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10Азометиновые хелаты
Azomethine Chelates
Макрогэтэроцмклы
Статья
Paper
http://macroheterocycles.isuct.ru
DOI: 10.6060/mhc140271k
Novel Polydentate Macroacyclic Schiff Base Ligands Based on 2,6-Diformylphenol
Yulia S. Kudyakova,@ Yanina V. Burgart, and Victor I. Saloutin
Dedicated to Academician Oleg Chupakhin on the occasion of his 80th birthday
I.Ya. Postovsky Institute of Organic Synthesis, Ural Branch of the Russian Academy of Sciences, 620990 Ekaterinburg, Russian Federation
@Corresponding author E-mail: [email protected]
[1+2] Condensation of 2,6-diformylphenol (1) with ethyl-2-[(2-aminophenyl)aminomethylidene]-1,3-dicarbonyl compounds (2) resulted in new macroacyclic bisazomethines 3 having 2-hydroxyphenyl spacer. They are capable of regulated selective modes of mono- and binuclear complexes 4, 5 with 3d metal ions in proper conditions. Crystal structure of 4d was confirmed with X-Ray data. A moderate tuberculostatic activity of Schiff base ligands 3c,d is reported.
Keywords: Schiff bases, 2,6-diformylphenol, condensation, tuberculostatic activity, 3d metal complexes.
Новые полидентатные макроациклические основания Шиффа на основе 2,6-диформилфенола
Ю. С. Кудякова,@ Я. В. Бургарт, В. И. Салоутин
Посвящается академику РАН Олегу Николаевичу Чупахину по случаю его 80-летнего юбилея
Институт органического синтеза им. И.Я. Постовского УрО РАН, 620990 Екатеринбург, Российская Федерация @Е-тай: [email protected]
В результате [1+2] конденсации 2,6-диформилфенола 1 с этил-2-[(2-аминофенил)аминометилиден]-1,3-дикарбонильными соединениями 2 получены новые макроациклические бис-азометины 3 с 2-гидроксифениль-ным спейсером, способные к регулируемому селективному формированию на их основе моно- и биядерных металлокомплексов 4, 5 с катионами переходных металлов. Выявлено умеренное туберкулостатическое действие синтезированных лигандов на лабораторный штамм микобактерий туберкулеза И37Ду.
Ключевые слова: Основания Шиффа, 2,6-диформилфенол, конденсация, туберкулостатическая активность, комплексы 3d металлов.
Introduction
Directed synthesis of polydentate organic compounds with various donor centers followed by metal complexes formation, their structures' definition and evaluation of regio-selective coordination factors play an important role in design of artificial models of biologically important objects[1,2] and searching for compounds with required physicochemical and applied properties,[3-5] e.g. magnetic,[67] catalytic,[8"10] medicobiological,[11] etc.
Previously we have reported on macroacyclic polydentate ligands via diethyl-2-[(2-aminophenyl)-amino-methylidene]malonate or ethyl-2-[(2-aminophenyl)amino-methylidene]-3-oxo-3-(polyfluoro)alkylpropionates with thiophene-2,5-dicarboxaldehyde.[1213] It was shown the structure of their coordination centers depends on the symmetry of 1,3-dicarbonyl fragment. These compounds were expected to form complexes with 3d metal ions; however our attempts to isolate stable chelates were unsuccessful because of sulfur atom in thiophene cycle seems to have the low donor ability for the formation of strong donor-acceptor bond with metal ion.[14]
Unlike thiophene-2,5-dicarboxaldehyde 2,6-diformyl-phenol have a hydroxy group that can provide the covalent bonding with metal ions. It is worth noting that 2,6-diformyl-phenol and its derivatives are widely used in the design of polydentate ligands which can form polynuclear complex
systems having magnetic interaction between the metal centers. Due to the study of stereochemical, electronic, magnetic, catalytic, spectroscopic and biological properties one can suggest for them some important applications.[15-18]
In this paper we describe the synthesis, coordination properties and tuberculostatic activity of new macroacyclic Schiff base ligands based on 2,6-diformylphenol 1 and ethyl-2-[(2-aminophenyl)aminomethylidene] - 1,3-dicarbonyl compounds 2a-d.
Results and Discussion
It was found the reaction of dialdehyde 1 with amines 2a-d in ethanol at room temperature proceeds regioselectively and gives [1+2] condensation products -diazomethines 3a-d in good yields (Scheme 1). Structures of 3a-d were characterized by IR, 1H, 19F NMR spectroscopy and elemental analysis.
An important point is that compounds 3a-d have labile hydrogen atom and therefore they can be involved in keto-enol and amine-imine tautomerism. The imino-enone, imino-enol, and/or amino-enone tautomers are possible for their structure. Furthermore, amino-enone tautomers of 3-oxoesters derivatives 3c,d can exhibit Z,£-isomerism because of different position of non-equivalent substituents relative to C=C bond.
COR
COR
2,3: R = R' = OEt (a); R = R' = Me (b); R = OEt: R' = Me (c), CF3 (d).
4: R = R' = OEt: M = Ni (a), Cu (b); R = R' = Me: M = Ni (c); R = OEt, R' = Me: M = Ni (d), Cu (e);
R = OEt, R' = CF3: M = Ni (f), Cu (g). 5: R = R' = Me, M = Ni (a); R = OEt: R' = Me, M = Ni (b), Cu (c); R = OEt: R' = CF3, M = Ni (d).
B = Py, DBU; X = CI, OAc.
Scheme 1.
Table 1. Щ NMR spectral data (5, ppm) of compounds 3c,d in CDCl3.
Compound R R' Isomer Methylene (=CH-) Azomethine (-HC=N-) Amine (-NH) Content, %
EE 8.59 9.00 13.19 85
3c Me
ZZ 8.58 8.89 12.59 15
OEt
EE 8.71 12.77 80
3d CF3 9.02
3 ZZ 8.57 12.08 20
A comparative analysis of IR spectra of azomethines 3a,b with symmetrical 1,3-dicarbonyl fragments revealed no substantial differences between them. Thus, their IR spectra have two high-frequency absorption bands corresponding to vibrations of ester (-CO2Et for 3a) or keto-groups (-COMe for 3b) of two types: free carbonyl group (1709-1655 cm-1) and carbonyl group involved in the formation of intramolecular hydrogen bond (IMHB) (1690-1619 cm-1) with the NH-group. The absorption bands of NH-groups are observed at 3208-3069 cm-1. Based on this analyze one can conclude the existence of compounds 3a,b as £/'s(amino-enone) tau-tomer in solid state. 'H NMR spectra of 3a,b in CDCl3 have one set of signals corresponds to £/'s(amino-enone) tautomer that confirmed the molecule symmetry preservation under dissolution.
The IR spectra of compounds 3c,d, having 3-oxoester fragment, are characterized by absorption bands of free ethoxycarbonyl groups (1700-1697 cm-1) and (fluoro)acyl carbonyl groups (1689-1633 cm-1) participated in IMHB with NH-groups (3176-3154 cm-1). In this case absorption bands are either doublet or broadened. Based on the IR spectra analogy we suggested for compounds 3c,d E,E-isomeric structure in which 6/'s(amino-enone) fragments stabilized with IMHB are in /raws-position relative to aromatic spacer similarly to described earlier[13] thiophene derivatives.
According to the *H and 19F NMR spectral data azomethines 3c,d in CDCl3 solutions exist as mixtures of E,E-and Z,Z-isomers and E,E-isomer is prevalent (Table 1). The E,E- and Z,Z-isomeric forms in the *H and 19F NMR spectra were attributed in accordance with our previous work[19] in which CH- and NH-protons of EE-isomer are observed at lower field compared to that of Z,Z-isomer.
There are two (N2O2- and N2O-) coordination centers capable of complex formation in the structure of compounds 3a-d. Their treatment with nickel(II) and copper(II) salts in equimolar ratio was shown to give mononuclear complexes 4a-g (yields 89-93 %). We were also succeeded in template synthesis of 4a-g from dialdehyde 1 and amines 2a-d with 3d metal ions (yields 80-95 %). In both cases tetradentate N2O2-center participated in the complex formation.
Elemental analyses data of complexes 4a-g correspond to M[L-H] structure (M = metal, L = ligand). IR spectra of 4a-g contain both high-frequency absorption bands (17271690 cm-1) corresponding to the vibrations of free carbonyl groups (CO2Et and R(F)C=O) and absorption bands of carbonyl groups which participate in the coordination with metal ions. The latter are characterized with low-frequency shift (1665-1615 cm-1). Absorption intensity decreasing of NH- and OH-groups in the field of stretching vibrations is also observed (3206-3125 cm-1).
1H NMR spectra of nickel(II) complexes 4a,c were suitable for the structure determination in solution. The absence of OH-group low field singlet and the presence of only one NH-group doublet indicate their involvement in covalent bonding with metal. Probably owing to the nickel(II) ion coordination only on one N2O2-center protons of symmetrical 1,3-dicarbonyl groups (-OEt for 4a and -Me for 4c) as well as protons of two H-C=N- and two =CH- groups become not equal (Figure 1). Thereby in 1H NMR spectra of 4a,c there are three different sets of signals corresponding to protons of ethyl and methyl groups respectively. 1H NMR spectrum of complex 4a in CDCl3 solution contains signals of H-C=N- and =CH-groups of chelate moiety as singlets with different chemical shifts while =CH-group of free N2O-site appears as doublet due to the spin-spin coupling with proton of NH-group.
Figure 1. Non-equal protons in 4a,c.
1H NMR spectra of complexes 4d,f were uninformative because of strong signals broadening.
According to single-crystal X-Ray diffraction, nickel(II) atom in 4d has slightly distorted square-planar coordination with two (N(3) and N(4)) nitrogen atoms of phenylenediamine fragment and two (0(3) and 0(4)) oxygen atoms of acyl and hydroxy groups belong to 1,3-dicarbonyl fragment and dialdehyde respectively (Figure 2). The distortion is caused by the difference between the lengths of a square N(3)-N(4)-0(3)-0(4) sides (maximum difference between N(3)-O(4) and O(3)-O(4) sides is 0.233 A).
N2O-center not participating in complex formation contains an intramolecular hydrogen bond (IMHB) N(2)-H(2) O(7). This IMHB is characterized by the following parameters: intramolecular distance O(7)^H(2) is 1.89(5)
Figure 2. X-Ray structure of 4d (thermal ellipsoids at 50 % probability level, ORTEP drawing).
A, N(2)-H(2) is 0.92(3) A, N(2)-O(7) is 2.61(8) A, angles N(2)-H(2) 0(7) and C(10)-0(7) H(2) are 133.5(0)° and 105.0(7)° respectively.
The molecule of 4d has an approximately planar conformation; bonds of metal cycle are coplanar with adjacent aryl moieties. The deviation of atoms Ni-N(3)-N(4)-0(3)-0(4), which form chelate center of the molecule, from its mean plane is not more than 0.10(5) A.
Three conjugated metal cycles (two six- and one five-membered) are formed in the molecule as a result of tetradentate coordination. Electron density of six-membered metal cycles is strongly delocalized that leads to the equalization of Ni-X, C-X and C-C bond lengths (X = N, O) of the metal cycle.
Molecular packing of 4d is formed by translational molecules stacks with the interplanar distance 3.43(1) Â (Figure 3). The cavities between the stacks are occupied by pyridine molecules. Stacks are packed in parallel layers owing to n-n stacking of phenyl rings of adjacent molecules.[20]
Reaction of ligand 3d with two equivalents of nickel(II) chloride and pyridine resulted in binuclear nickel complex 5d. The main requirement providing complex formation on two N2O-centers was the use of pyridine as a base in equimolar quantity that facilitates the deprotonation of ^^-groups. One-pot synthesis of binuclear complexes 5a-c from dialde-hyde 1 and ethyl-2-[(2-aminophenyl)aminomethylidene]-1,3-dicarbonyl compounds 2b,c on the nickel(II)/copper(II) ions template was also successful and in this case DBU was used as a base. Advantage of one-pot method is absence of additional stages of ligand isolation and purification and as a result a higher yield of metal complex.
Spectral data of 5a-d demonstrated both coordination centers involved in complex formation. Elemental composition of 5a-d corresponds to M2[L-OH]Cl2 structure (M = metal, L = ligand). IR spectra have high-frequency absorption bands at 1727-1668 cm-1 corresponding to the vibrations of carbonyl groups in ester and (fluoro)acyl moieties. A comparison of 4a-f and 5a-d IR spectra reveal their differences: in complexes 5a-d spectra there are no high-frequency absorption bands at 3100-3300 cm-1 corresponds to the stretching vibrations of NH-groups that denotes the participation of both N2O-coordination centers in complexation.
The structure of binuclear nickel(II) metal complexes 5a,b,d in solution was defined by means of 'H, 19F NMR
Figure 3. Molecular packing of nickel(II) complex 4d (along the b axis). Макрогетероцикnbl /Macroheterocycles 2014 7(1) 40-46
spectroscopy. In consequence of nickel(II) coordination on two N20-centers protons of symmetrical 1,3-dicarbonyl groups as well as H-C=N- and=CH-groups become equal and this fact is confirmed by the presence of one set of signals in spectra. It should be noted the covalent bond with metal ions in binuclear complexes 5 is realized via two NH-groups of the ligand 3 and counterions of corresponding salts (Cl-). In this case oxygen atoms of (fluoro)acyl C=O groups participate in coordination bonding. 'H NMR spectra of nickel(II) complexes 5a,b,d have low-field singlets correspond to free
hydroxy-group of 2,6-diformylphenol 1 (50
10.3-10.5
ppm). Complexation occurs on ketoendiimine fragment to form a symmetrical structure. The symmetry of functional groups' signals in *H, 19F NMR spectra points out at the equivalence of coordination centers.
To our best knowledge one of the antituberculous aspects of isoniazid (isonicotinic acid hydrazide) action is the ability to form metal complexes which alters the normal microorganisms' activity and prevents mycobacteria multi-plication.[21] Within this context and taking into account the complexing properties of diazomethines 3 we were estimated tuberculostatic activity of 3c,d in vitro by their effect on the growth inhibition of Mycobacterium tuberculosis H37Rv. Isoniazid was used as a reference drug with minimum inhibition concentration (MIC) 0.15 ^g/ml. The MIC was defined as the lowest concentration of drug required for M. tuberculosis H37Rv growth inhibition. Both non-fluori-nated diazomethine 3c and fluorinated one 3d demonstrated a moderate effect against M. tuberculosis H37Rv with MIC 6.2 ^g/ml.
Experimental
Equipment
Melting points were measured in open capillaries with a Stuart SMP3 apparatus for melting temperature determination. The IR diffuse reflectance spectra were recorded on a Perkin Elmer Spectrum 0ne Fourier FT-IR instrument in the interval 400-4000 cm-1 in the solid state as powders on a stick using a diffuse reflectance attachment (DRA). The 1H (400 MHz) and 19F (376 MHz) NMR spectra were recorded on a Bruker DRX-400 spectrometer with (CH3)4Si and C6F6 as internal standarts, respectively. Elemental analyses were performed on a Perkin Elmer PE 2400 series II elemental analyzer.
Tuberculostatic Activity Determination Method
Determination of 3c,d tuberculostatic activity was carried out with the use of solid culture medium Novaya by vertical diffusion method. For inoculation the laboratory strain H37Rv was prepared. The culture of laboratory strain was weighed on a torsion balance and sample (10 mg) was placed into porcelain mortar and triturated thoroughly; then the culture suspension was prepared by bacterial turbidity standard (100 million microbial bodies/ml). The suspension obtained (2 ml) was inoculated into tubes containing culture medium and a test compound (5 ml) of appropriate dilution. Prepared by serial dilution the following concentrations were used: 100, 50, 12.5, 6.2, 3.5, 1.5, 0.7, 0.3, 0.15 ^g/ml. The tube was incubated in calorstat for 7-10 days at 37 °C. Study of test substances effect on the growth of Mycobacterium tuberculosis H37Rv was performed in three parallel tubes at each concentration.
Materials
Reactions were monitored by thin layer chromatography (TLC) with 0.20 mm Alugram Sil G/UV254 pre-coated silica gel plates (60 F254). The column chromatography was carried out on Merck silica gel 60 (0.063-0.200 mm). Unless otherwise mentioned, all commercially available compounds and solvents were used as received (2,6-diformylphenol 1 (>98.0 %) was purchased from Tokio Chemical Industry Co., Ltd., pyridine (ACS 99 %) from Alfa Aesar, 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) (98 %) from Acros Organics). Ethanol was purified and dried according to standard procedures.[22] Diethyl 2-[(2-aminophenyl)aminomethylidene]-malonate 2a,[12] 3-[(2-aminophenyl) aminomethylidene]pentane-2,4-dione 2b[23] and ethyl 2-[(2-aminophenyl)aminomethylidene]-3-oxo-3-(polyfluoro)alkylpropionates 2c,d[24,25] were synthesized according to previously reported procedures.
X-Ray Crystallography
Crystallographic data for 4d: C34H32N4Ni07-C5H5N, M = 746.45, triclinic, space group P-1, a = 11.63424(5), b = 11.7919(11) and c = 14.4670(14) A, a = 74.476(9)°, |3 = 68.460(8)°, y = 76.303(8)°, V = 1757.4(2) A3, Z = 2, dcalc = 1.411 g-cm-3, ^(MoKa) = 0.611 cm-1, F(000) = 780. A total number of 12747 reflections were measured on an Xcalibur 3 diffractometer at 295(2) K [(a/20-scanning technique, MoKa radiation (X = 0.71073 A), graphite monochromator, CCD detector], 7084 independent reflections (Rint = 0.0394), 3602 reflections with Fo>4o(Fo). The structure was solved by direct methods and refined by the least-squares method with the use of SHELXL-97[26] program package to R1 = 0.0440, wR2 = 0.0653 and GOOF = 1.005 [based on reflections with I > 2o(T)].
CCDC 961402 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.
Synthesis
Diazomethines3a-d(generalprocedure). To a solution of 2,6-diformylphenol 1 (0.75 g, 5 mmol) in anhydrous Et0H (40 ml) the corresponding ester 2 (10 mmol) was added. After stirring for 4 h the precipitate formed was separated by filtration, crystallized from MeCN and dried to give products 3a-d as bright yellow powders.
Tetraethyl 2,2'-[1,3-(2-hydroxybenzylidene)-bis(amino-methylidene-2-iminophenylene)] dimalonate (3a). Prepared from ester 2a (2.78 g). Yield 3.19 g (95 %), mp 152-153 °C. Found: C 64.34, H 5.67, N 8.40 %. C36H38N409 requires C 64.47, H 5.71, N, 8.35. IR v cm-1: 3208, 3195 (N-H, 0-H); 3065, 2978 (C-H); 1709, 1690 (C=O); 1647 (C=N); 1614, 1566 (C=C, N-H). 1H NMR (CDCl3) 5 ppm: 1.33, 1.36 (two t, J = 7.1 Hz, both 6H, 4 OCH2CH3), 4.26, 4.34 (two q, J = 7.1 Hz, both 4H, 4 OCH2CH3), 7.10-7.36 (m, 10H, Ar), 8.17 (m, 1H, Ar), 8.60 (d, J = 13.9 Hz, 2H, 2 =CH), 9.00 (s, 2H, 2 H-C=N), 11.67 (br d, J = 13.9 Hz, 2H, 2 NH)
3,3'-[1,3-(2-Hydroxybenzylidene)-bis(aminomethylidene-2-iminophenylene)]-bis(pentane-2,4-dione) (3b). Prepared from ester 2b (2.18 g). Yield 2.48 g (90 %), mp 260-261 °C. Found: C 69.70, H 5.20, N 10.03 %. C32H30N405 requires C 69.80, H 5.49, N 10.18. IR v cm-1: 3069 (N-H); 2923, 2852 (C-H); 1655, 1619 (C=0); 1597 (C=N); 1580, 1560 (C=C, N-H). 1H NMR (CDCl3) 5 ppm: 2.40, 2.58 (two s, both 6H, 4 Me), 6.82-6.89, 7.08-7.37, "7.88-7.90, 8.138.16 (all m, 10H, Ar), 8.25 (br s, 1H, Ar), 8.33 (d, J = 12.9 Hz, 2H, 2 =CH), 9.01 (s, 2H, 2 H-C=N), 12.88 (s, 1H, OH), 13.18 (br d, J = 12.9 Hz, 2H, 2 NH).
Diethyl 2,2'-[1,3-(2-hydroxybenzylidene)-bis(aminomethyl-idene-2-iminophenylene)]bis(3-oxobutanoate) (3c). Prepared from ester 2c (2.48 g). Yield 2.99 g (98 %), mp 204-205 °C. Found: C 66.80, H 5.61, N 9.18 %. C34H34N407 requires C 66.87, H 5.61, N
9.17. IR v cm-1: 3210, 3185 (N-H, O-H); 2983 (C-H); 1700, 1689 (C=O); 1619 (C=N); 1597, 1586, 1560 (C=C, N-H). 1H NMR (CDCl3) 5 ppm: 7.15-7.25, 7.30-7.41 (two m, 10H, Ar), 8.20 (br s, 1H, Ar); E,E (85 %): 1.35 (t, J = 7.1 Hz, 6H, 2 OCH2CH3), 2.57 (s, 6H, 2 Me), 4.29 (q, J = 7.1 Hz, 4H, 2 OCH2CH3), 8.59 (d, J = 13.4 Hz, 2H, 2 =CH), 9.00 (br s, 2H, 2 H-C=N), 13.19 (br d, J = 13.4 Hz, 2H, 2 NH); Z,Z (15 %): 1.30 (t, J = 7.1 Hz, 6H, 2 OCH2CH3), 2.51 (s, 6H, 2 Me), 4.41 (q, J = 7.1 Hz, 4H, 2 OCH2CH3), 8.58 (d, J = 13.4 Hz, 2H, 2 =CH), 8.89 (s, 2H, 2 H-C=N), 12.59 (br d, J = 13.4 Hz, 2H, 2 NH).
Diethyl 2,2'-[1,3-(2-hydroxybenzylidene)-bis(aminomethyl-idene-2-iminophenylene)]bis(3-oxo-4,4,4-trifluombutanoate) (3d). Prepared from ester 2d (3.02 g). Yield 2.44 g (68 %), mp 140-141 °C. Found: C 56.72, H 3.88, F 15.80, N 7.86 %. C34H8F6N4O7
' ' ' 34 28 6 4 /
requires C 56.83, H 3.93, F 15.86, N 7.80. IR v cm-1: 3200, 3176 (N-H, O-H); 3074, 2986 (C-H); 1697 br (C=O); 1633 (C=N); 1603, 1587, 1564 (C=C, N-H); 1276-1149 (C-F). 1H NMR (CDCl3) 5 ppm: 7.18-7.24, 7.30-7.41, 7.45-7.47 (all m, 10H, Ar), 8.22 (br s, 1H, Ar), 9.02 (m, 2H, 2 H-C=N); E,E (80 %): 1.34 (t, J = 7.1 Hz, 6H, 2 OCH2CH3), 4.30 (q, J = 7.1 Hz, 4H, 2 OCH2CH3), 8.71 (d, J = 14.3 Hz, 2H, 2 =CH), 12.75 (s, 1H, OH), 12.77 (br d, J = 14.3 Hz, 2H, 2 NH); Z,Z (20 %): 1.35 (t, J = 7.1 Hz, 6H, 2 OCH2CH3), 4.31 (q, J = 7.1 Hz, 4H, 2 OCH2CH3), 8.57 (d, J = 14.3 Hz, 2H, 2 =CH), 12.08 (br d, J = 14.3 Hz, 2H, 2 NH), 12.77 (s, 1H, OH). 19F NMR (CDCl3) 5f ppm: E,E (80 %): 89.12 (s, 6F, 2 CF3); Z,Z (20 %): 90.00 (s, 6F, 2 CF3).
Mononuclear complexes 4 (generalprocedure):
A. To a solution of ester 3 (4 mmol) in refluxing ethanol (30 ml) the appropriate metal salt (Ni(OAc)2-4H2O or CuCl2-2H2O, 2 mmol) was added and the reaction mixture was cooled to room temperature under stirring. The precipitate formed was separated by filtration and crystallized from EtOH.
B. To a solution of 2,6-diformylphenol 1 (0.30 g, 2 mmol) in EtOH (20 ml) the appropriate metal salt (Ni(OAc)2-4H2O or CuCl2-2H2O, 2 mmol) was added. Mixture was slightly heated under stirring until reactants dissolved followed by the dropwise addition of solution of ester 2 (4 mmol) in EtOH (15 ml). The reaction mixture was stirred for 2 h at room temperature and the precipitation formed was filtered and crystallized from EtOH.
Mononuclear nickel(II) complex 4a. Yield 1.32 g (91 %) (A), 1.24 g (85 %) (B), mp 234-235 °C (red powder). Found: C 59.34, H 4.60, N 7.30, Ni 8.10 %. C36H36N4NiO9 requires C 59.44, H 4.99, N 7.70, Ni, 8.07. IR v cm-1: 3183 (N-H); 3054, 2979 (C-H); 1711, 1676, 1665 (C=O); 1648 (C=N); 1599, 1581, 1532 (C=C, N-H). 1H NMR (CDCl3) 5 ppm: 1.33, 1.35, 1.40 (all t, J = 7.1 Hz, 12H, 4 OCH2CH3), 4.21, 4.27, 4.36 (all q, J = 7.1 Hz, 8H, 4 OCH2CH3), 6.68-6.76, 6.94-7.22, 7.28-7.38, 7.49-7.56 (all m, 9H, Ar), 7.85 (dd, J = 7.4, 1.4 Hz, 1H, Ar), 7.98 (s, 1H, H2-C=N), 8.29 (s, 1H, =CH4), 8.52 (dd, J = 7.4, 1.4 Hz, 1H, Ar), 8.59 (d, J = 14.2 Hz, 2H, =CH1), 9.05 (s, 1H, H3-C=N), 11.97 (br d, J = 14.2 Hz, 1H, NH).
Mononuclear copper(II) complex 4b. Yield 1.36 g (93 %) (A), 1.27 g (87 %) (B), mp 203-204 °C (dark brown powder). Found: C 57.51, H 4.60, N 7.15, Cu 8.76 %. C36H36CuN4O9H2O requires C 57.63, H 5.11, N 7.47, Cu 8.47. IR v cm"1: 3206 (N-H); 3064, 2977 (C-H); 1708, 1658 (C=O); 1605 (C=N); 1582, 1535 (C=C, N-H).
Mononuclear nickel(II) complex 4c. Yield 1.09 g (90 %) (A), 1.13 g (93 %) (B), mp 304-305 °C (red powder). Found: C 63.11, H 4.56, N 9.23, Ni 9.60 %. C32H28N4NiO5 requires C 63.29, H 4.65, N 9.23, Ni 9.66. IR v cm-1: 3159 (N-H); 3059, 2994 (C-H); 1640, 1615 (C=O); 1599 (C=N); 1580, 1561, 1532 (C=C, N-H). 1H NMR (Py-d5) 5 ppm: 2.55, 2.57, 1.69 (all s, 12H, 4 Me), 7.14, 7.17 (two br s, 4H, Ar), 7.36-7.39, 7.43, 7.51, 7.76-7.78, 7.85 (all m, 7H, Ar), 8.50-8.55 (m, 2H, 2 H-C=N), 8.62 (d, J = 13.2 Hz, 2H, 2 =CH), 13.50 (br d, J = 13.2 Hz, 1H, NH).
Mononuclear nickel(II) complex 4d. Yield 1.18 g (89 %) (A), 1.07 g (80 %) (B), mp 262-263 °C (red powder). Found: C 61.05, H 4.76, N 8.39, Ni 9.03 %. C34H32N4NiO7 requires C 61.19, H 4.83,
N 8.40, Ni 8.80. IR v cm-1: 3125 (N-H); 2981, 2928 (C-H); 1701 br (C=O); 1643 (C=N); 1606, 1535 (C=C, N-H).
Mononuclear copper(II) complex 4e. Yield 1.22 g (91 %) (A),
1.28 g (95 %) (B), mp 248-249 °C (dark brown powder). Found: C 60.30, H 4.58, N 8.20, Cu 9.51 %. C34H32CuN4O7 requires C 60.75, H 4.80, N 8.34, Cu 9.45. IR v cm-1: 3163 (N-H); 3062, 2978 (C-H); 1700, 1689 (C=O); 1632 (C=N); 1602, 1539 (C=C, N-H).
Mononuclear nickel(II) complex 4f. Yield 1.38 g (89 %) (A), 1.41 g (91 %) (B), mp 253-254 °C (red powder). Found: C 52.77, H 3.19, F 14.39, N 7.38 %. C34H26F6N4NiO7 requires C 52.67, H 3.38, F 14.70, N 7.23. IR v cm"1: 3175 (N-H); 2985 (C-H); 1727, 1704 (C=O); 1639 (C=N); 1617, 1605, 1588 (C=C, N-H); 12821156 (C-F).
Mononuclear copper(II) complex 4g. Yield 1.36 g (87 %) (A), 1.40 g (90 %) (B), mp 265-266 °C (dark brown powder). Found: C 52.66, H 3.45, F 14.51, N 7.54 %. C34H26CuF6N4O7 requires C 52.35, H 3.36, F 14.61, N 7.18. IR v cm-1: 3182 (N-H); 3076, 2982 (C-H); 1726, 1704 (C=O); 1640 (C=N); 1607, 1590,1538 (C=C, N-H).
Binuclear complexes 5a-c (general procedure). To a solution of 2,6-diformylphenol 1 (0.30 g, 2 mmol) in EtOH (20 ml) the appropriate metal salt (NiCl2 or CuCl2-2H2O, 5 mmol) was added. Mixture was slightly heated under stirring until salt completely dissolved followed by the dropwise addition of DBU (0.61 g, 4 mmol) and solution of corresponding ethyl 2-[(2-aminophenyl) aminomethylidene]-1,3-dicarbonyl compound 2 (4 mmol) in EtOH (10 ml). The reaction mixture was stirred for 5 h at room temperature and the precipitation formed was filtered. Products were purified by column chromatography (eluent CHCl3:EtOH (5:1)).
Binuclear nickel(II) complex 5a. Prepared from ester 2b (0.87 g) and NiCl2 (0.65 g). Yield 1.03 g (70 %), mp 320-321 °C (orange powder). Found: C 52.36, H 3.90, N 7.55, Ni 16.00 %. C32H28Cl2N4Ni2O5 requires C 52.16, H 3.83, N 7.60, Ni 15.93. IR v cm-1: 299)4, 2924, 2855 (C-H); 1668 br (C=O); 1642 (C=N); 1601, 1562 (C=C). 1H NMR (CDCl3) 5 ppm: 2.46, 2.60 (two m, both 6H, 4 Me), 6.79 (br t, J = 7.6 Hz, 1H, Ar), 7.13-7.15 (m, 1H, Ar), 7.20,
7.29 (two br t, J = 7.6 Hz, 3H, Ar), 7.52-7.54 (m, 2H, Ar), 7.57 (br d, J = 8.3 Hz, 1H, Ar), 7.64 (dd., J = 7.6, 1.7 Hz, 1H, Ar), 7.71 (br d, J = 7.9 Hz, 1H, Ar), 7.96 (dd, J = 7.4, 1.7 Hz, 1H, Ar), 8.27, 8.28 (two s, both 1H, 2 =CH), 8.29 (s, 2H, 2 H-C=N), 10.59 (s, 1H, OH).
Binuclear nickel(II) complex 5b. Prepared from ester 2c (0.99 g) and NiCl2 (0.65 g). Yield 1.19 g (78 %), mp 212-213 °C (orange powder). Found: C 51.36, H 4.12, N 6.95, Ni 14.80 %. C34H32Cl2N4Ni2O7 requires C 51.24, H 4.05, N 7.03, Ni 14.73. IR v cm-1: 29823, 2862 (C-H); 1672 br (C=O); 1607 (C=N); 1575 (C=C). 1H NMR (CDCl3) 5 ppm: 1.37 (t, J = 7.1 Hz, 6H, 2 OCH2CH3), 2.55 (s, 6H, 2 Me), 43.27 (q, J = 7.1 Hz, 4H, 2 OCH2CH3), 6.75, 7.14, 7.24 (all br t, J = 7.5 Hz, 5H, Ar), 7.54, 7.60, 7.66, 7.91 (all dd, J = 7.9, 1.7 Hz, 6H, Ar), 8.25 (s, 2H, 2 =CH), 8.38 (s, 2H, 2 H-C=N), 10.53 (s, 1H, OH).
Binuclear copper(II) complex5c. Prepared from ester 2c (0.99 g) and CuCl2-2H2O (0.85 g). Yield 1.34 g (87 %), mp 275-276 °C (dark brown powder). Found: C 50.51, H 4.08, Cu 15.80, N 6.97 %. C34H32Cl2Cu2N4O7 requires C 50.63, H 4.00, Cu 15.76, N 6.95. IR v cm-1: 2979 (C-H); 1697 br (C=O); 1607 (C=N); 1582, 1540 (C=C).
Binuclear nickel(II) complex 5d. NiCl2 (0.52 g, 4 mmol) was dissolved in EtOH and added dropwise to a solution of ester 3d (1.44 g, 2 mmol) and pyridine (0.32 g, 4 mmol) in CHCl3 (30 ml). The reaction mixture was stirred for 3 h at room temperature; the precipitation formed was filtered, crystallized from EtOH and dried to give complex 5d as crystal red powder. Yield 1.60 g (92 %), mp 265-266 °C. Found: C 45.29, H 2.89, F 12.67, N 6.30 %. C34H26Cl2F6N4Ni2O7 requires C 45.13, H 2.90, F 12.60, N 6.19. IR v cm-1: 2953, 2923 (C-H); 1727, 1703 (C=O); 1637 (C=N); 1603, 1585 (C=C); 1281-1156 (C-F). 1H NMR (CDCl3) 5 ppm: 1.37 (t, J = 7.1 Hz, 6H, 2 OCH2CH3), 4.32 (q, J = 7.1 Hz, 4H, 2 OCH2CH3), 6.77 (t, J = 7.9 Hz, 2H, Ar), 7.23-7.30 (m, 3H, Ar), 7.56, 7.60, 7.69,
7.92 (all dd, J = 7.9, 1.7 Hz, 6H, Ar), 8.21 (s, 2H, 2 =CH), 8.33 (s, 2H, 2 H-C=N), 10.33 (s, 1H, OH). 19F NMR (CDCl3) SF ppm: 93.87 (s, 6F, 2 CF3).
Conclusions
Perspective approach to the polydentate acyclic ligands 3 based on [1+2]condensation of 2,6-diformylphenol 1 with ethyl-2-[(2-aminophenyl)aminomethylidene]-1,3-di-carbonyl compounds 2a-d was reported. Compounds 3a-d can form both mono- and binuclear complexes with 3d metal ions due to the presence of two coordination centers (N2O2-and N2O-) in structure. Directed one-pot method of metal complexes synthesis is more efficient. Unequal structure of coordination units accounts for different conditions of complexes formation: mononuclear complexes 4 were shown to be formed as a result of N2O2-center coordination with the participation of 2,6-diformylphenol OH-group in covalent bonding with the metal ion. In the case of binuclear complexes 5 two metal ions bind two N2O-centers and counterions are participated in covalent bonding leaving free OH-group. Diazomethines 3c,d exhibited the moderate inhibitor activity against growth of M. tuberculosis H37Rv (MIC 6.2 |ig/ml). Further work will be directed at the synthesis of supramolecular systems containing ions of different metals besides 3d metals, e.g. Pd(II) or Zn(II), and their applied properties study (catalytic, photoluminescent, etc.).
Acknowledgements. This work was financially supported by the Presidium of Ural Branch of the Russian Academy of Sciences (Programs no. 12-T-3-1025, 12-n-3-1020).
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Received 14.02.2014 Accepted 25.03.2014
