ATR-FTIR spectroscopic investigation of the cis- and trans-bis-(α-amino acids) copper(II) complexes

Article abstract of DOI:10.1016/j.molstruc.2017.02.023

The crystalline phases of the trans-(a) and cis-(b)-isomers of bis-(α-amino acids) copper(II) complexes [Cu(^bL)₂] 1–5 (^bL - bidentate ligand: gly (1), S-ala (2), R,S-val (3), (±)-thr (4), R,S-phe (5)) were studied by ATR-FTIR spectroscopy in the mid region IR spectrum. It was established that asymmetric ν_as(COO) and symmetric ν_s(COO) stretching vibrations of carboxylic groups of 1–5 are sensitive to change of the geometric structure and have a different maxima for the trans(a)- and cis(b)-isomers. It found that ν_as(COO) and ν_s(COO) stretching vibrations of cis-isomers are broadened and shifted to longer wavelengths (b) as compared with trans-isomers (a). Shown that peculiarities of crystal packing molecules of geometric isomers may affect on carboxylate stretching vibration bis-α-amino acids complexes copper(II) 1–5 a,b.

Full text of DOI:10.1016/j.molstruc.2017.02.023

Accepted Manuscript
ATR-FTIR spectroscopic investigation of the cis- and trans-bis-(α-amino acids)
copper(II) complexes
Tatyana V. Berestova, Lyudmila G. Kuzina, Natalya A. Amineva, Ilshat S.
Faizrakhmanov, Ismail A. Massalimov, Akhat G. Mustafin
PII:
S0022-2860(17)30156-4
10.1016/j.molstruc.2017.02.023
MOLSTR 23417
DOI:
Reference:
To appear in: Journal of Molecular Structure
Received Date: 29 April 2016
Revised Date: 4 February 2017
Accepted Date: 7 February 2017
Please cite this article as: T.V. Berestova, L.G. Kuzina, N.A. Amineva, I.S. Faizrakhmanov, I.A.
Massalimov, A.G. Mustafin, ATR-FTIR spectroscopic investigation of the cis- and trans-bis-(α-amino
acids) copper(II) complexes, Journal of Molecular Structure (2017), doi: 10.1016/j.molstruc.2017.02.023.
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Graphical Abstract
The cis-isomers and trans-isomers bis-(α-amino acids) copper(II) complexes were
studied by ATR-FTIR spectroscopy. It was established that asymmetric νas(COO) and symmetric
νs(COO) stretching vibrations of carboxylic groups have different maxima for the trans- and cis-
isomers. It found that νas(COO) and νs(COO) stretching vibrations of cis-isomers are shifted to
longer wavelengths as compared with trans-isomers.

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ATR-FTIR Spectroscopic Investigation of the Cis- and Trans-Bis-(α-
Amino Acids) Copper(II) Complexes
Tatyana V. Berestova*, Lyudmila G. Kuzina, Natalya A. Amineva, Ilshat S. Faizrakhmanov,
Ismail A. Massalimov, Akhat G. Mustafin
Bashkir State University, Department of Chemistry, 32 Zaki Validi Street, 450043, Ufa, Russia
Abstract
The crystalline phases of the trans-(a) and cis-(b)-isomers of bis-(α-amino acids)
copper(II) complexes [Cu(bL)2] 1-5 (bL - bidentate ligand: gly (1), S-ala (2), R,S-val (3), (±)-thr
(4), R,S-phe (5)) were studied by ATR-FTIR spectroscopy in the mid region IR spectrum.
It was established that asymmetric νas(COO) and symmetric νs(COO) stretching vibrations
of carboxylic groups of 1-5 are sensitive to change of the geometric structure and have a
different maxima for the trans(a)- and cis(b)-isomers. It found that νas(COO) and νs(COO)
stretching vibrations of cis-isomers are broadened and shifted to longer wavelengths (b) as
compared with trans-isomers (a). Shown that peculiarities of crystal packing molecules of
geometric isomers may affect on carboxylate stretching vibration bis-α-amino acids complexes
copper(II) 1-5 a,b.
Keywords: Bis-(α-Amino Acids) Copper(II) Complexes, Cis-, Trans-isomers, Glycine, S-
alanine, R,S-valine, (±)-Threonine, R,S-phenylalanine, ATR-FTIR-spectroscopy, XRD, Bond
Distances.
1. Introduction
Synthesis and identification of individual isomers of biologically active compounds is
one of the priority areas of pharmaceutical chemistry and fine chemical technology.
*
Corresponding author. Tel: +7 (347) 229 96 14
E-mail address: berestovatv@gmail.com

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It is known that nature of enzymes is strictly stereospecific and the amino acid and
peptide complexes of Cu(II) may be regarded as simplified model systems for studying
biochemical processes [1]. For example, amino acid chelate complexes of Cu(II) are active
intermediates in metabolic and enzymatic processes of the body [2-4]. Their usage in the
capacity of pharmaceuticals promotes rapid absorption of ions of biometals [5]. Also it is known
that the chelates Cu(II) can exhibit antibacterial, anticancer and other bioactivity [6-8], which is
dependent on the structure of ligands and the molecular design of the resulting compounds [9-
10].
The structural isomers of cis- and trans-bis-glycinate copper(II) [11-12] are studied most
of all. So, processes of cis-trans-isomerization of the bis-glycinate copper(II) were studied
through experimental and theoretical methods [13-16]. Recently, much attention has been paid to
their analogues [17]. Further, it was revealed that structural isomers of the bis-glycinate Cu(II)
have different characteristic strectching vibrations in the mid-IR spectra in aqueous solutions
[18]. This indicates their sufficient stability and probably different functional activity in
biological systems. In particular, was shows that mixed and bis-cis-isomers copper(II) complexes
can take part in the processes of the formation of biomolecules [19].
The previously published data include information about the identification of solid cis-
and trans-isomers by IR characteristics of stretching vibrations of N-Cu, O-Cu as the most
informative region [20-22]. Assuredly, the geometric isomers of amino acid complexes have
differences in the IR spectra, but their identification in the field of "fingerprint" causes
difficulties. Some aspects to identify the cis- and trans-isomers at characteristic frequencies in
the medium area are described in [23], but these data are fragmented and need to be generalized.
In this work the characteristic stretching vibrations of trans-(a) and cis-(b) isomers of bis-
α-amino acids copper(II) complexes [Cu(bL)2] 1-5 (bL = gly(1), S-ala(2), R,S-val(3), (±)-thr(4),
R,S-phe(5)) were studied by ATR-FTIR-spectroscopy in mid region IR spectrum.
2. Experimental
All reagents and chemicals were purchased from commercial sources (Avilon-
companychem, Russia; Sigma Aldrich) and used as received without further purification. All
used solutions were prepared by standard methods.
The FTIR spectra of the complexes 1-5 as compressed into thin plates, were recorded on
FTIR-8400S spectrometer (Shimadzu) in the mid-infrared attenuated total reflectance (ATR)
spectroscopy (HART Horizontal, PIKE, USA) (4000 – 850 cm–1, 2 cm–1 resolution, 20 scans) at
25oC. Frequency accuracy is estimated as ±1 cm-1. The final spectra were baseline corrected and
normalized.
The XRD patterns were recorded using DRON-4 diffractometer (CuKa: λ=1.5406 Å). For

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simulating of molecular structure of compounds, the ACD/3D viewer 8.04 version program was
used [24].
2.1. Method A. Synthesis of bis-cis-(amino acidato) copper(II) (1b) and bis-trans-
(amino acidato) copper(II) (2-5a(а′)) [Cu(bL)2] (bL = gly (1), S-ala (2), R,S-val (3), (±)-thr(4),
R,S-phe (5)
The complexes were prepared according to the published method [25] in which in the 100
ml flask equipped with a magnetic stirrer a solution of amino acid (6.6 mmol) in distilled water
(30 ml)was prepared. To a solution of amino acid an aqueous solution of CuSO4 (0.82 g, 3.3
mmol CuSO4·5H2O in 15 ml) was added. The reaction mixture was stirred for 1 h at room
temperature. Further, in the mixture Ba(OH)2 water solution (3.3 mmol) was added. The
reaction mixture was stirred for 1 h at room temperature. The resulting blue solution was twice
filtered and dried over anhydrous CaCl2. The blue powder of 1b was obtained. The light blue-
violet powder of 2-4a(a′) and 5a+b was obtained, including diastereomers 4a:4a′ in a ratio of
1:1. The received complexes were analyzed by ATR FTIR spectroscopy (br. broad; vs. very
strong; s. strong; m. medium; w. weak).
Yield cis-[Cu(gly)2] (1b): 91%. ATR FTIR (powder, cm-1): 3331w, 3289br (NH2, νas);
3268m (NH2, νs); 2925br, 2853br (CH, CH3, νas,s); 1605vs, 1593vs, 1580vs (COO, νas); 1576 –
1456w (NH2, δas,s); 1392s, 1404m (COO, νs).
Yield trans-[Cu(S-ala)2] (2a): 87%. ATR FTIR (powder, cm-1): 3306m, (NH2, νas);
3250m (NH2, νs); 2983m, 2970m, 2935m, 2877m (CH, CH3, νas,s); 1620vs (COO, νas); 1576-
1551w (NH2, δas,s); 1396s (COO, νs), 1356m (CH3,δs).
Yield trans-[Cu(R,S-val)2] (3a): 87%. ATR FTIR (powder, cm-1): 3300m (NH2, νas);
3254br (NH2, νs); 2962m, 2908m (CH, CH3, νas,s); 1618vs (COO, νas); 1587 – 1466w (NH2, δas,s);
1389s, 1373m (COO, νs), 1354m (CH3, δs).
Yield trans-[Cu((±)-thr)2] (4a,a'): 66%. Ratio 4a:4а′ ~ 1:1. ATR FTIR (powder, cm-1):
trans-[Cu(S-thr)2], [Cu(R-thr)2] (4a): 3307m, 3294br (NH2, νas); 3232br, 3208br (NH2, νs);
2988br, 2982m, 2919br, 2851br (CH, CH3, νas,s); 1614vs (COO, νas); 1578-1444w (NH2, δas,s);
1395s (COO, νas), 1352m (CH3, δs); trans-[Cu(R-thr)(S-thr)], [Cu(S-thr)(R-thr)] (4a'): 1612vs
(COO, νas); 1383s (COO, νs).
Yield trans-[Cu(R,S-phe)2] (5a): 59%. ATR FTIR (powder, cm-1): trans-[Cu(R,S-phe)2]
(5a) (major) 3342m (NH2, νas); 3269m (NH2, νs); 2921w, 2855 br (CH, νas,s); 1651vs (COO, νas);
1588 – 1456w (NH2, δas,s); 1397 (COO, νs). cis-[Cu(R,S-phe)2] (5b) (minor) 1647vs (COO, νas);
1388s (COO, νs).
2.2. Method B. Synthesis of bis-cis-amino acidato copper(II) 1-5b [Cu(bL)2] (bL = gly
(1), S-ala (2), R,S-val (3), (±)-thr(4), R,S-phe (5)
According to the published method [26] in the 100 ml flask equipped with a magnetic
stirrer solution of amino acid (6.6 mmol) in distilled water (20 ml) was prepared. To an aqueous
solution of amino acid 1M solution NaOH (6.6 mmol) was added. An aqueous solution of CuSO4
(0.82 g, 3.3 mmol CuSO4 ·5H2O in 10 ml) to protonated amino acid was added. The reaction
mixture was stirred for 2 days at room temperature and violet powder of 2-4b and light violet
powder of 5b were formed. The received complexes were analyzed by ATR FTIR-spectroscopy.
Yield cis-[Cu(gly)2] (1b): 75%.
Yield cis-[Cu(S-ala)2] (2b): 71%. ATR FTIR (powder, cm-1):, 3309m, (NH2, νas); 3267m
(NH2, νs); 2983br, 2970br, 2935br, 2877br (CH, CH3, νas,s); 1616vs (COO, νas); 1385s (COO, νs),
1354m (CH3, δs).
Yield cis-[Cu(R,S-val)2] (3b): 87%. ATR FTIR (powder, cm-1): 3304m (NH2, νas);
3240m (NH2, νs); 2962br, 2908br (CH, CH3, νas,s); 1615vs (COO, νas); 1587 – 1466w (NH2, δas,s);
1387m, 1373s (COO, νs), 1356m (CH3, δs).
Yield cis-[Cu((±)-thr)2] (4b,b′): 66%. Ratio 4b:4b′ ~ 1:1. ATR FTIR (powder, cm-1):

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cis-[Cu(S-thr)2], [Cu(R-thr)2] (4b): 3354-3224br, (NH2, νas, νs); 2988-2851br (CH, CH3, νas,s);
1610vs (COO, νas); 1576-1505w (NH2, δas,s); 1373s (COO, νas); cis-[Cu(R-thr)(S-thr)], [Cu(S-
thr)(R-thr)] (4b′): 1610vs (COO, νas); 1368s (COO, νs).
Yield cis-[Cu(R,S-phe)2] (5b): 46%.
3. Results and discussion
3.1. Synthesis and characterization of the geometric isomers 1-5a(a′),b(b′)
Vibrational criteria for cis- and trans-bis amino acid complexes of Cu(II) 1-5, which
were prepared by two methods [25, 26] (Scheme 1, Table 1) were studied by ATR-FTIR-
spectroscopy.
Predominantly trans-isomers (2-4a(a')) (Scheme 1, A) were obtained by procedure A.
Scheme 1
R
+
NH2
O
O
O
Cu
NH2
R
H
NH3
..
H
O
R
H
O
O
O
O
trans-[Cu(S(R)-R)2] - 2-5a
66-87%
Cu
2
+
Cu(II)
H3O+
..
O
O
R
R
NH2
O
O
H
O
R
NH3+
Cu
NH2
H
O
A
B
..
R
+
NH3
trans-[Cu(R(S)-R)(S(R)-R)] - 2-5a'
R
O
O
O
2 NaOH
-2H2O
O
O
R
H
O
Cu
O
NH2
NH2
R
H2N
..
H
O
2
R
O
46-94%
cis-1-5b(b') (major)
H
Cu
+
..
NH2
O
R
O
NH2
R
NH2
O
O
R
O
..
R
Cu
NH2
H
O
..
H
NH2
trans-2-5a(a') (minor)
R = H(1), CH3 (2), CH(CH3)2 (3), CH(CH3)OH (4), CH2-Ph (5)
Sometimes impurity of cis-isomers (2-4b(b')) up to 20% in IR spectra 2-4а(а′) were
observed. But cis-isomers were poorly soluble in water and after recrystallization almost pure
trans-isomers (2-4a(a')) were obtained. Regardless of method of synthesis of bis-glycinate
complexes Cu(II) (1b) was obtained only as cis-isomers, that is consistent with the literature data

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[27]. Apparently, this is due to the peculiarities of crystal packing effects of the cis-isomer
[11,15].
Following the procedure of B сomplexes 1-5 were obtained as a mixture of cis- and
trans-isomers (Scheme 1, B), but cis-isomers 1,3,5b are predominant. According to this
procedure, to solution of amino acid in deprotonated form a solution of CuSO4 was added.
During the reaction the suspensions of the complexes 1-3,5b were obtained.
Apparently, in most cases the acidity of an aqueous solution (pH<7) promotes the
formation of trans-isomers of 2-4а(а´) because protonated form of amino groups may push
away. But in neutral solution predominantly cis-isomers are formed although it is theoretically
possible formation of two isomers (Scheme 1, B). In addition, contribution to the formation of a
+
particular isomer will make substituent (R) of amino acids NH3 -CH(R)-COO-, which is able to
influence geometric structure of the complex due to additional interactions of functional groups
with the metal.
Initially, from solutions hydrated complexes 1-5a,b were isolated, evidenced by the
presence of absorption bands δ(H2O) in the IR spectra of the obtained compounds [28]. For
example, δ(H2O) were found in the region 1647 cm-1 for trans-[Cu(R,S-val)2]·2H2O and cis-
[Cu(R,S-val)2]·H2O, but it didn’t effect the shift of the maxima of the absorption bands of 1-
5a(a'),b(b') (table 1). After drying of 1-5a(a'),b(b') in the desiccators, the deformation
vibrations of water δ(H2O) are invisible in the infrared spectrum and are not detected in
stretching vibrations for hydroxyl group v(OH) 3400 cm-1.
3.2. FTIR-spectral analysis and identification of structural isomers 1-5a(a'),b(b')
Structural isomers of 1-5a(a'),b(b') were identified on the basis of experimental data of
IR, XRD [29] and an analysis of published data [11, 23, 26, 30-35] (Table 1).
The most informative absorption bands for identification of cis- and trans-isomers of 2-
3a,b in the IR spectra are in the range 3146-3384 cm-1 and correspond to the asymmetrical and
symmetrical stretching vibrations νas(NH2) and νs(NH2) (Table 1). These stretching vibrations
allow to define the coordination of amino group to ion of Cu(II). However, unambiguous criteria
for the identification of isomers in this area are not detected but for just visible minor broadening
and splitting of the absorption bands for the cis-isomers.

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In addition, in accordance with the literature data, the characteristic stretching vibrations
of carboxylate ion ν(COO) for complexes 1-5a,b corresponds to the frequency range 1580-1651
cm-1 for asymmetric νas(COO) and 1373-1404 cm-1 symmetric stretching vibrations νs(COO)
(Table 1). It was found that the absorption bands of the complexes 1-5a,b are shifted to shorter
region compared with the original α-amino acids (Fig. 1) and corresponds to the literature [22,
26, 28, 30-35].
We have found that stretching vibrations νas(COO) differ in intensity of peaks for trans-
(2-5a(a')) and cis-isomers (2-5b(b')). So, the maxima of the absorption bands for 2-5a(a') are
fixed at shorter waves (Fig. 1, Table 1). For complexes 2-5b(b') low intensity of peaks and a
slight shift of the maxima to longer wavelengths of region relative to the trans-isomer are
characteristic.
The symmetric stretching vibrations of carboxylate ion νs(COO) were more sensitive to
lateral interactions chelate compounds [36-37], that influence their intensity and the shift of the
absorption bands in the region 1373-1394 cm-1 with respect to the original amino acid. For
example, in the IR spectra of trans-isomer 3a observed intense absorption band in the region
1389(vs) band and in the infrared spectra of a mixture of 3a+3b isomer with predominance 3b
cis-isomer observed two absorption 1387(m) 1373(s) band cm-1, and the second one 1373 cm-1
was more intense than the first (Fig. 1).
Such differences in the IR spectra allow to identify geometric isomers 3a,b by the
characteristic value ꢀνas,s(COO) [38], which has a greater value for cis- isomer 3b as compared
to trans-isomer 3a. So, for cis-isomer (3b) ꢀνas,s(COO) of 242 cm-1 and trans-isomer (3a) of
229 cm-1 (Table 1).
3.3. Identification of structural isomers 1-5a(a'),b(b') by XDR
IR data for geometric isomers of 1-5 were confirmed by XDR. For example, in the
mixture of geometric isomers 3a+3b cis- and trans-isomers were identified in a ratio of 5:1 by
XRD method and comply for literature data [29] (Fig. 2).
An additional criterion for classifying geometric isomers in medium IR spectra are X-
rays of the complexes 3a,b [25, 39-40]. Thus, for cis-isomer 3b voltage carboxylate moiety will
be much greater compared to the trans-isomer 3a. For example, in crystalline samples of cis-
isomer 3b the bond C=O is smaller, but O-CO bond is longer compared to the similar bonds of
trans-isomer 3a [39-40] (Table 2), allowing to make the assumption about the tendency of the
"twist" on carboxylate ion of the cis-isomer 3b as compared to the trans-isomer 3a. Apparently,
this is due to the peculiarities of crystal packing of geometrical isomers in accordance with the

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type of crystal lattice monoclinic (Р21) for trans-isomer [41] и orthorhombic (Р212121) for cis-
isomer [42]). A similar trend changes in bond lengths is observed for geometrical isomers 1-2a,b
[11, 43-44] (Table 2) and other chelate complexes of Cu(II) [45] and amino acid Pt(II) complex
[46-47].
3.4. Identification of diastereomers 4a(a'),b(b')
The diastereomers of bis-complexes of Cu(II), containing in their composition fragments
(±)-threonine (4aa') were obtained as trans-isomer (>90%), consistent with the literature data
[48]. The broadening of the band of the asymmetric stretching vibration νas(COO) as compared
to the original amino acid and splitting lanes symmetric stretching vibrations carboxy νs(COO) in
the IR spectra of 4 leads to the assumption about formation of diastereomeric pairs 4aa'
complexes at a ratio of ~ 1:1. [25]. In this case, ꢀνas,s(COO) for 4a was 219 cm-1 and for 4a' 225
cm-1 (Table 1). Such value νs(COO) in amino acid complexes that do not contain a composition
of compounds with two chiral centers is not detected.
Tentative assignment of diastereomers 4aa' is also based on the phenomenon of a
"tightening" of the carboxyl group to the rest of the molecule. Apparently, this trend will
continue in the case of diastereomers, because one of them has more hindered geometry
relatively to the other one.
trans-[Cu(S-thr)(R-thr)] - 4a';
trans-[Cu(R-thr)(S-thr)] - 4a'
trans-[Cu(S-thr)2] - 4a;
trans-[Cu(R-thr)2] - 4a
1: 1
Since the R,S-isomer (4a) has a constrained geometry because of the mutual influence of
CH(CH3)OH groups, the conjugate structure will be created in this isomer. This apparently
results in the shift of the absorption band maximum νs(COO) in a short wave region [37] , which
is manifested in the IR spectrum as cleavage of the absorption bands 1395 and 1387 cm-1 for
trans-(4a) and 1381 and 1373 for cis-isomers (4b).

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4. Conclusion
Thus, by method of ATR-FTIR characteristic symmetric νas(COO) and symmetric
νs(COO) stretching vibrations of carboxylic group of cis- and trans-isomers of amino acid
complexes 1-5a(a'), b(b') were studied.
Established, that νas(COO) and νs(COO) stretching vibrations of carboxylic groups of 1-5
have a different maxima for the trans(a)- and cis(b)-isomers. In particular, asymmetric stretching
vibrations νas(COO) are different for trans-3a (1618vs) and cis-isomers 3b (1615vs). The
symmetric stretching vibrations νs(COO) are at 1389s for trans-(3a) and 1387m, 1373s for cis-
isomers (3b). So, differences in the IR spectra of geometric isomers 3a,b allow identify them by
value ꢀνas,s(COO), which for cis-isomer 3b (242 cm-1) has a greater value as compared to trans-
isomer 3a (229 cm-1). In case formation of diastereomers 4a(aʹ) two shoulders at 1395 and 1387
cm-1 in ratio of 1:1 were observed for νs(COO).
Shown that in crystalline cis-isomer 3b the bond length C=O is smaller, but O-CO bond
is longer compared to the similar bonds of trans-isomer 3a. Apparently, this fact may be due to
the influence of crystal packing of geometrical isomers. According to the literature [43-47], a
similar changes in bond length of carboxylic group is observed for trans- and cis-isomers 1-2a,b
and other chelate complexes of Cu(II) and Pt(II).
Acknowledgements
The authors are indebted to students Gulnaz V. Miftakhova, Gulnaz Yu. Amantaeva for
experimental assistance. The authors thank Prof. Gennadyi P. Mikhaylov and Dr. Vladimir V.
Lazarev (Ufa, State Aviation Technical University, Russia) for helpful discussion. The authors
are grateful to Dr. V.N. Danilenko for the XRD Analysis (Institute for Metals Superplasticity
Problems of the Russian Academy of Science).
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ACCEPTED MANUSCRIPT
Table1
Ref
Important Characteristic ATR-FTIR data (cm-1) of the ɑ-amino acids and bis-cis- and trans-complexes of Cu(II) 1-5a(a'),b(b')
Characteristic IR spectra
Compound
Glycine (glyH)
S-alanine (S-alaH)
Color
Yield, %
ν(COO)
ν(NH3, NH2)
ꢀνas,s
(COO)
190
183
178
179
179
208
209
210
173
170
201
δ
as
s
(H2O)
as
s
1595, 1608vs
1593vs
1412s
1410s
1412s
1409s
1416s
1362s
1417s
1418s
1414s
1411s
1404s,
1392m
1390s
3163
3078
1590vs
1588vs
1595vs
1570vs
1626vs
1626vs
1587vs
1581vs
30
31
3133
3114, 3215
3030, 3173
R,S-valine (R,S-valH)
(±)-threonine ((±)-thrH)
R,S-phenylalanine (R,S-pheH)
cis-[Cu(gly)2] (1b)
32
34
35
3026, 3169
2978, 2998
3033, 3065
3012, 3076
3331, 3289
blue
1580, 1593, 1605vs
3268
75-91
1580vs
202
198
210
224
231
3335, 3265
3333, 3262
3315, 3244
3306
23
28
28
cis-[Cu(gly)2]·H2O
1580, 1594, 1606vs 1403s,1389m
1676m
3162
3176
3250
3267
trans-[Cu(gly)2]·2H2O
trans-[Cu(S-ala)2] (2a)
cis-[Cu(S-ala)2] (2b)
1589, 1609vs
1620vs
1389s
1396s
1385s
1400s,
1394m
1400s
-
blue
violet
87
71
-
-
1616vs
3309
23
1620vs
222
3293, 3245
trans-[Cu(S-ala)2]
1619vs
1624vs
1618vs
1615vs
1618vs
219
-
-
28
28
cis-[Cu(S-ala)2]
trans-[Cu(R,S-val)2] (3a)
cis-[Cu(R,S-val)2] (3b)
55
87
54
98
58
-
-
blue
violet
light blue
light violet
1389s, 1373m 229, 245
1387m, 1373s 228, 242
1389s, 1373m 229, 245 1651m
1387m, 1373s 227, 241 1649m
-
-
3300
3304
3300
3301
3254
3240
3254
3255
trans-[Cu(R,S-val)2]·2H2O (3a·2H2O)
cis-[Cu(R,S-val)2]·H2O (3b·H2O)
trans-[Cu(S-val)2]
1614vs
1584vs
1390s
-
-
1395m
1387m
1381m
1373m
225
-
-
219
225
229
237
3300, 3272
3291, 3158
3284, 3159
23
26
26
trans-[Cu(R,S-val)2]
cis-[Cu(R,S-val)2]
1623, 1595vs
1627, 1585vs
1614vs
75
trans-[Cu(S-thr)2]; [Cu(R-thr)2] (4a)
trans-[Cu(R-thr)(S-thr)]; [Cu(S-thr)(R-thr)](4a΄)
cis-[Cu(S-thr)2], [Cu(R-thr)2] (4b)
cis-[Cu(R-thr)(S-thr)], [Cu(S-thr)(R-thr)](4b′)
trans-+ cis-[Cu(R,S-phe)2] (5a+5b)
3307, 3294
3307, 3294
3208, 3232
3208, 3232
bright
blue-violet
1612vs
51-66
1610vs
light violet
light violet
59
46
1651, 1647vs
1647vs
1397s, 1388s 254, 259
3342
3342
3269
3269
cis-[Cu(R,S-phe)2] (5b)
trans-[Cu(R,S-phe)2]
1388
1398, 1393
259
223
1625vs
3315, 3235
23

ACCEPTED MANUSCRIPT
1627vs
1614s
1377s
~1377s
250
~237
trans- + cis-[Cu(R,S-(phe)2]·H2O
3320, 3254, 3146
35
аR(S) – The absolute configuration of asymmetric carbon atom at the COO- and NH2-groups

ACCEPTED MANUSCRIPT
Table 2
X-ray Crystal Bond Distances (Å) and Valence Angles (deg) of 1-3a,b
cis-[Cu(gly)2] (1b)
trans-[Cu(gly)2] (1a)
1.29
1.91
1.97
Bond
Distances
1.54
1.54
1.44
1.62
1.94
1.93
1.25
1.09(7)/1.40(5) [11]
1.62(7) [11]
1.29(2) [11]
1.54(3) [11]
1.44(3) [11]
1.97(2) [11]
1.93(2) [11]
C=O
O-CO
1.36(8)/1.71(7) [11]
1.83(4)/1.95(4) [11]
1.94(3)/1.94(3) [11]
cis-[Cu(L-ala)2] (2b)
C(H)-CO
Cu-O
Cu-N
trans-[Cu(L-ala)2]·(2H2O) (2a)
1.26
1.99
1.33
1.99
1.55
1.53
2.02
1.75
1.94
1.23
1.239(2)/1.227(2) [43]
1.275(2)/1.275(2) [43]
1.534(2)/1.538(2) [43]
1.947(2)/1.937(2) [43]
1.990(2)/1.993(2) [43]
1.25/1.28 [44]
1.29/1.37 [44]
1.55/1.56 [44]
1.97/1.95 [44]
2.01/2.02 [44]
C=O
O-CO
C(H)-CO
Cu-O
Cu-N
Valence
Angles
O-C-O
122/116 [44]
116/119 [44]
O-C-C(H)
cis-[Cu(L-val)2]·(H2O) (3b)
trans-[Cu(L-val)2]·(2H2O) (3a)
2.01
1.984
1.48
1.54
1.282
1.93
1.35
1.20
1.90
1.224
1.20(3)/1.25(4) [39]
1.35(4)/1.36(3) [39]
1.48(4)/1.54(4) [39]
1.90(2)/1.90(2) [39]
2.010(2)/2.030(2) [39]
1.224/1.250 [40]
1.282/1.292 [40]
1.540/1.552 [40]
1.93/1.948 [40]
1.984/2.010 [40]
C=O
O-CO
C(H)-CO
Cu-O
Cu-N
Valence
Angles

ACCEPTED MANUSCRIPT
O-C-O
122(1)/122(1) [39]
117(1)/119(1) [39]
122.9/124.6 [40]
120.8/121.5 [40]
O-C-C(H)

ACCEPTED MANUSCRIPT
Fig. 1. Fragments of the FTIR spectrum of trans-isomers bis-[Cu(R,S-val)2] (3a) , cis- -
isomers bis-[Cu(R,S-val)2] (3b) and R,S-valH

ACCEPTED MANUSCRIPT
trans-[Cu(R,S-val)2] (3a)
cis-[Cu(R,S-val)2] (3b)
2θ [degree]
Fig. 2. Powder XRD patterns of trans-[Cu(R,S-val)2] (3a) (major) + cis-[Cu(R,S-val)2] (3b)
(minor)