A tetranuclear copper(II) complex with bis(o-aminobenzaldehyde) thiocarbohydrazone

Article abstract of DOI:10.1016/j.ica.2010.02.002

Bis(o-aminobenzaldehyde)thiocarbohydrazone (HL) forms with copper(II) nitrate a tetranuclear complex [Cu₂(L)(NO₃) ₃]₂·2H₂O, in which two dinuclear units are joined by nitrate bridges. The dihydrazone

Full text of DOI:10.1016/j.ica.2010.02.002

Inorganica Chimica Acta 363 (2010) 2065–2070
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Inorganica Chimica Acta
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A tetranuclear copper(II) complex with
bis(o-aminobenzaldehyde)thiocarbohydrazone
b,
c
b
d
Diana Dragancea a, , Anthony W. Addison , Matthias Zeller , Michael E. Foster , Michael J. Prushan ,
*
*
Laurence K. Thompson e, Mihail D. Revenco a, Allen D. Hunter c
a Laboratory of Coordination Chemistry, Institute of Chemistry, Academy of Sciences of Moldova, Academiei str. 3, MD-2028, Chisinau, Moldova
b Chemistry Department, Drexel University, Philadelphia, PA 19104-2816, USA
c STaRBURSTT – Cyberdiffraction Consortium and Chemistry Department, Youngstown State University, Youngstown, OH 44555-3663, USA
d Chemistry Department, LaSalle University, Philadelphia, PA 19141-1108, USA
e Chemistry Department, Memorial University, St. John’s, NF, Canada A1B 3X7
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 1 October 2009
Received in revised form 29 January 2010
Accepted 4 February 2010
Available online 12 February 2010
Bis(o-aminobenzaldehyde)thiocarbohydrazone (HL) forms with copper(II) nitrate a tetranuclear complex
[Cu2(L)(NO3)3]2ꢀ2H2O, in which two dinuclear units are joined by nitrate bridges. The dihydrazone ligand
behaves ditopically, providing NNS and NNN binding sites, with the four coppers essentially in a square-
pyramidal geometry. The tetranuclear molecule displays intramolecular magnetic interactions, with the
antiferromagnetic exchange (ꢁ2J = 210(1) cmꢁ1) between the copper(II) ions within each dinuclear moi-
ety dominant over weak interdimer ferromagnetic coupling.
Keywords:
Ó 2010 Elsevier B.V. All rights reserved.
Copper(II) complexes
Thiocarbohydrazone
Schiff base
X-ray structure
Antiferromagnetism
1. Introduction
tetranuclear copper(II) complex of a new ditopic chelating agent
derived from o-aminobenzaldehyde, a molecule itself of enduring
There has been a resurgence of interest in thiocarbohydrazone
and thiosemicarbazone metal chelates, because of their interesting
catalytic and magnetic properties, their mimicry of oligonuclearity
in metalloproteins [1–3] and also recently because of their poten-
tial antimicrobial and antiproliferative activity [4–8].
interest to inorganic chemists [26–29].
2. Experimental
For the copper chelates, mononuclear [9], dinuclear [10,11],
paired dinuclear [5,12] and an octanuclear system [13] have been
described. The paired dinuclear compounds entail a face-to-face
dimerisation of dinuclear molecules [12]. Following on from our
prior work [10,12], we now report a tetranuclear system of linear
topology, prepared from a novel Schiff base derived from thiocar-
bohydrazide and o-aminobenzaldehyde. Tetranuclear copper(II)
molecules are known with cubane [14–18], rectangular [5,19,20]
‘butterfly’ or ‘chair’ (out-of-phase butterfly) [21–23] and linear or
pseudo-linear shapes [24,25].
Thiocarbohydrazide, o-nitrobenzaldehyde, N-allylimidazole and
other reagents were used as received (TCI, Sigma–Aldrich, Fisher
Scientific). Elemental analyses were from Robertson Microlit, Mad-
ison NJ. FAB/LSIMS mass spectra were run on Micromass-VG 70SE
and Waters Micromass AutoSpec Ultima instruments (2-nitroben-
zyl alcohol matrix), and infrared spectra on a Perkin–Elmer Spec-
trum One FT spectrometer furnished with
a Universal ATR
sampling accessory. Optical spectra were obtained mainly from
MeOH solutions using a Perkin–Elmer Lambda-35 spectrophotom-
eter. Variable-temperature magnetic susceptibility data were col-
lected in the range 2–300 K on a Quantum Design MPMS5S squid
magnetometer at 0.1T in DC mode. Background corrections were
applied for the sample container assembly, and susceptibility data
were corrected for diamagnetism using Pascal’s constants [30].
Co[Hg(SCN)4] was used as a calibration standard, and samples
were placed in Al- or gel-capsules in 5 mm polymer straws. Data
Continuing our work [12] on the coordination chemistry of thio-
carbohydrazones, we report here the structure and properties of a
* Corresponding authors.
E-mail address: ddragancea@gmail.com (D. Dragancea).
0020-1693/$ - see front matter Ó 2010 Elsevier B.V. All rights reserved.
doi:10.1016/j.ica.2010.02.002

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D. Dragancea et al. / Inorganica Chimica Acta 363 (2010) 2065–2070
Table 1
were fitted on a Macintosh G5 platform, using the Microsoft Excel
Solver and the statistical macro SolvStat [31].
Crystallographic data for complex 1.
Complex 1
Crystal
Crystal size (mm)
Formula
Formula weight
Crystal system
a (Å)
Green rod
2.1. Synthesis and characterization of the thiocarbohydrazone and its
copper(II) complex
0.29 ꢂ 0.13 ꢂ 0.13
C30H34Cu4N18O20S2
1285.03
ꢀ
triclinic, P1
2.1.1. HL
7.3594(11)
10.3702(15)
15.343(2)
104.485(2)
92.440(2)
102.396(2)
1101.6(3)
100(2)
The carbonylic compound o-aminobenzaldehyde (anthranilal-
dehyde) was obtained by reduction of o-nitrobenzaldehyde with
iron(II) sulfate [32]. The thiocarbohydrazone ligand HL was pre-
pared by refluxing for 1 h the freshly-prepared aldehyde (0.60 g,
5 mmol) and thiocarbohydrazide (0.26 g, 2.5 mmol) in 50 mL of
EtOH containing a drop of acetic acid. The product precipitated in
90% yield as yellow microcrystals, which were filtered off and
air-dried. Anal. Calc. for C15H16N6Sꢀ1/4H2O: C, 56.9; H, 5.25; N,
26.5. Found: C, 56.9; H, 5.58; N, 26.9%. The mass spectrum shows
m/z = 313.1 (MH+) as 100%. Optical spectrum kmax (nm),
b (Å)
c (Å)
a
(°)
b (°)
c
(°)
V (Å3)
T (K)
Z
1
(10ꢁ3
e
Mꢁ1 cmꢁ1: in MeCN, 374 (16.9), 299 (17.4), 253 (15.7),
228 (20.6); in MeOH: 369 (15.1), 302 (17.5), 258 (sh, 20.9), 232
(26.9).
IR (cmꢁ1): 3457, 3273, 3146 (
mN–H), 3002 (mC–H), 1488, 1445,
(mC–C, mC–N), 1228 (mN–N), 957 (mC–S), 791, 742 (dC–H).
2.1.2. [Cu2(L)(NO3)3]2ꢀ2H2O (1)
For the preparation of the copper complex, 0.078 g of bis(o-
aminobenzaldehyde)thiocarbohydrazone was added to a solution
of 0.116 g of copper(II) nitrate hemi(pentahydrate) in 20 mL
MeOH. The suspension was stirred until the ligand dissolved,
after which the resulting green solution was filtered and allowed
to stand overnight. The small, dark green rectangular crystals
which appeared were filtered off and air-dried. Anal. Calc. for
C30H34Cu4N18O20S2: C, 28.0; H, 2.67; N, 19.6. Found: C, 28.1; H,
3.04; N, 19.6%. The complex is soluble in polar and/or coordinat-
ing solvents such as pyridine, 2-methoxyethanol, DMF and
DMSO, and sparingly so in MeOH. Optical spectrum (MeOH): kmax
Fig. 1. FAB-MS of the copper complex, showing the peak corresponding to Cu2L+ at
m/z = 437 (78%). The combination of copper contents and charges imply thermal
electron capture, with generation of copper(I) for some ions.
(nm), (10ꢁ3 Mꢁ1 cmꢁ1
e, : 630 (1.8), 415(sh, 17.8), 325 (67).
functional and basis set was chosen for its previous success in
determining J values of other Cu(II) complexes among other transi-
tion metal complexes [37–40].1
As hardware/software limitations prevented us from obtaining
a complete solution for the tetracopper system, we carried out
two dicopper(II,II) calculations, firstly replacing Cu(3) and Cu(4)
by Zn(II) to obtain an estimate of Ja, then similarly replacing
Cu(1) and Cu(4) for estimating Jb.
Changes in the spectrum with time suggest that the solutions
are photosensitive.
IR (cmꢁ1): 3504, 3287, 3162 (
mN–H), 1466, 1378, (mC–C, mC–N),
1263 (mN–N), 752 (mC–S).
2.2. Crystallographic measurements
X-ray data for the complex were collected at 100 K on a Bruker
AXS SMART APEX CCD diffractometer, using Mo K radiation
(k = 0.71073 Å, -scan mode. Structure solu-
= 7.08 cmꢁ1) in the
a
3. Results and discussion
l
x
tion and refinement were performed using SHELXTL [33]. The struc-
ture was solved using direct methods and all non-hydrogen
atoms were refined anisotropically. Water hydrogen atoms were
located in the difference density Fourier map, their O–H distances
were constrained to be 0.85 Å within a standard deviation of 0.02
and were isotropically refined. All other hydrogen atoms were
placed in calculated positions and were isotropically refined with
a displacement parameter of 1.5 (methyl) or 1.2 times (all others)
that of the adjacent carbon or oxygen atom. Crystallographic data
for complex 1 are in Table 1.
The FAB-mass spectrum (Fig. 1) shows the intended dinuclear
moiety Cu2L+ preserved, as a strong peak, with another (de)proton-
ated state superimposed. However, other higher-mass cupriferous
ions are also seen, though appearing at much lower intensity;
these include Cu2L(NO3)H+ (500) and [Cu4L2(NO3)–2H]+ (935).
3.1. Structure of the complex
In addition to the hydrazone/imine and anilino-nitrogens, the
dihydrazone ligand provides a thione sulfur and an additional
1
The coupling constant (J) can be related to the energy difference between the
2.3. Computations
broken symmetry (low-spin) and high-spin states, with the
a and b densities being
allowed to localize on different atomic centers (E. Ruiz, J. Cano, S. Alvarez, P. Alemany,
DFT calculations were performed with the GAMESS suite of
codes [34] using the unrestricted Kohn–Sham formulation with
the B3LYP exchange-correlation functional [35]. The Ahlrichs va-
lence triple zeta (VTZ) basis set [36] was applied to all atoms. This
J. Comput. Chem. 20 (1999) 1391–1400.) Using this approach, the coupling constant
EBS ꢁEHS
can be determined from: J ¼
where EHS is the energy of the high-spin state,
ð2S1S2 þS2
Þ
EBS is energy of the broken symmetry state, and S1 and S2 are the total spins for site 1
and 2, so that JCuꢁCu ¼ EBS ꢁ ET .

D. Dragancea et al. / Inorganica Chimica Acta 363 (2010) 2065–2070
2067
Fig. 2. Molecular structure, with numbering scheme, of the dinuclear unit of complex 1. Nonessential H-atoms are omitted for clarity of presentation; atoms are shown at the
70% probability level. Atoms N1 and N6 are the sp3-hybridised aniline nitrogens. The two coppers are 4.88 Å apart.
Table 2
nitrogen donor. The latter pertains as the result of deprotonation of
one of the hydrazine -nitrogens to yield a hydrazide. Note that no
Selected bond lengths (Å) and angles (°) for complex 1.
a
base was added during the chelation process; this ready displace-
ment of the proton from the hydrazine-NH echoes the same phe-
nomenon in the salicylaldehyde-derived copper complexes [12].
The ligand thus acts ditopically, with NNN and NNS binding sites
for the coppers, as shown in Fig. 2. Selected bond distances and an-
gles for 1 are listed in Table 2. The coppers are all pentacoordinate,
with the additional two donors in each case being nitrate oxygens.
Whereas the dinuclear salicylhydrazone molecules [12] are anti-
parallel-stacked to form noncovalent (H-bonded) dimers, the pres-
ent dinuclear molecules are joined end-to-end by coordinate bonds
with a pair of nitrate anions, which bridge the coppers Cu(2) in the
NNS binding sites, to form a dimer of dinuclear molecules similar
to one reported by Moubaraki et al. [41] (Fig. 3). These coppers
are thus the ‘inner’ metal ions in a centrosymmetric pseudolinear
tetranuclear structure, in which the dinucleating ligands’ mean
planes are antiparallel, to within 1°. The NNS donors occupy the
basal plane of the essentially square-pyramidal inner coppers(II)
Bond lengths
Complex 1
Angles
Complex 1
Cu(1)–O(1)
Cu(1)–O(4)
Cu(1)–N(1)
Cu(1)–N(2)
Cu(1)–N(4)
Cu(2)–S(1)
Cu(2)–N(5)
Cu(2)–N(6)
Cu(2)–O(7)
Cu(2)–O(7)
C(8)–S(1)
2.316(3)
2.003(2)
1.988(2)
1.961(3)
2.005(3)
2.2407(10)
1.980(3)
1.985(3)
1.987(2)
2.398(2)
1.708(3)
1.355(4)
1.329(3)
N(1)–Cu(1)–N(2)
O(4)–Cu(1)–N(2)
N(1)–Cu(1)–O(4)
N(2)–Cu(1)–N(4)
N(1)–Cu(1)–N(4)
O(4)–Cu(1)–N(4)
N(2)–Cu(1)–O(1)
N(1)–Cu(1)–O(1)
O(4)–Cu(1)–O(1)
N(4)–Cu(1)–O(1)
N(5)–Cu(2)–N(6)
N(5)–Cu(2)–O(7)
N(6)–Cu(2)–O(7)
N(5)–Cu(2)–S(1)
N(6)–Cu(2)–S(1)
O(7)–Cu(2)–S(1)
N(5)–Cu(2)–O(7)
N(6)–Cu(2)–O(7)
O(7)–Cu(2)–O(7)
S(1)–Cu(2)–O(7)
91.6(1)
161.7(1)
88.4(1)
80.3(1)
171.8(1)
99.7(1)
117.7(1)
92.7(1)
80.6(1)
90.3(1)
90.2(1)
170.0(1)
93.1(1)
87.4(1)
160.3 (1)
92.7(1)
95.8(1)
92.7(1)
74.6(1)
107.0(1)
C(8)–N(3)
C(8)–N(4)
(s = 0.17 [42]). A single nitrate–O acts as the bridging atom
Fig. 3. Inverse stereoview of the tetranuclear complex, viewed along the a-direction; nonessential H-atoms omitted for clarity of presentation, 75% thermal ellipsoids.

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D. Dragancea et al. / Inorganica Chimica Acta 363 (2010) 2065–2070
between the axial coordination site of one Cu(II) and a basal site of
the other Cu(II), trans- to the hydrazide-N. The Cu(II) are all closely
bound, with inner Cu–donor atom distances of 1.980 Å (imine N),
1.985 Å (aniline N), 1.987 Å (O–basal), 2.241 Å (thione S) and ‘out-
er’ (Cu(1)) Cu–donor distances of 1.988 Å (aniline N), 1.961 Å
(imine N) and 2.005 Å (hydrazide N). The outer two coppers,
Cu(1), each have a basal and an axial unidentate nitrate to com-
b-direction. As each molecule is step-shaped, with the Cu(2) con-
stituting the ‘risers’ and the ligands the ‘treads’, the lateral sheets
form the treads of ‘staircases’ which run in the c-direction, and
are stacked on top of one another.
3.2. Optical spectra
plete their square-pyramidal coordination (s = 0.16), with Cu–O
The optical spectrum shows a band maximizing at 630 nm (
e of
ca. 450 Mꢁ1 cmꢁ1 per Cu), which though principally d–d in nature,
is somewhat enhanced in intensity, as is often seen when sulfur
donors are present [42]. Ligand-localized transitions in the 250–
350 nm region appear reproduced in the copper complex, while
in the latter, absorption near 410 nm is likely associated with
LMCT.
(basal) of 2.002 Å. The axial nitrate oxygens are at 2.315 Å for the
outer coppers, and 2.398 Å for the bridged inner coppers, all these
bonds reflecting classical Jahn–Teller elongation. The hydrazide-N
to Cu distance is relatively the longest in the basal plane, presum-
ably reflecting the delocalisation of the anionic charge and its
redistribution toward the sulfur atom. Although little evidence of
any significant difference between Cu–S distances in protonated
vs. deprotonated versions of similar thiocarbohydrazones has been
observed, [43] it is generally the case that on deprotonation, the
imino-thiolate (Scheme 1 (a)) resonance form’s contribution in-
creases relative to the amidato-thione’s (b). This is evidenced by
a modest increase of typically ca. 2% in the C–S bond length be-
tween the free and the coordinated deprotonated forms [12].
Sometimes the deprotonation and coordination contribute equally
[12,34,43,44]. The decrease in C–S bond order on deprotonation is
necessarily associated with shortening of the C–N4 bond to the
hydrazide nitrogen (2% here), though this shortening is not general
even within the limited pyridyl–thiosemicarbazone subset of che-
lates [41].
3.3. Infrared spectra
Broad bands assignable to m .
(NH2) appear at ca. 3400–311 cmꢁ1
On coordination of the imine nitrogen, m(C@N) shifts to lower fre-
quency by ca. 10–35 cmꢁ1, so the band shifting from 1611 cmꢁ1 in
the uncomplexed thiocarbohydrazone’s spectrum to 1601 cmꢁ1 in
the spectrum of the complex 1 is assigned as
m(C@N). A sharp band
of medium intensity at 791 cmꢁ1 in HL is attributed to a dominant
contribution from
m(C@S), and is absent from the copper com-
plexes, where a new band appears at 752 cmꢁ1. This shift is consis-
tent with the transformation from thione character (Scheme 1 (a))
to deprotonated pseudothiolate character (b).
There are several hydrogen bonds associated with the structure.
The lattice water molecule’s O10 is an H-bond acceptor for H3A of
the hydrazine nitrogen’s N3. Simultaneously, the water’s protons
H10B and H10A link to an adjacent molecule’s monodentate ni-
trates’ O3 and O5, while the anilino-N’s H1B is linked to nitrate
O1 of an adjacent molecule. Consequently, the molecules include
sheet-like segments which are linked laterally (Fig. 4) along the
3.4. Magnetic studies
The magnetic behavior of a polycrystalline sample of 1 is shown
in Fig. 5. The value of
v
MT decreases from 1.357 cm3 K molꢁ1 at
ambient temperature to less than 0.0137 cm3 K molꢁ1 by 30 K, evi-
dencing a dominance of antiferromagnetic coupling within the tet-
ranuclear molecule.
Several related tetracopper systems have appeared in the liter-
ature, and a treatment of this spin topology (Fig. 6) has been given
by Fukuhara et al. [45], based on the original work by Hatfield and
Inman [46].
Variations in the molecular structure details have often enabled
certain of the Ja–Jd values to be approximated to zero in different
systems [21–23,25,47,48]. In anticipation of the analysis of the
magnetic data, it might be noted that the basal plane-basal plane
interactions Cu(1)–Cu(2) and Cu(3)–Cu(4) are similar to previously
described cases [5,12,42,49,50] with ꢁ2Ja in the range of 100 to
300 cmꢁ1, while it would appear unlikely that coupling of non-
adjacent coppers would be significant relative to such Ja values. In-
deed a simple dinuclear model [12,51] on Ja (approximating as
usual for the two copper environments by a single g-value) yields
a good fit (R2 = 1.2 ꢂ 10ꢁ4) of the data, with ꢁ2Ja = 210(1) cmꢁ1
,
g = 2.143(5), with TIP = 60 ꢂ 10ꢁ6 cgsu per Cu, and 0.2% paramag-
Scheme 1.
Fig. 4. Lattice view along the c-direction, showing ‘staircase’ stacking of the molecules (inverse stereoview).

D. Dragancea et al. / Inorganica Chimica Acta 363 (2010) 2065–2070
2069
a wide range of positive Jb values, but rises steeply if Jb
becomes negative.
The sign and magnitude of the couplings correlate satisfactorily
with the structural features. The essentially coplanar relationship
between the two coppers’ primary coordination cores means that
the exchange is dx2
ꢁ dx2
in nature, leading to antiferromag-
ꢁy2
ꢁy2
netic coupling, with the rather flat Cu–N–N–Cu bridges providing
an efficient -pathway for exchange. Other azine-bridged dicopper
systems with roughly parallel copper coordination planes also ex-
hibit moderate to large antiferromagnetic coupling,
r
[12,13,41,49,50] as elucidated by Thompson et al. [55]; the cou-
pling crosses over (i.e., ꢁ2J = 0) at an interplane twist angle of
about 85°. In the present instance, the Cu–N–N–Cu torsion angle
is 15° away from parallel, and the angle between the two 5 atom
coordination basal mean planes is 36°. These angles are slightly
larger than in our previously reported systems, where ꢁ2J was
about 180 cmꢁ1 [12–13]. It is also of interest to compare these re-
sults with those for two tetranuclear Schiff base complexes de-
scribed by Mukherjee et al. [24]; these molecules have a metal/
ligand/bridge layout very similar to 1, but the phenolate bridges
Fig. 5. Plot of
model.
vT vs. T for the copper compound. The solid line represents the fit
at 94° between the central coppers lead to a ꢁ2Jb of 70 cmꢁ1
.
4. Conclusions
A tetranuclear Cu(II) compound with NNN and NNS binding
sites for the copper has been described. Two dinuclear entities
are joined end-to-end by bridging nitrate anions, which mediate
a small ferromagnetic coupling. However, the magnetic properties
of the tetranuclear molecule are dominated by antiferromagnetic
interactions between the two coppers in each dinuclear chelate.
The molecule provides a rare example of a tetracopper system with
this numerical pattern of spin couplings.
Fig. 6. Scheme for the magnetic interactions amongst the four coppers. Connector
lengths reflect interaction weakness. The molecule’s outer Cu(1) correspond to the
spin locations 1 and 4, and the inner Cu(2) to locations 2 and 3.
netic impurity estimated from the low-T floor. Although Cu(2) and
Cu(3) are physically close, at 3.50 Å, the structure shows that the
nitrate bridge oxygens are disposed axially/equatorially. As a con-
sequence, these copper(II) ground state orbitals are mutually
orthogonal, so that significant antiferromagnetic coupling is not
expected. In any case, any outcome of this coupling is over-
whelmed by the strong Cu(1)–Cu(2) interaction. In at least one
prior tetranuclear case [19], the value of Jb was similarly so small
as to be negligible, and the data were likewise fitted by a Blea-
ney–Bowers model.
Acknowledgements
This work was supported by a Follow-On award MTFP-022/05
from the MRDA/CRDF foundation and partially by Supreme Council
for Science and Technological Development of R. Moldova, Project
no. 09.836.05.02A for D.D. A.W.A. thanks Drexel University for
support. We thank M.A. O’Connor and D. Hoole for assistance with
optical spectra and Dr. Konstantin V. Shuvaev for obtaining
magnetic data for the dinuclear compound 2.
Some further points relevant to this situation are:
(1) An allylimidazole complex structurally very similar to the
Cu(2), Cu(3) core in our tetranuclear system has been
described [52], and this has ꢁ2J = ꢁ2.1 cmꢁ1 (Fig. S2), con-
firming the absence of marked Cu(2)–Cu(3) coupling.
Appendix A. Supplementary material
CCDC 744024 contains the supplementary crystallographic data
for this paper. These data can be obtained free of charge from the
Cambridge Crystallographic Data Centre via www.ccdc.cam.ac.uk/
data_request/cif. Supplementary data associated with this article
can be found, in the online version, at doi:10.1016/j.ica.
2010.02.002.
(2) The DFT calculations (Tables 3 and S1) support these conclu-
sions, estimating Ja = ꢁ125 cmꢁ1 and Jb = +5 cmꢁ1
.
(3) Fitting of the data to the full tetranuclear Hatfield–Fukuhara
model yielded very large standard deviations for Jb, Jc and Jd,
and fits involving physically incompatible values of the J’s
were also easily realised, suggesting overparametrization.
Exploration of the dependence of R2 on the J-values as previ-
ously described [21,53,54] showed that even for a two-J
model (giving Jb = +1 cm-1), the value of R2 remains low for
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Table 3
UB3LYP/Ahlrichs-TZV-calculated energies (Hartrees) for the high-spin (EHS
broken symmetry spin (EBS) states, and the calculated J values.
)
and
)
Coupling constant
EBS
EHS
J (cmꢁ1
Ja
Jb
ꢁ11133.76308
ꢁ11133.77343
ꢁ11133.76251
ꢁ11133.77345
ꢁ125
+5

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