, Bull. Chem. Soc. Jpn. 66 (1993)
1627;
Acknowledgements
(b) P.H. Kasai, J. Am. Chem. Soc. 114 (1992) 2875.
[18] A. Klein, W. Kaim, Organometallics 14 (1995) 1176 (and
references therein).
We thank Dr. Amar Flood for some of the OTTLE
measurements.