Rhenium(I) and technetium(I) complexes of a novel pyridyltriazole-based ligand containing an arylpiperazine pharmacophore: Synthesis, crystal structures, computational studies and radiochemistry

Article abstract of DOI:10.1016/j.inoche.2010.11.002

The preparation of two M(CO)₃ complexes (M = Re and ^99mTc) from a novel pyridyltriazole-based ligand 2 bearing the bioactive (2-methoxyphenyl)piperazine pharmacophore are described. Spectral data, X-ray structure and DFT calculations

Full text of DOI:10.1016/j.inoche.2010.11.002

Inorganic Chemistry Communications 14 (2011) 238–242
Contents lists available at ScienceDirect
Inorganic Chemistry Communications
journal homepage: www.elsevier.com/locate/inoche
Rhenium(I) and technetium(I) complexes of a novel pyridyltriazole-based ligand
containing an arylpiperazine pharmacophore: Synthesis, crystal structures,
computational studies and radiochemistry
Achour Seridi a,b,1, Mariusz Wolff c,1, Alexandre Boulay a,b, Nathalie Saffon d, Yvon Coulais e, Claude Picard a,b
,
a,b,
Barbara Machura c, , Eric Benoist
⁎
⁎
a
CNRS, Laboratoire de Synthèse et Physico-Chimie de Molécules d'Intérêt Biologique, SPCMIB, UMR 5068, 118, Route de Narbonne, F-31062 Toulouse Cedex 9, France
Université de Toulouse, UPS, Laboratoire de Synthèse et Physico-Chimie de Molécules d'Intérêt Biologique, SPCMIB, UMR 5068, 118, Route de Narbonne, F-31062 Toulouse Cedex 9, France
Department of Crystallography, Institute of Chemistry, University of Silesia, 9th Szkolna St., 40-006 Katowice, Poland
Université de Toulouse, UPS and CNRS, Structure Fédérative Toulousaine en Chimie Moléculaire SFTCM FR2599, 118, Route de Narbonne, F-31062 Toulouse Cedex 9, France
Laboratoire “Traceurs et traitement de l'image”, Faculté de Médecine de Purpan, EA 3033, 133, Route de Narbonne, 31062 Toulouse Cedex 9, France
b
c
d
e
a r t i c l e i n f o
a b s t r a c t
The preparation of two M(CO)3 complexes (M=Re and 99mTc) from a novel pyridyltriazole-based ligand 2
bearing the bioactive (2-methoxyphenyl)piperazine pharmacophore are described. Spectral data, X-ray
structure and DFT calculations of the rhenium(I) complex as well as the 99mTc-labelling of 2 are reported. Both
complexes were neutral and iso-structural. Moreover, the 99mTc-complex presented a suitable lipophilic
character for its use as a CNS imaging agent.
Article history:
Received 16 September 2010
Accepted 3 November 2010
Available online 10 November 2010
Keywords:
© 2010 Elsevier B.V. All rights reserved.
Click chemistry
Bidentate ligands
Rhenium
Technetium
X-ray structure
DFT calculations
Over the past decade, the coordination chemistry of tricarbonyl
technetium(I) and tricarbonyl rhenium(I) cores has been intensively
studied, mainly due to the easy production of the hydrophilic air-stable
fac-[M(CO)3(H2O)3]+ precursor from the corresponding permetallates
MO−4 (M=99mTc or 186/188Re), and the extensive use of the 99mTc
and 186/188Re radioisotopes in the development of diagnostic and
therapeutic radiopharmaceuticals, respectively [1]. Interestingly, the
185/187Re(CO)3 complexes, which have been commonly used as a non-
radioactive alternative to technetium complexes for macroscopic-scale
synthesis and structural characterization, also could serve as luminescent
probes. In this latter case, the tricarbonyl rhenium core was coordinated
by heteroaromatic amine, e.g., diquinolinylamine (dqa) [2], or α,α′-
diimine such as 2,2′-bipyridine [3]. It is noteworthy that if Zubieta et al.
developed maleimide-dqa derivatives, leading to M(CO)+3 complexes
suitable for both imaging and radioimaging studies of proteins [4], the
development of functionalized bipyridines still remains a significant
challenge.
Within this contextand aiming at the development of novel rhenium
(I) and technetium(I) complexes as luminescent and/or radiopharma-
ceutical agents, we recently designed fluorescent rhenium(I) complexes
from mono-functionalized 2-pyridyl-1,2,3-triazole derivatives (or pyta)
as alternative ligands to 2,2′-bipyridines [5]. The mild reaction
conditions associated with the synthetic click approach allowed the
preparation of a large number of mono-functionalized pyta derivatives.
Nevertheless, only a few of them possess a tethering group for further
coupling to a biomolecule [5,6], and one example of pyta grafted on a
bioactive molecule (a glucose scaffold) was reported [7].
As a continuation of our research, in the present study, we
described a convenient synthesis of a novel pyta functionalized by the
bioactive (2-methoxyphenyl)piperazine moiety, this pharmacophore
being found in numerous selective 5-HT1A imaging agents [8]. The
preparation of this ligand as well as the investigation of its
coordinating ability with a tricarbonyl rhenium core has been herein
presented. Definitive characterization of the tricarbonyl rhenium(I)
complex 2-Re, of general formula [Re(CO)3Cl(k2-2)], was accomplished
by X-ray crystallography study and DFT calculations. Since bidentate
diimine are excellent ligands for the 99mTc(CO)3+ core, we also
investigated the labelling of the pyta derivative with 99mTc.
⁎
Corresponding authors. E. Benoist is to be contacted at the Université de Toulouse;
UPS; Laboratoire de Synthèse et Physico-Chimie de Molécules d'Intérêt Biologique,
SPCMIB, UMR 5068, 118, Route de Narbonne, F-31062 Toulouse Cedex 9, France.
Tel.: +33 5 61 55 64 80; fax: +33 5 61 55 60 11.
E-mail addresses: basia@ich.us.edu.pl (B. Machura), benoist@chimie.ups-tlse.fr
(E. Benoist).
1
Both authors equally contributed to the experiments.
1387-7003/$ – see front matter © 2010 Elsevier B.V. All rights reserved.
doi:10.1016/j.inoche.2010.11.002

A. Seridi et al. / Inorganic Chemistry Communications 14 (2011) 238–242
239
Scheme 1.
In order to minimize sterical interference between the metallic
chelating centre and the receptor binding part, an ethylene bridge was
used as a spacer. Thus, the azido-ligand 1, prepared by a three step
procedure, starting from the commercial chlorhydrate of (2-methox-
yphenyl)piperazine, was obtained in a 51% overall yield [9]. Compound 1
undergoes the click reaction with 2-ethynylpyridine to afford a pyta
derivative containing the (2-methoxyphenyl)piperazine pharmacophore
(scheme 1). In this case, the copper(II) salt/reducing agent system (Cu
(OAc)2.H2O, 20 mol.%/sodium ascorbate, 40 mol.%) revealed to be a
better efficient catalyst than copper(I) species used directly [10].
Compound 2 was fully characterized by classical spectroscopic methods
[11]. Crystals of 2 suitable for X-ray diffraction were obtained by the slow
evaporation of a dichloromethane/methanol solution [12]. Structural
features compare well to those observed for related pyta derivatives [13].
Compound 2 exhibits an anti arrangement adopted by the N(5) and N(6)
atoms of the triazole and pyridine rings, respectively, and an azo
character of the 1,2,3-triazole ring, the N=N bond distance of the 1,2,3-
triazole ring being shorter than the adjacent N–C and N–N bonds (N(4)=
N(5)=1.3133(15) Å vs. N(5)–C(15)=1.3633(15) Å and N(4)–N(3)=
1.3492(14) Å). Interestingly, a significant contribution to crystal
cohesion is provided by a network of intra-layer hydrogen bonds in
which the ligand and one lattice water molecule participate. The lattice
water molecule forms O–H···N bonds with one nitrogen of the
piperazinyl moiety of 2 (d(O(2)–H(2a)…N(2))=3.013 Å, O(2)–H(2a)–
N(2)=173.08°).
Santos group [16]. The fact that the bioactive fragment does not interact
significantly with the metal should suggest a suitable affinity for the
5-HT1A receptors.
The coordination geometry about rhenium in 2-Re is distorted
octahedral, as illustrated by the ORTEP view (Fig. 1). The three CO
ligands are coordinated to one face of the octahedron, maximizing
Re–CO back-bonding, whereas the other face is occupied by the
chlorine and the bidentate pyta ligand, leading to a neutral complex.
Corresponding bond lengths and angles in 2-Re are unexceptional
(Fig. 1) and compare well to those observed for related complexes
[5,7]. The Re–carbonyl bond lengths average 1.93 Å and lie in the middle
side of the range (1.92–1.94 Å) found for other tricarbonyl–rhenium
pyta derivatives [7]. Conversely, the Re(1)–Cl(1) distance (2.4657 Å) is
the shortest observed in the Re(CO)3 complexes based on pyta moieties
(mean 2.471–2.485 Å) [5,7]. The trans bond angles fall in the range of
172.1–176.6°, showing only moderate deviations from an idealized
octahedral geometry. The most significant angular distortion is
associated with the bite angle N–Re–N angle of 74.83°. This value is a
consequence of the formation of a strained five-membered chelate ring.
The rhenium complex 2-Re was prepared in moderate yield by
reacting ligand 2 with a slight excess of the Re(CO)5Cl precursor in
refluxing methanol (1.2:1 metal:ligand ratio). It was characterized by
the usual analytical techniques [11], including X-ray diffraction
analysis. The positive-ion DCI-MS spectrum of 2-Re showed the
parent peak [M+H]+ with the correct isotope distribution pattern
without significant fragmentation. The facial arrangement of the
carbonyl groups is evidenced from the CO-stretching absorptions in
the IR spectrum. The three strong ν(CO) stretching bands appear in
the region of 2021–1896 cm−1, indicating the presence of the fac-[Re
(CO)3]+ core [14]. In 1H NMR, a significant down-field shift (0.3 ppm)
of the signal for the triazole proton was observed, as expected [11].
Interestingly, the hydrogen resonances of the (2-methoxyphenyl)
piperazine moiety were either unchanged or exhibited very minor
shifts compared to those of the free ligand. The lack of appreciable
shifts confirms the pendant nature of the (2-methoxyphenyl)
piperazine framework. Therefore, interaction of the metal centre
with the bioactive part of the molecule can largely be excluded. This
structural feature was confirmed by the X-ray diffraction analysis of
2-Re [15]. As anticipated, the ethylene bridge keeps the (2-methox-
yphenyl)piperazine group at a large distance from the chelating part of
the molecule (Fig. 1), and precludes neither any coordinative or
hydrogen-bonding interactions with components near the coordination
sphere, nor the folding of the pendant arm towards the metal center, this
latter feature being observed with more flexible spacers, as reported by
Fig. 1. Molecular structure of 2-Re (ellipsoids drawn at 50% probability level); hydrogen
atoms have been omitted for clarity. Selected bond parameters: Re(1)–Cl(1)=2.4657
(10), Re(1)–N(5)=2.161(3), Re(1)–N(6)=2.210(3), Re(1)–C(21)=1.921(4), Re(1)–
C(22)=1.909(4), Re(1)–C(23)=1.957(4), N(3)–N(4)=1.346(4) Å; C(23)–Re(1)–Cl
(1)=176.63(11), C(22)–Re(1)–N(5)=172.11(13), C(21)–Re(1)–N(6)=173.82(14),
C(23)–Re(1)–N(5)=93.70(13), C(23)–Re(1)–N(6)=92.56(13), and N(5)–Re(1)–N
(6)=74.83(11)°.

240
A. Seridi et al. / Inorganic Chemistry Communications 14 (2011) 238–242
1.20
The gas phase geometry of 2-Re was optimized in a closed-shell
singlet (S=1) state without any symmetry restrictions with the DFT
method using the hybrid B3LYP functional of GAUSSIAN-03 [17,18]. The
calculations were performed using the ECP LANL2DZ basis set [19] with
an additional d and f functions with the exponents α=0.3811 and
α=2.033 [20] for the rhenium and the standard 6-31G basis set for the
other atoms, respectively. For chlorine, nitrogen and oxygen diffuse and
polarization functions were added [21,22]. The vibrations in the
calculated vibrational spectrum of 2-Re were real; thus, the geometry
of 2-Re corresponds to true energy minimum. The predicted bond
lengths and angles are in reasonable agreement with the values based
on the X-ray crystal structure data, and the general trends observed in
the experimental data are well reproduced in the calculations [23].
The partial molecular orbital diagram of 2-Re with several occupied
and virtual molecular orbital contours is presented in Fig. 2. The HOMO–
LUMO gap is equal to 3.32 eV. The low-lying virtual orbitals correspond
mainly to the π-antibonding orbitals of the chelate and carbonyl ligands.
The LUMO and LUMO+1 are centered at the 2-pyridyl-1,2,3-triazole
fragmentof the chelate ligand. The higher virtual orbitals are delocalized
among the carbonyls and Re atom or among carbonyls, Re and chelate
ligand. The three highest occupied molecular orbitals are localized on
the (2-methoxyphenyl)piperazine part of the chelate ligand. The
HOMO-3, HOMO-4 and HOMO-5 are predominantly of dRe orbital
character corresponding to the (5d2xy) (5dπ)4 occupation.
0.80
0.40
0.00
400.00
800.00
[nm]
Fig. 3. Experimental (black) and calculated (red) electronic absorption spectra of 2-Re;
λmax [nm] (ε [dm3 mol−1 cm−1]): 329.9 (3270), 276.8 (11250), 241.1 (19650), and
206.1 (39730).
polarizable continuum model with the integral equation formalism
(IEF–PCM) [25]. The experimental and calculated electronic spectra of
2-Re are compared in Fig. 3. Each calculated transition is represented by
The electronic spectrum of 2-Re was calculated with the TDDFT
method [24], and the solvent effect (methanol) was simulated using the
Fig. 2. Energy (eV), character and some contours of the occupied and unoccupied molecular orbitals of 2-Re.

A. Seridi et al. / Inorganic Chemistry Communications 14 (2011) 238–242
241
2
a Gaussian function y=ce−bx with the height (c) equal to the oscillator
the neutrality and the lipophilic character of both metallic complexes are
two important prerequisites for the design of central nervous system
(CNS) receptor-binding agents. The binding affinity and in vivo
biodistributions of 2-99mTc will be reported in another paper.
strength and b equal to 0.04 nm−2. The TDDFT/PCM calculations well
reproduce the absorption spectrum of 2-Re in methanol. The assign-
ment of the calculated orbital excitations to the experimental bands was
based on an overview of the contour plots and relative energy to the
occupied and unoccupied orbitals involved in the electronic transitions.
The longest wavelength experimental band of the rhenium complex at
329.9 nm originates in the HOMO-1→LUMO, HOMO-1→LUMO+1
and HOMO-4→LUMO transitions. As shown in Fig. 2, the LUMO and
LUMO+1 orbitals are centered at the 2-pyridyl-1,2,3-triazole part of
the chelate ligand, the HOMO-1 orbital has a substantial contribution
from the free electron pairs on the nitrogen atoms of the piperazine ring,
whereas the HOMO-4 is delocalized on the whole Re(CO)3Cl unit.
Accordingly, the transitions assigned to the longest wavelength
Acknowledgements
The Gaussian-03 calculations were carried out in the Wrocław
Centre for Networking and Supercomputing, WCSS, Wrocław, Poland,
http://www.wcss.wroc.pl.
Appendix A. Supplementary material
⁎
See the supplementary data for the materials and equipment, the
synthesis of compounds 2 and 2-Re and Table 1. CCDC 787115 and
CCDC 787116 contain the supplementary crystallographic data for this
paper. These data can be obtained free of charge from the
Cambridge Crystallographic Data Center via http://www.ccdc.cam.
ac.uk/data_request/cif. Supplementary materials related to this article
can be found online at doi:10.1016/j.inoche.2010.11.002.
experimental bands can be seen as mixed dRe→π (chelate) (MLCT)
⁎
and π(Cl)/π(chelate)→π (chelate) (LLCT) or a delocalized MLLCT
(metal–ligand–ligand CT) description can be used.
The experimental absorption bands at 276.8, 241.1 and 206.1 nm
are attributed to the metal-to-ligand charge transfer (occurring from
the rhenium ion to the π-antibonding orbitals of the chelate ligand or
π-antibonding orbitals of the carbonyl groups), ligand–ligand charge
transfer and intraligand (IL) transitions (see Table 1 in supplementary
data). As expected, 2-Re exhibited fluorescence at room temperature
in the MeOH solution (λexc =330 nm, and λem =522 nm) [26]. Its
observed that the quantum yield (Φ=0.32%) is in agreement with the
values measured for other Re(I) complexes of the type [Re(α,α′
diimine)(CO)3X] (α,α′-diimine=2,2′-bipy or pyta, X=halogene) [7].
The technetium-99m being one of the most relevant isotopes for
imaging purposes, the 99mTc-labelling of 2 was evaluated. The
radiocomplex 2-99mTc was prepared in excellent yield (N95%) using
the fac-[99mTc(CO)3(H2O)3]+ precursor (see supplementary data).
After 20°min at 80°C, [99mTc(CO)3(H2O)3]+ had disappeared completely
and the formation of a new product, 2-99mTc, was observed in the
radiochromatogram. Its radiochemical purity assessed by ITLCwasN98%
after RP-HPLC purification. In addition, we demonstrated that the
radiolabelling of 2 could be performed at room temperature but it
required a longer reaction time. The chemical identity of 2-99mTc was
determined by comparing its analytical HPLC profile with the HPLC
profile of the rhenium analog 2. Since the retention time of the
99mTc-complex is similar to that of the “cold” Re-complex (11.9°min for
2-Re vs. 11.3°min for 2-99mTc), it may be assumed that identical
structures are adopted by the species generated at the tracer level and
the complex produced and characterized on the macroscopic scale. As
previously reported by several teams, the chlorine atom present in the
radiolabelling medium replaces one of the H2O ligands of the [99mTc
(CO)3(H2O)3]+ precursor (thermodynamically favoured process)
[16,27], leading after reaction with 2, to the formation of the neutral
complex 2-99mTc of general formula [99mTc(CO)3Cl( 2-2)].
References
[1] (a) R. Schibli, R. Schwarzbach, R. Alberto, K. Otner, H. Schmalle, C. Dumas, A. Egli,
P.A. Schubiger, Bioconjug. Chem. 13 (2002) 750;
(b) R. Alberto, K. Otner, N. Weathley, R. Schibli, P.A. Schubiger, J. Am. Chem. Soc.
123 (2001) 3135.
[2] (a) K.A. Stephenson, S.R. Banerjee, T. Besanger, O.O. Sogbein, M.K. Levadala, N.
McFarlane, J.A. Lemon, D.R. Boreham, K.P. Maresca, J.D. Brennan, J.W. Babich,
J. Zubieta, J.F. Valliant, J. Am. Chem. Soc. 126 (2004) 8598;
(b) P. Schaffer, J.A. Gleave, J.A. Lemon, L.C. Reid, L.K.K. Pacey, T.H. Farncombe, D.R.
Boreham, J. Zubieta, J.W. Babich, L.C. Doering, J.F. Valliant, Nucl. Med. Biol. 35
(2008) 159.
[3] A. Coleman, C. Brennan, J.G. Vos, M.T. Pryce, Coord. Chem. Rev. 252 (2008) 2585.
[4] (a) S.R. Banerjee, J.W. Babich, J. Zubieta, Chem. Commun. (2005) 1784;
(b) S.R. Banerjee, P. Schaffer, J.W. Babich, J.F. Valliant, J. Zubieta, Dalton Trans.
(2005) 3886.
[5] (a) A. Boulay, Master's thesis, Paul Sabatier University, Toulouse, France,
2009b A. Boulay, C. Picard, E. Benoist, in: U. Mazzi, W.C. Eckelman, W.A. Volkert
(Eds.), Technetium and other radiometals in chemistry and medicine, SGE
Editoriali, Padova, Italy, 2010, pp. 111–112.
[6] B. Happ, C. Friebe, A. Winter, M.D. Hager, R. Hoogenboom, U.S. Schubert, Chem.
Asian J. 4 (2009) 154.
[7] M. Obata, A. Kitamura, A. Mori, C. Kameyama, J.A. Czaplewska, R. Tanaka, I.
Kinoshita, T. Kusumoto, H. Hashimoto, M. Harada, Y. Mikata, T. Funabiki, S. Yano,
Dalton Trans. (2008) 3292.
[8] (a) J. Passchier, A. van Waerde, Eur. J. Nucl. Med. 28 (2001) 113;
(b) I. Heimbold, A. Drews, R. Syhre, M. Kretzschmar, H.-J. Pietzsch, B. Johannsen,
Eur. J. Nucl. Med. 29 (2002) 82;
(c) M. Saidi, S. Seifert, M. Kretzschmar, R. Bergmann, H.-J. Pietzsch, J. Organomet.
Chem. 689 (2004) 4739;
(d) R. Garcia, L. Gano, L. Maria, A. Paulo, I. Santos, H. Spies, J. Biol. Inorg. Chem. 11
(2006) 769;
(e) J.S.D. Kumar, J. Prabhakaran, V.J. Majo, M.S. Milak, S.-C. Hsiung, H. Tamir, N.R.
Simpson, R.L. Van Heertum, J.J. Mann, R.V. Parsey, Eur. J. Nucl. Med. Mol.
Imaging 34 (2007) 1050;
(f) N. Aznavour, C. Benkelfat, P. Gravel, A. Aliaga, P. Rosa-Neto, B. Bedell, L.
Zimmer, L. Descarries, Eur. J. Nucl. Med. Mol. Imaging 36 (2009) 53;
(g) C. Bolzati, N. Salvarese, D. Carta, F. Refosco, A. Dolmella, H.-J. Pietzsch, R.
Bergmann, G. Bandoli, J. Biol. Inorg. Chem. (2010), doi:10.1007/s00775-010-
0712-48 and references therein.
The lipophilic character of this radiocomplex was assessed by the
determination of the partition coefficient (P) in physiological
conditions (0.1°M phosphate buffer pH 7.4/n-octanol) and was
expressed as logPo/w. A value of 2.34 was found, indicating that
2-99mTc is moderately lipophilic. It is noteworthy that this value is
within the range for related radiocomplexes able to cross the blood
brain barrier (logPo/w =0.5–2.5) [28].
[9] G. Campiani, S. Butini, F. Trotta, C. Fattorusso, B. Catalanotti, F. Aiello, S. Gemma, V.
Nacci, E. Novellino, J.A. Stark, A. Cagnotto, E. Fumagalli, F. Carnovali, L. Cervo, T.
Mennini, J. Med. Chem. 46 (2003) 3822.
In short, a novel pyta derivative grafted to a bioactive pharmacophore
was prepared, taking advantage of the trendy click chemistry. The
corresponding rhenium and technetium complexes were characterized
in the solid and solution states. If a Tc- or Re-tricarbonyl complex with a
tridentate ligand is less prone to cross-metallation, previous studies
showed that this kind of bidentate M(CO)+3 complexes with a chlorine
ligand (at the sixth position) was suitable for in vivo work and exhibited
high stability against histidine and cysteine challenge experiments [27a].
Thus, this bidentate ligand 2 can be considered: (i) a good starting point
for the preparation of novel technetium-99m 5HT1A imaging probes and
(ii) an alternative of 5HT1A imaging probes based on PET emitters. Then,
[10] C. Camp, S. Dorbes, C. Picard, E. Benoist, Tetrahedron Lett. 49 (2008) 1979.
[11] See supplementary data for the synthesis and the characterization of compounds
2 and 2-Re.
[12] Crystal data for 2.H2O: C20H26N6O2, monoclinic, space group P21/c, a=13.1340
(3), b=14.5355(3), c=10.1669(2) Å, α=γ=90° β=96.9350(10)° V=1926.75
(7) Å3, Z=4, Dc=1.318 Mg.m-3, 24351 reflections collected, 4753 unique,
Rint=0.0401, data/restraints/parameters: 4753/0/260; S=1.046; Final R indices
[I N2σ(I)] R1 = 0.0401, wR2 = 0.0935;
R indices (all data) R1 = 0.0554,
wR2=0.1020, Largest diff. peak and hole 0.251 and −0.174 e.Å-3, CCDC 787115.
[13] (a) J.D. Crowley, P.H. Bandeen, Dalton Trans. (2010) 612;
(b) D. Schweinfurth, R. Pattacini, S. Strobel, B. Sarkar, Dalton Trans. (2009) 9291.
[14] O. Karagiorgou, G. Patsis, M. Pelecanou, C.P. Raptopoulou, A. Terzis, T. Siatra-
Papastaikoudi, R. Alberto, I. Permettis, M. Papadopoulos, Inorg. Chem. 44 (2005)
4118.

242
A. Seridi et al. / Inorganic Chemistry Communications 14 (2011) 238–242
[15] Crystal data for 2-Re: C23H24ClN6O4Re, M=670.13, monoclinic, space group
P21/c, a = 20.2441(5), b = 8.6532(2), c = 15.6830(4) Å, α = γ = 90°
β=109.1070(10)° V=2595.94(11) Å3, Z=4, Dc=1.715 Mg m-3, T=193(2)
K. 33515 reflections collected, 6406 unique, Rint=0.0478, data/restraints/
[22] V.A. Rassolov, M.A. Ratner, J.A. Pople, P.C. Redfern, L.A. Curtiss, J. Comp. Chem. 22
(2001) 976.
[23] Calculated (experimental) bond lengths [Å]: Re(1)-C(22)=1.925 (1.909(4)), Re(1)-
C(21)=1.929 (1.921(4)), Re(1)-C(23)=1.914 (1.957(4)), Re(1)-N(5)=2.180
(2.161(3)), Re(1)-N(6)=2.241 (2.210(3)), Re(1)-Cl(1)=2.541 (2.4657(10));
calculated (experimental) bond angles [°]: C(22)-Re(1)-N(5)=169.88 (172.11
(13)), C(21)-Re(1)-N(6)=170.61 (173.82(14)), C(23)-Re(1)-Cl(1)=175.49
(176.63(11)), C(23)-Re(1)-N(6)=94.30 (92.56(13)), C(23)-Re(1)-N(5)=94.52
(93.70(13)), N(5)-Re(1)-N(6)=74.05 (74.83(11)).
parameters: 6406/0/317; S=1.037; Final
R indices [IN2σ(I)] R1=0.0290,
wR2=0.0749; R indices (all data) R1=0.0364, wR2=0.0802, Largest diff. peak
and hole 1.723 and -1.120 e.Å-3, CCDC 787116.
[16] E. Palma, J.D.G. Correia, A. Domingos, I. Santos, R. Alberto, H. Spies, J. Organomet.
Chem. 689 (2004) 4811.
[17] Gaussian 03, Revision D.01, M.J. Frisch, G.W. Trucks, H.B. Schlegel, G.E. Scuseria,
M.A. Robb, J.R. Cheeseman, J.A. Montgomery, Jr., T. Vreven, K.N. Kudin, J.C. Burant,
J.M. Millam, S.S. Iyengar, J. Tomasi, V. Barone, B. Mennucci, M. Cossi, G. Scalmani, N.
Rega, G.A. Petersson, H. Nakatsuji, M. Hada, M. Ehara, K. Toyota, R. Fukuda, J.
Hasegawa, M. Ishida, T. Nakajima, Y. Honda, O. Kitao, H. Nakai, M. Klene, X. Li, J.E.
Knox, H.P. Hratchian, J.B. Cross, V. Bakken, C. Adamo, J. Jaramillo, R. Gomperts, R.E.
Stratmann, O. Yazyev, A.J. Austin, R. Cammi, C. Pomelli, J.W. Ochterski, P.Y. Ayala, K.
Morokuma, G.A. Voth, P. Salvador, J.J. Dannenberg, V.G. Zakrzewski, S. Dapprich, A.
D. Daniels, M.C. Strain, O. Farkas, D.K. Malick, A.D. Rabuck, K. Raghavachari, J.B.
Foresman, J.V. Ortiz, Q. Cui, A.G. Baboul, S. Clifford, J. Cioslowski, B.B. Stefanov, G.
Liu, A. Liashenko, P. Piskorz, I. Komaromi, R.L. Martin, D.J. Fox, T. Keith, M.A. Al-
Laham, C.Y. Peng, A. Nanayakkara, M. Challacombe, P.M.W. Gill, B. Johnson, W.
Chen, M.W. Wong, C. Gonzalez, and J.A. Pople, Gaussian, Inc., Wallingford CT, 2004.
[18] (a) A.D. Becke, J. Chem. Phys. 98 (1993) 5648;
[24] M.E. Casida, in: J.M. Seminario (Ed.), Recent developments and applications in
modern density functional theory, Theoretical and Computational Chemistry,
Vol. 4, Elsevier, Amsterdam, 1996.
[25] (a) M.T. Cances, B. Mennucci, J. Tomasi, J. Chem. Phys. 107 (1997) 3032;
(b) M. Cossi, V. Barone, B. Mennucci, J. Tomasi, Chem. Phys. Lett. 286 (1998) 253;
(c) B. Mennucci, J. Tomasi, J. Chem. Phys. 106 (1997) 5151;
(d) M. Cossi, G. Scalmani, N. Rega, V. Barone, J. Chem. Phys. 117 (2002) 43.
[26] The quantum yield was calculated using the following reference. StephensonK.A. ,
et al., J. Am. Chem. Soc. 126 (2004) 8598.
[27] (a) A. Bourkoula, M. Paravatou-Petsotas, A. Papadopoulos, I. Santos, H.-J. Pietsch,
E. Livaniou, M. Pelecanou, M. Papadopoulos, Eur. J. Med. Chem. 44 (2009)
4021;
(b) R. Alberto, R. Schibli, P.A. Schubiger, U. Abram, H.-J. Pietzsch, B. Johannsen, J.
Am. Chem. Soc. 121 (1999) 6076;
(b) C. Lee, W. Yang, R.G. Parr, Phys. Rev. B 37 (1988) 785.
[19] P.J. Hay, W.R. Wadt, J. Chem. Phys. 82 (1985) 299.
[20] K. Eichkorn, F. Weigend, O. Treutler, R. Ahlrichs, Theor. Chem. Acc. 97 (1997) 119.
[21] P.C. Hariharan, J.A. Pople, Theor. Chim. Acta 28 (1973) 213.
(c) S. Mundwiler, M. Kundig, K. Ortner, R. Alberto, Dalton Trans. (2004) 1320.
[28] C. Fernandes, J.D.G. Correia, L. Gano, I. Santos, S. Seifert, R. Syhre, R. Bergmann, H.
Spies, Bioconjug. Chem. 16 (2005) 660.