Coordination studies of 5,6-diphenyl-3-(2-pyridyl)-1,2,4-triazine towards Cu2+ cation. X-ray studies, spectroscopic characterization and DFT calculations

Article abstract of DOI:10.1016/j.poly.2008.05.033

The reactions of 5,6-diphenyl-3-(2-pyridyl)-1,2,4-triazine with CuCl₂ · 2H₂O, Cu(NO₃)₂ · 3H₂O and CuSO₄ · 5H₂O have been examined, and four [CuCl₂(dppt)] (1), [CuCl

Full text of DOI:10.1016/j.poly.2008.05.033

Polyhedron 27 (2008) 2959–2967
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Polyhedron
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Coordination studies of 5,6-diphenyl-3-(2-pyridyl)-1,2,4-triazine towards
Cu2+ cation. X-ray studies, spectroscopic characterization and DFT calculations
a
b
c
c
d
B. Machura a, , A. Switlicka , R. Kruszynski , J. Mrozinski , J. Kłak , J. Kusz
*
´
´
a Department of Crystallography, Institute of Chemistry, University of Silesia, 9th Szkolna Street, 40-006 Katowice, Poland
b Department of X-ray Crystallography and Crystal Chemistry, Institute of General and Ecological Chemistry, Lodz University of Technology,
_
´
116 Zeromski Street, 90-924 Łódz, Poland
c Faculty of Chemistry, Wroclaw University, F. Joliot-Curie 14 Street, 50-383 Wrocław, Poland
d Institute of Physics, University of Silesia, 4th Uniwersytecka Street, 40-006 Katowice, Poland
a r t i c l e i n f o
a b s t r a c t
Article history:
The reactions of 5,6-diphenyl-3-(2-pyridyl)-1,2,4-triazine with CuCl2 ꢀ 2H2O, Cu(NO3)2 ꢀ 3H2O and
CuSO4 ꢀ 5H2O have been examined, and four [CuCl2(dppt)] (1), [CuCl2(dppt)2] ꢀ 2MeOH (2),
[Cu(dppt)2(H2O)2](NO3)2 (3) and [Cu(SO4)(dppt)(H2O)]n ꢀ nH2O (4) complexes have been obtained. All
the complexes have been structurally and spectroscopically characterized, and compound 4 has been
additionally studied by magnetic measurements. The electronic structure of 1 has been calculated with
the density functional theory (DFT) method, and the time-dependent DFT calculations have been
employed to calculate the electronic spectrum of 1.
Received 21 April 2008
Accepted 25 May 2008
Available online 7 July 2008
Keywords:
Copper complexes
5,6-Diphenyl-3-(2-pyridyl)-1,2,4-triazine
X-ray and electronic structure
DFT calculations
Ó 2008 Elsevier Ltd. All rights reserved.
1. Introduction
This work focuses on the complexation ability of 5,6-diphenyl-
3-(2-pyridyl)-1,2,4-triazine towards Cu2+. Some Cu(II) complexes
Numerous compounds containing the 1,2,4-triazine moieties
are well known in natural materials and show interesting biolog-
ical, pharmacological and medicinal properties. 4-amino-5oxo-3-
phenylamino-1,2,4-triazine has a powerful inhibiting effect on
the cell wall lignification catalysed by peroxidases, and alters
the integrity of chloroplast [1]. Some of the 3,5,6-trisubstituted-
1,2,4-triazines can be active as blood platelet aggregation inhibi-
tors and others exhibit antiviral inhibitory activity (against influ-
enza viruses for example), significant activity towards leukaemia
and ovarian cancer, and anti-HIV activity [2]. More recently, it has
been revealed that a zinc-dppt complex (dppt = 5,6-diphenyl-
3-(2-pyridyl)-1,2,4-triazine) associated to a biocide could have
significant biocidal effects on living cells including those of micro-
organisms (bacteria and fungi), cell culture system, plants and
animals [3].
of dppt have been prepared previously and studied as potential
catalytically active redox agents [6].
Here we present synthesis, spectroscopic and structural data for
[CuCl2(dppt)] (1), [CuCl2(dppt)2] ꢀ 2MeOH (2), [Cu(dppt)2(H2O)2]
(NO3)2 (3) and [Cu(SO4)(dppt)(H2O)]n ꢀ nH2O (4) complexes.
The electronic structure of 1 has been calculated with the den-
sity functional theory (DFT), and TDDFT/PCM calculations have
been employed to produce a hundred of doublet excited-states
starting from the optimized geometry.
Currently density functional theory (DFT) is commonly used to
examine the electronic structure of transition metal complexes. It
meets with the requirements of being accurate, easy to use and
fast enough to allow the study of relatively large molecules of
transition metal complexes [7]. Recent calculations with TD-DFT
method for open-shell of metal complexes (including copper
complexes) have also supported the TD-DFT method to be appli-
cable for such systems giving good assignment of experimental
spectra [8,9].
Another interesting property of the derivatives of 1,2,4-triazine
compounds is formation of coloured complexes when they are
coordinated to a metal ion. In particularly, the ligand 5,6-diphe-
nyl-3-(2-pyridyl)-1,2,4-triazine has been widely used as a sensitive
reagent for the determination of Fe(II) by spectrophotometric
methods, in natural and waste waters [4,5].
2. Experimental
2.1. General procedure
* Corresponding author.
E-mail addresses: basia@ich.us.edu.pl (B. Machura), rafal.kruszynski@p.lodz.pl
(R. Kruszynski), jmroz@wchuwr.chem.uni.wroc.pl (J. Mrozin´ ski).
All the reagents used to the synthesis were commercially avail-
able and were used without further purification.
0277-5387/$ - see front matter Ó 2008 Elsevier Ltd. All rights reserved.
doi:10.1016/j.poly.2008.05.033

2960
B. Machura et al. / Polyhedron 27 (2008) 2959–2967
IR spectra were recorded on a Nicolet Magna 560 spectropho-
2.6. Crystal structures determination and refinement
tometer in the spectral range 4000–400 cmꢁ1 with the samples
in the form of KBr pellets. Electronic spectra were measured on
a spectrophotometer Lab Alliance UV–VIS 8500 in the range
1100–180 nm in methanol solution. Elemental analyses (C H N)
were performed on a Perkin–Elmer CHN-2400 analyzer. EPR spec-
tra were recorded at room temperature and 77 K on a Bruker ESP
300 spectrometer operating at X-band equipped with an ER
035M Bruker NMR gaussmeter and HP 5350B Hewlett–Packard
microwave frequency counter.
The X-ray intensity data of 1, 2, 3 and 4 were collected on a KM-
4-CCD automatic diffractometer equipped with CCD detector and
graphite monochromated Mo Ka radiation (k = 0.71073 Å). Details
concerning crystal data and refinement are given in Table 1. Lor-
entz, polarization and numerical absorption correction [10] were
applied. The structures were solved by the partial structure expan-
sion method and subsequently completed by the difference Fourier
recycling. All the non-hydrogen atoms were refined anisotropically
using full-matrix, least-squares technique. The hydrogen atoms
were founded from the difference Fourier syntheses and were
treated as, ‘‘riding” on their adjacent atoms and assigned isotropic
temperature factors equal 1.2 times the value of equivalent tem-
perature factor of the aromatic parent atoms and equal 1.5 times
the value of equivalent temperature factor of the methyl parent
2.2. Preparation of [CuCl2(dppt)] (1)
A solution of dppt (0.58 mmol, 0.18 g) in methanol (15 ml) was
added to 0.10 g (0.58 mmol) of CuCl2 ꢀ 2H2O in 10 ml of methanol
and stirred for 2 h. The resulting solution was kept for evaporation
at room temperature, and after a few days dark red crystals were
obtained, filtered off and dried. Yield 75%.
Anal. Calc. for C20H14N4Cl2Cu: C, 54.01; H, 3.17; N, 12.60. Found:
C, 54.70; H, 3.46; N, 12.35%.
Table 1
Crystal data and structure refinement for 2, 3 and 4 complexes
IR (KBr;
UV–Vis (MeOH; kmax [nm] (
m .
/cmꢁ1): 1603(m) and 1515(s), mC@N and mN@N
2
3
4
e
; [dm3 molꢁ1 cmꢁ1])): 775.0 (100),
Empirical
formula
Formula weight 819.23
Temperature
(K)
Wavelength (Å) 0.71073
Crystal system
Space group
Unit cell dimensions
a (Å)
b (Å)
c (Å)
C
42H36Cl2N8O2Cu
C40H32N10O8Cu
C20H18N4O6SCu
445.8 (50), 328.4 (36500), 302.8 (59750), 242.4 (38910) and 204.8
(90870).
844.30
150(1)
505.98
291.0(3)
291.0(3)
2.3. Preparation of [CuCl2(dppt)2] ꢀ 2MeOH (2)
0.71073
monoclinic
P21/n
0.71073
triclinic
P1
monoclinic
C2/c
A procedure similar to that for [CuCl2(dppt)] was used with
CuCl2 ꢀ 2H2O (0.10 g, 0.58 mmol) and dppt (0.36 g, 1.16 mmol).
Green crystals of 2 were collected in 80% yield.
ꢀ
15.285(3)
8.286(2)
31.414(6)
8.4621(6)
6.4346(5)
34.2110(2)
7.0084(6)
10.1467(9)
15.2168(14)
93.711(7)
94.531(7)
104.345(7)
1041.10(16)
2
Anal. Calc. for C42H36N8Cl2O2Cu: C, 61.58; H, 4.43; N, 13.68.
Found: C, 60.95; H, 4.68; N, 13.20%.
/cmꢁ1): 3361(br)
m
O–H; 1607(m) and 1519(s) mCN and
a
(°)
b (°)
(°)
IR (KBr;
m
93.30(3)
93.200(6)
mN@N
.
c
; [dm3 molꢁ1 cmꢁ1])): 769.0 (225),
Volume (Å3)
Z
3972.0(14)
4
1.370
0.731
1859.9(2)
2
1.508
0.658
UV–Vis (MeOH; kmax[nm] (
e
507.6 (115), 339.4 (22600), 304.0 (35770) and 214.0 (68125).
Dcalc (Mg/m3)
Absorption
coefficient
1.614
1.196
2.4. Preparation of [Cu(dppt)2(H2O)2](NO3)2 (3)
(mmꢁ1
)
A solution of dppt (0.80 mmol, 0.25 g) in methanol (10 ml) was
added to 0.10 g (0.40 mmol) of Cu(NO3)2 ꢀ 3H2O in 10 ml of water
and stirred for 4 h. The resulting green precipitate was filtered
off and recrystallized from methanol. Crystalline precipitate of 3
was collected in 70% yield.
F(000)
Crystal size
(mm)
h Range for data 2.89–25.03
collection
1692
870
518
0.07 ꢂ 0.14 ꢂ 0.14 0.08 ꢂ 0.08 ꢂ 0.22 0.199 ꢂ 0.027 ꢂ 0.024
2.92–25.00
2.08–25.05
Index ranges
ꢁ17 6 h 6 18 ,
ꢁ6 6 k 6 9,
ꢁ35 6 l 6 37
12346
ꢁ10 6 h 6 6,
ꢁ7 6 k 6 7,
ꢁ40 6 l 6 39
11201
ꢁ8 6 h 6 8,
ꢁ12 6 k 6 11,
ꢁ18 6 l 6 18
10501
Anal. Calc. for C40H32N10O8Cu: C, 56.90; H, 3.82; N, 16.59.
Found: C, 57.35; H, 3.98; N, 16.25%.
Reflections
collected
Independent
reflections
(Rint
Completeness
IR (KBr;
mCN and
m mO–H; 1600 (w), 1530(s) and 1514(m)
/cmꢁ1): 3473(br)
m
N=N; 1384 cmꢁ1
(mNO ).
UV–Vis (MeOH; kmax [nm]3(e; [dm3 molꢁ1 cmꢁ1])): 676.1 (180),
479.9 (155), 340.1 (26460), 300.3 (46590), 240.7 (33920) and
205.7 (85180).
3494 (0.0638)
3254 (0.0450)
3684 (0.0243)
)
99.3%
99.2%
99.9%
to 2h = 50°
Maximum and
minimum
transmission
0.953 and 0.898
0.937 and 0.953
0.968 and 0.959
2.5. Preparation of [Cu(SO4)(dppt)(H2O)]n ꢀ nH2O (4)
Data/restraints/ 3494/0/252
parameters
3254/0/268
0.904
3684/0/289
1.091
A solution of dppt (0.40 mmol, 0.12 g) in methanol (15 ml) was
added to 0.10 g (0.40 mmol) of CuSO4 ꢀ 5H2O in 10 ml of water and
stirred for 4 h. The resulting green precipitate was filtered off and
recrystallized from methanol. Crystalline precipitate of 4 was col-
lected in 65% yield.
Goodness-of-fit
1.144
on F2
Final R indices
R1 = 0.0679
R1 = 0.0342,
R1 = 0.0600
[I > 2r(I)]
wR2 = 0.1678
R1 = 0.1095
wR2 = 0.0914
R1 = 0.0595
wR2 = 0.1863
R1 = 0.0692
Anal. Calc. for C20H18N4O6SCu: C, 47.48; H, 3.59; N, 11.07.
Found: C, 47.77; H, 3.33; N, 11.85%.
R indices (all
data)
IR (KBr;
1521(s) mC@N and
611 cmꢁ1
mSO ).
UV–Vis (MeOH; kmax [nm]): 682.3, 464.5, 331.2, 300.9, 240.5
and 202.8.
m
/cmꢁ1): 3650(m) and 3433(br)
m
O–H; 1606(br) and
wR2 = 0.1920
wR2 = 0.0977
wR2 = 0.1935
Largest
0.515 and ꢁ0.337 0.320 and ꢁ0.330 0.671 and ꢁ0.493
m
N@N; 1196, 1156(sh), 1129, 1021, 934 and
difference in
peak and
(
4
hole (e Åꢁ3
)

B. Machura et al. / Polyhedron 27 (2008) 2959–2967
2961
carbon atom or oxygen atom. All, except water molecule, hydrogen
atoms positions were idealised after each cycle of refinement. The
methyl and hydroxyl groups were allowed to rotate about theirs
local three-fold axes. SHELXS97 [11], SHELXL97 [12] and SHELXTL [13]
programs were used for all the calculations. Atomic scattering fac-
tors were those incorporated in the computer programs.
The complex 1 crystallises in the orthorhombic space group
Fdd2. The coordination geometry about Cu(II) is a trans distorted
square planar. The Cu ion is coordinated to pyridine and triazine
rings of 5,6-diphenyl-3-(2-pyridyl)-1,2,4-triazine ligand and two
chloride ions. As the X-ray structure of complex 1 has been re-
cently reported by Eltayeb et al. [22] and quality of our structure
is similar, the experimental data for 1 have not been included in
the paper.
2.7. Magnetic measurement
The copper atom of the compound 2 is located on the inversion
centre and occupies special position a of the C2/c space group, thus
the asymmetric unit consists of a half of complex molecule and
one methanol molecule. By symmetry the environment of cop-
per(II) ion in compound 2 adopts ideal tetragonal bipyramid
geometry. The equatorial plane is formed by two pyridine and
two triazine nitrogen atoms and the axial sites are occupied by
two chloride ions at rather large distances of 2.7062(16), as a con-
sequence of the Jahn–Teller effect. The two dppt ring systems are
strictly coplanar and they are bound to central ion in trans config-
uration. Each complex molecule is connected via medium strength
[23,24] O–Hꢀ ꢀ ꢀCl intermolecular hydrogen bonds with two solvent
molecules.
The magnetization of the powdered sample was measured over
the temperature range 1.8–300 K at magnetic field 0.5 Tesla, using
a Quantum Design SQUID-based MPMSXL-5-type magnetometer.
The superconducting magnet was generally operated at a field
strength ranging from 0 to 5 Tesla.
The SQUID magnetometer was calibrated with the palladium
rod sample. Corrections are based on subtracting the sample-
holder signal and contribution vD estimated from the Pascal con-
stants [14] and equal ꢁ276 ꢂ 10ꢁ6 cm3 molꢁ1 for complex. The
effective magnetic moment was calculated from the equation,
l
eff = 2.83(v
MT)1/2 (B.M.).
The copper atom of the compound 3 is located on the inver-
sion centre and occupies special position b of the P21/n space
group, thus the asymmetric unit consists of a half of complex
cation and one nitrate anion. The overall complex molecule con-
formation of compound 3 is very similar to these of compound 2.
By symmetry the environment of copper(II) ion adopts ideal
tetragonal bipyramid geometry. The equatorial plane is formed
by two pyridine and two triazine nitrogen atoms and the axial
sites are occupied by two water molecules at rather large dis-
tances of 2.3403(19) Å, as a consequence of the Jahn–Teller effect.
The two dppt ring systems are strictly coplanar and they are
bound to central ion in trans configuration. The medium strength
O–Hꢀ ꢀ ꢀO intermolecular hydrogen bonds of compound 3 joins the
molecules to form of hydrogen bonded chain along crystallo-
graphic b-axis.
2.8. Computational details
The geometry of 1 was optimized without any symmetry
restrictions in the doublet state using the hybrid B3LYP [15,16]
functional of GAUSSIAN-03 [17]. The geometry was fully optimised
in methanol utilising IEF-PCM formalism available in GAUSSIAN-03
[18]. The calculations were performed by using the LANL2DZ effec-
tive core potential (ECP) set of Hay and Wadt [19] for copper atom
**
*
and the standard 6-31+G basis for chloride and nitrogen, 6-31G
for carbon and 6-31G for hydrogen atoms.
Based on the optimized geometry, time-dependent density
functional level (TDDFT) calculations were performed at the same
B3LYP level and basis sets to calculate the electron transition
energies [20].
All atoms of compound 4 lie in general positions, but the inver-
sion centres located at respectively special positions d and f of the
P1 space group expand the molecule to the one dimensional, lad-
3. Results and discussion
ꢀ
3.1. Preparation and infrared data
der type, polymer along crystallographic a-axis (the asymmetric
unit consists of one Cu2+ cation one SO24ꢁ anion one ligand, one
coordinated and one uncoordinated water molecule). Each cop-
per(II) ion is six-coordinate and their coordination geometries are
best described as distorted tetragonal bipyramid with the equato-
rial plane defined by two nitrogen and two oxygen atoms (maxi-
mum deviation from the weighted least squares N(2), N(4), O(1),
O(2) plane exists for N(4) atom and it is equal to 0.127(2) Å) with
copper atom displaced 0.000(2) Å from above mentioned the
weighted least squares plane. The Cu(dppt)(H2O) units are linked
The complexes [CuCl2(dppt)] (1), [CuCl2(dppt)2] ꢀ 2MeOH (2),
[Cu(dppt)2(H2O)2](NO3)2 (3) and [Cu(SO4)(dppt)(H2O)]n ꢀ nH2O (4)
were prepared in good yield by the reaction of 5,6-diphenyl-3-
(2-pyridyl)-1,2,4-triazine (dppt) with the appropriate copper salt
and molar ratio.
The selected frequencies observed in the IR spectra of [CuCl2-
(dppt)] (1), [CuCl2(dppt)2] ꢀ 2MeOH (2), [Cu(dppt)2(H2O)2](NO3)2
(3) and [Cu(SO4)(dppt)(H2O)]n ꢀ nH2O (4) complexes are given in
Section 2. For all the examined complexes the stretching vibrations
of the C@N and N@N groups appear at considerable lower values
by two l
-sulfate-O,O0 bridges forming planar by symmetry Cu2O2
with respect to the m(C@N) and m(N@N) of the free 5,6-diphenyl-
3-(2-pyridyl)-1,2,4-triazine (dppt) supporting the coordination of
the triazine and pyridyl rings to the metal ion [3]. The bands
assignable to the bridging sulfate of 4 appear at 934, 1021, 1129,
1156 and 1196 cmꢁ1, whereas the band at 1384 cmꢁ1 for 3 sug-
gests the presence of uncoordinated nitrate ion. The broad bands
in the range 3650–3100 cmꢁ1 in the IR spectra of 2, 3 and 4 repre-
sent the existence of MeOH and H2O [21].
Table 2
Hydrogen bonds for 2, 3 and 4 complexes
D–Hꢀ ꢀ ꢀA
Hꢀ ꢀ ꢀA (Å) Dꢀ ꢀ ꢀA (Å) D–Hꢀ ꢀ ꢀA (°) Symmetry
code of A
Complex 2
O(99)–H(99)ꢀ ꢀ ꢀCl(1)
2.42
3.165(9)
152.5
Complex 3
O(4)–H(4O)ꢀ ꢀ ꢀO(1)
1.93
1.97
2.783(3)
2.845(3)
151.9
150.7
x, y + 1, z
ꢁx + 1, ꢁy + 1, ꢁz
3.2. Crystal structures
O(4)–H(4P)ꢀ ꢀ ꢀO(3)
Complex 4
The crystallographic data of 2, 3 and 4 complexes are summa-
rized in Table 1, The details of hydrogen bonds are given in Table 2,
and the molecular structures of 2, 3 and 4 are presented in Figs. 1–
3, respectively.
O(1)–H(1O)ꢀ ꢀ ꢀO(4)
O(1)–H(1P)ꢀ ꢀ ꢀO(3)
O(99)–
H(99P)ꢀ ꢀ ꢀO(5)
1.82
1.63
2.08
2.760(5)
2.600(5)
2.924(8)
159.2
164.8
179.4
ꢁx + 1, ꢁy + 2, ꢁz + 1

2962
B. Machura et al. / Polyhedron 27 (2008) 2959–2967
Fig. 1. The molecular structure of 2. Displacement ellipsoids are drawn at 50% probability.
Fig. 2. The molecular structure of the cation [Cu(dppt)2(H2O)2]2+ in the structure 3. Displacement ellipsoids are drawn at 50% probability.
Fig. 3a. Atoms forming asymmetry unit of 4. Displacement ellipsoids are drawn at 50% probability. The symmetry generated atoms bonded to the asymmetry unit atoms are
indicated by dashed lines.

B. Machura et al. / Polyhedron 27 (2008) 2959–2967
2963
Table 4
The experimental bond lengths (Å) and angles (°) for 3
Bond lengths
Experimental
Bond angles
Experimental
Cu(1)–N(1)
Cu(1)–N(4)
Cu(1)O(4)
2.028(2)
2.062(2)
2.3403(19)
N(1)–Cu(1)–N(4)
N(1)#1–Cu(1)–N(4)
N(1)–Cu(1)–O(4)#1
N(1)–Cu(1)–O(4)
N(4)–Cu(1)–O(4)
N(4)–Cu(1)–O(4)#1
79.84(8)
100.16(8)
89.30(8)
90.70(8)
84.93(7)
95.07(7)
#1: ꢁx + 1, ꢁy + 1, ꢁz.
Table 5
The experimental bond lengths (Å) and angles (°) for 4
Bond lengths
Experimental
Bond angles
Experimental
Cu(1)–O(1)
Cu(1)–O(2)
Cu(1)–O(2)#1
O(2)–Cu(1)#1
Cu(1)–N(2)
Cu(1)–N(4)
S(1)–O(2)
S(1)–O(3)
S(1)–O(4)
S(1)–O(5)
1.951(3)
1.966(3)
2.367(3)
2.367(3)
1.996(4)
1.995(4)
1.523(3)
1.464(3)
1.459(4)
1.455(4)
O(1)–Cu(1)–O(2)
O(1)–Cu(1)–N(2)
O(1)–Cu(1)–N(4)
O(2)–Cu(1)–N(4)
O(2)–Cu(1)–N(2)
N(4)–Cu(1)–N(2)
O(2)–Cu(1)–O(2)#1
O(1)–Cu(1)–O(2)#1
N(4)–Cu(1)–O(2)#1
N(2)–Cu(1)–O(2)#1
Cu(1)–O(2)–Cu(1)#1
88.50(14)
96.97(15)
172.52(14)
94.23(15)
171.29(14)
81.19(15)
79.51(13)
93.58(12)
93.76(14)
93.34(13)
100.49(12)
Fig. 3b. The fragment of polymer chain 4. Atoms not involved in the chain are
deleted for clarity. The copper atoms are cross-hatched, the sulphur atoms are
backslashed, the oxygen atoms are slashed and nitrogen atoms are dotted.
#1: ꢁx + 2, ꢁy + 2, ꢁz + 1.
moiety with two short [1.966(3) Å] and two longer Cu–O distances
[2.367(3) Å], two bridging Cu–O–Cu angles of 100.49(12)°, leading
to a Cuꢀ ꢀ ꢀCu separation of 3.3411(11) Å. The sulfate oxygen O(4) is
further coordinated to the copper atom of another binuclear unit,
resulting in a polymeric structure created by the four-membered
Cu2O2 and eight-membered Cu2O4S2 rings in the spiro arrange-
ment (in the second ring the Cuꢀ ꢀ ꢀCu distance is 4.8865(11) Å).
The structures with two bridging modes for the sulfate groups
in 1, 2 and 3 complexes are comparatively weaker. However, all
the Cu–N bond lengths are consistent with those found in related
systems [26].
3.3. Magnetic properties
(l
-O,O0 and
similar arrangement was observed for the [Cu4(TPPNOL)2(
l-O,O), in the same complex are unique. However, a
The magnetic properties of the complex 4 were determined
over the temperature range 1.8–300 K at magnetic field 0.5 Tesla.
The experimental data, plotted as temperature variations of the
l-
SO4)2](ClO4)2 [HTPPNOL (N,N,N0-tris-(2-pyridylmethyl)-1,3-diami-
nopropan-2-ol)] complex reported by Fernandes and co-workers
[25]. Different bridging modes for the sulfate groups are reflected
in the different S–O bond lengths: 1.523(3) Å for S(1)–O(1) and
1.459(4) Å for S(1)–O(4). The solvent water molecule is connected
to complex molecule via medium strength O–Hꢀ ꢀ ꢀO hydrogen
bond. The polymer chain is stabilised by medium strength O–
Hꢀ ꢀ ꢀO intramolecular hydrogen bonds.
vꢁM1 and
The value
(1.82 B.M.). The value of
v
MT, are shown in Fig. 4.
v
MT of at 300 K for complex equals 0.415 cm3 molꢁ1
K
v
MT product increases slightly with tem-
perature lowering and reaches 0.425 cm3 molꢁ1 K (1.85 B.M.) value
at 1.8 K.
The values of the Curie and Weiss constants determined from
the relation 1/
v
M = f(T) over temperature range 1.8–300 K are equal
The selected bond distances and angles of 2, 3 and 4 are col-
lected in Tables 3–5. The bite angle of, 6-diphenyl-3-(2-pyridyl)-
1,2,4-triazine ranges from 78.99(14)° to 81.19(15)°, and is similar
to that reported for the related [Cu(dppt)2(H2O)2](ClO4)2 complex
[79.7(2)°] [6].
For all three complexes, there is no significant difference be-
tween Cu–N (pyridine) and Cu–N (triazine) bond lengths, revealing
that the two nitrogens are equal in donor strength. The Cu–N bond
distances of mononuclear compounds are slightly longer than
those in the polymer structure suggesting that the Cu–N bonds
800
700
600
500
400
300
200
100
0.5
0.4
0.3
0.44
0.42
0.2
Table 3
0.40
The experimental bond lengths (Å) and angles (°) for 2
0.38
0.1
Bond lengths
Experimental
Bond angles
Experimental
0.36
Cu(1)–N(1)
Cu(1)–N(4)
Cu(1)–Cl(1)
2.023(4)
2.049(4)
2.7062(16)
N(1)–Cu(1)–N(4)#1
N(1)–Cu(1)–N(4)
101.01(14)
78.99(14)
87.22(11)
92.78(11)
90.88(11)
89.12(11)
87.22(11)
2
4
6
8
10
T [K]
0
0
0.0
N(1)–Cu(1)–Cl(1)#1
N(1)–Cu(1)–Cl(1)
N(4)–Cu(1)–Cl(1)
N(4)–Cu(1)–Cl(1)#1
N(1)#1–Cu(1)–Cl(1)
50
100
150
200
250
300
T [K]
Fig. 4. Temperature dependence of experimental vꢁM1 (ꢃ) and vM ꢀ T (ꢄ) for complex
4. The inset shows dependence
vMT vs. T (ꢄ) in the lowest temperature range. The
#1: ꢁx + 1, ꢁy, ꢁz.
solid line is the calculated curve for vMT.

2964
B. Machura et al. / Polyhedron 27 (2008) 2959–2967
to 0.415 cm3 molꢁ1 K and 0.04 K, respectively. A very small, posi-
tive value of Weiss constant confirms the occurrence of very weak
ferromagnetic interactions between the copper centers in the
dimer.
The molecular structure of [Cu(SO4)(dppt)(H2O)]n ꢀ nH2O (4)
(Fig. 4b) suggests the magnetic exchange interactions in alternat-
ing chain:
subunits (Cu2O2) arise from the value of bridging angle Cu(1)–O(2)–
Cu(1)#1 (100.49(12)°) [31].
Results of the calculations on the magnetic data indicated only
very weak ferromagnetic interaction between copper centers in-
side four-membered (Cu2O2) rings with value of the singlet–triplet
separation 2J = +0.2 cmꢁ1. The value of molecular field corrections
(zJ0 = 0) indicated total magnetic isolation of the four-membered
rings in the crystal lattice.
The variation of the magnetization M versus the magnetic field
H for complex 4 at 2 K was shown in Fig. 5. As the magnetic field
increases, the M versus H curve indicates linear relation up to
ꢅ1 T and then shows a sinusoidal variation up to 5 T near satura-
tion value at M = 0.97 B.M.
J
zJ’
J
Cum -1 Cum
Cum+1 Cum+2
where J and zJ0 are the exchange parameters via (–O–) and (–O–S–
O–) bridges, respectively.
3.4. EPR spectra
The path of the magnetic interaction between CuII centers in-
side eight-membered (Cu2O4S2) ring is considerably longer than in-
side four-membered (Cu2O2) ring. For that reason the dimer model
with pairwise interactions may be used as a good approximation
The EPR powder spectra of the complex 4 (Fig. 6) recorded in
the X-band at room temperature, 77 K and 4.2 K indicate two
poorly resolved lines related to g\ = 2.08 and g\ = 2.21 parameters.
The observed EPR spectrum is the average spectrum of two copper
centers in the ligand field of the distorted tetragonal–bipyramidal
symmetry Cu(1)N2O4 and Cu(2)N2O4, respectively.
~
~
[27]. Hamiltonian H ¼ ꢁ2JS1 ꢀ S2 for S1 = S2 = 1/2 leads to the Blea-
ney–Bowers expression (1) [28]. To elucidate the significance of
exchange between dimeric subunits in the chain, a molecular field
correction term was also included (Eq. (2)) [29]
3.5. Geometry optimisation
ꢀ
ꢁ
2Nb2g2
3kT
1
3
vM
¼
1 þ expðꢁ2J=kTÞ
ð1Þ
ð2Þ
The geometry of 1 was optimised in a doublet state by the DFT
method with the B3LYP functional. The optimized geometric
parameters of 1 are gathered in Table 6. In general, the predicted
bond lengths and angles are in agreement with the values based
upon the X-ray crystal structure data, and the general trends ob-
served in the experimental data are well reproduced in the
calculations.
vM
vcMorr
¼
2zJ0
1 ꢁ
ꢀ
vM
Nb2g2
where N is the Avogadro’s number, g – the spectroscopic splitting
factor, b – the Bohr magneton, k – the Boltzmann constant, J – ex-
change parameter and zJ0 – molecular field correction (interdimer
interaction). The least-squares fit of the experimental data using
these equations was limited to the temperature range from 1.8 K
up to 300 K and leads to singlet–triplet (2J) separation value equals
0.20 cmꢁ1, g = 2.10 and zJ0 = 0, as indicated by the solid curve in
Fig. 5. The agreement factor R is equal 4.02 ꢂ 10ꢁ5. The criterion
used in determination of the best fit was based on minimization
3.6. Electronic spectra
The experimental electronic spectra of 1, 2, 3 and 4 are pre-
sented in Fig. 7. The positions of absorption bands and values of
molar absorption coefficients for the complexes are given in the
Experimental Part. As can be seen from Fig. 7 the UV/Vis spectra
are rather indistinctive for molecular structure determination.
For all the complexes the visible region exhibit broad poorly re-
solved absorption bands with maxima at 775.0 and 445.8 nm for
1, 769.0 and 507.6 nm for 2, 676.1 and 479.9 nm for 3 and 682.3
and 464.3 nm for 4. The UV spectra of the1, 2, 3 and 4 are also very
similar in terms of the position, intensity and shape of the bands.
of
the
sum
of
squares
of
the
deviation:
sffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi,sffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi
n
n
À
Á
P
P
2
vei xp vci alc
ꢁ
2. Magnetic interaction in
1
1
R ¼
vexp
vexp
ð
Þ
ð
Þ
i
i¼1
i¼1
i
the dimeric copper compound strongly depends on Cu–O–Cu angle.
For angles close to 97° it is possible to found accidental orthogonal-
ity and consequently, J values ꢅ0 or positive [30,31]. The weak fer-
romagnetic interactions between the copper centers in the dimeric
1.2
1.0
0.8
0.6
0.4
0.2
0.0
g = 2.20
2
g = 2.084
ν=9.7625827GHz
T=293K
g = 2.212
g = 2.087
ν=9.5786068 GHz
T=77K
0
1000
2000
3000
H [G]
4000
5000
0
1
2
3
4
5
H [T]
Fig. 5. Field dependence of the magnetization for complex 4.
Fig. 6. EPR (X-band) spectrum of powdered 4 at room temperature and 77 K.

B. Machura et al. / Polyhedron 27 (2008) 2959–2967
2965
Table 6
1.20
The optimized bond lengths (Å) and angles (°) for 1
Bond lengths
Optimized
Bond angles
Optimized
79.47
173.71
94.51
94.14
173.65
91.82
Cu(1)–N(2)
Cu(1)–N(4)
Cu(1)–Cl(1)
Cu(1)–Cl(2)
2.067
2.073
2.344
2.325
N(4)–Cu(1)–N(2)
N(2)–Cu(1)–Cl(1)
N(4)–Cu(1)–Cl(1)
N(2)–Cu(1)–Cl(2)
N(4)–Cu(1)–Cl(2)
Cl(2)–Cu(1)–Cl(1)
0.80
0.40
0.00
3.00
2.00
1.00
0.00
400.00
800.00
[nm]
Fig. 8. The experimental (black) and calculated (red) electronic absorption spectra
of 1. (For interpretation of the references to colour in this figure legend, the reader is
referred to the web version of this article.)
For complex 1 the nature of the transitions observed in the UV–
Vis spectra has been studied by the time-dependent density func-
tional (TDDFT) method. The calculated electronic spectrum of 1 in
comparison with the experimental one is presented in Fig. 8. Each
400.00
800.00
calculated transition is represented by
a gaussian function
Fig. 7. The experimental electronic absorption spectra of 1 (black), 2 (red), 3 (green)
and 4 (blue). (For interpretation of the references to colour in this figure legend, the
reader is referred to the web version of this article.)
2
y ¼ ceꢁbx with the height (c) equal to the oscillator strength and
b equal to 0.04 nmꢁ2
.
Table 7
The calculated electronic transitions and their assignments to the experimental absorption bands of 1
The most important orbital excitations
Character
k (nm)
E (eV)
f
Experimental k (nm)
H-5(b) ? L(b)
H-8(b) ? L(b)
H(b) ? L(b)
H-14(b) ? L(b)
H-3(b) ? L(b)
H(b) ? L(b)
p
p
p
(Cl)/
(Cl)/d ? d
(dppt) ? d
p
(dppt)/d ? d
682.2
666.5
646.6
611.8
600.3
586.6
1.82
1.86
1.92
2.03
2.07
2.11
0.0004
0.0008
0.0003
0.0021
0.0088
0.0005
775.0
d/p(dppt) ? d
p
p
(Cl) ? d
(dppt) ? d
H-2(b) ? L(b)
H-4(b) ? L(b)
H-6(b) ? L(b)
H-8(b) ? L(b)
p
p
p
p
(dppt) ? d
(dppt)/p(Cl) ? d
471.1
467.6
437.2
403.0
2.63
2.65
2.84
3.08
0.0144
0.1251
0.0138
0.0659
445.8
328.4
(Cl)/
p(dppt)/d ? d
(Cl)/
p(dppt)/d ? d
H(
a
) ? L + 1(
a
) H(b) ? L + 2(b)
p
p
p
p
p
(dppt) ? p*(dppt)
(dppt) ? p*(dppt)
(dppt) ? p*(dppt)
(dppt) ? p*(dppt)
(dppt) ? p*(dppt)
369.6
364.7
361.9
347.3
345.5
342.3
333.1
3.35
3.40
3.42
3.57
3.59
3.62
3.72
0.0920
0.0500
0.0212
0.0515
0.0501
0.1187
0.0489
H(b) ? L + 2(b)
H-1(
H-3(
a
a
) ? L(
a
)
)
) ? L(
a
H-2(b) ? L + 1(b)
H-11(b) ? L(b)
H-1(b) ? L + 2(b)
r
p
(Cl) ? d
(dppt) ? p*(dppt)
H-2(b) ? L + 2(b)
H-2(b) ? L + 2(b)
H-12(b) ? L(b)
p
p
r
(dppt) ? p*(dppt)
320.8
319.4
308.7
298.4
3.86
3.88
4.02
4.16
0.1641
0.0789
0.0697
0.0990
302.8
242.4
204.8
(dppt) ? p*(dppt)
(Cl) ? d
H-5(a
) ? L + 2(
a
)
p
(Cl)/
p
(dppt) ? p*(dppt)
H-7(b) ? L + 2(b)
H-16(b) ? L(b)
H-8(b) ? L + 2(b)
H-8(b) ? L + 2(b)
p
(Cl)/
p
(dppt)/d ? p*(dppt)
269.6
269.4
265.9
264.8
4.60
4.60
4.66
4.68
0.1032
0.0626
0.0481
0.0647
n(dppt)/
p
p
r
(Cl)/d ? d
(Cl)/d ? p*(dppt)
(Cl)/d ? p*(dppt)
f – oscillator strength; H – highest occupied molecular orbital; L – lowest unoccupied molecular orbital.

2966
B. Machura et al. / Polyhedron 27 (2008) 2959–2967
Fig. 9. Contour plots and energy of the selected b-spin HOMO and b-spin LUMO orbitals active in the electronic transitions for complex 1. The orbitals were plotted with
contour values ꢁ0.04 (yellow) and 0.04 au (blue). (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.)
Table 7 presents the calculated spin allowed electronic transi-
tions of 1 and their assignments to the experimental bands. For
the high energy part of the spectrum, only transitions with oscilla-
tor strengths larger than 0.500 are listed in Table 7. The assignment
of the calculated orbital excitations to the experimental bands was
based on an overview of the contour plots and relative energy to
the orbitals HOMO and LUMO involved in the electronic transi-
tions. The several contours of occupied and unoccupied MOs (ac-
tive in the electronic transitions) of 1 are presented in Fig. 9.
The TDDFT/PCM calculations show that the two longest wave-
length experimental bands of 1 at 775.0 and 445.8 nm originate
in the transitions between some lowest b-spin HOMO orbitals
and b-spin LUMO orbital. As can be seen from the Fig. 9, the LUMO
(LMCT) and d ? d (LF). Thus, no ‘clear’ d–d transition bands occur
in the low-lying energy region for 1. The reason for this is probably
due to the fact that the dppt ligand provides high-lying occupied
p-
bonding orbitals, and as a result the high-lying occupied orbitals
are composed of the
dyl)-1,2,4-triazine.
p-bonding orbitals of 5,6-diphenyl-3-(2-pyri-
The experimental bands at 328.4, 302.8, 242.4 and 204.8 nm are
attributed to the intraligand (IL) ( (dppt) ?
*(dppt)) and ligand–
*(dppt)) transitions.
p
p
ligand charge transfer (p(Cl) ? p
4 Supplementary data
CCDC 684890, 684891, 684892 and 684893 contain the supple-
mentary crystallographic data for C20H14N4Cl2Cu, C42H36Cl2N8O2-
Cu, C40H32N10O8Cu and C20H18N4O6SCu. These data can be
obtained free of charge via http://www.ccdc.cam.ac.uk/conts/
retrieving.html, or from the Cambridge Crystallographic Data Cen-
tre, 12 Union Road, Cambridge CB2 1EZ, UK; fax: (+44) 1223-336-
033; or e-mail: deposit@ccdc.cam.ac.uk.
orbital with b-spin is mainly Cu dx2
orbital in character, the b-
ꢁy2
spin HOMO and HOMOꢁ1 orbitals are composed of the
p-bonding
orbitals of 5,6-diphenyl-3-(2-pyridyl)-1,2,4-triazine, and the
HOMOꢁ14, HOMOꢁ8, HOMOꢁ5 and HOMOꢁ3 are ligand (Cl or
dppt)
p-bonding orbitals with some contribution of dCu orbitals.
Accordingly, the transitions assigned to the two longest wave-
length experimental bands can be seen as mixed Cl/dppt ? Cu

B. Machura et al. / Polyhedron 27 (2008) 2959–2967
2967
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H.P. Hratchian, J.B. Cross, 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.
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Acknowledgements
The GAUSSIAN03 calculations were carried out in the Wrocław
Centre for Networking and Supercomputing, WCSS, Wrocław,
Poland.
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