New examples of chelating triketone-like ligands that promote formation of binuclear complexes Dedicated to the memory of Dr. Yury G. Yatluk, a teacher and colleague.

Article abstract of DOI:10.1016/j.poly.2015.12.056

The present work is to investigate of binding properties of chelating triketone-like ligands, which are able to forming of binuclear complexes. The studied compounds are able to exist in cyclic or 'close form' (phenyl substituted or unsubstituted 2-hydroxy-2-(trifluoromethyl)chroman-4-ones) as well as in their associated 'open form' (phenyl substituted or unsubstituted 1,1,1-trifluoro-4-(2-hydroxyphenyl)butan-2,4-diones). In this paper there is good evidence for the compounds are being in solid in 'close form' (pre-ligands), whereas in basic solutions and when involved in metal ion coordination sphere they are being in 'open form' (ligands). Protolytic equilibria of the compounds in aqueous ethylene glycol solutions were studied. Schemes of acid-base equilibria of these compounds were proposed. Apparent ionization constants of compounds containing electron-donor and electron-acceptor substituents in the benzene ring were determined using spectrophotometric method. The binding properties of 1,1,1-trifluoro-4-(2-hydroxyphenyl)butan-2,4-dione towards Cu(II), Ni(II) and Co(II) were studied. The formation of 2:2 metal-ligand complexes was observed. X-ray analysis gives evidence the formation of complexes in which the ratio metal to ligand can be 1:2 and 2:2. Similar to β-triketones the studied ligands tends to formation of binuclear complexes with transition metal ions.

Full text of DOI:10.1016/j.poly.2015.12.056

Accepted Manuscript
New examples of chelating triketone-like ligands that promote formation of bi-
nuclear complexes
Alexander V. Pestov, Liliya A. Khamidullina, Vyacheslav Y. Sosnovskikh,
Pavel A. Slepukhin, Igor S. Puzyrev
PII:
S0277-5387(15)00806-2
DOI:
http://dx.doi.org/10.1016/j.poly.2015.12.056
POLY 11755
Reference:
To appear in:
Polyhedron
Received Date:
Accepted Date:
30 June 2015
29 December 2015
Please cite this article as: A.V. Pestov, L.A. Khamidullina, V.Y. Sosnovskikh, P.A. Slepukhin, I.S. Puzyrev, New
examples of chelating triketone-like ligands that promote formation of binuclear complexes, Polyhedron (2016),
doi: http://dx.doi.org/10.1016/j.poly.2015.12.056
This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers
we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and
review of the resulting proof before it is published in its final form. Please note that during the production process
errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

New examples of chelating triketone-like ligands that promote formation of binuclear
*
complexes
a
b
b
Alexander V. Pestov , Liliya A. Khamidullina , Vyacheslav Y. Sosnovskikh , Pavel A.
a
a,b†
Slepukhin , Igor S. Puzyrev
a
I. Ya. Postovsky Institute of Organic Synthesis UB RAS, 620990, Sofia Kovalevskaya str. 22,
Ekaterinburg, Russia
b
Ural Federal University, 620002, Mira str. 19, Ekaterinburg, Russia
Abstract
The present work is to investigate of binding properties of chelating triketone-like ligands,
which are able to forming of binuclear complexes. The studied compounds are able to exist in
cyclic
or
‘close
form’
(phenyl
substituted
or unsubstituted
2-hydroxy-2-
(
trifluoromethyl)chroman-4-ones) as well as in their associated ‘open form’ (phenyl substituted
or unsubstituted 1,1,1-trifluoro-4-(2-hydroxyphenyl)butan-2,4-diones). In this paper there is
good evidence for the compounds are being in solid in ‘close form’ (pre-ligands), whereas in
basic solutions and when involved in metal ion coordination sphere they are being in ‘open form’
(
ligands). Protolytic equilibria of the compounds in aqueous ethylene glycol solutions were
studied. Schemes of acid-base equilibria of these compounds were proposed. Apparent ionization
constants of compounds containing electron-donor and electron-acceptor substituents in the
benzene ring were determined using spectrophotometric method. The binding properties of
1,1,1-trifluoro-4-(2-hydroxyphenyl)butan-2,4-dione towards Cu(II), Ni(II) and Co(II) were
studied. The formation of 2:2 metal-ligand complexes was observed. X-ray analysis gives
evidence the formation of complexes in which the ratio metal to ligand can be 1:2 and 2:2.
Similar to β-triketones the studied ligands tends to formation of binuclear complexes with
transition metal ions.
Keywords: chroman-4-ones, binuclear complexes, triketone-like ligands, transition metal
complexes
*
Dedicated to the memory of Dr. Yury G. Yatluk, a teacher and colleague
†
Corresponding author. Tel. +7 343 3623439. E-mail address: igor.puzyrev@gmail.com (I.
Puzyrev)
1

1. Introduction
Binuclear complexes with first transition metals have found applications in a great number
of areas. The most important ones include biomimetic enzymatic systems [1,2] including
nuclease mimetics [3], antibacterial activity [4,5], etc. The complexes of metal ions like
cobalt(II) [6], copper(II) [6–8], nickel(II) [6,8,9], palladium(II) [4], as well heterometallic
complexes such as Cr(III)–Mn(III) [10] are of particular interest for molecular magnets.
Enamino ketone derivatives [11,12], Schiff-bases [4,13], pyrazole based ligands [8,9], and
N-derivatives of 3-aminopropan-1-ol or β-alanine [14] are used for binuclear complexes
synthesis based on reasonable design of chelating organic ligands. Many works so far, however,
have concentrated mainly on the 2,6-disubstituted phenol derivatives [15] and β,δ-tricarbonyl
compounds [16] as chelating ligands, which undoubtedly made a formation of binuclear
complexes possible. β-Diketophenoles [17,18] – acyclic tautomers of 2-hydroxychroman-4-one
derivatives [19] are structural analogues of β,δ-tricarbonyl compounds. They are able to exist in
‘
open’ structure in solutions depending on chemical structure and solvent [20] and act as ligands
forming binuclear complexes [17]. Consequently they can found numerous opportunities when
being integrated with transition metal ions. Although much research concerns synthesis and
chemical properties, little attention has so far been paid to study the binding properties of ligands
that include chromone system [21–23]. Mentioned type of the ligands is valuable alternative for
2,6-disubstituted phenol derivatives [15] and β,δ-tricarbonyl compounds [16]. Introducing of
varied substituents into template structures of such ligands comes to the end of tether. So that,
radical modification of complexes electronic structure is impossible in this way. Therefore, it is
very motivating to study the binding properties of the 2-hydroxychroman-4-one derivatives in
solutions as well as to investigate the synthesis and crystal structures of metal complexes of the
ligands with transition metal ions.
In this work we focused on the properties of 2-hydroxy-2-(trifluoromethyl)chroman-4-one
(
1),
2-hydroxy-6-methyl-2-(trifluoromethyl)chroman-4-one
(2)
and
2-hydroxy-2,6-
bis(trifluoromethyl)chroman-4-one (3). These compounds were used as pre-ligands for
preparation of binuclear complexes with Co(II), Ni(II) and Cu(II). The structural characterization
of the metal complexes using such methods as UV-Vis spectrophotometry, FT-IR, X-ray single
crystallography, was performed.
2. Experimental
2.1. Chemicals
Reagent grade ethylene glycol was used without further purification. Distilled water was
used for preparation of all solutions.
2

2
-Hydroxy-2-(trifluoromethyl)chroman-4-one
(1),
2-hydroxy-6-methyl-2-
(
trifluoromethyl)chroman-4-one (2) and 2-hydroxy-2,6-bis(trifluoromethyl)chroman-4-one (3)
are the chromanone derivatives, which were prepared previously [19,24,25]. Other chemicals
were commercially available and of pure grade. The metal salts were prepared and analyzed
following the standard procedures.
1
NMR H of 1 (HOCD
2
CD
2
OH, δ, ppm, J/Hz): 2.96 (d, 1Н, СНН, JAB = 16.4); 3.31 (d, 1Н,
= 8.3); 7.21 (dd, 1Н, Н(6), J = 7.6, 7.4); 7.67 (ddd, 1Н,
= 1.6); 7.86 (dd, 1Н, Н(5), J = 7.8, J = 1.4).
H NMR of 1 (CDCl , δ, ppm, J/Hz): 3.04 (d, 1Н, CHH, JAB = 16.7); 3.10 (d, 1H, CHH,
AB = 16.7); 3.61 (s, 1H, OH); 7.07 (dd, 1H, H(8), J
СНН, JAB = 16.5); 7.14 (d, 1Н, Н(8), J
Н(7), J = 8.6, 7.0, J
o
o
o
m
o
m
1
3
J
o
= 8.3, J
m
= 1.0); 7.15 (ddd, 1H, H(6), J
o
=
=
7.8, 7.3, J
m
= 1.0); 7.58 (ddd, 1H, H(7), J
o
= 8.3, 7.3, J = 1.7); 7.93 (dd, 1H, H(5), J
m
o
= 7.8, J
m
1.7).
1
H NMR of 2 (CDCl
3
, δ, ppm, J/Hz): 2.33 (s, 3H, Me); 3.00 (d, 1H, CHH, JAB = 16.7);
= 8.4); 7.38 (dd, 1H, H(7),
3
.07 (d, 1H, CHH, JAB = 16.7); 3.60 (s, 1H, OH); 6.96 (d, 1H, H(8), J
o
J
o
= 8.4, J
m
= 2.2); 7.71 (d, 1 H, H(5), J
m
= 2.2).
1
2 6
H NMR of 3 (C D
SO, δ, ppm, J/Hz): 2.98 (d, 1H, CHH, JAB = 16.7); 3.07 (d, 1H, CHH,
JAB = 16.7); 3.58 (s, 1H, OH); 7.42 (d, 1H, H(8), J
o
= 8.4); 8.02 (dd, 1H, H(7), J
o
= 8.4, J
m
= 2.2);
8
.06 (d, 1H, H(5), J = 2.2).
m
1
9
F NMR of 1 (HOCD
2
2
CD
CD
2
2
OH, δ, ppm, C
6
6
F
6
): 77.71 (s, CF
3
3
(2)).
(2)); 101.18 (s, CF
1
9
F NMR of 3 (HOCD
OH, δ, ppm, C
F
6
): 77.86 (s, CF
3
(6)).
2.2. Solutions
Spectrophotometric experiments were carried out at 25 °C in the aqueous ethylene glycol
containing 70 % ethylene glycol by volume. The ionic strength was maintained at 0.1 with the
KCl stock solutions.
2.3. Apparatus
Microanalyses (C, H, N) were performed using a Perkin–Elmer РЕ 2400 elemental
analyzer. The UV–VIS spectra were recorded over the range 200–800 nm on a Shimadzu UV-
1
19
2
401 PC spectrophotometer. H and F NMR spectra were recorded on a Bruker 400 MHz FT
NMR (model Avance DRX-400). The FTIR spectra of compounds were recorded over the range
-1
4
000–400 cm using Spectrum One spectrophotometer (Perkin Elmer, USA). Single-crystal X-
ray diffraction performed on an Oxford Diffraction Xcalibur-3 diffractometer. TGA-DTA
-1
measurements were performed at heating rate of 5 °C min on instrument Mettler–Toledo
TGA/DSC 1. Approximately 12-16 mg of sample were heated in ceramic crucible in air.
3

2.4. Solution equilibria
All analyte concentrations were expressed in the molarity scale (mol/L, M). For
potentiometric and UV measurements, working solutions of HCl (0.1 M), NaOH (0.1 M),
chromanones (0.0025 M), CoCl ·5H O, NiCl ·5H O, CuCl ·5H O (0.05 M, containing HCl 0.1
2
2
2
2
2
2
M) were prepared and standardized. The starting solution for each titration and all working
solutions contained known amounts of KCl to assure a constant 0.1 M ionic strength during the
titrations.
UV measurements (Table 1) were carried out for solutions containing the chromanone
alone, and for solutions containing the chromanone and the metal ion, at various pH values. The
pK
a
values for the chromanones were computed by the program FTMT [26].
.5. Synthesis of binuclear complexes
.5.1. Synthesis of complexes Cu (L1)
2
2
2
2
[
2
2
2
2
2 2
Cu (L1) (H O) ] (4-1). To a solution of Cu(AcO) ·H O (0.86 g, 4.3 mmol) and urea (0.52
g, 8.6 mmol) in 20 mL of water the solution of 1 (0.5 g, 2.15 mmol) in 46 mL methanol. The
mixture was kept in water bath for 1 h, then at room temperature for 24 h, after that the product
was filtered off, washed with water and dried in vacuum. Yield: 0.6 g (92%). Anal. Calc. for
C
20
H
10
F
6
O
6
Cu
.90; F, 18.09; Cu, 20.32.
Cu (L1) (DMF) ] (4-2). After the recrystallization of 4-1 from DMF the solvate complex
was obtained. Anal. Calc. for C20 Cu ·2C NO (733.57): С, 42.57; H, 3.30; N, 3.82; F,
5.54; Cu, 17.33%. Found: С, 42.23; H, 2.91; N, 3.45; F, 15.26; Cu, 17.89%.
2
·2H
2
O (623.41): С, 38.53; H, 2.26; F, 18.29; Cu, 20.38%. Found: С, 38.91; H,
1
[
2
2
2
H
10
F
6
O
6
2
3 7
H
1
2.5.2. Synthesis of complex [Cu
2
(L2)
2 2
(DMF) ] (5)
To a solution of Cu(AcO)
2
·H O (0.42 g, 2 mmol) in 20 mL of water the solution of 2 (0.50
2
g, 2 mmol) and NaOH (0.16 g, 4 mmol) in 20 mL of methanol was added. The mixture was
stirred at room temperature for 1 h and then the product was filtered off, washed with water and
dried in vacuum. Yield: 0.62 g (98%). Anal. Calc. for C22
H
14
F
6
O
6
Cu
2
·H O (633.45): C, 41.71;
2
H, 2.55; F, 17.99; Cu, 20.06%. Found: С, 41.88; H, 2.62; F, 17.75; Cu, 20.46%.
After the recrystallization of product from DMF the solvate complex was obtained. Anal.
Calc. for C22
14 6 6 2 3 7
H F O Cu ·2C H NO (761.62): С, 44.16; H, 3.71; N, 3.68; F, 14.97; Cu, 16.69%.
Found: C, 43.95; H, 3.41; N, 3.44; F, 14.27; Cu, 17.26%.
2.5.3. Synthesis of complex [Cu
2
(L3)
2 2 4
(H O) ] (6)
To a solution of Cu(AcO)
2
·H O (0.42 g, 2 mmol) in 20 mL of water the solution of 3 (0.60
2
g, 2 mmol) and NaOH (0.16 g, 4 mmol) in 20 mL of methanol was added. The mixture was
4

stirred at room temperature for 1 h and then the product was filtered off, washed with water and
dried in vacuum. Yield: 0.70 g (88%). Anal. Calc. for C22 Cu ·4H O (795.44): C, 33.22;
H, 2.03; F, 28.66; Cu, 15.98%. Found: С, 33.26; H, 1.95; F, 28.28; Cu, 16.36%.
H
8
F
12
O
6
2
2
2
.5.4. Synthesis of complex [Ni
To a solution of Ni(AcO) ·4H
mmol) and NaOH (0.16 g, 4 mmol) in 20 mL of methanol was added. The mixture was stirred
2
(L1)
2 2 3
(H O) ] (7)
2
2
O (0.50 g, 2 mmol) in 10 mL of water the solution of 1 (0.46 g,
2
at room temperature for 1 h and then the product was filtered off, washed with water and dried in
vacuum. Yield: 0.60 g (95%). Anal. Calc. for C20 Ni ·3H O (631.72): C, 38.02; H, 2.55;
F, 18.04; Ni, 18.58%. Found: С, 37.72; H, 2.90; F, 16.98; Ni, 19.08%.
H
10
F
6
O
6
2
2
2
.5.5. Synthesis of complex [Co
To a solution of Co(AcO)
0.46 g, 2 mmol) and NaOH (0.16 g, 4 mmol) in 20 mL of methanol was added. The mixture was
stirred at room temperature for 1 h and then the product was filtered off, washed with water and
dried in vacuum. Yield: 0.56 g (98%). Anal. Calc. for C20 Co ·H O (596.17): C, 39.10;
H, 2.27; F, 18.56; Co, 19.21%. Found: С, 39.80; H, 2.17; F, 18.27; Co, 19.38%.
2
(L1)
2 2
(H O)] (8)
2
·4H
2
O (0.50 g, 2 mmol) in 20 mL of water the solution of 1
(
H
10
F
6
O
6
2
2
2.6. Synthesis of mononuclear complexes
[
Cu(HL1) (H O) ] (9-1). To a solution of Cu(AcO) ·H O (1.19 g, 6 mmol) in 120 mL of
2
2
2
2 2
water the solution of 1 (1.39 g, 6 mmol) in 60 mL of methanol was added. The mixture was
stirred at room temperature for 1 h and then the product was filtered off, washed with water and
dried in vacuum. Yield: 1.7 g (9562%). Anal. Calc. for C20
H, 1.87; F, 21.12; Cu, 11.77%. Found: С, 45.62; H, 2.20; F, 21.54%; Cu 12.09.
Cu(HL1) (DMSO) (H O) (9-2) and [Cu(HL1) (TMU) (9-3). After the
recrystallization of complex 4-2 from DMSO and TMU the complexes 9-2 and 9-3 were
obtained. Anal. Calc. for C20 Cu·2C SO·2H O (714.12): С 40.22; H 3.35; F 15.92; S
.93; Cu 8.93%. Found: С, 39.82; H, 2.62; F, 16.35; S, 9.21; Cu, 9.15%. Anal. Calc. for
Cu·2C O (754.14): С, 47.74; H, 4.24; N, 7.43; F, 15.12; Cu, 8.49%. Found: С,
H
8
F
6
O
6
Cu·2H O (539.83): С, 44.50;
2
[
2
2
2
2
]
2
2
]
H
8
F
6
O
6
2
H
6
2
8
C
20
H
8
F
6
O
6
5
H
12
N
2
47.49; H, 4.08; N, 7.13; F, 15.34; Cu, 8.56%.
2.7. Synthesis of 1,3-dimethyl-2-imidazolidinimine hydrochloride
A mixture of 1,3-dimethyl-2-imidazolidinone (20.7 g, 0.18 mol), triphosgene (15.14 g,
4
0.051 mol) in 50 mL CCl was stirred at room temperature for 5 h. The precipitate was filtered
off, washed with hexane and dried in vacuum. To the product at the temperature –50°С the NH
3
(
5 ml) was added twice until complete evaporating of ammonia. Yield: 4.4 g (12%). Anal. Calc.
5

for C
5
H
13
N
3
Cl·NH
4
Cl (204.12): С, 29.42; H, 8.39; N, 27.45; Cl, 34.74%. Found: С, 28.98; H,
9.28; N, 27.74; Cl, 35.40%.
2.8. Single crystal X-ray diffraction analysis and structure determination
Suitable single crystals of 1, 5, 9-3, and 10 were selected and XRD analyses were carried
out on an automated four-circle κ-geometry diffractometer with CCD detector by standard
o
procedure (graphite monochromated Mo Kα (λ = 0.71073 Å) radiation, ω-scanning with step 1
at r.t. T=295(2) K) by applying the CrysAlis CCD Software system, Version 1.171.29.9. Data
reduction has been done by the same programs.
The structures were solved by direct methods, and refined in SHELXL-97 [27], including
anisotropic displacement parameters for all non-H atoms. H-atoms at C-H bonds were included
in calculated positions and refined isotropically in ‘riding’ model, H-atoms of the OH-groups
refined independently in isotropic approximation.
The crystal parameters, data collection and refinement results for 1, 5, 9-3, and 10 are
summarized in Table 5.
3. Results and discussions
Studied in this paper substituted chroman-4-ones (2-hydroxy-2-(trifluoromethyl)chroman-4-
one (1), 2-hydroxy-6-methyl-2-(trifluoromethyl)chroman-4-one (2) and 2-hydroxy-2,6-
bis(trifluoromethyl)chroman-4-one (3)) served as pre-ligands. Possibility of existence of their
associated ‘open’ form (1,1,1-trifluoro-4-(2-hydroxyphenyl)butan-2,4-dione (H
trifluoro-4-(2-hydroxyphenyl-5-methyl)butan-2,4-dione (H L2), 1,1,1-trifluoro-4-(2-
hydroxyphenyl-5-trifluoromethyl)butan-2,4-dione (H L3)) is caused by ring–chain tautomerism
Scheme 1). The results of FT-IR study add considerable support for the existence of ‘close’
form of the compounds in solid state.
2
L1), 1,1,1-
2
2
(
Scheme 1. Structures of the compounds used in this study.
6

3.1. FT-IR spectroscopy of chroman-4-ones (pre-ligands)
The FT-IR spectra of 1-3 was registered (Fig. 1S, Supporting materials). The characteristic
IR bands and corresponding assignment are presented in Table 1. The assignments have been
made on the basis of the literature data of similar compounds [28–30]. The broad bands in the
-1
regions of 3470-3090, 3470-3060, 3470-3000 cm for 1, 2 and 3, respectively, are appeared for
ν(O–H) that is characteristic band of hydroxyl group. The characteristic stretching vibrations of
-1
chromone carbonyl are usually located in the region of 1690-1640 cm , whereas the bands of
-
1
enol form of β-diketones appeared at 1620-1600 cm . IR spectra showed characteristic
-
1
stretching vibrations in the region of 1680 (1), 1682 (2), and 1693 (3) cm due to ν(C=O)
-
1
vibrations of chromone carbonyl. Additionally, ν(C=O) vibration of 1 is observed at 1643 cm .
That confirms the existence of the studied compounds in ‘close’ form in solid. In the spectra
-1
three bands in the range of 1615-1467 (1), 1619-1492 (2), 1625-1500 (3) cm are assigned to the
skeletal C=C stretching modes in benzene ring. This is in a good agreement with the literature
values [28–30].
Mostly ν(C–C) as well as the bands of CF
but it ought to be noted that new strong bands at 1335 and 1235 cm , which can be assigned to
as(C–F) and ν (C–F) of CF group of benzene ring, were registered only for compound 3.
3
at chromone ring exist in similar wavenumber,
-1
ν
s
3
3.2. Protolytic properties
As we said above, the complexes of di- and triketonate ligands with metal ions are very
perspective for catalytic application. Thus, important task is studying binding properties of
studied compounds. For this reason it is necessary to evaluate their protolytic properties. Because
of the low solubility of chromanones in water, their properties can be evaluated in such solvents
like water/methanol, water/ethanol, water/DMA, water/EG [22,31]. However methanol and
ethanol are high volatile, N,N-DMA has high absorbance in the range 200-260 nm, we decided
to use water/EG 30/70 vol. as solvent for studying properties of chromanones. Ionic strength was
adjusted by KCl (0.1 mol/L). The determination of ionization constants as well as binding
properties were performed using spectrophotometry because this method is an ideal method
when a substance is insoluble for potentiometry [22].
The spectral changes of water/EG (30/70 v./v.) solutions of chroman-4-ones depending on
pH are presented in Fig. 2S–4S (Supporting materials). The pH change of solutions of 1 induces
absorption changes at several distinct bands. Two bands in Fig. 2aS, i.e. band-3 and band-4 are
-
associated with the concentration of the monobasic form (HL ), while band-1 band-2 and is a
part of the characteristic spectra of the acid form (H L). The presence of isosbestic points
2
confirms that spectral transitions occur between different species. Rationally suppose that band-5
7

with maximum at 360 nm as well as a band at a longer wavelength range (band-6) can be
assumed to sequential ionization of ligands (Scheme 2). However, the compounds are unstable in
strongly alkaline media and decompose. It can be observed from dramatic change of spectra
(
Fig. 2bS) above pH > 10.5. The solutions of the compound having pH > 9 were investigated
using GC-MS. The results proved the decomposition of the ligand at pH > 10.5. In the solutions
the starting materials – 2-hydroxyacetophenone and 1,1,1-trifluoroacetate were identified. For
this reason the second ionization constant could not be determined.
2 2
Scheme 2. Protonation/destruction patterns for 1–3 (H L1–H L3)
The graphical analysis of band-4 with λmax = 340 nm can be used to estimate the pKa1 value
of 1,1,1-trifluoro-4-(2-hydroxyphenyl)butan-2,4-dione. The spectral data were processed
mathematically using FTMT program [26]. Equilibrium constant is shown in Table 2.
Spectra of 2 and 3 generally have similar characteristic bands (Fig. 3S and 4S, Supporting
materials) with absorbance maxima differ from ones of 1. Destruction of third ligand is
accompanied by rising novel band-7 (Fig. 4bS). For calculation the pKa1 value of H
L3 wavelength 345 nm (λmax of band-4) was chosen.
The first protolytic constant of H L1, which does not have substituents in the benzene ring,
is рКa1=8.21±0.09. The H L2, where the methyl group is in 6 position, shows a higher acidity
respect to H L1, that is a decrease in pKa1 (8.12±0.06). The value of protonation constant for the
, which has a trifluoromethyl group in the 6 position, also increases (рКa1=7.20±0.07).
Introducing the CH group into the benzene ring has led to slight increase in acidity of OH-group
δlogК = logКa1(H
2
L2 and
H
2
2
2
2
3
3
(
a
2
L2) – logКa1(H
2
3
L1) = 0.09). At the same time presence of the CF group in
8

the 6 position significantly affect the ligand protonation constant (δlogК
a
= logК
a
(3) – logК (1)
a
=1.08).
3.3. Binding properties of 1,1,1-trifluoro-4-(2-hydroxyphenyl)butan-2,4-dione (H
2
L1) in solution
Upon addition of 1 to the aqueous ethylene glycol solutions of CoCl , NiCl
2
2
, and CuCl
2
their initial color (pink, green and blue, respectively) changed to yellow indicating an
octahedral–tetrahedral geometry change, giving evidence to formation of complex compounds.
Inasmuch as in the course of ionization chromanones 1–3 undergo ring–chain
rearrangement, it is evident that it is precisely ‘open’ form of the compounds that is the ligand
which involved in complexation with metal ions.
For the determination of optimum pH complexation of H L1 with Co(II), Ni(II), Cu(II) the
2
dependencies of absorbance of metal ions/ligand solutions on pH were studied (Fig. 5S,
Supporting materials). The new bands at approximate 400 nm originate from the formation of
metal ion – ligand charge-transfer complexes arise. As shown in the inset plots, which traced at
400 nm, optimum pH of complexation of the ligand with Co(II) – 10-11, with Ni(II) – 10-11,
with Cu in pH range 7.5-8.5.
To elucidate the stoichiometric composition of the complexes in the solution we originally
used the molar ratio method [32] and Job’s method [33]. In the molar ratio method, various
amounts of metal ions were added to the constant amount of the ligand (0.1 mM). The
absorbance of each solution was measured and plotted against the metal-to-ligand mole ratio at
pH 10 for cobalt and nickel, pH 7.5 for copper.
As it is shown in Fig. 6aS (Supporting materials), the increase of cobalt to ligand molar
ratio at pH 10 gives rise to new shoulder at 400 nm which is absent in chromanone solutions.
The new shoulder for nickel–chroman-4-one solutions spectra (Fig. 6bS) becomes a maximum
(
λ
max = 400 nm) in a gradual manner. In case of copper (Fig. 6cS) distinct maximum with λmax
15 nm is observed. In subsequent studies the mentioned wavelengths were maintained
throughout the experiment. The intercepts, arising from extrapolated tangent lines of the curves
in the inset plots, suggested the formation of complexes with the mole ratio M(II):H L1 = 1:1.
Job’s method (Fig. 1) clearly display ratios in the complexes are 1:1 for all studied metals
indeed. The absorbance of isomolar solutions containing Co(II), Ni(II) or Cu(II) and H L1 was
measured at the total concentrations C ) were 0.1 mM.
=
4
2
2
R
/(CMe+C
R
However, molar ratio method and Job’s method can only show the ratio of components in
the complexes. Meanwhile, theoretically the composition of the complexes can be 1:1, 2:2, etc.
We used Starik-Barbanel relative yield method [34] for determination molar ratios between the
components of the complexes and found that for all studied metal ions M(II) : H L1= 2 : 2.
2
9

Whereas studied ligand forms complexes with the composition M(II) : H
2
L1= 2 : 2, the
formation of bond between chroman-4-one ligands and metals in solid proceeds both 2:2 and 1:2.
3.4. Preparation of complexes
Complexes 2 : 2 can be prepared in an (aqueous) methanol solutions in the presence of
base (Scheme 3). Synthesis of the complexes without the addition of base leads to the formation
of complexes ML . The same composition can be obtained by recrystallization of M
complexes using DMSO or tetramethylurea (TMU).
2
2 2
L
Scheme 3. Synthesis of complexes
] (4-1) was prepared by the reaction of copper(II) acetate
hydrate and 1 in an aqueous methanol solution in the presence of urea. Recrystallization 4-1
from DMF resulted to complex [Cu (L1) (DMF) ] (4-2). Complexes 4-1 and 4-2 were
2 2 2 2
Complex [Cu (L1) (H O)
2
2
2
characterized by elemental analyses, complex 4-1 was characterized by FT-IR. However, single
crystal none of them, suitable for X-ray crystal structure analysis, was obtained.
2 2 2
Complex [Cu (L2) (DMF) ] (5) was prepared by the reaction of copper(II) acetate hydrate
and 2 in an aqueous methanol solution in the presence of sodium hydroxide and recrystallization
from DMF. The X-ray crystal structure analysis is reported here (See Section 3.5).
Complex [Cu
and 3 in an aqueous methanol solution in the presence of sodium hydroxide.
Complexes [Ni (L1) (H O) ] (7), and [Co (L1) (H O)] (8) were prepared by the reaction
2 2 2 4
(L3) (H O) ] (6) was prepared by the reaction of copper(II) acetate hydrate
2
2
2
3
2
2
2
of metal(II) acetate hydrate and 1 in an aqueous methanol solution in the presence of sodium
hydroxide. However, the efforts to grow the single crystals were also failed.
2 2 2
Complex [Cu(HL1) (H O) ] (9-1) was prepared by the reaction of copper(II) acetate
hydrate and 1 in an aqueous methanol solution without the addition of base for any initial ratio
Cu(II) : 1. Recrystallization of complex 4-2 from DMSO or TMU have changed the structure and
1
0

complexes [Cu(HL1)
2
(DMSO)
(H
2 2
O)
2
] (9-2) and [Cu(HL1)
2
(TMU)
2
] (9-3) have been obtained
(
Scheme 4).
F3C
F3C
O
O
O
O
O
O
O
OH (CH ) S=O
Cu(AcO)2
3 2
2
OH
CF3
Cu
Cu
Cu
or
O
OH
O
O
O
O
(
(CH ) N) C=O
3 2 2
CF3
CF3
H L1
4
9
2
Scheme 4.
Thus, the complexes of both compositions ML
coordinating. Increasing the donor properties of amide leads to the structural transformation
into ML ). It can be demonstrated in next example. After the recrystallization of 9-1 from
2
2 2
and M L are capable of amides
(
M
2
L
2
2
methanol solution of urea, urea was not included in coordination sphere; the composition of
complex did not change. At the same time, the crystallization of 6 from methanol solution of 1,3-
dimethyl-2-imidazolidinimine (DMI), which is more strong amide, resulted to displacement of
ligand 3 from [Cu
copper [Cu(DMI) ]Cl
crystallography (See Section 3.5).
2
(HL3)
2 2
(DMF) ] (6) by DMI (Scheme 5). The complex of four coordinated
4
2
(10) was obtained, its molecular structure have been determined by X-ray
Scheme 5.
3.5. Crystal structures
The X-ray crystal structure of 1, grown by slow evaporation of a methanol solution at room
temperature is presented in Fig. 2. The heterocyclic ring in 1 has a half-boat conformation. The
O2 – C7 and O3 – C9 bond distances are 1.2253 (18) and 1.4203 (17) Å, respectively.
Intermolecular O–H…O hydrogen bonds link the molecules into linear supramolecular chains
1
1

along the a-axis. The observed bond distances and angles (Table 5) are in a good agreement with
the previously reported data [35].
2 2 2 2 2
Molecular structure of [Cu (L2) (DMF) ] 5 and [Cu(HL1) (TMU) ] 9-3 are depicted in
Fig. 3 and 4. The crystallographic data with selected bond lengths and bond angles are listed in
Table 4 and 5. All the compounds crystallized in triclinic lattice with space group P-1.
The crystal substructure of 5 comprises centrosymmetric molecules Cu
2
2
L and two DMF
solvate molecules. Cu(II) centers exhibit a distorted square pyramid geometry comprising of two
equivalent dianionic ligands coordinated in a meridional fashion, whilst solvent DMF ligands
occupy axial coordination positions on Cu(II), thereby completing a square-pyramidal geometry
at the two centers, very common with this metal [36]. The basal plane of the pyramid is defined
by phenol deprotonated hydroxyl oxygen atom O1, oxygen O3, and two O2 atoms of both ligand
molecules. The central of the three O atoms of the ligands, O2, has a fundamentally different
coordination, as it interacts with both Cu atoms, similar to diacetylacetonate ligands [37]. Thus,
O2 exhibits longer Cu – O distances [1.950(4) and 1.966(4) Å] than O1 and O3 [1.857(4) and
i
1
.915(4) Å, respectively, for Cu1 – O1 and Cu1 – O3]. Two oxygen atoms O2 and O2 play a
bidentate-bridging function forming bridges between the copper ions. There are also two co-
crystallized DMF molecules (O4 axial oxygen atoms) in the structure of 5. The axial Cu1 – O4
bond distance [2.314(4) Å] is longer than the basal Cu – O bonds, which are almost equal
i
[
1.857(4), 1.966(4), 1.950(4), 1.915(4) Å, respectively, for Cu1 – O1, Cu1 – O2, Cu1 – O2 , Cu1
–
O3]. The ligand 2 in the complex 5 is nominally dianion. One of the negative charges is
localized on the phenol deprotonated hydroxyl oxygen atom O1, when another is delocalized
between two oxygen atoms O2 and O3. The shorter the C – O bond, the more double-bond
character it has; hence, the longer C7 – O2 [1.308(6) Å] bond possesses more single-bond
character, i.e. is slightly more enolate-like than C9 – O3 [1.262(6) Å] bond. However, the C7 –
C8 bond is slightly longer [1.393(8) Å] than the C8 – C9 bond [1.377(7) Å]. These observations
are in accord with the data for bis(diacetylacetonato)bis[pyridinecopper(II)] [37]. The bond
distance Cu – Cu is 3.013 Å. These values are in good agreement with those reported for other
structures involving triketone-like ligands [36,37]. Weak C–H…O hydrogen bonds link the
components of the structure into two-dimensional networks parallel to (011) and (101). The
O1…H12A and O3…H14A intermolecular interactions along the a-axis and O4…H13C
intermolecular interactions along the b-axis generate the 2D sheets along the ab-plane.
2
The crystal substructure of 9-3 comprises centrosymmetric molecules CuL and two
tetramethylurea solvate molecules. Cu(II) centers exhibit a square bipyramid geometry (4+2)
comprising of two equivalent monoanionic ligands coordinated in a meridional fashion. The
ligand is coordinated in a bidentate chelating mode forming six-membered chelate rings. The
1
2

basal plane of the bipyramid is defined by two hydroxyl oxygen O2 of enol and two carbonyl O3
atoms of both ligand molecules. The axial oxygen atoms O1 belong to two co-crystallized TMU
molecules. The phenol hydroxyl does not participate in the coordination to copper. In the same
way as for 5 in the crystal 9-3 the axial Cu1 – O1 bonds [2.440(2) Å] are longer than the bonds
in basal plane which are almost equal [1.928(17), 1.935(16) Å, respectively, for Cu1 – O2, Cu1 –
O3. The O1 – Cu1 – O1(A) and O2 – Cu1 – O2(A) trans angles were found as 180.00(1)° and
O2 – Cu1 – O3 angle was found as 92.71(7)°. These observations suggested that the
coordination geometry around the copper ion had almost not undergone distortion from a perfect
square bipyramid. The C12 – O3 [1.270(3) Å] bond is slightly longer, than C14 – O2 [1.258(3)
Å] bond, and the C12 – C13 bond is longer [1.410(3) Å] than the C13 – C14 bond [1.348 (3) Å].
Weak C–H…O and C–H…F hydrogen bonds link the components of the structure into two-
dimensional networks parallel to (110) and (011). The F3…H2C intermolecular interactions
along the a-axis and O1…H9A intermolecular interactions along the b-axis generate the 2D
sheets along the ab-plane.
Complex 10 crystallizes in centrosymmetric monoclinic space group P2(1). The ORTEP
drawing is depicted in Fig. 5. The complex 10 exhibits a tetrahedral geometry in which the
Cu(II) center is coordinated to four imino nitrogen atoms from four DMI ligands. The Cu(II)
center has also two second-sphere chlorine atoms. The DMI functions as a monodentate ligand.
The presence of electronegative chlorine atoms leads to the occurrence of intermolecular
hydrogen bonds in the crystal structure. The neighboring molecules interact through C–H…Cl
hydrogen bonds. In the crystal, the molecules are linked into chains parallel to (011) and (110).
In one of the interactions, the H-donor atoms are from a methyl carbon (C14) and imidazolyl
carbon (C17), with the bridging chlorine atom (Cl2) acting as the H-atoms acceptor. A two-
dimensional network structure is generated, lying along the a-axis. The second one occurs
between the imine groups, the methyl groups of the imidazolyl fragment and the free chlorine
ions. These intermolecular interactions form a layered structure, lying along the c-axis. As a
result the molecules are connected into a three-dimensional architecture by intermolecular
interactions. These hydrogen-bonded networks help to stabilize the crystal structure.
3.6. FT-IR spectra of complexes
In order to study IR spectra of ‘open’ structure, the potassium salt of 1,1,1-trifluoro-4-(2-
hydroxyphenyl)butan-2,4-dione has been obtained by the reaction between chroman-4-one 1 and
potassium hydroxide in methanol solution followed by evaporation of solvent in vacuum. FT-IR
spectrum of KHL1 were registered (Table 6); the assignments relied on the data of
trifluorobenzoylacetone [38]. The band assigned to chromone carbonyl is absent in the spectrum.
1
3

-1
In place of this band the very strong band at 1621 cm assigned to asymmetric С=C–С=O
stretching of the enol moiety coupled strongly to the OH in-plane bending motion appeared. New
-
1
very strong band at 1526 cm is assigned to symmetric С=C–С=O stretching. The strong band at
-
1
-1
1
467 cm of asymmetric O–С=C–С stretching shifts to 1478 cm upon opening of the
chromone ring and ionization. Spectral changes due to ring–chain rearrangement (1–KHL1) can
be followed as well in a wide range of frequencies.
The analysis of FT-IR spectra of copper [Cu
Cu(HL1) (TMU) ] (9-3), nickel [Ni (L1) (H O)
complexes compared to potassium salts of 1,1,1-trifluoro-4-(2-hydroxyphenyl)butan-2,4-dione
Table 6) gives evidence of significant π-electronic distribution due to tautomeric
transformations and coordinate bonds formation (taking into consideration that difference
between (1,1,1-trifluoro-4-(2-hydroxyphenyl)butan-2,4-dione (H L1) and 1,1,1-trifluoro-4-(2-
hydroxyphenyl-5-methyl)butan-2,4-dione (H L2) is insignificant). In spectra the bands of ligand
arised from С=С stretching mode shift in complexes. It is more significant that a shift of the
2
(L1)
2
(H
2
O)
2
] (4-1), [Cu
2
(L2)
2
(DMF)
2
] (5),
[
2
2
2
2
2
3
] (7), and cobalt [Co
2
(L1)
2
(H O)] (8)
2
(
2
2
-1
asymmetric С=C–С=O stretching at 1621 cm towards lower frequencies after β-diketone
coordination to the metallic center occurs as a result of the participation of carbonyl oxygen in
the coordination of metal ions. The frequency shifts for 4-1, 5, 7, 8 and 9-3 are 13, 15, 20, 17 and
-1
1
7 cm , respectively. The C=O stretching vibrations of coordinated DMF (5) and TMU (9-3) in
-
1
-1
comparison with the corresponding values for free DMF (1676 cm ) and TMU (1650 cm ) are
-1
-1
shifted to lower frequencies (1620 cm and 1640 cm , respectively), attesting that the metal
bound to this group. In support of the conjecture of ring–chain rearrangement during
complexation it should be noted that the band assigned to chromone carbonyl is absent in all
spectra of complexes.
4. Conclusions
In conclusion, substituted chroman-4-ones which are capable to undergo ring–chain
tautomerism have been used for the first time as pre-ligand and single crystals of metal
complexes were obtained. Protolytic properties of chroman-4-ones in aqueous ethylene glycol
solutions have been studied using UV-Vis spectrophotometry. It has been demonstrated that in
the process of ionization and complexation with metal ions the compounds go through opening
the chromone ring and act as mono- and dibasic di- and tridentate ligand. The mechanism of
ionization of studied compounds were suggested and the first ionization constants were
determined. The second ionization constant could not be determined because of the easy
decomposability of the compounds in strongly alkaline media. The complex formation between
Co(II), Ni(II), and Cu(II) and H L1 in aqueous ethylene glycol solutions was investigated
2
1
4

through spectroscopic method. It was shown that the composition of complexes for all studied
metals is 2:2. The complexes of ‘open form’ of studied compounds (1,1,1-trifluoro-4-(2-
hydroxyphenyl)butan-2,4-diones) with Co(II), Ni(II) and Cu(II) were synthesized and studied by
FT-IR spectroscopy, elemental analysis. It was shown that the complexes are capable of amides
coordinating. The structures of binuclear and mononuclear chroman-4-one complexes
[
Cu
2
(L2)
2
(DMF)
2
] 5 and [Cu(HL1)
2
(TMU) ] 9-3 were confirmed by single crystal X-ray
2
crystallography. It was shown that the crystallization of copper complex in the presence of strong
amide leads to the displacement of the ligand by amide, that also was confirmed by X-ray
crystallography.
Appendix A. Supplementary data
CCDC 1064086, 1064087, 1064088, and 1404509 contain the supplementary
crystallographic data for ligand 1 and complexes 5, 9-3, and 10. These data can be obtained free
of charge via http://www.ccdc.cam.ac.uk/conts/retrieving.html, or from the Cambridge
Crystallographic Data Centre, 12 Union Road, Cambridge CB2 1EZ, UK; fax: (+44)1223-336-
033; or e-mail: deposit@ccdc.cam.ac.uk.
Acknowledgments
This research was supported by UrFU under the Framework Programme of development of
UrFU through the «Young scientists UrFU» competition and the grant of the President of the
Russian Federation MK-7702.2015.3.
References
[
[
1] M. Carboni, J.-M. Latour, Coord. Chem. Rev. 255 (2011) 186–202.
2] M. Esmelindro, E. Oestreicher, H. Marquezalvarez, C. Dariva, S. Egues, C. Fernandes,
A.J. Bortoluzzi, V. Drago, O.A.C. Antunes, J. Inorg. Biochem. 99 (2005) 2054–2061.
3] D. Desbouis, I.P. Troitsky, M.J. Belousoff, L. Spiccia, B. Graham, Coord. Chem. Rev. 256
[
[
[
(
2012) 897–937.
4] B. Geeta, K. Shravankumar, P.M. Reddy, E. Ravikrishna, M. Sarangapani, K.K. Reddy, V.
Ravinder, Spectrochim. Acta Part A Mol. Biomol. Spectrosc. 77 (2010) 911–915.
5] M. Shebl, S.M.E. Khalil, A. Taha, M.A.N. Mahdi, Spectrochim. Acta Part A Mol. Biomol.
Spectrosc. 113 (2013) 356–366.
1
5

[
[
[
6] O.A. El-Gammal, G.M. Abu El-Reash, M.M. El-Gamil, Spectrochim. Acta Part A Mol.
Biomol. Spectrosc. 96 (2012) 444–455.
7] A.P. Neves, K.C.B. Maia, M.D. Vargas, L.C. Visentin, A. Casellato, M.A. Novak, A.S.
Mangrich, Polyhedron. 29 (2010) 2884–2891.
8] Z. Mahendrasinh, S. Ankita, S.B. Kumar, A. Escuer, E. Suresh, Inorganica Chim. Acta.
375 (2011) 333–337.
[
[
9] A. Solanki, M. Monfort, S.B. Kumar, J. Mol. Struct. 1050 (2013) 197–203.
10] S. Nastase, C. Maxim, F. Tuna, C. Duhayon, J.-P. Sutter, M. Andruh, Polyhedron. 28
(
2009) 1688–1693.
[
[
11] J.P. Costes, F. Dahan, J.P. Laurent, Inorg. Chem. 24 (1985) 1018–1022.
12] E. Kwiatkowski, M. Kwiatkowski, A. Olechnowicz, J. Mroziński, D.M. Ho, E. Deutsch,
Inorganica Chim. Acta. 158 (1989) 37–42.
[
[
[
[
[
[
[
13] S. Bhattacharya, A. Jana, S. Mohanta, Polyhedron. 62 (2013) 234–242.
14] A.V. Pestov, P.A. Slepukhin, V.N. Charushin, Russ. Chem. Rev. 84 (2015) 310–333.
15] T. Glaser, I. Liratzis, A.M. Ako, A.K. Powell, Coord. Chem. Rev. 253 (2009) 2296–2305.
16] P.A. Vigato, V. Peruzzo, S. Tamburini, Coord. Chem. Rev. 253 (2009) 1099–1201.
17] P. Guerriero, S. Tarnburini, P.A. Vigato, Coord. Chem. Rev. 139 (1995) 17–243.
18] D.J. Bray, J.K. Clegg, L.F. Lindoy, D. Schilter, Adv. Inorg. Chem. 59 (2006) 1–37.
19] V.Y. Sosnovskikh, I.S. Ovsyannikov, Russ. J. Org. Chem. (Zhurnal Organicheskoi
Khimii). 29 (1993) 2690–2706.
[
[
20] V.Y. Sosnovskikh, Russ. Chem. Rev. 72 (2003) 489–516.
21] M. Grazul, R. Sigel, C. Maake, E. Besic-Gyenge, I.-P. Lorenz, P. Mayer, M. Czyz, E.
Budzisz, Polyhedron. 67 (2014) 136–144.
[
22] Y.A. Davila, M.I. Sancho, M.C. Almandoz, S.E. Blanco, Spectrochim. Acta Part A Mol.
Biomol. Spectrosc. 95 (2012) 1–7.
[
[
[
23] Q.K. Panhwar, S. Memon, M.I. Bhanger, J. Mol. Struct. 967 (2010) 47–53.
24] W.B. Whalley, J. Chem. Soc. (1951) 3235–3238.
25] K. Takeo, F. Masaki, T. Takanao, S. Yusuke, M. Hiroshi. US Patent 2003109574 (A1),
2003.
[
26] V.P. Vasil’ev, V.A. Borodin, E.V. Kozlovskii, Primenenie EVM v khimiko-analiticheskikh
raschetakh (Computer-Aided Calculations in Analytical Chemistry), Vysshaya Shkola,
Moscow, 1993.
[
[
[
27] G.M. Sheldrick, Acta Crystallogr. Sect. A Found. Crystallogr. 64 (2008) 112–122.
28] A. Dziewulska-Kułaczkowska, A. Bartyzel, J. Mol. Struct. 997 (2011) 87–93.
29] A. Dziewulska-Kułaczkowska, L. Mazur, J. Mol. Struct. 985 (2011) 233–242.
1
6

[
30] V.Y. Sosnovskikh, V.Y. Korotaev, A.Y. Barkov, A.A. Sokovnina, M.I. Kodess, J. Fluor.
Chem. 141 (2012) 58–63.
[
[
31] G.T. Castro, O.S. Giordano, S.E. Blanco, J. Mol. Struct. (Theochem). 626 (2003) 167–178.
32] D.A. Skoog, D.M. West, F.J. Holler, S.R. Crouch, Fundamentals of Analytical Chemistry,
Brooks/Cole–Thomson Learning, Belmont, CA, 2004.
[
[
33] W.C. Vosburgh, G.R. Cooper, J. Am. Chem. Soc. 63 (1941) 437–442.
34] Y.A. Barbanel’, Russ. J. Inorg. Chem. (Zhurnal Neorganicheskoi Khimii). 9 (1964) 437–
446.
[
[
[
[
35] A.M. Asiri, H.M. Faidallah, K.A. Alamry, S.W. Ng, E.R.T. Tiekink, Acta Crystallogr.
Sect. E Struct. Reports Online. 68 (2012) o2299–o2299.
36] L.A. Barrios, D. Aguilà, O. Roubeau, P. Gamez, J. Ribas-Ariño, S.J. Teat, G. Aromi,
Chem. - A Eur. J. 15 (2009) 11235–11243.
37] J. Overgaard, M.-A. Chevallier, B.B. Iversen, Acta Crystallogr. Sect. E Struct. Reports
Online. 61 (2005) m922–m924.
38] S.F. Tayyari, M. Vakili, A.-R. Nekoei, H. Rahemi, Y.A. Wang, Spectrochim. Acta. A.
Mol. Biomol. Spectrosc. 66 (2007) 626–636.
1
7

Table 1
UV-Vis measurements.
-4
-4
Solution Cmetal (10 M) Cchromanone (10 M) pH
λ (nm)
1
1.0
1.0
1.0
1.0
1.0
1.0
6.5-10.5 340
2
6.5-10.5 345
6.5-10.5 345
3
Co(II)/1 1.0
Ni(II)/2 1.0
Cu(II)/3 1.0
10.5
10.5
7.5
400
400
415
Table 2
Frequencies of the absorption bands for chroman-4-ones 1-3.
-1
Frequency (cm )
Assignment
1
2
2
1
1
1
1
1
1
1
1
2
3
928w
821vw
680vs
643m
615s
2931w
2856vw
1682vs
2938w
2844vw
1693vs
ν
as(C–H)
ν
s
(C–H)
ν(C=O) chromone carbonyl
ν(C=O)
1619s
1625s
ν(C=C)
583m
477m
467s
1586m
1590m
ν(C=C)
ν(C=C), ν(C–O)
1492s
1422m
1359w
1500s
ν
as(O–C=C–C)
ν(C–O), δ (C–H)
ν(C–C), δ(C–H)
411m
365m
1442m
1355sh
s
1335s
νas(C–F)
1
1
1
316s
293s
246m
1318w
1287s
1248m
1318m
1276vs
1247m
ν(C–C), δ(C–H), νas(C–F)
ν
ν
ν
δ
as(C–O–C), ν(C–C), δ(C–H), νas(C–F)
as(C–Ph), ν(C–C), ν (C–F)
(C–F)
s
1235s
s
1
1
218s
1217s
as(C–H)
196vs
1201vs
ν(C–H), δ(COC), δ(CF)
ν(C–H), δ(COC), δ(CF)
ν(C–H), δ(COC), δ(CF)
1183s
1187s
1
156s
1151m
1
8

1
1
1
1
9
8
8
8
7
7
6
5
4
132vs
117s
078m
054m
95s
1131vs
1126vs
ν(C–H), δ(COC)
δ(CH), ν(C–O), ν
s
(CF
(C–O–C), γ(CH)
(C–O–C), γ(CH)
3
)
1070m
1053m
990m
894w
953w
829m
790w
717w
671m
548w
500m
1083m
1050m
991s
ν
ν
s
s
ν(C–C)
75w
56w
39m
68s
882vw
851m
836m
783vw
723m
642w
541w
503m
δ(CCC), γ(CH)
δ(CCC), γ(CH)
δ(CCC), γ(CH)
γ(CH)
13w
52w
43w
93m
γ(CH), δ
γ(CH), δ
γ(COC)
γ(COC)
s
(CF
3
)
)
s
(CF
3
Table 3
Equilibrium constants in aqueous ethylene glycol solutions.
Ligand
рКa1
H
H
H
2
2
2
L1
L2
L3
8.21±0.09
8.12±0.06
7.20±0.07
Table 4
Crystallographic and refinement data for 1, [Cu
2
(L2)
2
(DMF)
2
] (5), [Cu(HL1)
2
(TMU)
2
] (9-3),
and [Cu(DMI)
Compound
Empirical formula
Formula weight
Temperature (K)
Crystal system
Space group
a (Å)
4 2
]Cl (10).
1
5
9-3
10
C
10
H
7
F
3
O
3
C
28
H
28Cu
2
F
6
N
2
O
8
C
30
H
36CuF
6
N
4
O
8
20 2
C H44Cl CuN12
232.16
295(2)
761.60
295(2)
triclinic
P-1
758.16
295(2)
587.11
120(2)
triclinic
triclinic
monoclinic
P2(1)
P-1
P-1
6.0111(7)
8.7212(9)
10.2100(9)
67.127(9)
5.927(2)
10.386(3)
12.390(3)
100.84(2)
9.6801(12)
8.0304(4)
15.7767(9)
11.4534(7)
90.00
b (Å)
10.3078(14)
10.5037(14)
62.089(13)
c (Å)
α (°)
1
9

β (°)
γ (°)
80.261(9)
78.227(9)
480.39(9)
2
97.28(2)
91.43(3)
742.1(4)
1
68.581(12)
77.700(11)
861.1(2)
1
106.535(5)
90.00
3
V (Å )
1391.06(14)
2
Z
-3
D
calc (g cm )
1.605
1.704
1.462
1.402
-1
µ (mm )
F(000)
0.155
1.524
0.719
1.011
236
386
391
622
Θ range (°)
2.69-30.51
-8 ≤ h ≤ 5
3.47-26.37
-7 ≤ h ≤ 7
-12 ≤ k ≤ 12
0 ≤ l ≤ 154
2906
2.70-26.37
-12 ≤ h ≤ 12
-12 ≤ k ≤ 12
-13 ≤ l ≤ 13
11413
2.65-26.37
-5 ≤ h ≤ 10
-19 ≤ k ≤ 11
-14 ≤ l ≤ 14
4748
Index ranges
-
12 ≤ k ≤ 10
-
14 ≤ l ≤ 14
5797
Measured reflections
Independent reflections
Observed reflections [I ≥
2638
2906
3457
3920
1421
1460
2053
2618
2
σ(I)]
Final R indices [I >
σ(I)]
R
R
1
1
= 0.0438, wR
= 0.1118
2
2
R
R
1
1
= 0.0569, wR
= 0.1211
2
2
R
R
1
1
= 0.0426, wR
= 0.0930
2
2
R
R
1
1
= 0.0358, wR
0.0580
2
2
=
=
2
R indices [all data]
= 0.0869, wR
= 0.1303, wR
= 0.1322
= 0.0837, wR
= 0.1004
= 0.0544, wR
0.0593
=
0.1245
1.000
Goodness-on-fit
1.000
1.005
0.999
Maximum, minimum
0.233, -0.152
1.096, –0.546
0.403, –0.277
0.584,–0.460
-3
electron density (e Å )
Table 5
Selected bond lengths (Å) and bond angles (°).
1
Bond lengths
C(7)–O(2)
C(1)–O(3)
C(9)–O(3)
C(9)–O(1)
C(7)–C(8)
C(6)–C(7)
C(9)–C(10)
Bond angles
1.226(2) O(2)–C(7)–C(8)
1.387(2) O(2)–C (7)–C(6)
1.420(2) O(3)–C(1)–O(2)
1.384(2) C(1)–O(3)–C(9)
1.505(2) O(1)–C(9)–O(3)
1.466(2) O(1)–C(9)–C(8)
1.535(2) O(1)–C(9)–C(10)
121.4(1)
122.7(1)
170.46(17)
115.2(1)
111.5(1)
108.6(1)
109.4(1)
2
0

C(8)–C(9)
1.511(2) C(7)–C(8)–C(9)
111.5(1)
[
Cu
2 2 2
(L2) (DMF) ] (5)
Bond lengths
Bond angles
Cu(1)–O(1) 1.857(4) O(3)–Cu(1)–O(1)
Cu(1)–O(2) 1.966(4) O(2)–Cu(1)–O(1)
94.36(16)
92.50(16)
170.46(17)
98.92(18)
85.19(17)
i
Cu(1)–O(2) 1.950(4) O(3)–Cu(1)–O(2)
Cu(1)–O(3) 1.915(4) O(1)–Cu(1)–O(4)
Cu(1)–O(4) 2.314(4) O(3)–Cu(1)–O(4)
C(1)–O(1)
O(2)–C(7)
O(3)–C(9)
C(8)–C(7)
C(9)–C(8)
1.307(6)
1.308(6)
1.262(6)
1.393(8)
1.377(7)
Symmetry code: (i) –x, –y, –z.
[
2 2
Cu(HL1) (TMU) ] (9-3)
Bond lengths
Bond angles
Cu(1)–O(1) 2.440(2) O(1)–Cu(1)–O(1A) 180.00(1)
Cu(1)–O(2) 1.928(2) O(2)–Cu(1)–O(2A) 180.00(1)
Cu(1)–O(3) 1.935(2) O(2)–Cu(1)–O(3)
O(3)–C(12) 1.270 (3)
92.71(7)
O(2)–C(14) 1.258 (3)
C(13)–C(12) 1.410 (3)
C(13)–C(14) 1.348 (3)
[
Cu(DMI)
4 2
]Cl (10)
Bond lengths
Bond angles
Cu(1)–N(1) 1.966(3) N(1)–Cu(1)–N(4)
Cu(1)–N(4) 1.953(3) N(1)–Cu(1)–N(7)
99.9(1)
93.7(1)
Cu(1)–N(7) 1.958(4) N(1)–Cu(1)–N(10) 138.3(1)
Cu(1)–N(10) 1.955(3) N(4)–Cu(1)–N(7) 139.2(1)
N(4)–Cu(1)–N(10) 94.6(1)
N(7)–Cu(1)–N(10) 100.3(1)
2
1

Table 6
Frequency (cm )
-
1
Assignment
KHL1
4-1
5
7
8
9-3
1640vs ν(C=O)
1
620s
1
1
621vs
582w
1608m
1583s
1606m 1601s
1587s
1604vs 1604m
1590s
ν
as(С=C–С=O)
ν(C=C)
1
567w γ(N–H)
1530vs 1536vs 1525m (С=C–С=O)
1499vs Amide II
1
1
1
526vs
478s
1529vs 1527s
ν
s
1
502m
1464vs
1469vs
νas(O–C=C–C)
1
456m 1456vs 1454s
1452m ν(C=C), δas(C–O)
434m
1427w
1400w
1429w ν(C–O), δ
1407w as(C–C=C–O)
1368vs ν(C–N)
ν(C–C), δ
1313w ν(C–C), δ(C–H), νas(C–F)
s
(C–H)
1
378w
ν
1
384m
1
1
1
349w
316m
292m
1345s
1319s
s
(C–H)
1315w 1325s
1297w
1324s
ν
ν
ν
ν
ν
ν
as(C–O–C), ν(C–C), δ(C–H),
as(C–F)
1
286s
1284m 1279s
as(C–O–C), ν(C–C), δ(C–H),
as(C–F)
1
255vs
1250vs
1263m
as(C–Ph), ν(C–C), ν
as(C–O–C), ν(C–C), ν
as(C–H)
s
(C–F)
1
240m 1243vs 1246vs 1236m
1224m
s
(C–F)
1
213m
δ
1
1
187s
169s
1192s
1195m 1188vs 1193vs 1197w ν(C–H), δ(COC), δ(CF)
1171s 1172s ν(C–H), δ(COC), δ(CF)
1175m
1
130vs 1130vs 1137sh 1136vs 1135vs ν(C–H), δ(COC)
1119vs 1127vs δ(CH), ν(C–O), ν
(C–O–C), γ(CH)
1
1
112s
s
(CF )
3
045vw 1053vw 1080m 1053sh
52vw
1061m
ν
s
9
960vw
940w
859w
γ(OH)
9
8
8
8
7
35w
943m
869w
940w
942m
862w
849w
806w
785w
914m
δ(CCC), δ(CH)
δ(CCC), γ(CH)
61vw
42w
844w
800m
848vw δ(CCC), γ(CH)
γ(CH)
02vw
75vw
810m
794m
815w
775m
783m
γ(CH)
2
2

7
50s
766m
761w
738w
γ(CH)
γ(CH)
7
7
55m
13m
752m
710w
754s
708s
691w
750w
708m
708vw γ(CH), δ
s
(CF
(CF
(CF
(CF
3
3
3
3
)
)
)
)
7
6
6
5
5
02m
67vw
45m
75m
27w
690w
671w
627vw
574m
528w
γ(CH), δ
s
693vw
650w
562w
517w
682vw γ(CH), δ
s
657m
566m
527w
651vw γ(CH), δ
s
575w
578w
554m
γ(COC), ν(M–O)
γ(COC), ν(M–O)
2
3

Figure captures
Fig. 1. The determination of stoichiometry of M(II)-H L1 complexes by Job’s method,
2
absorbance measured at 400 nm for Co and Ni (pH 10), at 415 nm for Cu (pH 7.5).
Fig. 2. ORTEP drawings of 1. Ellipsoids are plotted at 50% probability level, hydrogen atoms
are omitted.
Fig. 3. ORTEP drawings of 5. Ellipsoids are plotted at 50% probability level, hydrogen atoms
are omitted.
Fig. 4. ORTEP drawings of 9-3. Ellipsoids are plotted at 50% probability level, hydrogen atoms
are omitted.
Fig. 5. ORTEP drawings of 10. Ellipsoids are plotted at 50% probability level, hydrogen atoms
are omitted.
Figures in Supporting materials
Fig. 1S. FTIR spectra of chroman-4-ones.
Fig. 2S. Absorption spectra of water/EG 1 solutions (0.1 mM, I = 0.1 M) depending on the pH
(
a) 1.00-9.79 and (b) 9.79-12.01.
Fig. 3S. Absorption spectra of water/EG 2 solutions (0.1 mM, I = 0.1 M) depending on the pH
a) 1.08-10.64 and (b) 10.64-11.83.
Fig. 4S. Absorption spectra of water/EG 3 solutions (0.1 mM, I = 0.1 M) depending on the pH
a) 1.33-9.48 and (b) 9.16-11.75.
Fig. 5S. Absorption spectra of water/EG M(II)/H
depending on the pH: M = Co, pH 1.33-11.70 (a), M = Ni, pH 1.30-11.57 (b), M = Cu, pH 2.40-
1.48 (c).
Fig. 6S. The determination of stoichiometry of M(II)-H
absorbance measured at pH 10 for Co and Ni, at pH 7.5 for Cu.
(
(
2
L1 (1:1) solutions (0.1 mM, I = 0.1 M)
1
2
L1 complexes by molar ratio method,
2
4

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5