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Synthesis, structural and biological properties of some transition metal complexes with 4,6-bis(4-chlorophenyl)-2-amino-1,2-dihydropyridine-3- carbinitrile

S.A. Sadeeka,*; M.S. El-Attara,b, M.S. Ibrahimc

aDepartment of Chemistry, Faculty of Science, Zagazig University, Zagazig, Egypt

bDepartment of Medical Chemistry, Preparatory Year Deanship,

Jazan University, Saudi Arabia,

cAlfa Miser For Industrial Investment

Abstract

In the study presented three new metal complexes of 4,6-bis(4-
chlorophenyl)-2-amino-1,2-dihydropyridine-3-carbinitrile with Cr(III), Mn(II) and Fe(III) were synthesized and their structure was elucidated through elemental analysis, melting point, molar conductivity, magnetic prosperities, spectroscopic techniques (IR, 1H NMR, UV-vis., mass spectra) as well as thermogravimetric analysis. These investigations suggest that L interacts with the metal ions as a bidentate ligand bound to the metal through amino N and carbinitrile N atoms having [M(L)2 (H2 O)2]n+ formula where M=metal ions. The central metal in each complex is six-coordinate and distorted octahedral geometry is proposed. The lowest energy model structures of the metal ions complexes have been determined using density functional theory (DFT). Also, the antibacterial and antifungal activities of the ligand, metal salts and complexes were tested on six microorganisms (four bacteria and two fungi). The complexes showed increased antibacterial profile in comparison to the free ligand.

Keywords: Pyridine derivative, metal complexes, IR, 1H NMR

∗ Corresponding author. Tel.: +20 01220057510

; fax: +20 0553208213. E-mail addresses: s_sadeek@zu.edu.eg

1. Introduction

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An exciting development in the synthesis of nitrogen heterocycles compounds has commenced in last few years due to their importance in pharmaceutical and agrochemical applications [1-5]. Heterocyclic compounds have been receiving increasing attention in recent years for their diverse therapeutic properties and exhibited antibacterial, anticancer, antiulcer, antifungal and antiviral properties [6]. Metal chelates continue to be quite active research field because of their biological activity which increased after complexation with transition metal ion [7].
A detailed litreture research has shown that no work is reported on the
4,6-bis(4-chlorophenyl)-2-amino-1,2-dihydropyridine-3-carbinitrile (L). Thus, in the present work, the complexes of L with certain transition ions Cr(III), Mn(II) and Fe(III) were isolated. For characterization of the compounds, following spectroscopic and analytical techniques were employed: IR, UV-Vis., 1H NMR, mass spectra, thermal stabilities, elemental analysis, magnetic properties and molar conductivity as well as some results of bioactivity tests are also included. Octahedral geometry for metal chelates is proposed.
Density functional theory (DFT) was used to compute the cation type influence on theoretical parameters of the Cr(III), Mn(II) and Fe(III) complexes of L and detect the exact structure of these complexes with different coordination numbers. Profiles of the optimal set and geometry of these complexes were simulated by applying the GAUSSIAN 98W package of programs [8] at B3LYP/CEP-31G [9] level of theory.

2. Materials and methods

2.1. Chemicals

All chemicals and solvents used for the preparation of the ligand and their metal complexes were of analytical reagent grade, commercially available from different sources and used without further purification.4-
chloroacetophenone, 4-benzaldehyde, ethyl cyanoacetate, ammonium acetate,

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glacial acetic acid, ethanol, acetone and all solvents were purchased from Fluka Chemical Co. Cr(CH3COO)3, MnSO4.6H2O, Fe(NO3 )3 .9H2O from Aldrich Chemical Co.

2.2. Preparation of L (CR18RHR11RNR3RClR2R )

A mixture of 5,7-bis(4-chlorophenyl)-tetrazolopyridine-8-carbonitrile (0.01mol), zinc dust (0.01mol) and glacial acetic acid (10 ml) was stirred at room temperature for 2 h and then heated on water bath at 80 οC for 8 h. The reaction mixture was poured into water, extracted with chloroform and the extract was evaporated under reduced pressure. The formed solid compound was recrystallized using ethanol as a solvent. The proposed formula of the ligand (CR18R HR11RNR3RClR2R, M.Wt.=340) is in good agreement with mass spectrum

(M.+) at m/z=339.0 (25%) and confirmed by IR spectral data.

2.3. Preparation of the metal complexes

The grey solid complex [Cr(L)R2R(HR2RO)R2R](CHR3RCOO)R3 Rwas prepared by adding 0.5 mmol (0.164 g) of chromium acetate Cr(CHR3RCOO)R3R in 20 ml ethanol drop-wisely to a stirred suspended solution 1mmol (0.340 g) of L in

50 ml ethanol. The reaction mixture was stirred for 15 h at 35 οC in water bath. The grey precipitate was filtered off and dried under vacuum over anhydrous CaClR2R. Yellow and orange, of [Mn(L)R2R(HR2RO)R2R ]SOR4R.3HR2RO and [Fe(L)R2R(HR2RO)R2R ](NOR3R )R3R.4HR2RO were prepared in similar manner described above by using acetone as a solvent and using MnSOR4R.6HR2R O and Fe(NOR3R )R3R , respectively, in 1:2 molar ratio.

Elemental C, H and N analysis was carried out on a Perkin Elmer CHN
2400. The percentage of the metal ions were determined gravimetrically by transforming the solid products into metal oxide or metal sulphate, and also determined by using atomic absorption method. Spectrometer model PYE- UNICAM SP 1900 fitted with the corresponding lamp was used for this
purposed. IR spectra were recorded on FTIR 460 PLUS (KBr discs) in the

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range from 4000-400 cm-1, 1H NMR spectra were recorded on Varian Mercury VX-300 NMR Spectrometer using DMSO-d6 as solvent. TGA-DTG measurements were carried out under N2 atmosphere with rate flow 30.0 ml/min within the temperature range from room temperature to 800 οC using TGA-50H Shimadzu, the mass of sample was accurately weighted out in an aluminum crucible. Electronic spectra were obtained using UV-3101PC Shimadzu. The solid reflection spectra were recorded with KBr pellets. Mass spectra were recorded on GCMS-QP-1000EX Shimadzu (ESI-70ev) in the range from 0-1090. Magnetic measurements were carried out on a Sherwood scientific magnetic balance using Gouy method using Hg[Co(SCN)] as calibrant. Molar conductivities of the solution of the ligand and metal complexes in DMF at 1×10-3 M were measured on CONSORT K410. All measurements were carried out at ambient temperature with freshly prepared solution.

2.4. Antimicrobial Investigation

Antibacterial activity of the ligand and its metal complexes was investigated by a previously reported modified method of Beecher and Wong [10] against different bacterial species, such as Staphylococcus aureus (S. aureus), Bacillus subtilis (B. subtilis), Escherichia coli (E. coli) and Pseudomonas aeruginosa (P. aeruginosa) and antifungal screening was studied against two species, Candida albicans and Aspergillus fumigatus. The tested microorganisms isolates were isolated from Egyptian soil and identified according to the standard mycological and bacteriological keys for identification of fungi and bacteria as stock cultures in the microbiology laboratory, Faculty of Science, Zagazig University. The nutrient agar medium for antibacterial was (0.5% Peptone, 0.1% Beef extract, 0.2% Yeast extract,
0.5% NaCl and 1.5% Agar-Agar) and czapeksDox medium for antifungal
(3% Sucrose, 0.3% NaNO3, 0.1% K2 HPO4 , 0.05% KCl, 0.001% FeSO4 , 2% Agar-Agar) was prepared [11] and then cooled to 47 οCand seeded with

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tested microorganisms. Sterile water agar layer was poured, solidified then pour, the prepared growth medium for fungi and bacteria (plate of 12 cm diameter, 15 ml medium plate). After solidification 5 mm diameter holes were punched by a sterile cork-borer. The investigated compounds, i.e., ligand and their complexes, were introduced in Petri-dishes (only 0.1 ml) after dissolving in DMF at 1.0×10-3 M. These culture plates were then incubated at 37 οC for 20 hr for bacteria and for seven days at 30 οCfor fungi. The activity was determined by measuring the diameter of the inhibition zone (in mm). Bacterial growth inhibition was calculated with reference to the positive control, i.e., Ampicilin, Amoxycillin and Cefaloxin.

3. Results and discussion

A new complexes [Cr(L)2 (H2O)2](CH3 COO)3, [Mn(L)2 (H2O)2 ]SO4.3H2O and [Fe(L)2 (H2O)2 ](NO3 )3.4H2O, with a color characteristic of the metal ion formed in the reaction of L with Cr(III), Mn(II) and Fe(III) in ethanol and acetone as a solvents at room temperature. The complexes are characterized through their elemental analysis, IR, UV–Vis.,

1H NMR, melting point, molar conductivity, magnetic properties as well as

thermogravimetric analyses. The results enable us to characterize the complexes and make an assessment of the bonding and structures inherent in them. All the prepared complexes contain water molecules and the number of bound water molecules in these complexes being different. The IR spectroscopic and thermogravimetric data confirm water in the composition of the complexes. Qualitative reactions revealed the presence of acetate, sulphate and nitrate ions as counter ions i.e., outside the coordination sphere of the metal ions [12]. Also the molar conductance value of free L ligand is
10.5 S cm2 mol−1 at room temperature and the corresponding values of the
complexes at the same temperature and solvent were found to be in the range from 197 to 235.8 S cm2 mol−1, this indicate the presence of anions outside the complex sphere. Conductance data show that the metal complexes are

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electrolyte compared with free ligand alone (Table 1). The magnetic moments (as B.M.) of the complexes were measmed at room temperature and the Cr(III), Mn(II) and Fe(III) complexes found as paramagnetism with measmed magnetic moment values at 3.82, 5.93 and 5.72B.M.

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Table 1

Elemental analysis and physico-analytical data for L and its metal complexes

Compounds

M.Wt. (M.F.)

Yield%

Mp/ οC

Color

Found (Calcd.) (%)

μReff R(B.M.)

Λ

(S cm2 mol-1)

C

H

N

M

Cl

L

340 (CR18RHR11RNR3RClR2R)

85.70

325-327

Dark yellow

(62.98)

62.72

(3.22)

3.20

(12.30)

12.25

-

(20.79)

20.78

Diamagnetic

10.5

[Cr(L)R2R(HR 2RO)R2R](CHR3RCOO)R 3

944.99 (CR42R HR 35RNR 6ROR8RClR4RCr)

78.55

>360

Grey

(53.30)

53.28

(3.68)

3.63

(8.85)

8.81

(5.40)

5.38

(15.00)

15.02

3.82

197

[Mn(L)R2R(HR2RO)R2R]SOR 4R.3HR 2RO

920.93 (CR36R HR 32RNR 6ROR9RClR4RMn)

79.12

>360

Yellow

(46.88)

46.83

(3.42)

3.40

(9.11)

9.09

(5.86)

5.90

(15.38)

15.32

5.93

190

[Fe(L)R 2 R (HR 2RO)R 2R](NOR 3R )R 3R.4HR 2RO

1029.80 (CR36RHR34RNR 9ROR15RClR 4RFe)

70.23

330-332

Orange

(41.96)

41.94

(3.27)

3.24

(12.21)

12.20

(5.38)

5.32

(13.75)

13.73

5.72

235.8

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3.1. IR absorption spectra

The mid infrared spectra of LR Rand their metal complexes were recorded from KBr discs. These spectra are shown in figure 1. The spectral bands are resolved and assigned to their vibrational modes and compiled in table 2. As expected, the absorparion bands characteristic of L acting as bidentate unit in the complexes are observed with small changes in band intensities and wavenumber. Before discussing the assignments of the infrared spectra, the proposed structures of the complexes must be considered. Here, metal ions react with the bidentate ligand forming complexes of monomeric structure where the metal ions is six coordinated (Scheme 1) [13-16] where the equatorial positions are occupied by the four nitrogen atoms of the two carbinitrile and two amino groups of the ligand and the axial positions are occupied by the oxygen atoms of the two coordinated water molecules. The structures of these complexes possess two planes of symmetry and two fold

axis and hence may belong to CRR symmetry [17-19].

n+



Cl Cl

CN

N H2N

OH2


M

OH2

NC

NH2 N

Cl Cl

M= Cr(III), Mn(II) and Fe(III)
n=3 for Cr(III), Fe(III) and 2 for Mn(II) Scheme 1: The coordination mode of M with L.

n+

The CRR complexes, [M(L)R2R(HR2RO)R2R ]

(M= Cr(III), Mn(II), Fe(III)) are
expected to display 219 vibrational fundamentals, respectively, which are all

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monodegenerate. These are distributed between A 1, A2 , B 1 and B2 motions; all are IR and Raman active, except for the A2 modes which are only Raman active.

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Fig. 1: Infrared spectra for (A) L, (B) [Cr(L)R2R(HR2RO)R2R](CHR3RCOO)R3R, (C) [Mn(L)R2R(HR2RO)R2R]SOR4R.3HR2RO and (D) [Fe(L)R2R(HR2RO)R2R](NOR3R)R3R.4HR2RO.

Table 2

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A

B

C

D

Assignment

3488mbr

3420mbr

3455mbr

νH2 O

3392ms

3389vw

3148s

3378vw

ν (N-H)

3100vw

3040vw

3178mbr

3044m

3144mbr

3022vw

ν (C-H)

2205s

2206m

2066sh

2230w

ν (C N)

1606vs

1582vs

1544s

1492ms

1452w

1432w

1364m

1606vw

1589vw

1551vw

1456sh

1404vs

1344sh

1605ms

1567sh

1544vw

1408vs

1323vw

1644vw

1589ms

1544vw

1533sh

1393vs

ν (C=N);

ν (C=C) and phenyl

breathing modes and

ν (N-O); NO -

RasR R3R

1257m

1174w

1265m

1133vw

1256vw

1144vw

ν (C-C);

ν (C-N)

1093m

1012ms

821vs

773w

1103m

1049m

818s

772w

1084vs

984vw

822w

783w

1092m

1041w

1011w

876w

826ms

789sh

-CH; bending phenyl

ν(SO -2) and

R4R

νRsR(N-O); NOR3

724w

669w

631w

504w

444w

722sh

683m

617m

532m

455vw

710w

621m

548sh

511vw

710m

633vw

600w

470w

436w

ν (M-N);

ring deformation

and δ (SO -2)

RbR R4R

Keys: s=strong, w=weak, v=very, m=medium, br=broad, sh=shoulder, ν=stretching,

δRbR=bending

3.2. UV–Visible solid reflection spectra

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The formation of the metal complexes was also confirmed by UV– visible spectra. Figure 2 shows the electronic solid reflection spectra of L, and their metal complexes in the wavelength interval from 200 to 800 nm. It can be seen that free ligand reflected at 210 and 298 nm (Table 3). The first band at 210 nm may be attributed to π-π*transition and the second band observed at 298 nm is assigned to n-π*transitions, these transitions occur in case of unsaturated hydrocarbons which contain amine or carbinitrile groups.
The absent of the band at 210 nm and the shift of the reflection band at
298 nm to higher values (bathochromic shift) in case of Mn(II), Fe(III) and lower in case of Cr(III) complexes and the presence of new bands in the reflection spectra of complexes indicated that the formation of their metal complexes. Also, the complexes have new bands in the range from 499 to
688 nm which may be assigned to the ligand to metal charge-transfer and d-d transition [20-23].

Fig. 2: Electronic reflection spectra for (A) L, (B) [Cr(L)R2R(HR2RO)R2R](CHR3R COO)R3R, (C) [Mn(L)R2R(HR2RO)R2R]SOR4R.3HR2RO and (D) [Fe(L)R2R(HR2RO)R2R](NOR3R)R3R.4HR2RO.

Table 3

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UV-Vis. spectra of L and its metal complexes

Assignments (nm)

L

L complex with

Cr(III)

Mn(II)

Fe(III)

π-π* transitions

210

-

-

-

n-π* transitions

298

277

325

327, 336

Ligand-metal charge transfer

-

499, 522

520

492, 519

d-d transition

-

568, 608,

617, 688

570, 619

569, 620,

672

3.3. The 1H NMR spectra

The formation of the metal complexes was also confirmed by 1H NMR spectra. Figure 3 represents the 1H NMR spectra of L and thier metal complexes. On comparing main peaks of L with its complexes, it is observed that all the peaks of the free ligand are present in the spectra of the complexes with chemical shift upon binding of ligand to the metal ion (Table 4) [24]. The 1H NMR spectrum of L showed peak at δ: 6.89 ppm corresponding to

1

ـــNHR2R of amin group and at 7.08-8.14 ppm for ــCH aromatic. The

H NMR
spectra for complexes exhibit new peak in the range 3.32-3.55 ppm, due to the presence of water molecules in the complexes and peaks in the range
7.20-7.25 ppm to aromatic.

ـــNHR2R of amine and at the range 7.24-8.42 ppm for ــCH

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Fig. 3: 1H NMR spectra for (A) L, (B) [Cr(L)

(H O)

](CH

COO) ,

R2R

(C) [Mn(L)R2R(HR2RO)R2R]SOR4R.3HR2RO and (D) [Fe(L)R2R(HR2RO)R2R](NOR3R)R3R.4HR2RO.

Table 4

R2R

R2R

R3R

R3R

1H NMR values (ppm) and tentative assignments for (A) L , (B) [Cr(L)R2R(HR2RO)R2R](CHR3R COO), (C) [Mn(L)R2R(HR2RO)R2R]SOR4R3HR2RO and

(D) [Fe(L)R2R(HR2RO)R2R](NOR3R)R3R.4HR2RO

A

-

6.89

7.08-8.14

B

3.32

7.24

7.26-8.16

C

3.55

7.20

7.24-8.10

D

3.32

7.25

7.33-8.42

Assignments

δH, HR2RO

δH, -NHR2R amin

δH, -CH aromatic

3.4. Thermal analysis

Thermogravimetric (TGA) and differential thermogravimetric (DTG) analyses for L and their isolated solid complexes were carried out to get information about the thermal stability of these new complexes and to suggest a general scheme for thermal decomposition as well as to ascertain the nature of associated water molecules. Figure 4 represent the TGA and DTG curves and Table 5 gives the maximum temperature values for decomposition along with the corresponding weight loss values for each step
of the decomposition reaction. The obtained data strongly support the

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proposed chemical formulas for complexes. The L is thermally stable at room temperature. Decomposition of the L started at 50 οC and finished at 350 οC with one stage at 316 οC maximum and is accompanied by a weight loss of
82.35% [25].
The thermal decompostion of [Cr(L)2(H2O)2 ](CH3COO)3 and [Mn(L)2 (H2O)2 ]SO4.3H2O complexes exhibit one main degradation step. The step of decomposition occurs at one symmetric temperature maximum for each complex at 222 and 326 οC. The found weight lose associated with decomposition are 75.44% and 81.02% which is in good agreement with calculated values of 76.72% and 81.00% (Table 5).
For [Fe(L)2(H2O)2 ](NO3)3.4H2O complex, the thermal degradation exhibit two degradation steps. The first step of decomposition occurring at 62 οC is accompanied by a weight loss of 7.00% corresponding to the loss of four water molecules. Loss of water crystallization at a relatively low temperature may indicate weak H-bonding involving the H2 O molecules and the complex. The second decomposition stage is associated with remaining water molecules and ligand unites (L). This step occurs at 240 οC and is accompanied by a weight loss of 86.38%, respectively. The infrared spectra of the final product of the thermal analysis for all above complexes supported
these conclusion.

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Fig. 4: TGA and DTG diagram for (A) L, (B) [Cr(L)R2R(HR2RO)R2R](CHR3RCOO)R3R, (C) [Mn(L)R2R(HR2RO)R2R]SOR4R.3HR2RO and (D) [Fe(L)R2R(HR2RO)R2R](NOR3R)R3R.4HR2RO.

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Table 5

The maximum temperature Tmax (οC) and weight loss values of the decomposition stages for L, Cr(III), Mn(II) and Fe(III) complexes

ο

Compounds

Decomposition

TRmaxR( C)

Weight loss (%)

Lost species

Calc.

Found

L

First step

316

82.35

82.35

5CR2RHR2R+HCN+2NCCl

(CR18RHR11RNR3R ClR2R)

Total loss

82.35

82.35

Residue

17.64

17.64

5C

[Cr(L)R2R(HR2RO)R2R](CHR3R COO)R3

First step

222

76.72

75.44

15CR2RHR2R+4HCl+6NO+0.5HR2RO

(CR42RHR35RNR6ROR8RClR4RCr)

Total loss

76.72

75.44

Residue

23.28

24.56

0.5CrR2ROR3R+12C

[Mn(L)R2R(HR2RO)R2R]SOR4R.3HR2RO

First step

326

81.00

81.02

15CR2RHR2R+3NR2R+HR2R O+ 4CO+2ClR2

(CR36RHR32RNR6ROR9RClR4RMn)

Total loss

81.00

81.02

Residue

18.99

18.98

MnSOR4R+2C

[Fe(L)R2R(HR2R O)R2R](NOR3R)R3R.4HR2R O

First step

62

6.99

7.00

4HR2RO

(CR36RHR34RNR9ROR15RClR4RFe)

Second step

240

86.42

86.38

13CR2RHR2R+2NO+3.5NR2R +9CO+2ClR

Total loss

93.41

93.38

2

Residue

6.58

6.62

Fe+C

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3.5. Mass spectra

The idea of mass spectrometer builds up on the separation of fragments ions dependent to the variation of these ions with the ratio of mass to charge (m/z). Mass spectrum of the synthesized free ligand (L) (Figure 5) is in a good agreement with the suggested structure (Scheme 2). The ligand (L) showed molecular ion peak (M.+) at m/z=339 (25%) and M+2 at m/z=341 (12%). The molecular ion peak [a] losses Cl2 to give fragment [b] at m/z=269
(12%) and it losses Cl- to give fragment [c] at m/z=304 (11%). It loses CN- to
give [d] at m/z=313 (12%). The molecular ion peak [a] gave fragment [e] at m/z=323 (17%), [f] at m/z=91 (45%), [g] at m/z=85 (34%), [h] at m/z=117 (6%), [i] at m/z=215 (10%), [j] at m/z=228 (5%) and also [k] at m/z=212 (22%). The fragmentation patterns of our studied complexes were obtained from mass spectra (Figure 5). The mass spectra of Cr(III), Mn(II) and Fe(III) complexes displayed molecular peaks at 942, 918 and 1027 which refer to M.Wt. of these complexes with the abundance at 6%, 8% and 5%
respectively.

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CN

N NH2 Cl

N NH2

[i] 215 (10 %)

CN

N NH2

Cl [j] 228 (5 %)

[h] 117 (6 %)

CN

N

CN [g] 85 (34 %)

N Cl

Cl

[k] 212 (22 %)

N NH2

[f] 91 (45 %)

CN

N NH2 Cl

Cl

[a] m/z 339 (25 %) M+2 341 (89 %)

-NH2

CN CN

N NH2

N

Cl [e] 323 (17%)

[b] 269 (12 %)

Cl

CN

N NH2

N NH2

Cl [d] 313 (12%)

Cl [c] 304 (11%)












Scheme 2: Fragmentation pattern of L

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Fig. 5: Mass spectra diagrams for (A) L, (B) [Cr(L)R2R(HR2RO)R2R](CHR3RCOO)R3R, (C) [Mn(L)R2R(HR2RO)R2R]SOR4R.3HR2RO and (D) [Fe(L)R2R(HR2RO)R2R](NOR3R)R3R.4HR2RO.

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3.6. Antimicrobial activity

The susceptibility of certain strains of bacterium, such as Staphylococcus aureus (S. aureus), Bacillus subtilis (B. subtilis), Escherichia coli (E. coli) and Pseudomonas aeruginosa (P. aeruginosa) and antifungal screening was studied against two species Candida albicans and Aspergillus fumigatus towards L and its complexes was judged by measuring size of the inhibition diameter. As assessed by color, the complexes remain intact during biological testing (Table 6 and Figure 6). A comparative study of ligand and their metal complexes showed that the metal complexes exhibit higher antibacterial activity for Gram-positive and Gram-negative and antifungal activity. Fe(III) is highly significant for Escherichia coli (E. coli) and Pseudomonas aeruginosa (P. aeruginosa) and significant for Bacillus subtilis (B. subtilis), Staphylococcus aureus (S. aureus) and Candida albicans (C. albicans). All metal salts showed no antibacterial activity except for Fe(III) showed antibacterial activity against gram negative bacteria (Table 6). The results are promising compared with the previous studies [26-29]. Such increased activity of metal chelate can be explained on the basis of the oxidation state of the metal ion, overtone concept and chelation theory. According to the overtone concept of cell permeability, the lipid membrane that surrounds the cell favors the passage of only lipid-soluble materials in which liposolubility is an important factor that controls the antimicrobial activity. On chelation the polarity of the metal ion will be reduced to a greater extent due to overlap of ligand orbital and partial sharing of the positive charge of the metal ion with donor groups. Further it increases the delocalization of π-electrons over the whole chelate ring and enhances the lipophilicity of the complexes [27]. This increased lipophilicity enhances the penetration of complexes into the lipid membranes and blocks the metal
binding sites in enzymes of microorganisms.

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60

50

40

E. coli

30

P. aeruginosa

20 B. subtilis

S. aureus

10 C. albuicans

0

Tested compounds

Fig. 6: Statistical representation for biological activity of L and its metal complexes.

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Table 6

The inhibition diameter zone values (mm) for L1 and its metal complexes.

compounds Microbial species

Bacteria fungi

E. coli P. aeruginosa B. subtilis S. aureus C. Albicans A. Fumigatus

L1 10

±0.22

L / Cr(III) 21+2

±0.22

L / Mn(II) 20+2

±0.22

L / Fe(III) 22+2

±0.22

12

±0.11

18+1

±0.11

15NS

±0.11

20+2

±0.11

15

±0.09

20+1

±0.09

19+1

±0.09

22+1

±0.09

18

±0.05

20NS

±0.05

22+1

±0.05

23+1

±0.05

14

±0.01

16NS

±0.01

18+1

±0.01

20+1

±0.01

16

±0.10

18NS

±0.10

19NS

±0.10

17NS

±0.10

Fe(NOR3R)R3R.9HR2RO 10

±0.33

12

±0.11

0 0 0 0

Cr(OCOCHR3R)R3 0 0 0 0 0 0

MnSOR4R.6HR2RO 0 0 0 0 0 0

Control (DMSO) 0 0 0 0 0 0

Standard Ampicilin 0 0 28

±0.40

0 0 0

Amoxycili n

0 0 22

±0.11

18 0 0

±1.73

Cefaloxin 24

±0.34

0 27

±1.15

16 0 0

±0.52

ND: non-detectable. i.e., the inhibition zones exceeds the plate diameterStatistical significance PNS P not

significant, P >0.05; P+1 P significant, P<0.05; P+2 P highly significant, P <0.01; P+3 P very highly significant, P <0.001; student’s t-test (Paired).

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4- Computational details

4-1 Computational method

The geometric parameters and energies were computed by density functional theory at the B3LYP/CEP-31G level of theory, using the GAUSSIAN 98W package of the programs, on geometries that were optimized at CEP-31G basis set. The high basis set was chosen to detect the energies at a highly accurate level. The atomic charges were computed using the natural atomic orbital populations. The B3LYP is the keyword for the hybrid functional [30], which is a linear combination of the gradient functionals proposed by Becke [31] and Lee, Yang and Parr [32], together with the Hartree-Fock local exchange function [33].

4-2 Structural parameters and models

4.2.1. 4,6-bis(4-chlorophenyle)-2-amino-1,2-dihydropyridine- carbinitrile

( L )

Table 7 gives Equilibrium geometric parameters bond lengths (Å), bond angles (˚), dihedral angles (˚) and charge density of L ligand by using DFT/B3LYP/CEP-31G and Scheme 3 shows the optimized geometry of L as obtained from B3LYP/CEP-31G calculations. The molecule is not highly sterically-hindered, the two benzene rings in the same plane of the pyridine ring. This observation is supported by the values of calculated dihedral angles. The dihedral angles C13C9C15N16 is 0.00˚ and C8C9C15N16 is
180.00˚ which confirms –CN group in the same plane of molecule. The value of bond angle C9C15N16 is 152.54˚ reflects on sp hybridization of C15. The values of bond distances are compared nicely with that obtained from X-ray data [34].
There is a significant built up of charge density on the nitrogen atoms of amino and cyano groups so we expect that L molecule can behave as bi- dentate ligand through Namino and Ncyano atoms and the molecule is not highly dipole µ= 1.366 because the planarity of the L and the energy value is -
186.23 au.

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Scheme 3: the optimized geometrical structure of L by using B3LYP/CEP-
31G
Table(7): Equilibrium geometric parameters bond lengths (Å), bond angles (˚), dihedral angles (˚) and charge density of L ligand by using DFT/B3LYP/CEP-31G.

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Bond length (Å)

C15-N16 1.218 C20-Cl23 1.738

C1-Cl7 1.737 C8-C9 1.401

C9-C13 1.413 C13-N12 1.355

C13-N14 1.398 C8-C10 1.400

C11-N12 1.361

Bond angle (˚)

C9 C15 Nl6 152.54 C5 C8 C10 129.74

C9 C8 C10 116.04 N14 C13 C9 116.15

C10 C11 C12 123.63 C11 N12 C13 117.34

N14 C13 N12 122.57 C17 C11 N12 114.09

C8 C9 C15 129.25 H33 N14 H34 123.42

Dihedral angles (˚)

C8C9C15N16 -180.00 C4C5C8C9 -180.00

N14C13C9C15 0.00 C13C9C15N16 0.00

N14C13N12C11 0.00 C8C9C13N14 -180.00

C21C17C11N12 180.00 C18C17C11N12 0.00

C21C17C11N12 180.00 C9C8C5C6 0.00

Charges

Cl7 -0.287 Cl23 -0.292

N16 -0.315 C20 0.244

C15 0.155 C13 0.328

N14 -0.403 C11 0.192

N12 -0.312 C1 0.242

Total energy/au -186.223

Total dipole moment/D 1.366

4.2.2. The Cr(III) L complexes

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The experimental data set that the Cr(III) complex is six-coordinate and consists of four coordinate bonds with two L molecules through Namino and Ncyano atoms of each molecule and two coordinated bonds may be with two water molecules or one acetate ion CH3COO-, one acetate ion and one
water molecule or two water molecules. The acetate group can be chelated
with metal ion through one oxygen atom and behaves as monodentate ligand or chelated with metal ion through two oxygen atoms and behaves as bidentate ligand as reported [35]. In this part we study theoretically the all possible structures can be obtained [Cr(C18 H11N3OCl2)2(CH3COO)]2+, [Cr(C18H11N3 OCl2 )2 (CH3COO)(H2 O)]2+
and [Cr(C18 H11N3 OCl2 )2 (H2O)2]3+. The three complexes have been
constructed to investigate which is more stable and show all crystal structure properties for both complexes and also detect the exact structure of them.

4.2.2.1. Description of the structure of [Cr(C18H11N3 OCl2)2(CH3 COO)]2+

Table 8 lists selected inter atomic distances and angles. The structure of complex with atomic numbering scheme are shown in Scheme 4. The complex consists of two units of L and one acetate group with Cr(III). The complex is six-coordinate with distorted octahedral environment around the metal ion. The bond lengths and the angles around Cr(III) were calculated [36-39]. The values of angles differ legally from these expected for a regular octahedron. The energy of the complex is -430.331 au and the dipole moment
is 2.775 D.

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Scheme 4: optimized geometrical structure of trans-isomer of
[Cr(C18 H11N3OCl2)2(CH3COO)]2+ complex by using B3LYP/CEP-31G
Table (8): Equilibrium geometric parameters bond lengths (Å), bond angles (˚) and charge density of [Cr(C18 H11 N3OCl2)2(CH3COO)]2+ by using DFT/B3LYP/CEP-31G.

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Bond length (Å)

Cr-N21 1.995 Cr –O3 1.849

Cr –N23 1.806 C20-N21 1.529

Cr –N50 2.002 C45-N50 1.528

Cr –N43 1.807 C22-N23 1.147

Cr –O2 1.825 C42-N43 1.147

Bond angle (˚)

N50 Cr N43 74.87 N43 Cr N23 158.48

N50 Cr O2 103.97 N43 Cr N21 94.07

N50 Cr O3 165.79 O2 Cr O3 62.92

N50 Cr N23 87.53 O3 Cr N23 99.36

N50 Cr N21 97.25 O3 Cr N21 96.50

N43 Cr O2 98.05 O2 Cr N23 98.14

N43 Cr O3 100.58 O2 Cr N21 157.68

N23 Cr N21 75.68

Charges

Cr 0.055 N21 -0.234

N43 -0.094 N23 -0.099

N50 -0.234 C20 0.282

N47 -0.269 C22 0.147

C44 - 0.042 C16 -0.048

C45 0.278 O2 -0.435

C42 0.150 O3 -0.345

N19 -0.271

Total energy/au -430.331

Total dipole moment/D 2.775

4.2.2.2 Description of the structure of

[Cr(C18 H11N3OCl2 )2 (CH3COO)(H2O)]2+

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Table 9 lists selected inter atomic distances and angles. The structure of complex with atomic numbering scheme are shown in Scheme 5. The complex consists of two units of L molecule and one acetate group as monodentate ligand through one oxygen atom and one water molecule to complete the cordination number to six with metal ion Cr(III). The complex is six-coordinate with distorted octahedral environment around the metal ion. The bond lengths for different coordinate bonds were calculated [36-41] and the angles around the central metal ion Cr(III) with surrounding donor atoms vary from 75.07˚ to 167.94˚; these values differ legally from these expected for a regular octahedron. The energy of this complex is -417.467 au while the
dipole moment is 10.211 D.

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Scheme 5: optimized geometrical structure of trans-isomer of
[Cr(C18 H11N3OCl2)2(CH3COO)(H2O)]2+ complex by using B3LYP/CEP-31G

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Table 9: Equilibrium geometric parameters bond lengths (Å), bond angles (˚) and charge density of [Cr(C18 H11N3 OCl2)2(CH3COO)(H2O)]2+ by using DFT/B3LYP/CEP-31G.

Bond length (Å)

Cr-N21 2.005 Cr –O42 1.855

Cr –N23 1.811 C20-N21 1.529

Cr –N53 2.004 C48-N53 1.528

Cr –N46 1.806 C22-N23 1.147

Cr –O2 1.815 C45-N46 1.147

Bond angle (˚)

N53 Cr N46 75.55 N21 Cr N46 166.66

N53 Cr O2 102.42 N21 Cr N23 75.07

N53 Cr O42 167.94 O2 Cr O42 84.24

N53 Cr N23 86.64 O42 Cr N23 90.65

N53 Cr N21 91.11 O42 Cr N46 93.72

N21 Cr O2 85.02 O2 Cr N23 158.35

N21 Cr O42 99.54 O2 Cr N46 97.86

N23 Cr N46 103.47

Charges

Cr 0.384 N50 -0.269

N21 -0.267 N53 -0.261

N23 -0.232 C45 0.306

N19 -0.261 C47 -0.076

C16 - 0.079 C48 0.324

C20 0.299 O2 -0.437

C22 0.269 O42 -0.275

N46 -0.202

Total energy/au -417.467

Total dipole moment/D 10.211

4.2.2.3 Description of the structure of [Cr(C18H11N3 OCl2)2(H2 O)2]3+

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The complex is six-coordinate with distorted octahedral environment around the metal ion. The Cr(III) is coordinated to one Namino and one Ncyano atoms of each L molecule and two oxygen atoms of two water molecules as shown in Scheme 6. Table 10 lists selected inter atomic distances and angles. The bond angle between N20CrN49 is 93.86˚ ( ≈ 90˚ ) and also the angle between N22CrN42 is 162.29˚ ≈ 180˚ so L molecules are not lying in the same plane they are perpendicular respect to each other with angle equal 90˚. The angle between O1CrO4 is 89.69˚ this value reflects that the two water molecules are perpendicular to each other. The data indicate that the angles around the central metal ion Cr(III) vary from 75.10˚ to 169.26˚; these values agree with these expected for a distorted octahedron.
In acetate complex, the charge accumulated on Namino is -0.234 and -
0.234 and on Ncyano is -0.099 and -0.094, while, in acetate-water complex the charge on Namino is -0.267 and -0.261 and on N cyano is -0.232 and -0.202 and for water complex, the charge on Namino is -0.271 and -0.284 and on Ncyano is
-0.264 and -0.259. There is a strong interaction between Cr(III) which has charge equal +0.414 in case of water complex while, in case of acetate and acetate-water complexes the charges accumulated on Cr(III) are 0.055 and
0.384, respectivly. The energy of the water complex is more negative than acetate complexes -448.424 au and a highly dipole 17.99D. The Cr(III) favor
coordinated with two water molecules to complete the octahedron structure.

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Scheme 6: optimized geometrical structure of trans-isomer of
[Cr(C18 H11N3OCl2)2(H2O)]3+ complex by using B3LYP/CEP-31G.

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Table 10: Equilibrium geometric parameters bond lengths (Å), bond angles (˚) and charge density of [Cr(C18 H11N3OCl2 )2 (H2 O)]3+ by using DFT/B3LYP/CEP-31G.

Bond length (Å)

Cr-N20 2.001 Cr –O4 1.855

Cr –N22 1.808 C19-N20 1.528

Cr –N49 2.001 C44-N49 1.529

Cr –N42 1.807 C21-N22 1.147

Cr –O1 1.854 C41-N42 1.147

Bond angle (˚)

N22 Cr N20 75.55 N20 Cr N49 93.86

N22 Cr O4 93.28 N20 Cr N42 93.86

N22 Cr O1 99.66 O1 Cr O4 89.69

N22 Cr N49 90.92 O1 Cr N49 169.26

N22 Cr N42 162.29 O4 Cr N49 91.53

N20 Cr O4 167.45 O4 Cr N42 97.83

N20 Cr O1 87.11 O1 Cr N42 94.16

N49 Cr N42 75.10

Charges

Cr 0.414 N49 -0.284

N20 -0.271 N46 -0.258

N22 -0.264 C41 0.331

N18 -0.258 C43 -0.093

C15 - 0.094 C44 0.306

C19 0.315 O1 -0.281

C21 0.336 O4 -0.288

N42 -0.259

Total energy/au -448.424

Total dipole moment/D 17.99

4.2.3 The Mn(II) L complexes

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The experimental data set that Mn(II) complex is six-coordinate and the complex consists of two L molecules with two water molecules or one sulfate group. In this part we study theoretically the all possible structures can be obtained [Mn(C18H11N3OCl2 )2(SO4 )] and
[Mn(C18 H11N3 OCl2 )2 (H2O)2 ]2+. The two complexes have been constructed
to investigate which is more stable, crystal structure properties for both complexes and also detect the exact structure of them.

4.2.3.1 Description of [Mn (C18H11N3 OCl2)2(SO4)] structure

Table (11) lists selected inter atomic distances and angles. The structure of complex with atomic numbering scheme are shown in Scheme 6. Mn(II) is coordinated with one Namino and one Ncyano atoms of each L and two oxygen
atoms of SO4 2- group. The bond lengths and the angles around the central
metal ion Mn(II) with surrounding four nitrogen atoms and two oxygen atoms were calculated [40,41].
The energy of this complex is -422.55 au while the dipole moment is slightly weak 6.619D and the charge accumulated on N14 and N16 of the first molecule are -0.281 and -0.219, respectively while on N36 and N43 of the second molecule are -0.226 and -0.279, respectively. The bond angle of
O72SO73 of sulfate group is 130.76˚ [41].

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Scheme 7 optimized geometrical structure of trans Oc-isomer of [Mn
(C18 H11N3OCl2)2 (SO4)] complex by using B3LYP/CEP-31G

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Table (11): Equilibrium geometric parameters bond lengths (Å), bond angles (˚) and charge density of [Mn (C18H11N3OCl2 )2 (SO4)] by using DFT/B3LYP/CEP-31G.

Bond length (Å)

Mn-N14 1.989 C38-N43 1.532

Mn-N16 1.794 C13-N14 1.529

Mn-N43 1.988 C35-N36 1.147

Mn-N36 1.795 C15-N16 1.147

Mn-O72 1.849 S-O72 1.652

Mn-O73 1.849 S-O73 1.651

Bond angle (˚)

N43 Mn N36 75.66 N36 Mn N16 164.33

N43 Mn O73 92.53 N36 Mn N14 93.53

N43 Mn O72 163.77 O73 Mn O72 76.82

N43 Mn N16 95.02 O73 Mn N16 94.32

N43 Mn N14 100.60 O73 Mn N14 163.99

N36 Mn O73 98.60 O72 Mn N16 97.94

N36 Mn O72 93.62 O72 Mn N14 92.09

N16 Mn N14 75.57

Charges

Mn 0.161 N43 -0.279

N14 -0.281 N40 -0.269

N16 -0.219 C35 0.261

N12 -0.269 C37 -0.083

C9 -0.083 C38 0.304

C13 0.304 O73 -0.262

C15 0.265 O72 -0.172

N36 -0.226 S 1.509

Total energy/au -422.555

Total dipole moment/D 6.619

4.2.3.2 Description of [Mn (C18H11N3 OCl2)2(H2 O)2]2+ structure

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The complex as shown in Scheme 6, the bond angle between N43MnN14 is 95.33˚ ( ≈ 90˚ ) and also the angle between N36MnN16 is 163.15˚ ≈ 180˚ so the two L molecules are not lying in the same plane they are perpendicular respect to each other with angle equal 90˚. The angle between O69MnO72 is
89.56˚ (Table 12) this value reflects that the two water molecules not in trans- form respect to each other but they are lying in cis-form and then they are perpendicular to each other.
The Mn-N14 and Mn-N43 bond lengths (1.996Å and 1.995Å) [37,38] are longer than Mn-N16 and Mn-N36 (1.798Å and 1.799Å) [39] and the bond distance between Mn(II) and oxygen atom of water molecule vary between 1.846 Å and 1.846 Å for Mn-O72 and Mn-O69, respectively [42-
45]. Also the angles around the central metal ion Mn(II) with surrounding oxygen atoms vary from 73.44˚ to 166.15˚; these values agree with these expected for a distorted octahedron.
The charge accumulated on Namino is -0.281 and -0.279 and on Ncyano is
-0.219 and -0.226, in sulfate complex while, on Namino is -0.264 and -0.276 and on Ncyano is -0.284 and -0.236, in water complex. The charge on Mn(II) in case of water complex is +0.289 while in case of sulphate complex is
0.161 this indicate that a strong interaction between Mn(II) in case of water complex than in sulphate complex. The total energy of the water complex (-463.380) is more negative than in sulfate complex (-422.554) and relatively weak dipole 9.33D. For all these reasons the water complex is more stable and Mn(II) favor coordinated with two molecules of water more than one
molecule of sulfate ion to complete the octahedron structure.

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Scheme 8: optimized geometrical structure of tras O-isomer of
[Mn (C18 H11N3OCl2 )2 (H2 O)2 ]2+ complex by using B3LYP/CEP-31G

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Table (12): Equilibrium geometric parameters bond lengths (Å), bond angles (˚) and charge density of [Mn (C18 H11N3OCl2 )2 (H2 O)2]2+ by using DFT/B3LYP/CEP-31G.

Bond length (Å)

Mn-N14 1.996 C38-N43 1.529

Mn-N16 1.798 C13-N14 1.529

Mn-N43 1.995 C35-N36 1.147

Mn-N36 1.799 C15-N16 1.147

Mn-O69 1.846

Mn-O72 1.846

Bond angle (˚)

N43 Mn N36 75.28 N36 Mn N16 163.15

N43 Mn O69 88.74 N36 Mn N14 92.17

N43 Mn O72 165.44 O69 Mn O72 89.56

N43 Mn N16 94.29 O69 Mn N16 91.13

N43 Mn N14 95.33 O69 Mn N14 166.16

N36 Mn O69 101.66 O72 Mn N16 100.21

N36 Mn O72 90.92 O72 Mn N14 89.72

N16 Mn N14 75.41

Charges

Mn 0.289 N43 -0.276

N14 -0.264 N40 -0.269

N16 -0.284 C35 0.245

N12 -0.204 C37 -0.073

C9 -0.044 C38 0.299

C13 0.239 O69 -0.306

C15 0.171 O72 -0.313

N36 -0.236

Total energy/au -463.380

Total dipole moment/D 9.330

4.2.4 The Fe(III) L complexes

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The Fe(III) may be chelated with two molecules of L through Namino and N cyano atoms of each molecule. The experimental data set that the result complex is six-coordinate so, the complex consists of four coordinate bonds with two L molecules and two coordinated bonds may be with two water molecules or one nitrate ion NO3 -. In this part we study theoretically the two possible structures [Fe (C18 H11N3 OCl2)2(NO3 )](NO3 )2 or [Fe (C18 H11N3OCl2)2 (H2 O)2 ](NO3 )3 .

4.2.4.1 Description of the structure of [Fe (C18H11N3 OCl2 )2 (NO3 )]2+

Table (13) lists selected inter atomic distances and angles and the structure of complex shown in Scheme 9. The complex is six-coordinate with distorted octahedral environment around the metal ion. The nitrate ion may be coordinated by a single oxygen atom or by two oxygen atoms with Fe(III) [46], here we study the probability of coordination of nitrate ion by two oxygen atoms. The angles around Fe(III) with surrounding oxygen atoms and nitrogen atoms vary from 66.13˚ to 162.48˚; these values differ legally from these expected for a regular octahedron. The energy of this complex is -
429.763 au while the dipole moment is 11.190D.

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Scheme 9: optimized geometrical structure of trans-isomer of
[Fe(C18 H11N3OCl2)2(NO3 )]2+ complex by using B3LYP/CEP-31G

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Table (13): Equilibrium geometric parameters bond lengths (Å), bond angles (˚) and charge density of [Fe(C18 H11N3OCl2 )2 (NO3)]2+ by using DFT/B3LYP/CEP-31G.

Bond length (Å)

Fe-N14 1.996 C13-N14 1.525

Fe-N16 1.799 C38-N43 1.432

Fe-N43 1.876 C15-N16 1.147

Fe-N36 1.809 C35-N36 1.261

Fe-O70 1.849 N69-O70 1.361

Fe-O71 1.848 N69-O71 1.362

Bond angle (˚)

N43 Fe N36 88.78 N36 Fe N16 162.48

N43 Fe O71 95.74 N36 Fe N14 88.64

N43 Fe O70 161.19 O70 Fe O71 66.13

N43 Fe N16 89.23 O71 Fe N16 100.71

N43 Fe N14 102.49 O71 Fe N14 161.08

N36 Fe O71 96.82 O70 Fe N16 94.98

N36 Fe O70 92.30 O70 Fe N14 95.64

N16 Fe N14 74.82

Charges

Fe 0.160 N43 -0.260

N14 -0.269 N40 -0.292

N16 -0.059 C35 0.188

N12 -0.239 C37 -0.082

C9 - 0.047 C38 0.308

C13 0.298 O70 -0.338

C15 0.202 O71 -0.324

N36 -0.149

Total energy/au -429.763

Total dipole moment/D 11.19

4.2.4.2 Description of [Fe (C18H11N3 OCl2 )2 (H2 O)2 ]3+ structure

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Table (14) lists selected inter atomic distances and angles and the structure of the complex shown in scheme 8. The bond angle between N43FeN14 is 95.39˚ ( ≈ 90˚ ) and also the angle between N36FeN16 is
163.20˚ ≈ 180˚ so the two L molecules are not lying in the same plane and they are perpendicular respect to each other with angle equal 90˚. The angle between O69FeO72 is 89.53˚ this value reflects that the two water molecules are perpendicular to each other. The complex is six-coordinate with distorted octahedral environment around the metal ion. Also the angles around the central metal ion Fe(III) with surrounding oxygen atoms vary from 75.28˚ to
166.15˚; these values agree with these expected for a distorted octahedron.
The charge accumulated on Namino and Ncyano is -0.269, -0.260 and-
0.059 , -0.149, in nitrate complex while, on Namino and Ncyano is -0.259, -0.272 and-0.259 , -0.263, in water complex. There is a strong interaction between Fe(III) which become has charge equal +0.299 in case of water complex while, in case of nitrate complex the charge accumulated on Fe(III) is 0.160. The energy of the water complex is more negative than nitrate complexes -
455.1641 au and a highly dipole 15.352D. For all these reasons the water complex is more stable than nitrate complex and Fe(III) favor coordinated with two molecules of water more than one molecule of nitrate ion to
complete the octahedron structure.

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Scheme 10: optimized geometrical structure of trans-isomer of
[Fe (C18 H11N3OCl2)2 (H2O)2 ]3+ complex by using B3LYP/CEP-31G

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Table (14): Equilibrium geometric parameters bond lengths (Å), bond angles (˚) and charge density of [Fe(C18 H11N3OCl2 )2(H2O)2 ]3+ by using DFT/B3LYP/CEP-31G.

Bond length (Å)

Fe-N14 1.996 Fe-O72 1.846

Fe-N16 1.798 C13-N14 1.529

Fe-N43 1.995 C38-N43 1.529

Fe-N36 1.799 C15-N16 1.147

Fe-O69 1.846 C35-N36 1.147

Bond angle (˚)

N43 Fe N36 75.28 N36 Fe N16 163.20

N43 Fe O69 88.76 N36 Fe N14 92.23

N43 Fe O72 165.43 O69 Fe O72 89.53

N43 Fe N16 94.34 O72 Fe N16 100.17

N43 Fe N14 95.39 O72 Fe N14 89.67

N36 Fe O69 101.61 O69 Fe N16 91.16

N36 Fe O72 90.91 O69 Fe N14 166.15

N16 Fe N14 75.38

Charges

Fe 0.299 N43 -0.272

N14 -0.259 N40 -0.254

N16 -0.259 C35 0.351

N12 -0.252 C37 -0.091

C9 - 0.089 C38 0.321

C13 0.319 O69 -0.282

C15 0.352 O72 -0.291

N36 -0.263

Total energy/au -455.164

Total dipole moment/D 15.352

Conclusion

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The three new solid complexes were obtained as colored powdered materials and were characterized using magnetic measurements, melting point, molar conductance, infrared, electronic, 1H NMR spectra and thermogravimetric analyses. The elemental analyses were in good agreement with the complexes. From the antibacterial activity data, it is observed that the complexes exhibit higher activity against Staphylococcus aureus (S. aureus), Bacillus subtilis (B. subtilis), Escherichia coli (E. coli) and Pseudomonas aeruginosa (P. aeruginosa) compared with the free ligand,
metal salt and the standard compounds. The increase in antibacterial activity of the complexes may be due to metal chelation. The enhancement of the antibacterial activity is considered according to the kind of the metal ion that we used with the ligand. 4,6-bis(4-chlorophenyle)-2-amino-1,2- dihydropyridine-3-carbinitrile(L) has two donating centers Namino and Ncyano, when chelated with metal ions as, Cr(III), Mn(II) and Fe(III) there are six- coordinated bonds are formed four with two L molecules and other two with two water molecules. The water complex is more stable than other complexes for some reasons (i) in water complexes there are more negative charges are accumulated over oxygen atoms and large positive charge is formed over central metal ion. (ii) water complexes is highly dipole greater than other complexes. The product complexes ares treated as distorted octahedral complexes.

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