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Mixed-Metal Triple-Decker Sandwich Complexes with the PorphyrinPhthalocyaninePorphyrin Ligand System.

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Mixed-Metal Triple-Decker Sandwich Complexes
with the Porphyrin/Phthalocyanine/Porphyrin
Ligand System**
Porphyrin and porphyrin-phthalocyanine double-decker
sandwich complexes [M(p),] and [M(p)(pc)] can be expanded to
symmetric and asymmetric triple-decker sandwich complexes
of the form [M,(P),1, [M,(P),(PC)l. and [M,(PC),(P)l (M =
trivalent metal ion; p = porphyrin dianion, pc = phthaiocyanine dianion) .[I -41 The electronic structures of these tripledecker molecules have been probed by means of the electrochemical, magnetic, and spectroscopic properties of their neutral
and one-electron oxidized and reduced states. UV/Vis and electrochemical studies and magnetic susceptibility measurements indicate that upon oxidation of the [(tpp)M(pc)M(tpp)] (tpp =
tetraphenylporphyrin dianion) complexes in which no Ce"' center
is present (M = La"', Gd"'), the phthalocyanine dianion is preferentially oxidized to the radical m o n ~ a n i o n . lIn~ ~contrast, magnetic studies and X-ray photoelectron spectroscopy show that in
[(tpp)Ce(pc)Ce(tpp)], one Ce"' center is oxidized to Ce'v.[4bl
We have now synthesized and characterized the following
mixed-metal complexes: [(tpp)M(pc)M'(tpp)] (I(M,M')), containing no oxidizable metal (M = La, M' = Y) or one oxidizable metal (M = Ce, M = Gd, Lu, U), and [(tpp)Ce(pc)Gd(oep)] (2(Ce,Gd), oep = octaethylporphyrin dianion). The
complex 2(Ce,Gd) is the first heteronuclear triple-decker sandwich complex with mixed ligands that has been analyzed by a
crystal structure determination. The structural formulas of the
ligands and a diagrammatic representation of the triple-decker
complex is shown in Scheme 1 . Electrochemical studies of these
i 1 1
tPP
PC
P = tPP
2(Ce, Gd), p = oep
P
Scheme 1. Structural formulas of the p and pc Iigands and a schematic representation of the triple-decker complexes 1 and 2
Ldboratoire de Cristdllochimie et de Chimie Structurale (UA 424)
Instttut Le Bel. Universite LOUIS
Pasteur
4. rue Blaise Pascal. F-67070 Strdsbours (France)
Fax: Int. code +(88)415363
['*I
We thank Professor Jack FaJeT of the Department of Applied Science.
Brookhaven National Laboratory, Upton. NY (USA), for valuable discussions and helpful comments and Prof. D r Roger Guilard. Universltk de Bourgogne (France). for a sample of octaethylporphyrin. This work was supported
by the Centre National de la Recherche Scientifique ( U A 424).
mixed-metal sandwich complexes lead to two different linear
correlations of the first oxidation potentials with the mean ionic
radii of the metals ([ri(M) +rj(M')]/2) that depend on the presence or absence of an oxidizable Ce"' ion.
The synthesis of the heteroleptic, heteronuclear complexes
l(M,M') is described in the experimental procedure. However,
all attempts to grow suitable Crystals of these complexes for
X-ray crystal structure analysis failed. Instead we therefore synthesized the Ce"'/Gd"' derivative with tetraphenylporphyrin,
phthalocyanine, and octaethylporphyrin as ligands. This compound yielded crystals of composition 2(Ce,Gd).2 C,H,CI ,(61
which contain discrete molecules of 2(Ce,Gd) (Fig. I).''] The
triple-decker molecules do not exhibit any bonding interactions
with one another nor with the chlorobenzene molecules of solvation. As shown in Figure 1, both the Ce and Gd atoms are
octacoordinated. The outer oep and central pc rings are rotated
by an angle of 44.8(4)" relative to their eclipsed orientation.
Consequently, the coordination polyhedron of the Gd atom is a
slightly distorted square antiprism. In contrast, the outer tpp
and central pc rings are almost eclipsed, the rotation angle being
only S . O ( l ) O . Therefore, the coordination polyhedron of the Ce"'
ion is a slightly distorted cube. The displacements of the
metals relative to the four pyrrole-nitrogen and isoindolenitrogen mean planes of the macrocycles are as follows:
Ce-tpp =1.330(4), Ce-pc =1.987(4), Gd-pc =1.775(4), and
Gd-oep = 1.190(4) A. The outer tetraphenylporphyrin and octaethylporphyrin rings adopt conformations that are domed
towards the Gd and Ce
The phthalocyanine ring is
also domed, with the result that the mean plane of its four
isoindole-nitrogens lies closer to the Gd cation than the mean
plane through the inner 24 atoms of the ring framework.[*' This
particular conformation of the pc ring arises probably both
because the ionic radius of Gd"' is smaller than that of Ce"' and
because JL-TI interactions between the oep and pc are stronger
than those between the tpp and pc rings. It had been previously
noticed that the n-T interactions in [Zr(oep),] were stronger
than those in [Zr(tpp),] .I9The UV/Vis spectra of all the complexes l(M,M') (M = La.
M' = Y; M = Ce, M' = Gd, Eu, or Y) and 2(Ce,Gd) obtained
in solution are very similar to each other (see Experimental
Procedure) and to the spectra of triple-decker systems with two
identical metals l(M.M) (M = La. Ce. Pr, Nd, Eu, Gd).[4b1
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They are also similar to those displayed by thin films of l(Ce,Ce)
obtained by sublimation under vacuum.['21These spectral properties thus confirm that the triple-decker sandwich structures,
observed in the solid state for 2(Ce,Gd) and l(Ce,Ce),I4"l are
retained in solution for both series of complexes I(M,M') and
l(M,M). The redox behavior of the mixed-metal complexes
l(M.M') was determined by cyclic voltammetry (CH,CI,, 0.1 M
NBu,PF,,). The cyclic voltammograms of these species parallel
those of the systems with two identical metals.[4b)All the complexes belonging to the two series l(M,M') and l(M,M) undergo
three reversible oxidations and two reversible reductions. Moreover, as shown in Figure 2a and 2b, the first oxidation potentials
1(Ce. Y). yield 96 mg (70%); correct C.H,N elemental anal>sis; MS (FAB'): m / z
(Yo) =I966 (100) [Mi]; UVIVis (CH,CI,) i,,,, (Ige) = 350 15.5). 415 ( 5 6). 424
(5.6).488 (5.3).558 (5.l), 607 (5.2).
](La,Y). yield 94 mg (69%); correct C , H , N elemental analysis; MS (FAB'): m/z
(%) =1965 (100) [M']; UV'Vis (CH,CI,) i,,, (lgc) = 350 (5.5). 414 (5.6).424
(5.6).487 (5.3).558 (5.2).607 (5.3);' H N M R (300 MHL. CDCI3. 25 C. TMS):
6 =10.3(d.4H).9.48(m.XH),8.44(rn.8H).8
.35(t.4H).7.75(t.4H).7.71 (s.8H).
7.51 (t.4H).7.37(t.4H).7.11(t.4H).6.94(s.8H).6.84(t.4H).6.57(d.4H).630
(d. 4 H ) . 5.48 (d. 4 H ) .
Received. October 16, 1995
Revised version- January 26. 1996 [Z 8476 IE]
German version: A n p w . Chem 1996. 108. 942-944
Keywords: lanthanide compounds
phyrinoids sandwich complexes
-
phthalocyanines
.
por-
e
/
1
I
//
0 45 -i
,'
1L?(Ce, L L l )
105
I
4
115
1.2
I
04-1 1
r,lA
Fig 2 C orrelation between the first OXiddtion potentials €7 of the triple-decker
smdwiih iomplexe\ I ( M M') and I(M M ) and the mean ionic radii of M and M o r
the ionic r'ldii of M A cerium-containing complexes. cerium-free complexes
(q)of the mixed-metal complexes l(M,M')
examined to date
also show a linear correlation with the mean ionic radii of their
metal cations. However, as in the complexes containing two
identical metal cations l(M,M), the slopes of the correlations
depend on the presence o r absence of a Ce"' metal center. These
results thus confirm that the presence o r absence of an oxidizable Ce"' metal ion controls whether the first oxidation occurs
at the central atom o r the ligand.[4h.51
E.qcperinimfal Procedure
I(M.M') and Z(Gd.C'e): A solution of the metal acetylacetonate [M'(acac),.nH,O]
and the inetal-free poi-phyrin H i p (H,tpp or H,oep) (about 0.10 mmol) in 1.2.4trichlorobenzene was heated at reflux in a three-neck flask for four hours under
argon. After cooling. ii solid sample (about 0.07mmol) of a heteroleptic sandwich
complex [(tpp)M(pc)J(M = La. Ce) was added. and the resulting mixture was
heated at reflux for another eight hours under argon. After cooling. a crude solid
was precipitated b) addition of pentane. This solid was then extracted several times
with dichloroiiieth:iiie. 'The extracts were combined. and the resulting solution was
coriccntratcd under vacuum and then chromatographed on a silica gel column
(3'18c m ) Elution with toluene yielded successively some porphyrin H,p
and the olive green triple-decker complex [(tpp)M(pc)M'(tpp)] I(M.M') o r
[(tpp)Cc(pc)(;d(oey))Z(Ce.Gd). which were precipitated by addition of pentane
I(C'e. G d ) - yield 112 ing (79%). correct C.H,N elemental analysis; MS (FAB').
ni'r ( % ) = 2034 (100) [ M '1 . U V Y i s (CHZCI,) i
,
,
[nm]
, (Igi:) = 354 (5.4).418
(5 6). 4Y0 ( 5 2 ) . 55.: (5.1). 605 (5 1)
Z(C'e. G d ) : yield I 1 0 ins (81'50). correct C.H.N elemental analysis: MS (FAB'):
n i , z ( ' % ) = 1954(100)[;t4'1. UV~Vis(CH,CI,)i.,,,[nm](lgc) = 351 (5.4).395(5.3).
410 (5.4).465 (4.X).516(5.2).595 (4.8).
Id 91 mg(04%). Correct C.H.Nelementalanalysis: MS(FAB+).n?:z
("A, I = 2052 ( l O O ) [ M '1: U V f V i s (CH2CI,) i.,,, [nm] (Igc) = 350(5.5).413 (5.6).424
(5.6). 4x9 (5.3).55X ( 5 1). 608 ( 5 2 ) .
[I] a ) J. W. Buchler. B. Scharbert. 1 Am. Chem Soc 1988. llO.4272-4276;b)J. W.
Buchler. H. G. Kapellmann. M. Knoff, K . L. Lay, S . Pfeifer. Z Nuturforsch.
5 1983. 38, 1339-1345: c) J. W.Buchler, P. Hammerschmitt, I. Kaufeld. J.
Loffler, Chem. Ber. 1991. 124. 2151-2159.
[2] D. Chabach, M. Tahiri. A. De Cian. J. Fischer, M. El Malouli-Bibout. R.
Weiss, J. Am. Cheni. Soc. 1995. 117, 8548-8556.
[3] a) I. W. Buchler. M. Knoff in 0,micuI Pvopwrrer und Srrui fiirp of Tetrupsrrok~s
(Eds.: G . Blauer . H. Sund), De Gruyter. Berlin. 1985. pp. 91 - 105; b) J. W.
Buchler, K. Elsdsser, M. Kihn-Botulinski, B. Scharbert, S.Tdnsil. ACS Svmp.
Ser. 1986. 321, 94-104; c) J. W. Buchler, A. De Cian. J Fischer. M. KihnBotuhnski. H. Paulus. R. Weiss. J A m . Chem Socc 1986. /Oh'. 3652- 3659;d)
J. W. Buchler, A. De Cian. J. Fischer. M. Kihn-Botulinski, R. Weiss. Inorg.
Chem. 1988.27,339- 345:e) J. W Buchler. M. Kihn-Botuhnski. J. Loffler. M.
Wicholas. !hid. 1989, 28, 3770-3772;f) J. W. Buchler, M Kihn-Botuhnski. J.
Loffler. B Scharbert. New J. Chem. 1992, 16, 545 -553.
[4] a) D. Chabach. M Lachkar. A. De Cian, J. Fischer. R. Weiss. New 1 Chm7.
1992. 16. 431 -433: b) D. Chabach, Doctoral Thesis. Universite Louis Pasteur
de Srrasbourg. January 1994.
[5] T. H . Tran-Thi, T. Mattioli. D. Chabach. A. De Cian, R.Weiss. 1 PI7j.s. Chenl.
1994, 34, 8279 -8288.
M =
[6] Crystal data for 2(Ce.Gd).2(C,HSCI): C,,,H,,N,,CeGd-2C,H,Cl.
2180 5. tric1inic.spacegroupPi.u =17.212(5),h =19.777(6),~=15.050(5) A.
3L = 91.10(2).
p =104.46(2),
= 89.6312)'.
v = 4959 x A'. i)ra,cd =
1.460
Z = 2. p(CuKz)= 36.18cm-' (graphite monochromator). A total of 10922 reflections were collected at -100 C with a Philips PW 1100/16
automatic diffractometer. The resulting data set was analyzed with the EnrdfNonius SDPjVAX package. The structure was solved with the heavy atom
method and refined to R ( F ) = 0.046 (Rw(F) = 0.074) using 8056 reflections
with I > 3u(1).Crystallographic data (excluding structure factors) for the structure reported in this paper have been deposited with the Cambridge Crystallographic Data Centre as supplementary publication no. CCDC-179.10. Copies
of the data can be obtained free of charge on application to The Director.
CCDC. 12 Union Road, Cambridge CB2 1EZ. UK (fax rnt. code +(1223)
336-033;e-mail: teched(17cherncrys.cam.ac.uk)
[7]ORTEP 11: C.K. Johnson, 1976. ORNL-5138.
[8] The separations between the mean planes through the coordinated nitrogen
atoms and the mean planes through the inner 24 atoms of the framework of the
oep. tpp. and pc rings are 0.208(4), 0.196(4), and 0.077(4)A. respectively.
[9] R D. Shannon. C. T. Prewitt. Acto Cr~sru[IogrSw/. 5 1969. 25, 828-829
[lo] a ) K. Kim. W. S. Lee. H. J. Kim, S. H.Cho, G. S . Girokaml, P. A. Gorlin, K. S.
Suslick, Inorg. Chem. 1991, 30, 2652-2656; b) J. W. Buchler. A. De Cian, J.
Fischer. P. Hammerschmitt, R. Weiss, Chem. Eer. 1991, 124. 1051 -1058.
[ I t ] 1.W. Buchler. A. De Cian. S . Elschner. J. Fischer. P. Hammerschmitt, R. Weiss,
Chem. E w . 1992, 125. 107-115.
[12] T Fournier. Docrorul Thesh, UniversitC de Paris 1X. 1994.
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