Cyclometallated Rh(III) complexes based on 4,6-diphenylpyrimidine, with ethylenediamine, ortho-phenanthroline and 2,2'-bipyridyl

Full text of DOI:10.1134/S1070363209100284

ISSN 1070-3632, Russian Journal of General Chemistry, 2009, Vol. 79, No. 10, pp. 2272–2273. © Pleiades Publishing, Ltd., 2009.
Original Russian Text © E.V. Ivanova, K.P. Balashov, 2009, published in Zhurnal Obshchei Khimii, 2009, Vol. 79, No. 10, pp. 1749–1750.
LETTERS
TO THE EDITOR
Cyclometallated Rh(III) Complexes Based
on 4,6-Diphenylpyrimidine, with Ethylenediamine,
ortho-Phenanthroline and 2,2'-Bipyridyl
E. V. Ivanova and K. P. Balashov
Hertzen Russian State Pedagogical University, nab. r. Moiki 48, St. Petersburg, 191186 Russia
e-mail: balashevk@mail.ru
Received June 18, 2009
DOI: 10.1134/S1070363209100284
The specificity of the electronic structure of
complexes of cyclometalled platinum group metals
with heterocyclic ligands characterized by long-lived
excited electronic state and reversible nature of the
process of electroreduction determines their promising
application as components of optoelectronic devices
[1, 2]. It was shown earlier [3] that cyclometalled
Pt(II) and Pd(II) complexes with 4,6-diphenyl-
pyrimidine form a metal system with a spatial transfer
of photoexcitation energy between the peripheral and
bridging components in their structure.
is characterized by a low-frequency shift of (C=N)
stretching vibra-tions of the pyrimidine part of
cyclometallated ligand, and by typical [5,6] change of
in-plane bending (C–H) vibrations as a result of
metallation of the phenyl rings.
The UV spectrum of [Rh(Hdphpm)2 (N^N)]ClO4
complexes in the region of (λ < 330 nm) is charac-
terized besides the intraligand adsorption bands by the
presence of specific long-wave absorption band (λ =
390–410 nm) and vibration-structured phosphore-
scence (λ = 463–487 nm) as a result of the spin-
allowed and spin-restricted optical transition between
the orbitals localized on the metal complex fragment of
(Rh(Hdphpm)2). The availability in the compositions
of [Rh(Hdphpm)2phen]ClO4 and [Rh(Hdphpm)2bpy]
ClO4 of two cyclometallated and one chelating
heterocyclic ligands determines the presence of three
ligand-centered one-electron waves of reduction of the
complexes as a result of electron transfer on the
unoccupied π* orbitals of each ligand Substitution of
heterocyclic bpy and phen by aliphatic En leads to the
existence of two [Rh(Hdphpm)2En]ClO4 reduction
waves as a result of the electron transfer on the π*
orbitals of two cyclometallating ligands.
1
In this work we obtained and characterized by H
NMR, IR, electron absorption and emission spectro-
scopy, and voltammetry the complexes of the type
[Rh(Hdphpm)2(N^N)]ClO4 [Hdphpm is monodeproto-
nated form of 4,6-diphenylpyrimidine, (N^N)-chelating
ligands: ethylenediamine (En), ortho-phenanthroline
(phen) and 2,2'-bipyridyl (bpy)].
These complexes are stable both in solid state and
in solution in (CH3)2CHOH, CH3CN, (CH3)2SO. In the
1H NMR spectra of these complexes the proton
resonances are observed of both two magnetically
equivalent cyclometallating ligands Hdphpm-, and
chelating ligands (En, Bpy, Phen). The upfield shift of
the proton resonance of metallated phenyl ring of
Hphpm– in the ortho-position to the metal [Δδ 1.2 and
–0.9 ppm] as compared with the non coordunated
ligand indicates the cis-configuration of the metallated
phenyl rings of two 4,6-diphenylpyrimidine ligands in
the inner sphere of the complexes, resulting in the
anisotropic action of the circular current of one
metallated ring on the chemical shift of protons of
another ring [4]. IR spectrum of [Rh(Hdphpm)2En]ClO4
4,6-Diphenylpyrimidine was obtained along the
procedure in [7]. The Rh(III) complexes were obtained
according to the general methodology that included the
formation of [Rh(Hdphpm)2(μ-Cl)]2 precipitate by
refluxing 1 equivalent of RhCl3·3H2O with 8 equi-
valents of 4,6-diphenylpyrimidine in 2-methoxyetanol
followed by the substitution of chloride ligands by
ethylenediamine, 1,10-phenanthroline or 2,2'-bipyridyl
by the reaction of the suspension in methanol of
2272

CYCLOMETALLATED Rh(III) COMPLEXES
2273
4
bridging Rh(III) chloride complex with the chelating
liands. Precipitation of the complexes from the
methanol solution was performed by adding NaClO4 to
the reaction mixture. The resulting precipitate
containing complex was filtered, washed with cold
methanol, then with ether, and dried in air.
(3JHH 5.0, 8.0, JHH 1.5; 2H), 7.22 d.d.d (3JHH 7.6, 7.4;
4JHH 1.3; 2H), 7.12 d.d.d (3JHH 7.6, 7.4; JHH 1.3; 2H),
4
6.62 d (3JHH 7.7; 2H). Electron absorption spectrum
(CH3CN), λmax, nm (ε×10–3, l mol–1 cm–1) nm: 279
(30.1), 297 sh (26.4), 309 (25.7), 331 (19.2), 395 (6.4).
Parameters of phosphorescence [77 K, (CHON(CH3)2:
CH3C6H5, 1:1), λmax., nm, (τ, ms)]: 464, 494, 524 (14).
Reduction voltammogram [CHON(CH3)2, relatively to
the Fc+/Fc redox system], V: E1/2 –1.69, –1.92, Epeak
–2.10.
Bis[(4-phenyl-3-ido)(6-phenylpyrimidino)]etylene-
diaminorhodium(III) perchlorate [Rh(Hdphpm)2En]·
1
ClO4. Yield 65%. H NMR spectrum (CD3CN), δ,
ppm (J, Hz): 9.23 s (2H), 8.53 d (3JHH 1.1; 2H), 8.41 d
4
1
(3JHH 7.5; 4H), 8.09 d.d (3JHH 7.8, JHH 1.3; 2H), 7.67
The H NMR spectra were registered on a JNM-
ECX400A instrument at 293 K in CD3CN. Electron
absorption spectra were taken on
4
m (6Н), 7.05 d.d.d (3JHH 7.8, 7.4; JHH 1.2; 2H), 6.95
4
d.d.d (3JHH 7.3, 7.4, JHH 1.14; 2H), 6.48 d (3JHH 7.7;
a
SF-2000
2H), 3.49 d (3JHH 9.2; 2H), 3.03 m (2H), 2.88 d (3JHH
9.1; 2H), 2.77 d (3JHH 4.3; 2H). Parameters of the IR
spectrum (KBr), ν, cm–1: 693 and 747 (C6H5), 740 (C6
H4), 1585 (C=N). The electron absorption spectra
(CH3CN), λmax., nm (ε×10–3, l mol–1 cm–1): 278 (15),
324 (10.1), 410 (3.2). Parameters of phosphorescence
[77 K, CHON(CH3)2: CH3C6H5, 1:1], λmax., nm (τ, ms):
487, 505, 559 (13). Reduction voltammogram [(CHON
(CH3)2, relatively to the Fc+/Fc redox system], V:
E1/2 –1.90, –2.10
spectrophotometer from CH3CN solutions. IR spectra
were recorded from KBr pellets on a Prestige-21
Shimadzu IR spectrometer. Luminescent studies were
conducted on KSVU-1 setup with a pulse laser
photoexcitation (LGI-21, l 337 nm, τ 10 ns) at 77 K
from glassy matrices (CH3)2CHOH: CH3C6H5 (1:1)
[8]. Voltammograms were registered on EAC-1B setup
at 293 K in a three-electrode cell with the separated
space of working (Pt), auxiliary (C) and reference (Ag)
electrodes in the presence of 0.1 M [N(C4H9) ]BF4
4
from solutions in CHON(CH3)2 [9]. Potentials are
given relatively to the redox system ferrocenyl-
ferrocene (Fc+/Fc).
Bis[(4-phenyl-3-ido)(6-phenylpyrimidine)](1,10-
phenanthroline)rhodium(III) perchlorate [Rh
1
(Hdphpm)2phen]ClO4. Yield 67%. H NMR spec-
trum (CD3CN), δ, ppm (J, Hz): 8.73 d.d (3JHH 8.3, 4JHH
1.5; 2H), 8.49 d (3JHH 1.1; 2H), 8.38 d.d (3JHH 4.9, 4JHH
1.4; 2H), 8.24 s (2H), 8.04 s (2H), 8.24 d.d (3JHH 7.8,
REFERENCES
1. Zhou, G-J., Wang, X-Z., Wong, W-Y., Yu, X-M.,
Kwok, H-S., and Lin, Z., J. Organomet. Chem., 2007,
vol. 692, no. 16, p. 3461.
4
4JHH 1.4; 4H), 8.18 d.d (3JHH 8.2, JHH 1.5; 2H), 7.86
d.d (3JHH 4.9, 8.3; 2H), 7.56 m (6Н), 7.26 d.d.d (3JHH
4
4
7.7, 7.4; JHH 1.4; 2H), 7.17 d.d.d (3JHH 7.6, 7.4; JHH
1.4; 2H), 6.72 d (3JHH 7.4; 2H). The electron
absorption spectra (CH3CN), λmax, nm (ε × 10–3,
l mol–1 cm–1): 222 (54.9), 272 (66.2), 330 (31.3), 393
(10.5). Parameters of phosphorescence [77 K, CHON
(CH3)2: CH3C6H5, 1:1], λmax., nm, (τ, ms): 463, 494,
524 (14). Reduction voltammogram [(CHON(CH3)2,
relatively to the Fc+/Fc redox system], V: E1/2 –1.68, –
1.94, Epeak –2.16.
2. Kim, S-Y., Kim, J-H., Ha, Y., Lee, S-H., Seo, J-H., and
Kim, Y-K., Current Appl. Phys., 2007, vol. 7, no. 4, p. 380.
3. Ivanova, E.V., Puzyk, M.V., and Balashev, K.P., Optika
i Spektr., 2009, vol. 106, no. 3, p. 409.
4. Steel, P.J., J. Organometal. Chem., 1991, vol. 408, no. 3,
p. 395.
5. Caygill, G.B. and Steel, P.J., J. Organomet. Chem.,
1987, vol. 7, no. 1, p.115.
6. Caygill, G.B., Hartsorn, R.M., and Steel, P.J., J. Orga-
nomet. Chem., 1990, vol. 382, no. 3, p. 455.
Bis[(4-phenyl-3-ido)(6-phenylpyrimidine)](2,2'-
bipyridyl)rhodium(III) perchlorate [Rh(Hdphpm)2bpy]·
7. Brederick, H., Gompper, R., and Morlock, G., Chem.
Ber., 1957, vol. 90, p. 942.
8. Vasil’ev, V.V., Balashev, K.P., and Shagisultanova, G.A.,
Opt. i Spektr., 1983, vol. 54, no. 5, p. 876.
9. Kotlyar, V.S. and Balashev, K.P., Elektrokhimiya, 1996,
1
ClO4. Yield 65%. H NMR spectrum (CD3CN), δ,
ppm (J, Hz): 8.52 d (3JHH 8.2; 2H), 8.49 d (3JHH 1.0;
2H), 8.24 d.d (3JHH 7.8, 4JHH 1.5; 4H), 8.21 s (2H), 8.20
4
d.d (3JHH 7.7; 2H), 8.17 d.d.d (3JHH 8.0, 7.8, JHH 1.5;
2H), 8.05 d (3JHH 4.8; 2H), 7.59 m (6Н), 7.54 d.d.d
vol. 32, no. 11, p. 1358.
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