Copper(i) complexes of 1,10-phenanthroline and heterocyclic thioamides: An experimental and theoretical (DFT) investigation of the photophysical characteristics

Article abstract of DOI:10.1039/c2dt32167j

A series of luminescent mixed ligand complexes of copper(i) halides with 1,10-phenanthroline and the heterocyclic thioamides pyridine-2(1H)-thione (py2SH), pyrimidine-2(1H)-thione (pymtH), 4,6-dimethylpyrimidine-2(1H)-thione (dmpymtH), 1,4,5,6-tetrahydropyrimidine-2-thione (tHpymtH), 1,3-imidazolidine-2- thione (imtH₂) and 4,5-diphenyl-2-oxazolethiol (dpoxtH) have been synthesized and characterized. The molecular structures of two representative compounds have been established by single-crystal X-ray diffraction. The mononuclear complexes feature the metal in a distorted tetrahedral environment surrounded by the two N atoms of the chelating 1,10-phenanthroline, the thione-S atom of the thioamide, and the halogen atom. The molecular structure, the electronic and photophysical properties and the energetics of the metal-ligand interactions for [CuI(phen)(py2SH)] have been studied by means of density functional calculations.

Full text of DOI:10.1039/c2dt32167j

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PAPER
Copper(I) complexes of 1,10ꢀphenanthroline and heterocyclic
thioamides: an experimental and theoretical (DFT) investigation of the
photophysical characteristics
Ioannis Papazoglou,a Philip J. Cox,b Anastasios G. Papadopoulos,c Michael P. Sigalasc and Paraskevas
5
Aslanidisa*
Received (in XXX, XXX) Xth XXXXXXXXX 20XX, Accepted Xth XXXXXXXXX 20XX
DOI: 10.1039/b000000x
A series of luminescent mixed ligand complexes of copper(I) halides with 1,10ꢀphenanthroline and the
heterocyclic thioamides pyridineꢀ2(1H)ꢀthione (py2SH), pyrimidineꢀ2(1H)ꢀthione (pymtH), 4,6ꢀ
10 dimethylpyrimidineꢀ2(1H)ꢀthione (dmpymtH), 1,4,5,6ꢀtetrahydropyrimiꢀdineꢀ2ꢀthione (thpymtH), 1,3ꢀ
imidazolidineꢀ2ꢀthione (imtH2) and 4,5ꢀdiphenylꢀ2ꢀoxazolethiol (dpoxtH) have been synthesized and
characterized. The molecular structures of two representative compounds have been established by singleꢀ
crystal Xꢀray diffraction. The mononuclear complexes feature the metal in a distorted tetrahedral
environment surrounded by the two N atoms of the chelating 1,10ꢀphenanthroline, the thioneꢀS atom of
15 the thioamide, and the halogen atom. The molecular structure, the electronic and photophysical properties
and the energetics of the metalꢀligand interactions for [CuI(phen)(py2SH)] have been studied by means of
density functional calculations.
bending substituents in the 2,9ꢀpositions of the phenanthroline
ligand. Subsequent work involved the development of mixedꢀligand
copper(I) complexes which possess, in addition to their ability to
overcome solventꢀinduced exciplex quenching, enhanced emission
50 characteristics (intensity, lifetime, and quantum yield). As well as
the use of sterically hindered phenanthroline ligands, electronic
factors induced by suitable spectator coꢀligands might also influence
the oxidative instability of these complexes.
It is well known that the coordination chemistry of the soft acid
55 copper(I) is largely based upon coordination to ligands containing
soft donor atoms such as P or S. In this sense, copper(I) complexes
containing heterocyclic thioamides have received a great deal of
attention during the past few decades,21–24 whereby plenty of
interesting structures, in which the neutral thioamide molecules were
1. Introduction
Much attention has been paid in the past two decades to emissive
20 coordination compounds of many transition metals in view of their
applications as dopants to increase the electroluminescence
efficiency of organic light emitting diodes,1–3 as sensitizers in solarꢀ
energy conversion,4,5 as components for luminescentꢀbased chemical
sensors,6–9 in display devices10,11 and as photocatalysts. In this
25 respect, first row transition metal complexes are particularly
attractive, being considered as inexpensive, less toxic and more
easily available potential alternatives to the currently used thirdꢀrow
noble metal complexes. Among the emissive tetrahedral copper(I)
complexes investigated so far, the most promising class involve
30 polypyridineꢀ and phenanthrolineꢀtype ligands,12,13 often combined
with other rigid chelating ligands such as diphosphanes.14–17 One o6f0 generally found to bind the metal through the exocyclic sulfur atom,
were obtained. Exploring the photochemistry of such mixedꢀligand
the most interesting findings of the earlier investigations on
copper(I) complexes incorporating neutral heterocyclic thiones or
copper(I) bisꢀphenanthroline complexes was the fact that their
thiolates in the coordination sphere we recently reported on two
spectral characteristics were related to the distortions from the
series of Cu(I) compounds formulated as [Cu(κ3ꢀtriphos)(thiolate)]25
35 tetrahedral geometry induced by the substituents on the chelating
and [CuX(DPEphos)(thione)]26, respectively. Noticeably, the
ligands. In fact, it could be shown than [Cu(I)(2,9ꢀdimethylꢀ1,106ꢀ5
emission energy of these complexes proved to be tunable by
phenanthroline)2]+ exhibits photoluminescence in dichloromethane
modifying the ligands as well as introducing electronꢀdonating or ꢀ
but not in methanol or acetonitrile, whereas solutions of [Cu(I)(1,10ꢀ
accepting substituents to the heterocyclic rings. In an attempt to
phenanthroline)2]+ are not emissive.18–20 This was attributed to a
elucidate whether and how far the heterocyclic thione ligands could
40 distortion in the MLCT excited state due to a change of the formal
70 affect the photophysical properties of mixedꢀligand copper(I)
oxidation state from Cu(I) to Cu(II), generating a more flattened
phenanthroline complexes and to test the expectation that oxidative
geometry around the formed d9 metal ion, which offers a further
instability of the complexes can be suppressed due to the
coordination site for nucleophilic attack by species such as solvent
pronounced tendency of thioamides to stabilize copper in its lower
molecules. This flattening distortion, responsible for the quenching
oxidation state, we present herein a series of novel complexes,
45 of the excited state, is efficiently prevented by the presence of
75 which turn out to exhibit quite interesting luminescent properties.
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Further, density functional calculations for the complex show that PBE1PBE functional give better results than B3LYP in
[CuI(phen)(py2SH)] are used to interpret the relationship between calculating the molecular structure. Furthermore, PBE1PBE gave
structure electronic and photophysical properties, as well as to better results for spectrum analysis than BP86. Thus, the PBE1PBE
explore the energetics of the metalꢀligand interactions.
55 functional has been chosen both for geometry optimizations and for
calculating the spectra. Visualization of the MOs of interest was
done with GaussView 4.1.
5
2. Experimental Section
2.4. Synthesis
2.1. Materials and instrumentation
To a 40 ml roundꢀbottom flask flushed with argon and equipped
60 with a stirrer bar was added 15 ml of degased acetonitrile and 0.5
mmol of copper halide (49.5 mg for CuCl, 71.7 mg for CuBr or 95.2
mg for CuI) and the mixture was stirred at 50 oC under a continuous
argon stream. To the resulting clear solution, a 10 ml degassed
methanol solution containing 90 mg (0.5 mmol) 1,10ꢀphenanthroline
65 and 0.5 mmol of the respective thioamide was then added,
whereupon the colour of the solution immediately changed to red.
The reaction mixture was stirred for 5 min and then filtered off and
All air sensitive manipulations were performed under argon using
standard Schlenk techniques. Commercially available copper (I)
halides and 1,10ꢀphenanthroline were used as received, whereas the
10 heterocyclic thioamides pyridineꢀ2(1H)ꢀthione (py2SH), pyrimidineꢀ
2(1H)ꢀthione (pymtH), 4,6ꢀdimethylpyrimidineꢀ2(1H)ꢀthione
(dmpymtH), 1,4,5,6ꢀtetrahydropyrimidineꢀ2ꢀthione (thpymtH), 1,3ꢀ
imidazolidineꢀ2ꢀthione (imtH2), 4,5ꢀdiphenylꢀ2ꢀoxazolethiol
(dpoxtH) and 1,3ꢀdiphenylꢀ2ꢀthiobarbituric acid (dptba) (Scheme 1)
15 were recrystallized from hot ethanol. All the solvents were purified
by respective suitable methods and allowed to stand over molecular
sieves. Infraꢀred spectra in the region of 4000–200 cmꢀ1 were
obtained in KBr discs with a Nicolet FTꢀIR 6700 spectrophotometer.
Electronic absorption spectra in dichloromethane solutions were
20 measured with a Shimadzu 160A spectrophotometer, while a Hitachi
Fꢀ7000 fluorescence spectrophotometer was used to obtain the
excitation and emission spectra. Melting points were measured in
o
collected into a Schlenk flask which was capped and stored at 5 C
for 24 h, whereupon dark red crystals deposited which were
70 collected by filtration and dried in vacuo.
Alternative procedure: To a Schlenk flask flushed with argon and
equipped with a stirrer bar was added 10 ml of degased acetonitrile
and 0.25 mmol of copper halide (24.7 mg for CuCl, 35.8 mg for
CuBr or 47.6 mg for CuI) and the mixture was stirred at 50 oC under
75 a continuous argon stream until a clear solution resulted. After
cooling to room temperature, 45 mg (0.25 mmol) 1,10ꢀ
phenanthroline and 0.25 mmol of the respective thioamide,
dissolved in a minimum amount of ~3 ml degassed dichloromethane
was added, whereupon the microcrystalline product was deposited
80 within minutes.
open tubes with
uncorrected.
a
STUART scientific instrument and are
CH3
Ph
NH
NH
NH
NH
NH
NH
Ph
S
S
N
O
N
S
N
S
S
H3C
N
S
H
H
dpoxtH
pymtH
dmpymtH
imtH2
tHpymtH
py2SH
25
2.4.1. [CuCl(phen)(py2SH)] (1). Red crystals (92 mg, 47 %), m.p.
195 oC; Anal. Calc. for C17H13CuClN3S: C, 52.30; H, 3.36; N, 10.76.
Found: C, 52.16; H, 3.19; N, 10.45 %. IR (cmꢀ1): 3151w, 3044w,
2952w, 2878m, 1603s, 1576vs, 1506s, 1418s, 1367s, 1131vs, 996s,
85 843vs, 751vs, 723vs, 486m, 449s; UVꢀVis (λmax, log ε): 234 (4.80),
263 (5.32), 300 (3.37), 429 (3.03).
Scheme 1 The heterocyclic thioamides used as ligands with their
abbreviations
2.2. Crystal structure determination
Single crystals of 3 suitable for crystal structure analysis were
30 obtained from an acetonitrile/methanol mixture of the complex at
5oC under argon, whereas crystals of
7
were grown in
a
2.4.2. [CuBr(phen)(py2SH)] (2). Red crystals (111 mg, 51 %), m.p.
203 oC; Anal. Calc. for C17H13CuBrN3S: C, 46.95; H, 3.01; N, 9.66.
Found: C, 46.23; H, 2.91; N, 9.45 %. IR (cmꢀ1): 3142w, 3040m,
90 2957m, 2855m, 1603s, 1571vs, 1502s, 1409s, 1362s, 1131vs, 992s,
843vs, 746vs, 727vs, 486s, 449s; UVꢀVis (λmax, log ε): 232 (4.78),
270 (5.32), 396 (3.81), 435 (3.66).
dichloromethane/acetonitrile solution at room temperature. Xꢀray
diffraction data were collected on Rigaku Saturn 724+
a
diffractometer by the NCS27 using CrystalClearꢀSM Expert28 for
35 cell refinement, data collection and data reduction. The structure was
solved with SHELXS9729 and refined with SHELXL97. The program
used for Molecular graphics was PLATON.30 Tables for publication
were prepared with SHELXS97 and WINGX.31
2.4.3. [CuI(phen)(py2SH)] (3). Red crystals (108 mg, 45 %), m.p.
o
208 C; Anal. Calc. for C17H13CuIN3S: C, 42.38; H, 2.72; N, 8.72.
95 Found: C, 42.31; H, 2.63; N, 8.73 %. IR (cmꢀ1): 3138w, 3045m,
2976m, 2910s, 1604s, 1566vs, 1502s, 1418s, 1362s, 1219m,1131vs,
992s, 839vs, 741vs, 727vs, 486s, 449s; UVꢀVis (λmax, log ε): 232
(4.83), 270 (5.10), 366 (4.93), 422sh (3.52).
2.3. Computational details
40 DFT and TDꢀDFT calculations of CuI(phen)(py2SH) (compound 3)
were carried out with Gaussian 03W32 software package under the
PCM33ꢀ35 algorithm implemented in it. Geometry optimizations were
carried out in ground state (S0) and in triplet state (T1). A frequency
calculation after each geometry optimization ensured that the
45 calculated structures are real minima in the potential energy surface
of the molecules. The calculations were carried out not only in gas
phase, but in dichloromethane solution as well using the PCM
model. The PBE1PBE36,37functional of Perdew, Burke and
Ernzerhof was used in combination with the 6ꢀ311++G(d,p)38–42
50 basis set for the elements C, N, H, S and the SDD effective core
potentials and basis set for the elements Cu and I. Test calculations
2.4.4. [CuCl(phen)(pymtH)] (4). Red microcrystals (86 mg, 44 %),
o
100 m.p. 200 C; Anal. Calc. for C16H12CuClN4S: C, 49.10; H, 3.09; N,
14.31. Found: C, 48.98; H, 3.15; N, 14.22 %. IR (cmꢀ1): 3051m,
2922m, 1603s, 1563vs, 1514s, 1425vs, 1376vs, 1331s, 1176vs,
975s, 850vs, 771m, 726vs, 46ms; UVꢀVis (λmax, log ε): 231 (4.77),
271 (5.05), 404 (3.55); UVꢀVis (λmax, log ε): 234 (4.31), 261 (4.23),
105 290 (3.98), 403 (2.85).
2.4.5. [CuCl(phen)(pymtH)] (5). Red microcrystals (85 mg, 39 %),
2
|
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o
m.p. 206 C; Anal. Calc. for C16H12CuBrN4S: C, 44.10; H, 2.77; N, (2.98).
5
5
12.85. Found: C, 43.92; H, 2.58; N, 12.82 %. IR (cmꢀ1): 3133w,
3054m, 2985m, 1594vs, 1557vs, 1474s, 1418s, 1316vs, 1214s,
1172vs, 973vs, 871m, 783s, 737s, 454s; UVꢀVis (λmax, log ε): 231
(4.77), 271 (5.05), 317sh (3.81), 404 (3.55).
2.4.14. [CuBr(phen)(imtH2)] (14). Red powder (68 mg, 32 %),
o
m.p. 254 C; Anal. Calc. for C15H14CuBrN4S: C, 42.31; H, 3.31; N,
13.16. Found: C, 42.33; H, 3.30; N, 13.08 %. IR (cmꢀ1): 3263s,
3156s, 3045m, 2892m, 1619m, 1539vs, 1518vs, 1489s, 1418vs,
1321s, 1284s, 1205vs, 1131m, 839vs, 727vs, 700s, 574s, 496s; UVꢀ
5
2.4.6. [CuI(phen)(pymtH)] (6). Red powder (113 mg, 47 %), m.p
60
.
o
214 C; Anal. Calc. for C16H12CuIN4S: C, 39.80; H, 2.50; N, 11.60. Vis (λmax, log ε): 233 (4.59), 272 (5.05), 295 (4.79), 434 (2.99).
Found: C, 38.98; H, 2.68; N, 11.24 %. IR (cmꢀ1): 3093m, 3050m,
Table 1 Crystal Data and Structure Refinement for [CuI(phen)(py2SH)] (3)
3010m, 2918m, 2855m, 1599s, 1556vs, 1467s, 1421vs, 1371s,
and [CuCl(phen)(dmpymtH)].CH2Cl2 (7)
10 1211m, 1197m, 1173vs, 1137m, 1045m, 979s, 840vs, 762s, 725vs,
470m; UVꢀVis (λmax, log ε): 231 (4.80), 271 (5.12), 325sh (3.77),
410 (3.50).
3
7
[(C18H16ClCuN4S)(C
H2Cl2)]
Molecular formula
C17H13CuIN3S
Formula weight
Temperature
Wavelength
Crystal system
Space group
Unit cell dimensions
481.80
100(2) K
0.71073 Å
Triclinic
504.33
100(2) K
2.4.7. [CuCl(phen)(dmpymtH)] (7). Red crystals (84 mg, 40 %),
m.p. 208 C; Anal. Calc. for C18H16CuClN4S: C, 51.55; H, 3.85; N,
o
0.71073 Å
Monoclinic
Cc
a = 25.97(2) Å
b = 11.156(8) Å
c = 16.699(13) Å
α= 90°
15 13.36. Found: C, 50.91; H, 3.22; N, 13.28 %. IR (cmꢀ1): 3050m,
2897m, 1613vs, 1562vs, 1423s, 1233vs, 1182s, 982s, 843vs, 723vs,
460m; UVꢀVis (λmax, log ε): 231 (4.85), 271 (5.23), 285sh (4.98),
419 (3.32).
Pī
a = 7.9266(11) Å
b = 9.2093(16) Å
c = 13.107(3) Å
α= 85.396(18)°
β= 72.771(13)°
γ = 67.540(14)°
2.4.8. [CuBr(phen)(dmpymtH)] (8). Red microcrystals (97 mg, 42
20 %), m.p. 218 oC; Anal. Calc. for C18H16CuBrN4S: C, 46.61; H, 3.48;
N, 12.08. Found: C, 46.58; H, 3.42; N, 11.98 %. IR (cmꢀ1): 3050m,
2915m, 2850m, 1604vs, 1557vs, 1469m, 1423s, 1372s, 1325s,
1210m, 1172vs, 1042m, 978s, 843s, 769m, 723s, 460m; UVꢀVis
(λmax, log ε): 233 (3.68), 275 (4.58), 295sh (3.08) 414 (3.33).
β= 118.877(14)°
γ = 90°
Volume
3
3
844.0(3) Å
2
4236(6) Å
8
Z
Density (calculated)
3
3
1.896 Mg/m
1.581 Mg/m
Absorption
coefficient
F(000)
ꢀ1
ꢀ1
3.248 mm
1.521 mm
468
2048
0.10 x 0.06 x 0.02
25 2.4.9. [CuI(phen)(dmpymtH)] (9). Red crystals (97 mg, 38 %),
Crystal size
0.20 x 0.06 x 0.02
o
m.p. 228 C; Anal. Calc. for C18H16CuIN4S: C, 42.32; H, 3.16; N,
3
3
mm
mm
10.97. Found: C, 41.97; H, 3.17; N, 10.86 %. IR (cmꢀ1): 3040m,
2952m, 1608vs, 1557vs, 1506m, 1413s, 1228vs, 1186vs, 9828s,
843vs, 817s, 767m, 727vs, 460m; UVꢀVis (λmax, log ε): 229 (4.76),
30 269 (4.78), 290sh (3.28), 412 (3.70).
Theta range for data
collection
Index ranges
2.85 to 27.50°
1.65 to 31.27°
ꢀ10<=h<=10
ꢀ11<=k<=9
ꢀ17<=l<=16
7844
3805 [R(int) =
0.0184]
98.0 % (theta =
27.50°)
0.9379 and 0.5628
ꢀ36<=h<=35
ꢀ16<=k<=16
ꢀ20<=l<=23
31791
10710 [R(int) =
0.0698]
92.9 % (theta =
31.27°)
1.00 and 0.77
Reflections collected
Independent
reflections
Completeness to theta
= 27.50°
Max. and min.
transmission
2.4.10. [CuCl(phen)(tHpymtH)] (10). Red powder (71 mg, 36 %),
o
m.p. 270 C; Anal. Calc. for C16H16CuClN4S: C, 48.60; H, 4.08; N,
14.17. Found: C, 48.45; H, 3.95; N, 14.09 IR (cmꢀ1): 3179m, 3114m,
2985m, 1619m, 1566vs, 1506s, 1423vs, 1366s, 1214vs, 1141m,
35 843vs, 767m, 727vs, 635m; UVꢀVis (λmax, log ε): 234 (4.35), 256
(4.25), 321 (3.46), 435 (3.04).
Refinement method
Fullꢀmatrix leastꢀ
Fullꢀmatrix leastꢀ
2
2
2.4.11. [CuBr(phen)(tHpymtH)] (11). Red powder (88 mg, 40 %),
squares on F
squares on F
o
Data / restraints /
parameters
3805 / 0 / 208
10710 / 2 / 510
m.p. 274 C; Anal. Calc. for C16H16CuBrN4S: C, 43.69; H, 3.66; N,
12.74. Found: C, 43.52; H, 3.55; N, 12.69 %. IR (cmꢀ1): 3179m,
40 3118m, 2965m, 1621m, 1575vs, 1566vs, 1505s, 1422s, 1371s,
Goodnessꢀofꢀfit on F2
Final R indices
0.977
1.115
R1 = 0.0173, wR2 =
0.0408
R1 = 0.0201, wR2 =
0.0412
R1 = 0.0775, wR2 =
0.1741
R1 = 0.0930, wR2 =
0.1861
1320s, 1209vs, 1134m, 843vs, 727vs, 635s, 565m; UVꢀVis (λmax
,
[I>2sigma(I)]
R indices (all data)
log ε): 237 (5.25), 269 (5.24), 326 (5.08), 435 (2.99).
2.4.12. [CuI(phen)(tHpymtH)] (12). Red crystals (90 mg, 37 %),
Final weighting
scheme
calc
calc
o
w=1/σ2[(Fo2)+(0.0183 w=1/σ2[(Fo2)+(0.0694
m.p. 279 C; Anal. Calc. for C16H16CuIN4S: C, 39.47; H, 3.31; N,
P)2+ 0.0000P], where
P=(Fo2+2Fc2)/3
P)2+ 8.9316P], where
P=(Fo2+2Fc2)/3
0.0(2)
45 11.51. Found: C, 39.11; H, 2.88; N, 10.65 %. IR (cmꢀ1): 3193s,
3040m, 2957m, 1617m, 1576vs, 1548vs, 1506s, 1418vs, 1372m,
1321s, 1200vs, 945m, 839vs, 723vs, 630m, 467s; UVꢀVis (λmax, log
ε): 234 (4.94), 267 (5.24), 3.26 (5.36), 437 (2.91).
Absolute structure
parameter
Largest diff. peak and
hole
ꢀ
ꢀ3
0.656 and ꢀ0.426 e.Å 3
0.942 and ꢀ0.861 e.Å
2.4.13. [CuCl(phen)(imtH2)] (13). Red powder (63 mg, 33 %),
o
50 m.p. 248 C; Anal. Calc. for C15H14CuClN4S: C, 47.24; H, 3.70; N,
ꢀ1
65 2.4.15. [CuI(phen)(imtH2)] (15). Red powder (92 mg, 39 %), m.p.
14.69. Found: C, 47.23; H, 3.71; N, 14.63 %. IR (cm ): 3263s,
o
259 C; Anal. Calc. for C15H14CuIN4S: C, 38.10; H, 2.98; N, 11.85.
3115s, 3050m, 2897m, 1616m, 1543vs, 1515vs, 1486s, 1422vs,
1321s, 1284s, 1210vs, 1135m, 1033m, 839vs, 727vs, 579s, 500s,
419m; UVꢀVis (λmax, log ε): 229 (4.59), 270 (4.95), 297 (3.43), 426
Found: C, 38.07; H, 2.97; N, 11.42 %. IR (cmꢀ1): 3217s, 3140s,
2878m, 1622m, 1502vs, 1423vs, 1325s, 1274s, 1191s, 839vs, 765m,
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727vs, 666m, 602m, 489m; UVꢀVis (λmax, log ε): 232 (4.79), 27155
(5.26), 288 (4.23), 422 (3.13).
The electronic absorption spectra of all compounds are
dominated by two intense UV bands in the range ~230 and ~270 nm.
Exact assignment of these bands is difficult since both the thiones
ligands and phenanthroline strongly absorpts in these two regions. A
third broad band of lower intensity in the 300ꢀ360 nm region can be
60 ascribed to thione originating intraligand transitions, which may
possess partial charge transfer CT character. The lowestꢀenergy band
of the absorption spectra for the complexes consisting of a band with
maxima in the 400–435 nm near UV region have been assigned to
metal to ligand charge transfer (MLCT) bands of the phenanthroline
65 ligand.43–44
2.4.16. [CuCl(phen)(dpoxtH)] (16). Red powder (101 mg, 38 %),
m.p. 218 oC; Anal. Calc. for C27H19CuClN3OS: C, 60.90; H, 3.60; N,
7.89. Found: C, 60.43; H, 3.12; N, 7.85 %. IR (cmꢀ1): 3054m,
2925w, 1507s, 1492vs, 1425vs, 1182vs, 1021m, 955s, 848s, 764vs,
727s, 695vs, 598m, 556s, 520m; UVꢀVis (λmax, log ε): 230 (4.76),
268 (5.06), 322 (3.39), 417 (3.04).
5
2.4.17. [CuBr(phen)(dpoxtH)] (17). Red powder (68 mg, 32 %),
o
10 m.p. 223 C; Anal. Calc. for C27H19CuBrN3OS: C, 56.21; H, 3.32;
N, 7.28. Found: C, 55.82; H, 3.32; N, 7.22 %. IR (cmꢀ1): 3023m,
2860m, 1505s, 1492vs, 1423vs, 1182vs, 1027m, 964s, 848vs, 760vs,
695vs, 587m, 556s, 517m; UVꢀVis (λmax, log ε): 233 (4.74), 270
(5.19), 317 (4.39), 403 (3.06).
3.3. Xꢀray structural analysis
The Xꢀray crystal structures of [CuI(phen)(py2SH)] (3) and
[CuCl(phen)(dmpymtH)].CH2Cl2 (7) (details of crystal and structure
refinement are shown in Table 1) corroborate the spectroscopic
70 results discussed above. Main bond lengths and angles are listed in
Tables 2 and 3, whereas plots for the two molecules showing the
atom numbering appear in Figures 1 and 2 respectively. The crystals
of 7 were twinned and the extent of the available data was limited to
93% of that normally expected. The alternate space group, C2/c,
75 was considered as a pseudo centre of symmetry is present but
refinement in this space group was unstable. Τhere are two
molecules in the asymmetric unit of 7, with small geometrical
differences between them; table 3 contains selected bond lengths
and angles only for one of these molecules.
15 2.4.18. [CuI(phen)(dpoxtH)] (18). Red powder (106 mg, 34 %),
o
m.p. 228 C; Anal. Calc. for C27H19CuIN3OS: C, 51.97; H, 3.07; N,
6.73. Found: C, 51.42; H, 2.92; N, 7.08 %. IR (cmꢀ1): 3028m,
2906m, 1505s, 1492vs, 1418vs, 1177vs, 1021m, 964s, 843vs, 760vs,
727vs, 690vs, 583m, 556s, 517m; UVꢀVis (λmax, log ε): 232 (4.97),
20 272 (5.35), 330 (4.26), 407 (3.30).
3. Results and discussion
3.1. Synthesis
Compounds 1ꢀ18 are accessible via the direct treatment of copper(I)
halides with equivalent amounts of 1,10ꢀphenanthroline and the
25 corresponding heterocyclic thioamide under mild conditions. The
complexes formed immediately after mixing the solutions of the
components, which becomes apparent from the dark red colour of
the reaction mixture, are quite unstable in solution. In fact, their
solutions undergo gradual reꢀcolouring from red to green, which
30 indicates oxidation of copper(I) to copper(II). Thus, the choice of the
proper reaction medium in order to gain control over the speed of
the subsequent crystal deposition, was crucial for the successful
isolation of the desired compounds in pure form. In this respect,
rapid and very efficient precipitation was obtained in acetonitrile/
35 dichloromethane solutions, whereas the acetonitrile/methanol
mixture, though less suitable for the more sensitive derivatives,
proved to be an appropriate medium for better crystal growth.
Interestingly, the above oxidation process was also found to depend
on the type of the thioamide used. Indeed, in some cases solutions
40 tended to undergo decomposition within minutes, whereas in the
specific case of tHpymtH the corresponding complexes (compounds
10ꢀ12) were less sensitive to oxidation and their solutions remained
stable for relative long time.
80
Fig. 1 A molecular plot of [CuI(phen)(py2SH)] (3)
Table 2 Selected bond lengths [Å] and angles [o] for 3
Cu(1)–I(1)
Cu(1)–N(2)
2.6216(5) Cu(1)–N(1)
2.1177(15) Cu(1)–S(1)
1.7081(19)
2.0836(16)
2.2343(6)
S(1)–C(13)
_
3.2. Spectroscopy
_
_
_
79.74(6)
122.12(5)
108.18(4)
111.35(7)
112.14(4)
106.12(4)
120.331(19)
N(1) Cu(1) N(2)
N(1) Cu(1) S(1)
45 In the infrared1spectra of compounds 1ꢀ18, recorded in the range
_
_
_
_
4000–250 cmꢀ 1 the two very strong phenanthroline bands at ~840
N(2) Cu(1) S(1)
N(1) Cu(1) I(1)
1
and ~740 cmꢀ display a red shift of about1 15 cmꢀ upon
_
_
_
_
N(2) Cu(1) I(1)
S(1) Cu(1) I(1)
coordination, whereas a strong band at ~620 cmꢀ
appears blueꢀ
_
_
1
C(13) S(1) Cu(1)
Hydrogen bridge
shifted by about 10 cmꢀ . Further multiple strong bands in the range
1
50 1590–1430 cmꢀ attributable to the phenathroline molecule remain
practically unshifted upon coordination. In addition, the spectra of
all compounds contain the expected four characteristic “thioamide
bands”, with shifts due to coordination indicative of an exclusive Sꢀ
coordination mode.
N(3)–H(3)
NH(3)–I(1)
0.8800
2.6100
N(3) … I(1)
3.4440(16)
I(1)…H(3)–N(3) 158.3o
4
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In 3 the shortest intermolecular π...π stacking interaction is
The fourꢀcoordinate monomers reveal a copper coordination
sphere consisting of two N atoms of the phenanthroline molecule, 3.513(1) Å between N3ꢀC13ꢀC14ꢀC15ꢀC16ꢀC17 rings separated by
the S atoms from two corresponding thione unit and the halogen30 the symmetry operation 1ꢀx,1ꢀy,ꢀz. There is also a H... π interaction
atom. The angular deviations from the ideal tetrahedral value are of 2.58 Å between C14ꢀH14 and the centre of the N2ꢀC10ꢀC9ꢀC8ꢀ
remarkable but not at all unexpected, at least regarding the acute N– C7ꢀC11 ring when the coordinates of the ring atoms are displaced by
Cu–N angle which is 79.74(6)o in 3 and 80.2(2)o in 7, restricted by x,1+y,z.
5
the narrow bite angle of the rigid phenanthroline unit. This angle is
very close to that of 79.93(10)o observed in [CuI(phen)(PPh3)],45
In 7 the shortest intermolecular π...π stacking interaction is
o
3
r
5
3.423(5)Å between rings N7ꢀC31ꢀN8ꢀC34ꢀC33ꢀC32 and N3ꢀC13ꢀ
80.6(1)o found in [Cu2(ꢁꢀI)2(phen)2],46 and within the range of N4ꢀC16ꢀC15ꢀC14 when coordinates of the latter ring atoms are
10 values found in other related complexes.47–49
transformed by 0.5+x,0.5ꢀy,ꢀ0.5+z. The only H... π interaction is
The CuNCCN framework in 3 shows the formation of an almost between C17ꢀH17b and the centre of ring N1ꢀC1ꢀC2ꢀC3ꢀC4ꢀC12
planar fiveꢀmembered chelate ring, whereas in the structure of 7, in when the coordinates of the ring atoms are transformed by x,ꢀ
one of the two molecules the Cu1 atom is displaced from a mean40 y,0.5+z..
plane through the N1,N2,C1ꢀC12 atoms by 0.25A, whereas in the
15 other molecule the Cu2 atom is almost coꢀplanar, i.e., it is only
3.4. Luminescence
The RT luminescence spectra of the complexes in degassed CH2Cl2
solutions have been studied. The excitation and emission spectrum
of a representative compound, [CuCl(phen)(dmpymtH)], is shown in
45 Figure 3 while excitation and emission data of the complexes under
investigation are summarized in Table 4.
displaced by 0.05A from the N5,N6,C19ꢀC30 plane.
Table
4 Room temperature excitation and emission maxima of the
complexes in 10ꢀ4 M CH2Cl2 solution
50
Compound
λexc [nm]
387
λem [nm]
481
[CuCl(phen)(py2SH)]
[CuBr(phen)(py2SH)]
[CuI(phen)(py2SH)]
[CuCl(phen)(pymtH)]
[CuBr(phen)(pymtH)]
[CuI(phen)(pymtH)]
[CuCl(phen)(dmpymtH)]
[CuBr(phen)(dmpymtH)]
[CuI(phen)(dmpymtH)]
[CuCl(phen)(tHpymtH)]
[CuBr(phen)(tHpymtH)]
[CuI(phen)(tHpymtH)]
[CuCl(phen)(imdztH)
[CuBr(phen)(imdztH)
[CuI(phen)(imdztH)
[CuCl(phen)(dpoxtH)]
[CuBr(phen)(dpoxtH)]
[CuI(phen)(dpoxtH)]
350
541
340
527
346, 376
375
430, 647
650
386, 430
376
540, 648
511
353
484
372
513
Fig. 2 The asymmetric unit of [CuCl(phen)(dmpymtH)].[CH2Cl2] (7)
Table 3 Selected bond lengths [Å] and angles [o] for 7
364
537
383
490
390
525
Cu(1)–Cl(1)
Cu(1)–N(2)
S(1)–C(13)
2.307(2)
2.136(7)
1.732(7)
80.2(2)
Cu(1)–N(1)
Cu(1)–S(1)
2.112(6)
2.241(2)
311
533
385
540
309
535
364
440
_
_
_
_
105.93(17)
119.01(17)
116.59(9)
N(1) Cu(1) N(2)
N(1) Cu(1) S(1)
363
438
_
_
_
_
122.64(18)
107.82(18)
111.3(2)
353
442
N(2) Cu(1) S(1)
N(1) Cu(1) Cl(1)
_
_
_
_
N(2) Cu(1) Cl(1)
S(1) Cu(1) Cl(1)
After excitation at 376 nm, the RT emission spectrum of
[CuCl(phen)(dmpymtH)] consists of a broad band with maximum at
511 nm, clearly redꢀshifted by 74 and 102 nm when compared with
_
_
C(13) S(1) Cu(1)
Hydrogen bridge
55 the emission maxima of both the free ligands dmpymtH and
phenanthroline respectively. This result may be considered as
evidence for participation of an S→Cu charge transfer in the
emissive excited state.53 In a similar manner, the emission spectra of
the other complexes are simple, with bands in the 430–650 nm
60 window, with the λmax(em) values strongly depending on the nature of
the thione present, whereby the higher energy emissions are
registered for the derivatives containing 4,5ꢀbiphenylꢀ2ꢀoxazolinoꢀ2ꢀ
thione (dpoxtH). These variations of the emission bands are
obviously associated with the electronic characteristics of the thione
65 ligands which determine the strength of the Cu–S bond. Indeed,
N(4)–H(4)
0.8800
2.2700
N(4)…Cl(1)
3.1470(6)
174.3o
NH(4)–Cl(1)
Cl(1)…H(4)–N(4)
20
The Cu–N(1) and Cu–N(2) bond distances of 2.084 and 2.118 Å
in 3, slightly shorter than the corresponding bond distances in 7 are
in good agreement with the lengths in analogous compounds.
Likewise the Cu–I bond length in 3 and the Cu Cl bond length in
7 are comparable to those reported for other tetrahedrally
_
25
coordinated copper(I) complexes with terminal iodine and chlorine
donors respectively.50ꢀ52
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recent studies on complexes of type CuXL (L = heteroaromatic gas phase and dichloromethane solution.
ligand) showed that the energy of the emitting excited state can be
modulated by modifying the electrophilic properties of L,54 however
precise statements can not be made on the basis of the compounds
under investigation.
5
50 Scheme 2 Skeletal structure of [CuI(phen)(py2SH)] (3), studied in this work.
(a) The numbering of the main atoms and (b) NBO charges in the singlet (S0)
and triplet (T1) states (in parentheses). The hydrogen atoms are omitted for
sake of clarity
Fig. 3 Room temperature excitation (a) and emission (b) spectrum of
[CuCl(phen)(dmpymtH)] in CH2Cl2 solution
According to the above observations, the lowest energy emissive
10 excited state can be assigned to MLCT transitions of type CuI →
thione, since is very likely for the d10 ion to express strong tendency
for charge transfer of this type. Nothing certainly can be said with
regard to the role of the halogen present in each case, though it is
very likely for the halogen to participate, to some extent, in the
15 emissive excited states with charge transfer processes of type X→
CuI or X→thione.
An additional possibility for lowꢀenergy excitation in the
complexes under investigation offers the CuI → phenanthroline
charge transfer. However, excitation in the region 400ꢀ430 nm,
20 where the lowest energy band, attributable to this MLCT transition
in the UVꢀvis spectra of the complexes lies, unexpectedly does not
cause any emission, except for the three pymtH derivatives, whose
spectra contain two emission bands at two different regions, ~ 440
and ~ 650 nm, produced by two different excitations at ~ 340 and ~
25 380 nm, respectively. The emissive states in these later compounds
could be of mixed MLCT character including both the phenantroline
and the thione ligand.
55
Fig. 4 Optimized geometries of [CuI(phen)(py2SH)] (3), for the ground state,
S0, (a) and for the triplet state, T1, (b) calculated at the PBE1PBE/6ꢀ
311++G(d,p), SDD level of theory
3.5. Computational studies
The skeletal structure of CuI(phen)(py2SH)] is shown in Scheme 2.
30 The molecular structure of the complex in its ground state (S0) and
in its triplet state (T1) has been optimized under the density
functional level of theory using the PBE1PBE functional, in gas
phase and in dichloromethane solution. Figure 4 shows the
optimized structures, whereas selected calculated bond lengths and
35 dihedral angles concerning the coordination sphere are given in
Table 5.
gas phase and dichloromethane solution. Distortion is also observed
60 in the dihedral angles C13ꢀS1ꢀCu1ꢀN2 and C13ꢀS1ꢀCu1ꢀN1 between the
gas phase and dichloromethane solution in ground state. A
comparison between ground and triplet state, in gas phase, reveals
elongation of the Cu1–I1 and Cu1–S1 bond distances in triplet state,
while the Cu1–N1 and Cu1–N2 bonds are shortened in the excited
65 state in comparison with the singlet state. The same is observed in
dichloromethane solution, except from the Cu1–I1 bond, which
shows a shortening in the triplet state.
The ground state (S0) of [CuI(phen)(py2SH)] adopts a tetrahedral
geometry, while a flattening distortion from the tetrahedral geometry
by approximately 30 degrees appears in the triplet state (T1), as
40 expected. In gas phase the triplet state is higher in energy than the
singlet state by 1.339eV, while in dichloromethane solution the
energy difference between singlet and triplet state is 1.622eV. In the
ground state there is an elongation of the Cu1–I1 bond in
dichloromethane solution compared to gas phase. The other bond
45 distances (Cu1–N1, Cu1–N2 and Cu1–S1) are almost the same in both
As it becomes obvious in Scheme 2 (b), the transition of the
complex in its lowest triplet excited state is accompanied by an
70 electronic charge displacement from the atoms constituting the
chromophore (Cu, S, I) towards the skeleton of the diimine moiety.
So, in a first step this leads to an elongation of the bond lengths
within the chromophore, which is in accordance to what is observed
for the Cu–S and Cu–I bonds. Additionally, the increment of the
75 positive charge of the metal core renders the Cu center to a harder
6
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Table 5 Relative energies, selected bond distances (Å) and dihedral angles
(deg) calculated for complex [CuI(phen)(py2SH)] (3) in gas phase and in
dichlorometane solution tooa
dichloromethane solution are represented in Table 6. The calculated
excitation energies are also shown in Figure 6, where representative
25 density diagrams of the MOs participating in each electron transition
with the higher CI coefficient are also depicted, in order to
intuitively understand the absorption process. The computed
electronic transitions are in good agreement with the experimental
ones.
S0
T1
Gas Phase
ꢁΕ (eV)
0.0
1.339
30
Bond Lengths
2.144
2.144
2.626
2.275
1.989
1.983
2.638
2.356
Cu1ꢀN1
Cu1ꢀN2
Cu1ꢀI1
Cu1ꢀS1
Dihedral Angles
C13…S1…Cu1…N2
136.5
115.6
C13…S1…Cu1…N1
N2…C11…C12…N1
ꢀ136.8
0.0192
ꢀ167.3
ꢀ1.676
CH2Cl2 Solution
ꢁΕ (eV)
0.0
1.622
Bond Lengths
Fig. 5 Experimental absorption spectrum of [CuI(phen)(py2SH)] (3) along
2.133
2.129
2.693
2.269
1.993
1.977
2.656
2.329
Cu1ꢀN1
with the calculated excitation energies appeared as vertical lines.
Cu1ꢀN2
There is a good resemblance of the calculated excitation energies
35 with the experimental spectra as shown in figure 5. The simulated
absorption spectrum shows an intense high energy band in the
ultraviolet region (250ꢀ300 nm) and a low energy band of lower
intensity in the visible region (400ꢀ450 nm). The low energy
absorption band involves HOMOꢀ1, HOMOꢀ2, HOMOꢀ3 → LUMO
40 excitations and HOMO, HOMOꢀ1→ LUMO+2 excitations. Figure 6
shows that the first three excitations involving MLCT and XLCT
transitions, arise from electronic transitions between low energy
MOs, which are consisted of Cu 3d AOs, p orbitals located on the
iodine ligand and p orbitals located on the sulfur atom of the py2SH
45 ligand, and the high energy LUMO orbital, which is a highly
delocalized unoccupied π∗ꢀMO of the phenanthroline.
The second pair of excitations is of the same character (MLCT
and XLCT). In particular, the electronic transitions include HOMO
and HOMOꢀ1 orbitals, which are consisted of Cu 3d AOs, p orbitals
50 located on the iodine ligand and p AOs of all atoms of py2SH ligand,
and the high energy LUMO+2 orbital, which is a highly delocalized
unoccupied π∗ꢀMO of the py2SH moiety.
Cu1ꢀI1
Cu1ꢀS1
Dihedral Angles
C13…S1…Cu1…N2
129.6
ꢀ141.0
0.149
108.9
ꢀ171.6
ꢀ1.539
C13…S1…Cu1…N1
N2…C11…C12…N1
5
a Numbering scheme as in Scheme 2a.
Lewis acid and this diminishes its affinity towards the S and I atoms
which are typical soft bases, thus contributing further to the
elongation of these bonds. On the other hand the increment of the
10 negative charge observed for the N atoms along with atoms C11 and
C12 results in a more negative overall charge located in the
chelating region (N1ꢀC11ꢀC12ꢀN2) of the phenanthroline ligand.
Thus, the higher opposite charges on the metal center and the
chelating unit of the phenanthroline ligand when compared to the
15 corresponding ones in the ground state of the system result in a
shortening of the Cu–N bond distances in the T1 state.
The simulated absorption spectrum of CuI(phen)(py2SH)] (3),
computed with TDꢀDFT method at the PBE1PBE/6ꢀ
311++G(d,p),SDD level of theory on the optimized singlet ground
20 state in dichloromethane solution, is depicted schematically in
Figure 5. Selected TDꢀDFT principal singletꢀsinglet electronic
transitions, excitation energies and oscillator strength in
The excitation at 359.8 nm (HOMOꢀ3 → LUMO+1) appears to be
of MLCT and XLCT character, considering that it arises from
55 electronic transitions between HOMOꢀ3 orbital, which includes Cu
3d AOs, p orbitals located on iodine ligand and p AOs of all atoms
of py2SH ligand, to the high energy LUMO+1 orbital, which is a
delocalized unoccupied π∗ꢀMO of the phenanthroline.
60
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Table 6 Selected principal singletꢀsinglet transitions in the absorption spectra of complex [CuI(phen)(py2SH)] (3), in dichloromethane solution, calculated
at the PBE1PBE/6ꢀ311++G(d,p)//SDD level of theory
Excitation
E/eV
λ/nm
Orbital Nature
Character
OS, f
HOMOꢀ2→LUMO,
HOMOꢀ1→LUMO
2.864
432.9
3dCu/πI → π*phen
0.1212
MLCT/XLCT
HOMOꢀ3→LUMO
2.994
414.2
3dCu/πI/πpy2SH → π*phen
0.0555
MLCT/XLCT
MLCT/XLCT
MLCT/XLCT
HOMOꢀ1→LUMO+2,
HOMO→LUMO+2
HOMOꢀ3→LUMO+1
3.089
3.446
401.4
359.8
3dCu/πI/πphen → π*py2SH
3dCu/πI/πpy2SH → π*phen
0.0352
0.0275
HOMOꢀ9→LUMO+1,
HOMOꢀ6→LUMO+4
MLCT/XLCT/IL
MLCT/IL
4.803
258.2
3dCu/πI/πpy2SH /πphen → π*phen
0.1285
HOMOꢀ9→LUMO,
HOMOꢀ4→LUMO+3
MLCT/XLCT/IL
MLCT/IL
4.815
4.885
257.5
253.8
3dCu/πI/πpy2SH /πphen → π*phen /π*py2SH
3dCu/πI → π*phen
0.5045
0.1511
HOMOꢀ1→LUMO+6
MLCT/XLCT
The high energy absorption band involves a series of electronic
transitions, the most important of them are referred in Table 5 and
10 depicted in Figure 6. These excitations are also MLCT, XLCT and
IL in character and include transitions from occupied orbitals,
composed of Cu 3d AOs, p orbitals located on the iodine ligand and
p AOs of all atoms of py2SH ligand (at 257.5 and 253.8 nm) or p
AOs of the phenanthroline (at 258.2 and 257.5 nm), to high energy
15 unoccupied orbitals, which are consisted of delocalized π∗ꢀMOs of
the phenanthroline or py2SH ligands.
Finally, TDꢀDFT calculations were performed at the PBE1PBE/6ꢀ
311++G(d,p),SDD level on the optimized first excited triplet state of
complex CuI(phen)(py2SH)] (3) in dichloromethane solution, in
20 order to calculate the emission spectrum according to the proposed
methodology.55,56 The simulated emission spectrum exhibits a band
with a maximum at 514 nm (2.41eV), which is close to the
experimentally observed one. The FCꢀtransition from the T1 state of
the complex to its ground state (S0), resulting to the emission
25 observed is due to a transition from a πꢀorbital of the diimine ligand
to an orbital located on the Cu 3d AOs with a small participation
from the pi orbitals of the iodine atom.
4. Conclusions
In this paper we have described the synthesis and characterization of
30 eighteen mixedꢀligand copper(I) halide complexes (1–18), bearing
1,10ꢀphenanthroline and heterocyclic thioamides as ligands. The
new compounds formed immediately after mixing of equivalent
amounts of the components under mild conditions, are quite instable
and their solutions undergo gradual reꢀcolouring from red to green,
35 which indicates oxidation of copper(I) to copper(II). The molecular
structures of two representative compounds (3 and 7), established by
singleꢀcrystal Xꢀray diffraction, feature the metal in a distorted
tetrahedral environment surrounded by the two N atoms of the
chelating 1,10ꢀphenanthroline, the halogen atom and the thioneꢀS
atom of the thioamide. The Sꢀcoordination mode of the latter could
be verified by the appearance of the four characteristic ‘thioamide
5
Fig. 6 Excitation energies and singleꢀelectron transition with the higher C4I0
coefficient in the TDꢀDFT calculations for [CuI(phen)(py2SH)] (3)
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60 14 D. G. Guttell, S.ꢀM. Kuang, P. E. Fanwick, D. R. McMillin and R. A.
Walton, J. Am. Chem. Soc., 2002, 124, 6.
15 S. M. Kuang. D. G. Guttell, D. R. McMillin, P. E. Fanwick and R. A.
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MLCT/XLCT/IL character. As expected, there is a flattening65
distortion from the tetrahedral geometry by approximately 30
degrees in the triplet state (T1) of complex 3 when compared to its
5
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ground state (S0). The ꢂΕΤ1ꢀS energy gap in the gas phase and in
0
dichloromethane solution is 1.339eV and 1.622eV respectively.
70
10 Upon S0→T1 excitation elongation of the Cu–I and Cu–S bond
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from the atoms constituting the chromophore (Cu, N, S, I) towards
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15 in the range 490–650 nm is observed for all the complexes under
investigation. According to the TDꢀDFT calculations performed on
the optimized first excited triplet state of complex
3 in
dichloromethane solution, the emitting excited state consists of π8ꢀ0
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a Aristotle University of Thessaloniki, Faculty of Chemistry, Inorganic
Chemistry Laboratory P.O. Box 135 GRꢀ541 24 Thessaloniki, Greece; Eꢀ
mail: aslanidi@chem.auth.gr
30 b School of Pharmacy and Life Sciences, The Robert Gordon University,
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