Synthesis and characterization of emissive mononuclear Cu(I) complexes with 5-tert-butyl-3-(pyrimidine-2-yl)-1 H-1,2,4-triazole

Article abstract of DOI:10.1080/00958972.2014.908465

A new series of mononuclear copper(I) halide complexes possessing 5-tert-butyl-3-(pyrimidine-2-yl)-1H-1,2,4-triazole (bpmtzH) and PPh₃, Cu(bpmtzH)(PPh₃)X (X = I (1); Br (2); Cl (3)), have been synthesized and characterized. As reveal

Full text of DOI:10.1080/00958972.2014.908465

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Synthesis and characterization of
emissive mononuclear Cu(I) complexes
with 5-tert-butyl-3-(pyrimidine-2-
yl)-1H-1,2,4-triazole
Jing-Lin Chenabc, Xiu-Zhen Tana, Xing-Feng Fua, Xiu-Xiu Chena, Jin-
Yun Wangb, Li-Hua Hea & He-Rui Wena
a School of Metallurgy and Chemical Engineering, Jiangxi
University of Science and Technology, Ganzhou, PR China
b State Key Laboratory of Structural Chemistry, Fujian Institute
of Research on the Structure of Matter, Chinese Academy of
Sciences, Fuzhou, PR China
Click for updates
c Beijing Synchrotron Radiation Facility, Institute of High Energy
Physics, Chinese Academy of Sciences, Beijing, PR China
Accepted author version posted online: 25 Mar 2014.Published
online: 22 Apr 2014.
To cite this article: Jing-Lin Chen, Xiu-Zhen Tan, Xing-Feng Fu, Xiu-Xiu Chen, Jin-Yun Wang, Li-Hua
He & He-Rui Wen (2014) Synthesis and characterization of emissive mononuclear Cu(I) complexes
with 5-tert-butyl-3-(pyrimidine-2-yl)-1H-1,2,4-triazole, Journal of Coordination Chemistry, 67:7,
1186-1197, DOI: 10.1080/00958972.2014.908465
To link to this article: http://dx.doi.org/10.1080/00958972.2014.908465
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Journal of Coordination Chemistry, 2014
Vol. 67, No. 7, 1186–1197, http://dx.doi.org/10.1080/00958972.2014.908465
Synthesis and characterization of emissive mononuclear Cu(I)
complexes with 5-tert-butyl-3-(pyrimidine-2-yl)-1H-1,2,
4-triazole
JING-LIN CHEN*†‡§, XIU-ZHEN TAN†, XING-FENG FU†, XIU-XIU CHEN†,
JIN-YUN WANG‡, LI-HUA HE† and HE-RUI WEN†
†School of Metallurgy and Chemical Engineering, Jiangxi University of Science and Technology,
Ganzhou, PR China
‡State Key Laboratory of Structural Chemistry, Fujian Institute of Research on the Structure of
Matter, Chinese Academy of Sciences, Fuzhou, PR China
§Beijing Synchrotron Radiation Facility, Institute of High Energy Physics, Chinese Academy of
Sciences, Beijing, PR China
(Received 19 March 2013; accepted 5 February 2014)
A new series of mononuclear copper(I) halide complexes possessing 5-tert-butyl-3-(pyrimidine-2-
yl)-1H-1,2,4-triazole (bpmtzH) and PPh3, Cu(bpmtzH)(PPh3)X (X = I (1); Br (2); Cl (3)), have been
synthesized and characterized. As revealed via X-ray crystallography, 1–3 show a chiral, distorted
tetrahedral N2PX arrangement, in which bpmtzH is a neutral bidentate chelating ligand using the
4-N of the 1,2,4-triazolyl ring and one N donor from the 2-pyrimidyl ring, consistent with the
computational results. A comparatively weak low-energy absorption tail is observed between 320
and 450 nm for CH2Cl2 solutions of 1–3 at room temperature, ascribing to charge-transfer transitions
with appreciable metal-to-ligand charge transfer (MLCT) character. Complexes 1–3 in the solid state
have good luminescence at ambient temperature, although they are non-emissive in solution.
The solid-state emission, most likely originating from both 3MLCT and 3XLCT transitions, can be
modulated via alteration of the halide bound to {Cu(bpmtzH)(PPh3)} motif.
*Corresponding author. Email: gzchenjinglin@126.com
© 2014 Taylor & Francis

Emissive Cu(I) complexes
1187
Keywords: Copper(I) complex; 5-Tert-butyl-3-(pyrimidine-2-yl)-1H-1,2,4-triazole, Crystal structure;
Photoluminescence; Halide
1. Introduction
Emissive copper(I) complexes have been intensively studied owing to their intriguing spec-
troscopic properties with promising applications in materials science [1–9]. Cu(I) complexes
possessing diimine and phosphine ligands are normally air-stable and emissive in solution
and solids, and the electronic and structural characters of the ligands coordinated to Cu(I)
have an important impact on the photoluminescence of the Cu(I) species [6–11]. The choice
of the diimine ligand is critical for modulation of the emissive properties of the resulting
Cu(I) complexes, since the lowest unoccupied molecular orbital (LUMO) is basically local-
ized on the diimine ligand [7–11]. Moreover, orbitals of auxiliary ligands such as phos-
phines and halides are often involved in the highest occupied molecular orbital (HOMO)
with a dominant metal d(Cu) character [10–21].
Cu(I) systems with 2,2′-bipyrimidine (bpym) are luminescent at ambient temperature [22,
23], whereas Cu(I) complexes containing 3-(2-pyrimidinyl)-1,2,4-triazine (pmtz) are all
non-emissive in solution and as solids at room temperature [24]. In fact, pmtz has only an
additional nitrogen donor relative to bpym, clearly implying that the emissive properties of
Cu(I) complexes are related to the structural characteristics of the diimine ligand. To explore
further the relationship between the luminescence properties of Cu(I) complexes and the
structure of the N-heterocyclic chelating ligand, it is necessary to synthesize more Cu(I)
complexes with multi-nitrogen-containing heterocyclic chelates. Herein, we describe the
syntheses, crystal structures, and photophysical properties of a new series of mononuclear
Cu(I) halide complexes featuring 5-tert-butyl-3-(pyrimidine-2-yl)-1H-1,2,4-triazole
(bpmtzH), Cu(bpmtzH)(PPh3)X (X = I (1); Br (2); Cl (3)), where bpmtzH serves as a neutral
bidentate chelate utilizing the 4-N of the 1,2,4-triazolyl ring and one N from the 2-pyrim-
idyl ring, as suggested by density functional theory (DFT) calculations. It is demonstrated
that 1–3 with the 1,2,4-triazolyl five-membered ring bearing a tert-butyl group are all emis-
sive in the solid state at room temperature, in marked contrast to the non-emissive Cu–pmtz
complexes with the 1,2,4-triazinyl six-membered ring, and that the ancillary halide bound
to {Cu(bpmtzH)(PPh3)} has a significant influence on the structural features and lumines-
cent properties of the Cu(I) complexes.
2. Experimental
2.1. General procedures and materials
All reactions were performed under N2 using anhydrous solvents. Commercially available
reagents were used without purification unless otherwise stated. Dichloromethane used in
the spectroscopic analyses was freshly distilled from CaH2 under nitrogen. 5-Tert-butyl-3-
(pyrimidine-2-yl)-1H-1,2,4-triazole (bpmtzH) was prepared according to the literature
method [25].

1188
J.-L. Chen et al.
2.2. Physical measurements
The 1H and 31P{1H} NMR spectra were recorded on a Bruker Avance III (400 MHz)
spectrometer with SiMe4 as the internal reference (1H) and 85% H3PO4 as the external
reference (31P). C, H, N elemental analyses were carried out on a Perkin-Elmer model
240C elemental analyzer. Fourier transform infrared (FT-IR) spectra were collected on an
ALPHA FT-IR spectrometer (Bruker Optics, Billerica, MA, USA) using KBr pellets.
Electronic absorption spectra in dichloromethane solutions were measured on a Perkin-
Elmer Lambda 25 UV–vis spectrometer. Solid-state emission spectra were recorded on a
Perkin-Elmer LS 55 luminescence spectrometer with a red-sensitive photomultiplier type
R928.
2.3. Synthesis of Cu(bpmtzH)(PPh3)I (1)
A mixture of CuI (18.9 mg, 0.099 mM) and PPh3 (49.8 mg, 0.190 mM) was stirred in
CH2Cl2 (15 mL) for 3 h at room temperature. A CH2Cl2 solution (3 mL) of bpmtzH
(20.2 mg, 0.099 mM) was added dropwise to the resulting colorless solution. The mixture
was stirred for another 4 h, and then the solvent was evaporated at reduced pressure to give
a yellow residue. The residue was redissolved in CH2Cl2 and yellow crystals (51.1 mg,
0.078 mM, 78.7% yield) were afforded by slow diffusion of petroleum ether into the
1
CH2Cl2 solution. H NMR (DMSO-d6, 400 MHz): δ 14.66 (s, 1H), 8.89–8.80 (m, 2H),
7.61–7.36 (m, 16H), 1.32 (s, 9H). 31P{1H} NMR (DMSO-d6, 202.3 MHz): δ –6.78
(s, PPh3). Elem. Anal. Calcd for C28H28ICuN5P: C, 51.27; H, 4.30; N, 10.68. Found: C,
51.03; H, 4.12; N, 10.87%. Selected IR (KBr, cm−1): 3442(s), 3123(m), 3050(m),
2969(m), 1629(w), 1575(s), 1528(w), 1479(m), 1456(m), 1421(s), 1393(s), 1366(m),
1297(w), 1267(w), 1225(w), 1181(w), 1094(m), 1042(w), 822(w), 747(s), 695(s), 641(w),
523(s), 493(m).
2.4. Synthesis of Cu(bpmtzH)(PPh3)Br (2)
Complex 2 was prepared following the procedure for 1, using CuBr (19.6 mg, 0.137 mM),
PPh3 (71.7 mg, 0.273 mM), and bpmtzH (27.8 mg, 0.137 mM). Yellow crystals (64.6 mg,
0.106 mM, 77.6% yield) were obtained by slow diffusion of Et2O into a 3 : 1 blend of DMF
1
and CH3CN. H NMR (DMSO-d6, 400 MHz): δ 14.58 (s, 1H), 8.89–8.78 (m, 2H), 7.58–
7.38 (m, 16H), 1.31 (s, 9H). 31P{1H} NMR (DMSO-d6, 202.3 MHz): δ –5.62 (s, PPh3).
Elem. Anal. Calcd for C28H28BrCuN5P: C, 55.22; H, 4.63; N, 11.50. Found: C, 55.38; H,
4.42; N, 11.67%. Selected IR (KBr, cm−1): 3443(s), 3047(s), 2971(s), 1626(w), 1573(s),
1558(m), 1527(m), 1479(m), 1456(m), 1435(s), 1394(s), 1368(m), 1302(w), 1227(w),
1183(w), 1095(m), 1042(w), 827(w), 750(s), 696(s), 524(s), 506(m).
2.5. Synthesis of Cu(bpmtzH)(PPh3)Cl (3)
Complex 3 was prepared following the procedure for 1, using CuCl (16.8 mg, 0.170 mM),
PPh3 (89.3 mg, 0.340 mM), and bpmtzH (34.5 mg, 0.170 mM). Yellow crystals (64.8 mg,
0.115 mM, 67.6% yield) were obtained by slow diffusion of Et2O into a 2 : 1 blend of CH2Cl2
1
and CH2ClCH2Cl. H NMR (DMSO-d6, 400 MHz): δ 14.53 (s, 1H), 8.89–8.78 (m, 2H),

Emissive Cu(I) complexes
1189
7.57–7.33 (m, 16H), 1.31 (s, 9H). 31P{1H} NMR (DMSO-d6, 202.3 MHz): δ –5.13 (s, PPh3).
Elem. Anal. Calcd for C28H28ClCuN5P: C, 59.57; H, 5.00; N, 12.41. Found: C, 59.43; H,
5.18; N, 12.34%. Selected IR (KBr, cm−1): 3448(m), 3046(s), 2971(s), 1637(w), 1573(s),
1558(m), 1527(m), 1479(m), 1457(m), 1436(s), 1395(s), 1371(m), 1306(w), 1228(w),
1095(m), 1041(w), 997(w), 827(w), 751(s), 697(s), 639(w), 524(s), 506(m).
2.6. X-ray crystallography
Crystals of 1 and 2 were measured on a MAR CCD 165 nm diffractometer by the oscilla-
tion scan technique using the Beijing Synchrotron Radiation Facility with a 3W1A beam
(λ = 0.71073 Å) at 194(2) K. The cell refinement and data reduction were computed using
the HKL2000 software. Absorption corrections were carried out based on spherical harmon-
ics expansion of the absorption surface using the HKL2000 software [26]. A crystal of 3
was measured on a Bruker SMART CCD area detector using graphite-monochromated
Mo-Kα radiation (λ = 0.71073 Å) at 296(2) K. All the crystal structures were solved by the
direct method using SHELXS-97 [27] and all non-hydrogen atoms were refined with aniso-
tropic thermal parameters. Hydrogens were placed in idealized geometries and their contri-
butions were added to the structure factor calculations. Full-matrix least-squares refinement
was based on F2 with the SHELXL-97 program [28]. The maximum theta value of 1 is low
and thus its crystal data completeness is 0.914, but the other parameters are all in typical
range and reasonable. Moreover, the absolute structure of 1 was confirmed by its Flack
parameter of 0.083(13) [29].
2.7. Computational methodology
To clearly understand the binding of bpmtzH with Cu(I), theoretical calculations were
implemented using Gaussian 03 program package [30]. The DFT [31] method at the
Figure 1. ORTEP drawing of 3 with 30% probability thermal ellipsoids and atom-labeling scheme. Hydrogens
except H4A are omitted for clarity.

1190
J.-L. Chen et al.
gradient-corrected correlation functional PBE1PBE level [32] was used to optimize the
structures of Cu(I) complexes bearing the N1^N3 and N1^N5 chelating modes (atom labels
as in figure 1) of bpmtzH in the ground state without considering any symmetry restriction.
The Lanl2dz effective core potential was used to describe the inner electrons of Cu, P, and
Cl [33–35], while its associated double-ζ basis set of Hay and Wadt was employed for the
remaining outer electrons with f-[Cu (αf = 0.24)] and d-type [P (αd = 0.34), Cl (αd = 0.514)]
polarization functions [36]. N, C, and H were described by the all-electron basis set of
6-31G(p,d) [37].
3. Results and discussion
3.1. Synthesis and characterization
This project was carried out to prepare emissive, bpmtzH-based mono-copper(I) halide com-
plexes and explore the preferred binding mode of bpmtzH with Cu(I). Mononuclear Cu(I)
halide complexes of bpmtzH, Cu(bpmtzH)(PPh3)X (X = I (1); Br (2); Cl (3)), are accessible
by treatment of cuprous halide with two equivalents of PPh3 in CH2Cl2 solution followed by
addition of one equivalent of bpmtzH (scheme 1). The unisolated intermediate has been iden-
tified as the di-copper(I) halide cluster (PPh3)2Cu(μ-X)2Cu(PPh3) via X-ray crystallography
[38], and it is air-stable and soluble in CH2Cl2, CHCl3, and CH2ClCH2Cl. Copper(I) halide
complexes 1–3 are soluble in DMF and DMSO, and only sparingly soluble in CH2Cl2,
CHCl3, and CH2ClCH2Cl. Moreover, 1–3 are air-stable in the solid state and for extended
periods of time (3–5 days) in solution. The infrared spectra of 1–3 show all the bands
required due to the presence of bpmtzH and PPh3. Compared with free bpmtzH (3424 cm−1,
figure S1 see online supplemental material at http://dx.doi.org/10.1080/00958972.2014.
908465), the ν(N–H) of coordinated bpmtzH in 1–3 appears as a single broad absorption at
slightly higher frequency, 3440–3450 cm−1 (figures S2–S4). Upon P–Cu(I) coordination, the
characteristic ν(P–CPh) peak of PPh3 in 1–3 occurs at slightly higher frequency (~1095 cm−1)
1
relative to that of free PPh3 (1089 cm−1) [39]. In the H NMR spectra of 1–3 in DMSO-d6
N
N
N
N
N
N
N
N
N
N
N
NH
N
N
bpym
pmtz
bpmtzH
X
X
Ph3P
Ph3P
CH2Cl2
+
CuX 2 PPh3
Cu
Cu PPh3
HN
N
PPh3
X
N
N
(1)
(2)
(3)
X = I
Br
Cl
bpmtzH
CH2Cl2
Cu
N
Scheme 1. Synthetic route to 1–3.

Emissive Cu(I) complexes
1191
(figures S5, S7, and S9), besides the aromatic proton signals (8.9–7.3 ppm) and the C–H res-
onance of the tert-butyl group as a singlet at 1.3 ppm, the characteristic N–H proton of the
1,2,4-triazolyl ring occurs at approximately 14.6 ppm as a broad singlet, implying that
bpmtzH coordinates to Cu(I) as a neutral ligand without cleavage of the N–H bond, as
revealed by X-ray crystallography. The 31P{1H} NMR spectra exhibit broad singlets at
–6.78, –5.62, and –5.13 ppm for 1–3, respectively (figures S6, S8, and S10), implying that
the coordinated PPh3 is affected by the ligand-field strength of the halide (I − < Br− < Cl−)
[15].
3.2. Crystal structure
X-ray crystallographic studies of 1–3 were performed to investigate the preferred binding
mode of bpmtzH and the effects of the halide on coordination around Cu(I). The crystallo-
graphic data and structure refinement parameters of 1–3 are summarized in table 1 and
selected bond lengths and angles of 1–3 are listed in table 2. Complexes 1–3 adopt a chiral,
Table 1. Crystallographic data and structural refinement parameters for 1–3.
Compound
1
2
3
Empirical formula
Formula weight
C
28H28ICuN5P
C28H28BrCuN5P
608.97
C28H28ClCuN5P
564.51
655.96
Crystal system
Triclinic
P1
Monoclinic
Cc
10.586 (2)
16.742 (3)
15.561 (3)
Monoclinic
Cc
10.5488 (3)
16.7272 (5)
15.5976 (5)
Space group
a, Å
b, Å
c, Å
α, °
β, °
8.7560 (18)
9.3260 (19)
18.872 (4)
79.17 (3)
86.49 (3)
66.01 (3)
1382.7 (5)
2
98.23 (3)
97.030 (2)
γ, °
V, Å3
Z
2729.5(9)
4
1.482
2731.54 (14)
4
1.373
ρ
Calcd, g/cm−3
1.576
1.990
μ, mm−1
2.349
0.982
Reflections collected/unique
R(int)
7724/7724
0.0000
7433/5998
0.0212
11,989/5622
0.0216
GOF
1.215
1.235
1.000
R1, wR2 (I > 2σ(I))
0.0372, 0.0980
3.045 and –1.625
0.0376, 0.1033
2.266 and –1.181
0.0324, 0.0753
0.536 and –0.287
Largest diff. peak and hole (e Å−3
)
Table 2. Selected bond distances [Å] and angles [°] for 1–3.
1a
2
3
Cu1–N1 (Cu2–N6)
Cu1–N5 (Cu2–N10)
Cu1–P1 (Cu2–P2)
Cu1–X1 (Cu2–X2)
2.135 (4), 2.183 (4)
2.092 (5), 2.084 (4)
2.2166 (15), 2.2075 (17)
2.6777 (10), 2.5757 (12)
2.193 (3)
2.063 (3)
2.1984 (9)
2.4240 (9)
2.229 (2)
2.086 (2)
2.2044 (7)
2.2936 (7)
N1–Cu1–N5 (N6–Cu2–N10)
N1–Cu1–P1 (N6–Cu2–P2)
N1–Cu1–X1 (N6–Cu2–X2)
N5–Cu1–P1 (N10–Cu2–P2)
N5–Cu1–X1 (N10–Cu2–X2)
P1–Cu1–X1 (P2–Cu2–X2)
80.11 (17), 79.13 (16)
118.17 (13), 103.10 (12)
97.67 (14), 106.80 (13)
128.76 (15), 125.01 (14)
113.36 (14), 114.42 (13)
110.84 (5), 116.99 (5)
79.08 (11)
110.70 (9)
109.62 (8)
122.92 (9)
111.27 (9)
116.50 (3)
77.63 (8)
110.36 (6)
108.35 (6)
122.03 (6)
111.72 (6)
118.39 (3)
aThere are two independent molecules in the asymmetric unit of 1. The first measurement refers to the molecule containing
Cu1 and the second measurement as well as parenthetical atom labels refer to the molecule containing Cu2.

1192
J.-L. Chen et al.
distorted tetrahedral N2PX arrangement around Cu(I) due to the restricted bite angle of the
bpmtzH chelate, and it is composed of two nitrogens from bpmtzH, one PPh3, and one
halide (figures S11, S12 and 1). The bpmtzH adopts a neutral chelating coordination mode
using the 4-N of 1,2,4-triazolyl and one N of the 2-pyrimidyl. Only one enantiomer is
found in the structure of 1, as indicated by the chiral space group P1, while both enantio-
mers are present in the structures of 2 and 3. The Cu–Npyrimidyl bond lengths (avg. 2.159
(4), 2.193(3), and 2.229(2) Å for 1, 2, and 3, respectively) are much longer than the
Cu–Ntriazolyl bond lengths (avg. 2.088(4), 2.063(3), and 2.086(2) Å for 1, 2, and 3, respec-
tively), suggesting a stronger bonding of Cu(I) to 4-N of the 1,2,4-triazolyl ring than to the
2-pyrimidyl ring, a possible result of introducing the strong electron-donating tert-butyl
group and different from the near equivalence of the two Cu–N bond distances in literature
complexes [24]. Similar Cu–N distances are also observed in other tetrahedral Cu(I) com-
plexes with an asymmetrical N^N chelate [8, 12, 19–21, 40–42]. The Cu–Npyrimidyl bond
lengths of 1–3 are slightly elongated with decrease of electron-donating ability of the halide
(I− > Br− > Cl−), whereas the Cu–Ntriazolyl bond distances have no apparent dependence on
the ancillary halide, implying that the halide has impact only on the pyrimidyl fragment,
and not the entire bpmtzH ligand. The Cu–X bond lengths in 1–3 become shorter as the
van der Waals radius of X decreases. Different from [CuI(PPh3)(pmtz)] [24], a weak π–π
interaction between the bpmtzH ligands of two adjacent molecules has been not observed in
1–3, as a possible result of the 1,2,4-triazolyl ring with a bulky tert-butyl group in place of
the 1,2,4-triazinyl ring [42].
3.3. Photophysical properties
The UV–vis absorption spectra of bpmtzH and its Cu-halide complexes 1–3 in CH2Cl2
solution at ambient temperature are presented in figure 2. The free bpmtzH displays a
broad absorption centered at 255 nm attributed to 1π–π* transitions. Complexes 1–3
exhibit strong absorptions (ε ≈ 104 M−1 cm−1) at 230–320 nm, probably originating from
bmptzH and PPh3, supported by a close match between bpmtzH and 1–3 in the high-
energy region (≤320 nm) of the absorption spectra. In addition to the high-energy
1.2
4
1
2
0.8
3
3
bpmtzH
0.4
2
0.0
300
350
400
450
1
0
250
300
350
400
450
Wavelength (nm)
Figure 2. Absorption spectra of bpmtzH and 1–3 in CH2Cl2 solution (1 × 10−5 M) at ambient temperature.

Emissive Cu(I) complexes
1193
absorptions, 1–3 have a relatively weaker low-energy absorption tail (ε < 3000 M−1
cm−1) at 320–450 nm showing no apparent dependence on the halide. This absorption
may be regarded as a 1MLCT transition from the dπ orbital of the (3d10)Cu+ to the
unoccupied π* orbital of the bpmtzH, perhaps mixed with some ligand-to-ligand charge
transfer (1LLCT) character (X/PPh3 → bpmtzH). Different from the apparent broad
absorption band of pmtz complexes [24], only a weak low-energy absorption tail has
been observed in 1–3, similar to the reported Cu(I) halide complexes possessing 1,2,4-
triazolyl [42]. This suggests that the 1,2,4-triazolyl five-membered ring with a tert-butyl
group in place of the 1,2,4-triazinyl six-membered ring has an impact on the electronic
absorption spectroscopic properties of the resulting Cu(I) complexes.
The solid-state luminescence spectra of 1–3 were measured on powder samples at
room temperature (figure 3). All were strongly emissive in the solid state and exhibit a
broad solid-state emission with maxima at 574, 584, and 598 nm upon excitation at 363
nm at ambient temperature for 1–3, respectively; the Cu(I)–pmtz complexes containing a
1,2,4-triazinyl ring are all non-emissive in the solid state. This indicates that the five-
membered 1,2,4-triazolyl ring in place of the six-membered 1,2,4-triazinyl ring plays a
key role in the photoluminescence of the resultant Cu(I) complexes, and the substituent
on the 1,2,4-triazolyl ring has an influence on the emission color of the Cu(I) species
[42]. The emission wavelength maxima (λmax) are in the order 1 < 2 < 3, consistent with
that of the ligand field strength of the halide (I− < Br− < Cl−), implying that λmax is
related to the ligand field strength of the halide [15]. Therefore, the electronic nature of
the triplet emissive state of 1–3 is affected to some degree by X → bpmtzH charge
transfer transitions. With reference to previous work [1, 2, 8–23, 42, 43], the HOMOs
of 1–3 are believed to be spread over the Cu(I) center and the halide, probably
involving some contributions from PPh3, while the LUMOs are thought to reside basi-
cally on the bpmtzH chelate. Hence, the emissive excited states of 1–3 are assigned as
the 3MLCT states with some mixing of the 3LLCT transitions (PPh3/X ← bpmtzH).
However, no detectable emission is observed for 1–3 in degassed CH2Cl2 and DMF
solutions at room temperature, likely a result of fast structural relaxation occurring in the
1.0
1
2
0.8
0.6
0.4
0.2
0.0
3
450
500
550
600
650
700
750
800
Wavelength (nm)
Figure 3. Solid-state emission spectra of 1–3 (λex = 363 nm) at room temperature.

1194
J.-L. Chen et al.
low viscosity solutions, as opposed to the bright solid-state emissions of 1–3 at ambient
temperature due to the retardation of structural relaxation in the rigid medium. Therefore,
this rigidochromism, which has been reported for Cu(I) systems bearing the diimine and
phosphine ligands [8, 13, 42], seems to be operative for 1–3. Additionally, it is shown
that the absorption and emission spectroscopic properties of 1 are not affected by its
crystalline chirality.
Table 3. Calculated energies of Cu(I) complexes with the N1^N3 and N1^N5 coordination of the bpmtzH ligand.
Chloride complex
N1^N3 coordination
N1^N5 coordination
Optimized geometry
E (a.u.)
–1573.712377
0
–1573.7186944
–16.586345324
16.586345324
Relative value (kJ M−1
)
ΔE (kJ M−1
)
Figure 4. Electron charge distributions on the bpmtzH ligand calculated by Mulliken (top) and Natural Population
Analysis (bottom).

Emissive Cu(I) complexes
1195
3.4. Theoretical investigations
To gain insight into the binding of bpmtzH with the Cu(I) center, theoretical computa-
tions were performed according to the optimized ground-state geometries of Cu(I) com-
plexes with the N1^N3 and N1^N5 chelating modes of bpmtzH (see labeling scheme
in figure 1). As indicated in table 3, the energy of Cu(I) chloride complexes with the
N1^N5 chelating is much lower than that of Cu(I) chloride complexes with the N1^N3
mode, implying that the bpmtzH ligand should preferentially coordinate with Cu(I)
using the N1^N5 chelating mode. Moreover, as shown in figure 4, the N5 of bpmtzH
displays a relatively higher electron density than the N3 donor of bpmtzH, further sug-
gesting that bpmtzH easily binds to the Cu(I) utilizing N1^N5 coordination instead of
N1^N3.
4. Conclusion
A new series of emissive monomeric Cu(I) complexes with 5-tert-butyl-3-(pyrimidine-2-
yl)-1H-1,2,4-triazole (bpmtzH), Cu(bpmtzH)(PPh3)X (X = I (1); Br (2); Cl (3)), have been
synthesized and characterized. BpmtzH coordinates to {Cu(PPh3)X} using one N of the 2-
pyrimidyl and the 4-N of 1,2,4-triazolyl rings as a neutral bidentate chelating ligand, in
agreement with the computational results. Complexes 1–3 with a 1,2,4-triazolyl five-mem-
bered ring are all emissive in the solid state at room temperature. Both the five-membered
1,2,4-triazolyl ring in place of the six-membered 1,2,4-triazinyl ring and the ancillary halide
ligand bound to {Cu(bpmtzH)(PPh3)} play major roles in influencing the molecular struc-
tures and luminescence properties of Cu(I) complexes. The results presented herein provide
new insight into the design and synthesis of emissive Cu(I) complexes with a functionalized
bpmtzH ligand.
Supplementary material
Figures of the IR spectra of bpmtzH and 1–3, 1H and 31P NMR spectra of 1–3, and ORTEP plots of the
structures of 1 and 2. Crystallographic data for the structural analysis have been deposited at the
Cambridge Crystallographic Data Center with the deposition numbers of CCDC 973017, 973016, and
914171 for 1–3, respectively. Copies of this information may be obtained free of charge from the
Director, CCDC, 12 Union Road, Cambridge, CB2 1EZ, UK (Fax: +44 1223 336033; E-mail:
deposit@ccdc.cam.ac.uk or www: http://www.ccdc.cam.ac.uk/deposit).
Funding
The authors thank the financial supports from the NSFC [grant numbers 21163009, 21001057, and
21161008]; the Key Project of Chinese Ministry of Education [grant number 211088]; the Advanced
Program for the Retuned Overseas Chinese Scholars of MOHRSS [grant number 474[2011]]; the
Training Program for Jiangxi Provincial Young Scientists [grant number 20122BCB23016]; the Key
Project of Education Department of Jiangxi Province [grant number GJJ13436]; the Foundation of
State Key Laboratory of Structural Chemistry [grant number 20110015]; and the Scientific Research
Foundation of Jiangxi University of Science and Technology [grant number JXXJ12072].

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J.-L. Chen et al.
References
[1] N. Armaroli, G. Accorsi, F. Cardinali, A. Listorti. Top. Curr. Chem., 280, 69 (2007).
[2] A. Barbieri, G. Accorsi, N. Armaroli. Chem. Commun., 44, 2185 (2008).
[3] D.R. McMillin, K.M. McNett. Chem. Rev., 98, 1201 (1998).
[4] T. Bessho, E.C. Constable, M. Graetzel, A.H. Redondo, C.E. Housecroft, W. Kylberg, M.K. Nazeeruddin,
M. Neuburger, S. Schaffner. Chem. Commun., 44, 3717 (2008).
[5] S. Perruchas, X.F.L. Goff, S. Maron, I. Maurin, F. Guillen, A. Garcia, T. Gacoin, J.-P. Boilot. J. Am. Chem.
Soc., 132, 10967 (2010).
[6] M. Nishikawa, K. Nomoto, S. Kume, K. Inoue, M. Sakai, M. Fujii, H. Nishihara. J. Am. Chem. Soc., 132,
9579 (2010).
[7] N. Armaroli, G. Accorsi, M. Holler, O. Moudam, J.-F. Nierengarten, Z. Zhou, R.T. Wegh, R. Welter. Adv.
Mater., 18, 1313 (2006).
[8] C.-W. Hsu, C.-C. Lin, M.-W. Chung, Y. Chi, G.-H. Lee, P.-T. Chou, C.-H. Chang, P.-Y. Chen. J. Am. Chem.
Soc., 133, 12085 (2011).
[9] G.F. Manbeck, W.W. Brennessel, R. Eisenberg. Inorg. Chem., 50, 3431 (2011).
[10] Q. Zhang, Q. Zhou, Y. Cheng, L. Wang, D. Ma, X. Jing, F. Wang. Adv. Mater., 16, 432 (2004).
[11] M.G. Crestani, G.F. Manbeck, W.W. Brennessel, T.M. McCormick, R. Eisenberg. Inorg. Chem., 50, 7172
(2011).
[12] T. McCormick, W.-L. Jia, S. Wang. Inorg. Chem., 45, 147 (2006).
[13] J. Min, Q. Zhang, W. Sun, Y. Cheng, L. Wang. Dalton Trans., 40, 686 (2011).
[14] P.C. Ford, E. Cariati, J. Bourassa. Chem. Rev., 99, 3625 (1999).
[15] M. Hashimoto, S. Igawa, M. Yashima, I. Kawata, M. Hoshino, M. Osawa. J. Am. Chem. Soc., 133, 10348
(2011).
[16] C.K. Ryu, M. Vitale, P.C. Ford. Inorg. Chem., 32, 869 (1993).
[17] A. Tsuboyama, K. Kuge, M. Furugori, S. Okada, M. Hoshino, K. Ueno. Inorg. Chem., 46, 1992 (2007).
[18] J.-L. Chen, X.-F. Cao, W. Gu, B.-T. Su, F. Zhang, H.-R. Wen, R. Hong. Inorg. Chem. Commun., 15, 65
(2012).
[19] L.-H. He, J.-L. Chen, F. Zhang, X.-F. Cao, X.-Z. Tan, X.-X. Chen, G. Rong, P. Luo, H.R. Wen. Inorg. Chem.
Commun., 21, 125 (2012).
[20] J.-L. Chen, X.-F. Cao, W. Gu, H.-R. Wen, L.-X. Shi, G. Rong, P. Luo. Inorg. Chem. Commun., 14, 1894
(2011).
[21] J.-L. Chen, W. Gu, X.-F. Cao, H.-R. Wen, R. Hong. J. Coord. Chem., 64, 1903 (2011).
[22] C. Vogler, H.-D. Hausen, W. Kaim, S. Kohlmann, H.E.A. Kramer, J. Rieker. Angew. Chem. Int. Ed., 28, 1659
(1989).
[23] C.L. Linfoot, P. Richardson, T.E. Hewat, O. Moudam, M.M. Forde, A. Collins, F. White, N. Robertson.
Dalton Trans., 39, 8945 (2010).
[24] J.-L. Chen, B. Wu, W. Gu, X.-F. Cao, H.-R. Wen, R. Hong, J. Liao, B.-T. Su. Transition Met. Chem., 36, 379
(2011).
[25] P.M. Hergenrother. J. Heterocycl. Chem., 6, 965 (1969).
[26] P.R. Evans. In Proceedings of the CCP4 Study Weekend. Recent Advances in Phasing, K.S. Wilson,
G. Davies, A.W. Ashton, S. Bailey (Eds.), p. 97, Daresbury Laboratory, Warrington (1997).
[27] G.M. Sheldrick. SHELXS-97 Program for Crystal Structure Solution, University of Göttingen, Germany
(1997).
[28] G.M. Sheldrick. SHELXL-97 Program for Crystal Structure Refinement, University of Göttingen, Germany
(1997).
[29] H.D. Flack. Acta Cryst., A39, 876 (1983).
[30] M.J. Frisch, G.W. Trucks, H.B. Schlegel, G.E. Scuseria, M.A. Robb, J.R. Cheeseman, J.A.J. Montgomery, 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, J.A. Pople.
Gaussian 03 (Revision D.02), Gaussian, Inc., Wallingford, CT (2004).
[31] A.D. Becke. J. Chem. Phys., 98, 5648 (1993).
[32] J.P. Perdew, K. Burke, M. Ernzerhof. Phys. Rev. Lett., 77, 3865 (1996).
[33] P.J. Hay, W.R. Wadt. J. Chem. Phys., 82, 270 (1985).
[34] W.R. Wadt, P.J. Hay. J. Chem. Phys., 82, 284 (1985).
[35] P.J. Hay, W.R. Wadt. J. Chem. Phys., 82, 299 (1985).

Emissive Cu(I) complexes
[36] P. Pyykkö, F. Mendizabal. Inorg. Chem., 37, 3018 (1998).
1197
[37] M.M. Francl, W.J. Pietro, W.J. Hehre, J.S. Binkley, M.S. Gordon, D.J. DeFrees, J.A. Pople. J. Chem. Phys.,
77, 3654 (1982).
[38] J.-L. Chen, P. Song, J. Liao, H.-R. Wen, R. Hong, Z.-N. Chen, Y. Chi. Inorg. Chem. Commun., 13, 1057
(2010).
[39] G.B. Deacon, R.A. Jones. Aust. J. Chem., 16, 499 (1963).
[40] A. Wada, Q. Zhang, T. Yasuda, I. Takasu, S. Enomoto, C. Adachi. Chem. Commun., 48, 5340 (2012).
[41] D. Tzimopoulos, A. Czapik, S. Kotoulas, J. Mohanraj, M. Gdaniec, P.D. Akrivos. J. Coord. Chem., 65, 393
(2012).
[42] J.-L. Chen, X.-F. Cao, J.-Y. Wang, L.-H. He, Z.-Y. Liu, H.-R. Wen, Z.-N. Chen. Inorg. Chem., 52, 9727
(2013).
[43] L.H. He, J.L. Chen, J.Y. Wang, X.X. Chen, X.Z. Tan, X.F. Cao. Chin. Chem. Lett., 23, 1169 (2012).