analyses were obtained for C, H and N {trans-[PtCl
18Cl Pt. Found (Calc.) C, 19.1 (19.27); H, 2.9 (2.91); N, 13.5
13.49)%}.
b) To a solution of trans-[PtCl
]11 (0.3 mmol) in water (10 ml)
4 3 2
(NH ) ]·2Hmura,
C
10
H
4 6 4
N O
(
(
4 3 2
(NH )
was added Hmura (0.6 mmol); the mixture was briefly heated until all solid
material had dissolved. Slow evaporation at room temp. gave crystals of
N(3b)
4 3 2
trans-[PtCl (NH ) ]·2Hmura (identified by IR spectroscopy) in 93%
yield.
O(4b′)
‡ Crystal data: C10
P4/n, a = b = 15.496(2), c = 7.580(2) Å, U = 1820.2(6) Å , Z = 4,
4 4 6
H18Cl O N Pt; M = 623.19, tetragonal, space group
3
O(4a′)
2
3
21
F(000) = 1192; D = 2.274 Mg m ; m(Mo-Ka) = 8.326 mm yellow
c
N(3aa)
cube; size, 0.15 3 0.15 3 0.15 mm. Data collection and processing: Enraf-
Nonius-Mach3 diffractometer (graphite-monochromated Mo-Ka radia-
tion), T = 293(2) K; w–2q scans; q range 2.63–24.97°; index ranges 213
Na(1)
N(3a)
O(4aa)
@
h @ 18, 213 @ k @ 18, 0 @ l @ 9; 3280 reflections measured, 1600
> 4s(F )]. Structure
O(4ba)
independent (Rint = 0.0259); 1356 observed [F
solution and refinement: Patterson syntheses (SHELXS-86 ), full-matrix
o
o
12
N(3ba)
2
13
least squares on F (SHELXL-93 ); hydrogen atoms found in difference
Fourier synthesis and refined isotropically, all other atoms anisotropic; 140
parameters refined; empirical absorption correction (y-scans); min., max.
1 2
corrections 0.5515, 0.9972; R = 0.0306; wR = 0.0496 (all data); max.,
2
3
min. residual electron density 0.596, 20.764 e Å . Atomic coordinates,
bond length and angles, and thermal parameters have been deposited at the
Cambridge Crystallographic Data Centre (CCDC). Any request to the
CCDC for this material should quote the full literature citation and the
reference number 182/505.
4 4
Fig. 4 View of quartet III as found in [Na(Hmura) ][AuCl ]. The four
Hmura bases are coplanar with Na(1). The protons at the N(3) sites are at
calculated positions. Selected interatomic distances (Å): O(4aA)···N(3b)
2.83(2), O(4aA)···O(4bA) 3.28(2), O(4aA)···Na(1) 2.336(7), O(4bA)···Na(1)
2.301(8).
4 3 2
§ The IR spectrum of trans-[PtCl (NH ) ]·2Hmura (KBr pellet; Bruker
14
FTIR spectrometer IFS 28) and that of Hmura differ, as expected, but the
former is not a simple superposition of spectra of Hmura and trans-
1
5
21
[
PtCl
e.g. Hmura: 870s (br), 805s, 757s, 722m; trans-[PtCl
trans-[PtCl (NH ]·2Hmura: 823s, 782s, 758m, 738w, 719m. Similarly, in
4
(NH
3
)
2
]. This is particularly well seen in the 900–700 cm region,
The difference in hydrogen-bond formation between Hmura
7
4
(NH ]: 878m (br);
3 2
)
[
pairwise N(3)H···O(4) hydrogen bonds of 2.814(2) Å] and that
4
3 2
)
observed in [PtCl
4 3 2
(NH ) ]·2Hmura is also reflected in differ-
the Raman spectra (solid state; Jobin Yvon, T 64000; Spectra Physics laser,
l = 514.5 nm) both the intense n(Pt–Cl) and n(Pt–N) modes15 of trans-
PtCl (NH ) ] and the characteristic Hmura ring modes have undergone
4 3 2
shifts as compared to the pure components.
ences in the IR spectra.§
In the course of this work, it occurred to us that we had,
[
8
without recognizing it then, prepared a planar uracil quartet III
already two years prior to the first report of U
4
in a RNA
tetraplex.2 In [Na(Hmura)
][AuCl ] (Fig. 4) the four O(4)
4 4
8
References
oxygens form a square of 3.28 Å and four hydrogen bonds,
1
J. R. Williamson, Annu. Rev. Biophys. Biomol. Struct., 1994, 23, 703
and references therein.
C. Cheong and P. B. Moore, Biochemistry, 1992, 31, 8406.
G. Gupta, A. E. Garcia, Q. Guo, M. Lu and N. R. Kallenbach,
Biochemistry, 1993, 32, 7098.
4 M. H. Sarma, J. Luo, K. Umemoto, R.-d. Yuan and R. H. Sarma,
J. Biomol. Struct., Dyn., 1992, 9, 1131.
5 P. Scheibel, A. Hoser, W. Prandl, G. Heger, W. Paulus and P. Schweiss,
J. Phys. Condens. Mater., 1994, 11, 10989; R. Essmann, G. Kreiner,
A. Niemann, D. Rechenbach, A. Schmiedering, T. Sichla, U. Zachwieja
and H. Jacobs, Z. Anorg. Allg. Chem., 1996, 622, 1161.
From a strictly geometrical point of view, I could be considered a model
of a T quartet. If atoms are interchanged, e.g. N(1)CH is considered a
C(5)CH group of T, O(2) a O(4) in T etc., the resulting entity would
correspond to T with the methyl groups pointing to the center of the
quartet and no hydrogen bonds between the four thymines; cf. also
discussions in ref. 3.
+
between N(3) and O(4) sites of ca. 2.83 Å, with Na in the
center.
2
3
In summary, the apparent ease of quartet formation of Hmura
+
in the presence of suitable partners (Pt–NH
suggests that U
than generally anticipated. Stabilization may not only be
brought about by a G support and/or alkali-metal ion binding,
but also by additional hydrogen bonding. The NH
3
groups, Na )
4
structures in RNA may be more readily formed
4
+
3
group of
lysine, which is ubiquitous in many nucleic acid binding
proteins, could be a candidate in this respect. Finally,
PtCl (NH ) ]·2Hmura represents, to the best of our knowledge,
4 3 2
6
[
3
the first example of a neutral metal ammine complex interacting
with a nucleobase in a specific manner. Hydrogen bonding of
3
4
3
+
cationic metal complexes, e.g. of [Co(NH
3
)
6
]
with DNA is
9
known to have dramatic effects on the DNA stucture.
We thank the Deutsche Forschungsgemeinschaft (DFG) and
the Fonds der Chemischen Industrie (FCI) for financial support
of this work.
7 W. Micklitz, B. Lippert, H. Sch o¨ llhorn and U. Thewalt, J. Heterocycl.
Chem., 1989, 26, 1499.
B. Fischer, H. Preut, B. Lippert, H. Sch o¨ llhorn and U. Thewalt,
Polyhedron, 1990, 9, 2199.
8
9
R. V. Gessner, G. J. Quigley, A. H.-J. Wang, G. A. Van der Marel,
J. H. van Boom and A. Rich, Biochemistry, 1985, 24, 237.
Footnotes
*
†
E-mail: lippert@pop.uni-dortmund.de
trans-[PtCl (NH ]·2Hmura was obtained in two ways: (a) trans-
(0.65 mmol; obtained from trans-
and 2–3 equiv. of Hmura in a similar way to the
10 D. Neugebauer and B. Lippert, J. Am. Chem. Soc., 1982, 104, 6596.
11 G. B. Kauffman and D. O. Cowan, Inorg. Synth., 1963, 7, 237.
12 G. M. Sheldrick, Acta Crystallogr., Sect. A, 1990, 46, 467.
13 G. M. Sheldrick, SHELXL-93, Program for crystal structure refinement,
University of G o¨ ttingen, 1993.
4
3 2
)
2
]
3
[
[
Pt(NH
Pt(NH
3
3
)
)
2
(mura-N )
(H O) ][NO ]
2
2
0
2
3 2
1
cis-isomer) was suspended in water (10 ml) at 40 °C; 4 m HCl (4 ml) was
added dropwise until all the solid was dissolved. Heating was continued for
14 H. Susi and J. S. Ard, Spectrochim. Acta Part A, 1974, 30, 1843.
15 D. W. James and M. J. Nolan, J. Raman Spectrosc., 1973, 1, 271.
1
h and a pale yellow precipitate {trans-[PtCl
spectroscopy} was removed by filtration. Slow evaporation of the filtrate at
room temp. gave crystals of trans-[PtCl (NH ]·2Hmura in 12% yield.
Oxidation has apparently been brought about by air. Satisfactory elemental
2 3 2
(NH ) ] identified by IR
3
)
2
Received in Basel, Switzerland, 24th March 1997; Com.
7/02035J
4
1316
Chem. Commun., 1997