Design, synthesis and properties of a trinuclear copper(I) cluster with a triazenide ligand

Article abstract of DOI:10.1016/j.inoche.2010.07.027

The reaction of methyl anthranilate, sodium nitrite, and 2-aminobenzothiazole produces a new triazenide, namely, 1-[(2-carboxymethyl) benzene]-3-[benzothiazole]triazene (HL). In the presence of Et₃N, the reaction of HL and CuCl in THF/methanol gives a trinuclear copper(I) cluster [Cu₃L₃] THF CH₃OH (1 THF CH₃OH), which has been characterized by X-ray crystallography, cyclic voltammogram and emission spectrum. CV of 1 reveals two reversible waves at -0.06 and 0.83 V, which correspond to two one-electron oxidation of Cu₃ units ([Cu ₃]⁴⁺/[Cu₃]³⁺) and ([Cu ₃]⁵⁺/[Cu₃]⁴⁺), respectively. 1 appears photoluminescent (λ_max = 502 nm) at room temperature.

Full text of DOI:10.1016/j.inoche.2010.07.027

Inorganic Chemistry Communications 13 (2010) 1325–1328
Contents lists available at ScienceDirect
Inorganic Chemistry Communications
journal homepage: www.elsevier.com/locate/inoche
Design, synthesis and properties of a trinuclear copper(I) cluster with a
triazenide ligand
⁎
⁎
Wen-jun Lei, Xing-wu Tan, Li-jun Han, Shu-zhong Zhan , Bai-tao Li
College of Chemistry & Chemical Engineering, South China University of Technology, Guangzhou, 510640, China
a r t i c l e i n f o
a b s t r a c t
Article history:
The reaction of methyl anthranilate, sodium nitrite, and 2-aminobenzothiazole produces a new triazenide,
namely, 1-[(2-carboxymethyl) benzene]-3-[benzothiazole]triazene (HL). In the presence of Et3N, the
reaction of HL and CuCl in THF/methanol gives a trinuclear copper(I) cluster [Cu3L3] THF CH3OH (1 THF
CH3OH), which has been characterized by X-ray crystallography, cyclic voltammogram and emission
spectrum. CV of 1 reveals two reversible waves at –0.06 and 0.83V, which correspond to two one-electron
oxidation of Cu3 units ([Cu3]4+/[Cu3]3+) and ([Cu3]5+/[Cu3]4+), respectively. 1 appears photoluminescent
(λmax = 502 nm) at room temperature.
Received 1 June 2010
Accepted 21 July 2010
Available online 29 July 2010
Keywords:
Trinuclear copper(I) cluster
Triazenido ligand
Crystal structures
Luminesence
© 2010 Elsevier B.V. All rights reserved.
The design and synthesis of new ligands that support transition
metal complexes and/or clusters are often inspired by systems in
bioinorganic, materials, and catalysis chemistry. By designing the
appropriate ligand, we can chelate metal centers in special frame and
control the electron withdrawal from the metal ion core, thereby
modifying the intramolecular exchange interactions. The use of
different bridging and well-designed polydentate ligands has afforded
an impressive array of nuclear coordination complexes with new
architectures. Among them, the triazenide ligands have attracted our
attention, as these compounds can serve as a monodentate (a) [1,2], a
bidentate chelating (b) [3–7], and a bridging ligands (c) [8–12]
(Scheme 1).
With this mind, our work focuses on the sign, synthesis and their
reactivity with transition metals of new bridging ligands (Scheme 1d)
which can delocalize electron density through their B-bonding
network and strongly donate π electron density to the metal atoms
and control the organization of polynuclear metal complexes [13].
We have synthesized a new triazenide ligand, 1-[(2-carboxy-
methyl)benzene]-3-[benzothiazole]triazene (HL) by modification of a
literature procedure [14]. The reaction of HL and CuCl in THF/
methanol gives a trinuclear copper(I) cluster 1. In this communica-
tion, we present the synthesis and characterization of HL and its
compound 1, as well as the electrochemical and photoluminescent
properties of 1.
Fig. s1.1H NMR spectrum]. In the presence of Et3N, the reaction of HL and
CuCl in THF/methanol provides a red cluster CuI3L3 1 in good yield [16],
which is solvable in DMF, THF, CH2Cl2 and CH3CN.
As shown in Fig. 1, HL contains a rigid N(1)=N(3) double bond and
a potential NNNCN donor set, and making it −1 anionic ligand (L−
)
when deprotonated [17]. The N(1)–N(3) and N(2)–N(3) bond
distances are 1.313(3) and 1.264(3)Å, respectively. The bond angles
of N(2)–N(3)–N(1) and N(4)–C(4)–N(2) are 112.8(2) and 120.9(3)o,
respectively.
X-ray quality crystals of 1 were grown from THF/methanol by slow
evaporation of the solvent. An ORTEP view of 1, excluding solvent
molecules, is illustrated in Fig. 2 [18]. 1 consists of a tricopper [Cu3L3]
unit, which is supported by three L− ligands via the 2 + 1
arrangement with one free N=N group. Two L− ligands are bonded
in a tri(bidentate) manner bridging three metal centers, and the third
L− ligand is bonded in a bis(bidentate) manner bridging two metal
centers. The terminal Cu(1) is three coordinated by two nitrogen
atoms from two L− ligands and one M–M bond, the Cu–N distances
are 1.90(9) and 1.910(8) Å, which are shorter than those found in
copper(II) triazenide 1.973 to 2.088 Å [19]. Another terminal Cu(3) is
four coordinated by three nitrogen atoms from three L− ligands and
one M–M bond, the Cu–N distances are 1.946(9), 1.962(9), and 1.987
(10) Å. The mean central Cu(2) is linked by three nitrogen atoms from
three L− ligands and two M–M bonds, the Cu–N distances are 1.958
(9), 1.978(9), 1.997(10) Å.
The reaction of methyl anthranilate, sodium nitrite, and 2-amino-
benzothiazole gives a triazenide compound (HL) in 69% yield [15] and
Unlike some polynuclear metal chain complexes, such as [Cu(μ3-
dpa)4]Cl2 (∠Cu(1)-Cu(2)-Cu(3)=178.12o) (dpa=bis(2-pyridyl)
amine ion) [20], and [Pt3(μ-dppm)3]2+ (Pt–Pt–Pt angles fall in the
range 176 to 179o) (dppm=bis(diphenylphosphino)methane) [21,22],
⁎
Corresponding authors. Fax: +86 20 87112053.
E-mail address: shzhzhan@scut.edu.cn (S. Zhan).
1387-7003/$ – see front matter © 2010 Elsevier B.V. All rights reserved.
doi:10.1016/j.inoche.2010.07.027

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W. Lei et al. / Inorganic Chemistry Communications 13 (2010) 1325–1328
Scheme 1. Generic triazene and triazenido binding modes.
Fig. 1. ORTEP view of ligand (HL). Selected bond distances (Å) and angles (o) are as follows: N(2)–N(3), 1.264(3); N(3)–N(1), 1.313(3); N(2)–C(4), 1.387(3); N(4)–C(4), 1.308(4); N
(1)–N(3)–N(2), 112.8(2); N(3)–N(2)–C(4), 113.1(2); N(3)–N(1)–C(8), 121.5(2); N(4)–C(4)–N(2), 120.9(3).
the Cu–Cu–Cu unit in 1 significantly deviates from a linear arrangement
(∠Cu(1)–Cu(2)–Cu(3)=151.02(9)o).
1 resides on a general position with two independent Cu–Cu
distances of 2.5386(8) and 2.5983(7) Å, which are longer than those
of the triazenide copper(I) dimeric complex [Cu(Ar–NNN–Ar)]2
(2.4289 Å) (Ar=o-C6H4-CO2CH3) [23], and the polypyridylamine
copper(II) trinuclear complex [Cu3(bipyam-H)4Cl2] (2.471(1) Å)
(bipyam-H=bis(2-pyridyl)amide) [24]. However, in the triazenide
Fig. 2. ORTEP view of 1. THF and methanol molecules are omitted for clarity. Selected bond distances (Å) and angles (o) are as follows: Cu(1)–N(9), 1.967(3); Cu(1)–N(5), 1.976(3);
Cu(1)–N(2), 2.006(4); Cu(1)–Cu(2), 2.5983(7); Cu(2)–N(10), 1.959(3); Cu(2)–N(6), 1.991(4); Cu(2)–N(1), 2.002(4); Cu(2)–Cu(3), 2.5386(8); Cu(3)–N(12), 1.915(4); Cu(3)–N(8),
1.929(4); C(30)–N(1), 1.319(5); C(30)–N(2), 1.346(5); Cu(1)–Cu(2)–Cu(3), 151.62(3); N(8)–Cu(3)–N(12), 165.49(15); N(6)–Cu(2)–N(10), 127.27(15); N(5)–Cu(1)–N(9), 135.08
(15); N(2)–Cu(1)–N(5), 85.64(10); N(2)–Cu(1)–N(9), 85.27(10); N(1)–Cu(2)–N(6), 127.27(15); N(1)–Cu(2)–N(10), 118.86(14).

W. Lei et al. / Inorganic Chemistry Communications 13 (2010) 1325–1328
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cluster. Currently we are exploring this further, as well as the reactions
of HL with other metals.
Acknowledgments
This work was supported by the Research Foundation for Returned
Chinese Scholars Overseas of Chinese Education Ministry (No. B7050170),
and the National Science Foundation of China (No. 20971045), and the
Student Research Program (SRP) of South China University of Technology.
Appendix A. Supplementary material
CCDC 773556 and 775010 contain the supplementary crystallo-
graphic data for triazenide ligand (HL) and complex 1, respectively.
These data can be obtained free of charge via http://www.ccdc.cam.ac.
uk/conts/retrieving.html, or from the Cambridge Crystallographic
Data Centre, 12 Union Road, Cambridge CB2 1EZ, UK; fax: (+44)
1223-336-033; or e-mail: deposit@ccdc.cam.ac.uk. Supplementary
data associated with this article can be found, in the online version, at
doi:10.1016/j.inoche.2010.07.027.
Fig. 3. Emission spectrum of 1 in CH3CN.
silver(I) dimer [Ag(Ar-NNN-Ar)]2, the Ag–Ag distance is quite long
(2.707(2) Å) [23]. This observation leads us to conclude that the
triazenide ligands are not solely responsible for the M–M distances.
Compared with the structure of HL, the triazenide ligand in 1
shows a little variation of the bonding on coordination. For example,
the N(2)–C(4) and N(4)–C(4) bond distances are 1.387(3) and 1.309
(4) Å, respectively. It would be expected that the N–C bond distances
would be dissimilar as a consequence of the different bond order
between these atoms. The corresponding bond distances (N(2)–C(30)
and N(1)–C(30)) are 1.346(5) and 1.319(5) Å, respectively.
The emission spectrum of 1 in CH3CN solution was measured at
room temperature. As shown in Fig. 3, when excited upon 412 nm, 1
shows a strong band at 502 nm. It is possible that the emitting state is
related to the metal-centered excited state 3d10 of Cu(I), modified by
the copper–copper interaction, due to configuration mixing of the
filled orbital of d parentage with the appropriate empty orbitals
derived from the higher 4 s and 4p atomic orbitals of the dimeric
copper unit (d–s) [25].
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vacuo (2.16 g, 69%). Calcd for C15H12N4O2S: C, 57.63; H, 3.84; N, 17.93. Found: C,
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ρ
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a=13.813(2), b=14.407(2), c=15.304(2) Å, α=116.840(2), β=105.563(2),
Fig. 4. Cyclic voltammogram of1inCH3CN/0.1 mol L−1 [Bu4N]ClO4 at 100 mV s−1 scan rate.

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W. Lei et al. / Inorganic Chemistry Communications 13 (2010) 1325–1328
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