Abstract:
This inventive subject matter relates to novel transitional metal complexes of Quinoxalines, methods for making such compounds, and methods for using such compounds for treating diseases and disorders mediated by kinase activity. 
     The present invention relates to new substituted Quinoxaline compounds, their tautomers, stereoisomers, polymorphs, esters, metabolites, and prodrugs, to the pharmaceutically acceptable salts of the compounds, tautomers, stereoisomers, polymorphs, esters, metabolites, and prodrugs, to compositions of any of the aforementioned embodiments together with pharmaceutically acceptable carriers, and to uses of any of the aforementioned embodiments, either alone or in combination with at least one additional therapeutic agent, in the prophylaxis or treatment of cancer.

Description:
CLAIM OF PROVISIONAL APPLICATION RIGHTS 
       [0001]    This application claims the benefit of U.S. Provisional Patent Application No. 61/065,159 filed on Feb. 11, 2008. 
     
    
     TECHNCIAL FIELD OF INVENTION 
       [0002]    The present invention is related to new chemical moieties, and more specifically it is related to novel quinoxaline-metal complexes with Cu and Ni metal ions that have shown anticancer activity. 
       BACKGROUND OF INVENTION 
       [0003]    Quinoxalines are a class of fused six-membered nitrogen heterocyclics containing two nitrogens in mutually para disposition. These compounds have a wide range of applications in pharmacology, bacteriology and mycology 1-6 . Previous studies have shown the synthesis of heterocyclic quinoxalines that demonstrated anti-viral properties when evaluated for their biological activities 21 . Recently, structure-activity relationship evaluation performed at 2,6 positions of 8-phenylquinoxaline and 8-quinoxaline yielded a novel series of quinoxaline molecules that exhibited promising c-Met kinase (involved in tumor formation) inhibiting property 22 . Similarly, yet another group has synthesized functionalized pyrido[2,3-g]quinoxaline derivatives. These fused heterocyclic quinoxaline series showed interesting anti-microbial and anti-cancer properties 23 . Apart from these, there are several reports on substituted quinoxalines possessing interesting pharmacological properties, for example: quinoxaline 1,4-dioxides and 2,3-bifunctionalized quinoxalines showed anti-cancer activities 24-25 . These compounds have potent donor groups and despite this, the studies directed towards exploring the ligational behaviour of these compounds are limited. Previous studies show investigations pertaining to new copper and vanadyl complexes with quinoxaline N 1 ,N 4 -dioxide derivatives that were synthesized and characterized by different spectroscopic methods 26-28 . In one instance, the novel metal compixes of quinoxalines were tested for cytotoxicity in V79 cells and the ligands, labeled Cu-L1 and Cu-L2 showed good cytotoxicity in normoxia and hypoxia conditions, respectively 26-27 . In an other example, insulin mimetics of vanadyl complexes of quinoxaline were reported 28 . For this reason, we report, herein, the synthesis and characterization of copper(II) complexes of 2-hydroxybenzaldehyde-1-(3-chloro-2-quinoxalinyl)hydrazone [RM2] ( FIG. 2 ), 2-Hydroxy-3-methoxybenzaldehyde-1-(3-chloro-2-quinoxalinyl)-hydrazone [RM5] ( FIG. 3 ), 2-hydroxy-1-naphthaldehyde-1-(3-chloro-2-quinoxalinyl)hydrazone [RM8] ( FIG. 4 ), 2-furaldehyde-2-(3-chloro-2-quinoxalinyl)hydrazone [RM14] ( FIG. 5 ) and 2-pyridinecarbaldehyde-2-(3-chloro-2-quinoxalinyl)hydrazone [RM1 1] ( FIG. 6 ) and nickel(II) complexes of 2-hydroxy-1-naphthaldehyde-1-(3-chloro-2-quinoxalinyl)hydrazone [RM7] ( FIG. 7 ) and 2-pyridinecarbaldehyde-2-(3-chloro-2-quinoxalinyl)hydrazone [RM10] ( FIG. 8 ). 
       Platinum-Based Antitumor Metal Complexes: 
       [0004]    Cisplatin shows its best activity against testicular carcinoma (cures in most cases) and is effective against ovarian carcinomas, tumors of the head and neck as well as bladder tumors (prolongation of survival time and cures in some cases). Since its discovery by Barnett Rosenberg, a wealth of information published on interactions of cisplatin with nucleotides and DNA, which states that cisplatin enters healthy as well as tumor cells and reacts with intracellular DNA, binding to the N7 atom of the DNA base guanine which can result in inter or intrastrand cross linking of adjacent or opposing guanine moieties as well as cross-links between guanine and a protein molecule. 
         [0005]    Carboplatin (cis-diamine(1,1-cyclobutane-dicarboxylato)platinum(II), direct analog of cisplatin had less nephrotoxicity, and ototoxicity. The dose limiting toxicity for carboplatin is myelosuppression, mainly thrombopenia 29 . Oxaliplatin is a third generation platinum compound that differs from cisplatin and carboplatin in several important ways. In some model systems it has promising activity against cisplatin and carboplatin resistance tumor cells. The dose liminting side effect of oxaliplatin is neurotoxicity unlike myelosuppresssion or nephrotoxicity of cisplatin and carboplatin. It is active against colon carcinoma against which cisplatin and carboplatin have essentially no activity 30 . 
       Non-Platinum Antitumor Metal Complexes: 
       [0006]    Because cisplatin and direct platinum analogues are only active against a limited number of cancers, metal complexes with non-platinium metals, e.g. germanium(IV), titanium(IV), tin(IV), ruthenium(III), gold(III), and copper(II), palladium have been developed over the last ten years 31 . Several of them exhibit high in-vitro and in-vivo antitumor activity. 
         [0007]    Non-platinum compounds which have entered clinical trials-Two titanium(IV) complexes, budotitane and titanocene dichloride, have undergone phase I studies after showing promising antitumor activity in experimental colon tumor models. Their main side effects include liver and kidney toxicity, and their myelotoxicity is not pronounced. 
         [0008]    Hence, we synthesized novel copper compixes of quinoxaline derivatives to overcome drug resistance and toxicity issues observed with platinum and non-platinum based chemotherapeutics. The novel metal complexes of quinoxaline derivatives that we submitted in this application showed potent anti-cancer activity when tested in a human ovarian cancer cell line model. 
       Prior Art 
       [0009]    The patent, PCT/US2008/063010, entitled “δ3-Substituted quinoline or quinoxalinederivatives and their use as phosphatidylinositol 3-kinase (PI3K) inhibitors” issued to Chen et al. describes substituted quionoxaline derivatives that were synthesized and evaluated for their biological activity. The claims made in this invention include halopyridine-based quinoxaline analogues and encompasses racemic mixtures, partially racemic mixtures, separate enantiomers and diastereomers. The compounds showed efficacy against PI3K and had potential to inhibit PI3K. PI3K is one of the critical kinases involved in several diseases incluing autoimmune, inflammatory, neurodegenerative and other related dieases. 
         [0010]    The patent, U.S. Pat. No. 5,563,140, entitled “Use of 1-(aminoalkyl)-3-(benzyl)-quinoxaline-2-one derivatives for the preparation of neuroprotective compositions” issued to Ehrenberger and Felix, claims in the invention that, 1-(aminoalkyl)-3-(benzyl)-quinoxaline-2-ones are novel chemical derivatives of quinooxaline that belong to a potent, reversible and selective class of glutamate receptor antagonists. These benzyl-functionalized quinoxaline derivatives were shown to have an effect on the excitatory efferent synapses of the cochlear inner hair cells. 
         [0011]    The patent, U.S. Pat. No. 6,180,632, entitled “Quinoline and quinoxaline compounds which inhibit platelet-derived growth factor and/or p56lck tyrosine kinases” issued to Myers et al. had claims for invention of quinoxaline derivatives having interesting biological properties. In this invention, Cycloalkyl derivatives of quinoxaline were foind effective in inhibiting PDGF-R tyrosine kinase activity and or Lck tyrosine kinase activity, and thus producing the desired therapeutic effect. The novel quinoxaline derivatives were reported to be useful as anti-cancer, ant-hypertensive and anti-coagulant agents. 
         [0012]    The patent, U.S. Pat. No. 5,326,763, entitled “Methods for using (2-imidazolin-2-ylamino) quinoxaline derivatives” issued to the inventors Gluchowski et al. describes imidazoline-based quinoxaline compounds shown to be effective in the treatment of inflammatory disorders. In this invention, halogen-substituted imidazoline-based quinoxalines have been shown to be effective as anti-inflammatory in pharmacological studies with animal tissues. 
         [0013]    Amongst the quinoxaline compounds invented so far for therapeutic usage in various cases of disease pathogenesis, very few metal complexes of Quinooxaline and halogen-substituted quinoxaline derivatives thus far have been reported. The innovation of the investigation presented in this patent application is that novel quinoxaline derivatives and their halo-substituted versions have been cornplexed with a metal ion into six-coordinate structures. These novel chemical entities of quinoxaline have been investigated against a human ovarian cancer cell line and were shown to exhibit promising and interesting anti-cancer properties. 
       SUMMARY OF INVENTION 
       [0014]    Novel copper complexes of quinoxaline derivatives were synthesized and characterized by various spectroscopic analysis methods. Chemical structural analysis showed dimeric units of each in solid state. Stability analysis indicated quinoxaline derivatives to be stably co-ordinated to the metal ions. Compounds were investigated for their ability to be cytotxic in human ovarian cancer cell lines. Of the synthetic heterocyclic and halogen-substituted quinoxaline derivatives, structures designated as RM2, RM5, RM7, RM8, RM10, RM11 and RM14 showed percent survival cells &lt;1% when represented with respect to DMSO-treated controls in the MTT assay performed using A2780 human ovarian cancer cell line. The significance of our patent appplication is the novelty in the chemical structures of metal complexes coordinated to substituted quinoxaline derivatives that showed potent cytotoxic acivities in a human ovarian cancer cell line model. 
     
    
     
       BRIEF DESCRIPTION OF FIGURES 
         [0015]      FIG. 1  (Structure I): Basic structure of quinoxaline metal complex 
           [0016]      FIG. 2  (RM2): 2-Hydroxybenzaldehyde-1-(3-chloro-2-quinoxalinyl)hydrazone 
           [0017]      FIG. 3  (RM5): 2-Hydroxy-3-methoxybenzaldehyde-1-(3-chloro-2-quinoxalinyl)hydrazone 
           [0018]      FIG. 4  (RM8*): 2-Hydroxy-1-naphthaldehyde-1-(3-chloro-2-quinoxalinyl)hydrazone (diastereomer) 
           [0019]      FIG. 5  (RM14): 2-Furaldehyde-2-(3-chloro-2-quinoxalinyl)hydrazone 
           [0020]      FIG. 6  (RM11**): 2-Pyridinecarbaldehyde-2-(3-chloro-2-quinoxalinyl)hydrazone 
           [0021]      FIG. 7  (RM7*): 2-hydroxy-1-naphthaldehyde-1-(3-chloro-2-quinoxalinyl)hydrazone 
           [0022]      FIG. 8  (RM10**): 2-pyridinecarbaldehyde-2-(3-chloro-2-quinoxalinyl)hydrazone 
           [0023]      FIG. 9 : MTT ASSAY OF METAL COMPLEXES 
           [0024]    Note: *, **: Stereoisomers (geometric isomers, E- and Z-isomers, cis- and trans-isomers) 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0025]    In the current invention, synthesis, characterization and biological evaluation of copper(II) complexes of 2-hydroxybenzaldehyde-1-(3-chloro-2-quinoxalinyl) hydrazone [RM2], 2-Hydroxy-3-methoxybenzaldehyde-1-(3-chloro-2-quinoxalinyl)-hydrazone [RM5], 2-hydroxy-1-naphthaldehyde-1-(3-chloro-2-quinoxalinyl)hydrazone [RM8], 2-furaldehyde-2-(3-chloro-2-quinoxalinyl)hydrazone [RM14] and 2-pyridinecarbaldehyde-2-(3-chloro-2-quinoxalinyl)hydrazone [RM11] and nickel(II) complexes of 2-hydroxy-1-naphthaldehyde-1-(3-chloro-2-quinoxalinyl)hydrazone [RM7] and 2-pyridinecarbaldehyde-2-(3-chloro-2-quinoxalinyl)hydrazone [RM10] are presented in detail in this section. 
         [0000]    a. Materials and Methods 
         [0026]    All the chemicals and reagents used were of analytical grade. 2-Chloro-3-hydrazinoquinoxaline was prepared as reported earlier 7 . The ligands were synthesized by stirring equimolar quantities of 2-Chloro-3-hydrazinoquinoxaline and the respective aldehydes in DMF, for 2 hrs. at RT. Copper complexes of the ligands were prepared taking copper(II) acetate. Nickel complexes of the ligands were prepared taking nickel(II) acetate. In the preparation of the metal complexes, the metal and the ligand were combined in 1:2 mole ratio using required quantities of methanol or water for the metal salts and methanol for the ligands. The contents were refluxed on a water bath for 2-3 hrs; the solid that separated was filtered, washed with water, hot methanol and ether and dried in air. 
         [0027]    The elemental analyses were carried out by Carlo Erba 1108 elemental analyzer at CDRI, Lucknow. Conductance measurements on the complexes were made in DMF at 10 −3  M concentration on a Digisun digital conductivity meter DI 909 model. Gouy balance calibrated with Hg[Co(SCN) 4 ] was used to measure the magnetic susceptibility of the metal complexes at room temperature. The infrared spectra of the ligands and the metal complexes were recorded in KBr pellets in the range 4000- 400 cm −1  on Perkin Elmer-BX spectrophotometer at Central Instrumentation Center, Kakatiya University. The electronic spectra of the metal complexes in DMF were recorded on ELICO SL-159 UV-Vis spectrophotometer. The JEOL FE1X ESR spectrometer operating in the frequency range 8.8-9.6 GHz available with the Department of Physics, Sri Venkateswara university, Tirupati, India, was employed in recording the ESR spectra of Cu(II) complexes in DMF at LNT. The  1 H-NMR spectra of the ligands were recorded in DMSO-d 6  solution employing Bruker avance 300 MHz spectrometer. 
         [0000]    b. Characterization of the Ligands: 
         [0028]    The basic chemical structure of the quinoxaline-metal complexes synthesized in this invention is shown in  FIG. 1 . 
         [0029]    All the ligands employed in the present investigation are stable at room temperature and are non-hygroscopic. They are insoluble in water, slightly soluble in methanol and acetone and fairly soluble in hot methanol and dimethylformamide. The ligands have been characterized by analytical, mass,  1 H-NMR and IR spectral data. 
       2-Hydroxybenzaldehyde-1-(3-chloro-2-quinoxalinyl)hydrazone 
       [0030]    From the analytical data, the molecular formula C 15 H 11 N 4 OCl for the ligand has been adjudged which agrees well with a product resulting from 1:1 condensation between 2-chloro-3-hydrazinoquinoxaline and salicylaldehyde with the elimination of water molecule. This is supported by mass,  1 H-NMR and IR spectral data (Table 1). 
         [0031]    The mass spectrum shows parent peak at m/z 299, which corresponds with the presented molecular formula in  FIG. 2  or RM2. 
         [0000]    
       
         
               
             
               
               
               
               
             
           
               
                 TABLE 1 
               
               
                   
               
               
                 The  1 H-NMR and IR spectral assignments of the structure RM2 
               
               
                   
               
             
             
               
                   
               
             
          
           
               
                   
                   1 H-NMR spectral data: 
                   
                   
               
               
                   
                 Phenolic —OH 
                 δ 10.9 
                 ppm 
               
               
                   
                 —NH proton of hydrazine side chain 
                 δ 10.7 
                 ppm 
               
               
                   
                 —CH proton of azomethine group 
                 δ 8.6 
                 ppm 
               
               
                   
                 Aromatic protons 
                 δ 6.6-7.9 
                 ppm 
               
               
                   
                 IR spectral data: 
               
               
                   
                 νNH 
                 3432 
                 cm −1   
               
               
                   
                 νOH 
                 3230 
                 cm −1   
               
               
                   
                 νC═N (free) 
                 1620 
                 cm −1   
               
               
                   
                 νC═N (ring) 
                 1581 
                 cm −1   
               
               
                   
                 νC—O (phenolic) 
                 1231 
                 cm −1   
               
               
                   
                   
               
             
          
         
       
     
         [0032]    The integral strengths and the ratios of signals due to the protons agree well with the expected structure. 
       2-Hydroxy-3-methoxybenzaldehyde-1-(3-chloro-2-quinoxalinyl)hydrazone 
       [0033]    The mass,  1 H-NMR and IR spectra of the ligands are presented in the following sections (Table 2). 
         [0034]    The analytical data are in agreement with the molecular formula C 16 H 13 N 4 O 2 Cl corresponding to monohydrazone resulting from 1:1 condensation between 2-chloro-3-hydrazinequinoxaline and 2-hydroxy-3-methoxybenzaldehyde. The mass spectrum showed parent peak at m/z 329, which is consistent with the molecular formula shown in  FIG. 3  or RM5. 
         [0000]    
       
         
               
             
               
               
               
               
             
           
               
                 TABLE 2 
               
               
                   
               
               
                 The  1 H-NMR and IR spectral assignments of the structure RM5 
               
               
                   
               
             
             
               
                   
               
             
          
           
               
                   
                   1 H-NMR spectral data: 
                   
                   
               
               
                   
                 Phenolic —OH 
                 δ 11.9 
                 ppm 
               
               
                   
                 —NH proton of hydrazine side chain 
                 δ 11.4 
                 ppm 
               
               
                   
                 —CH proton of azomethine group 
                 δ 8.4 
                 ppm 
               
               
                   
                 —OCH 3  protons 
                 δ 3.9 
                 ppm 
               
               
                   
                 Aromatic protons 
                 δ 6.6-7.9 
                 ppm 
               
               
                   
                 IR spectral data: 
               
               
                   
                 νNH 
                 3432 
                 cm −1   
               
               
                   
                 νOH 
                 3237 
                 cm −1   
               
               
                   
                 νC═N (free) 
                 1620 
                 cm −1   
               
               
                   
                 νC═N (ring) 
                 1577 
                 cm −1   
               
               
                   
                 νC—O (phenolic) 
                 1249 
                 cm −1   
               
               
                   
                   
               
             
          
         
       
     
       2-Hydroxy-1-naphthaldehyde-1-(3-chloro-2-quinoxalinyl)hydrazone 
       [0035]    From the analytical data, the molecular formula C 19 H 13 N 4 OCl for the ligand corresponding to monohydrazone resulting from 1:1 condensation between 2-chloro-3-hydrazinoquinoxaline and 2-hydroxy-1-naphthaldehyde has been assigned. 
         [0036]    The mass spectrum shows parent peak at m/z 349, Table 3, which is consistent with the molecular formula shown in  FIG. 4  or RM8. 
         [0000]    
       
         
               
             
               
               
               
               
             
           
               
                 TABLE 3 
               
               
                   
               
               
                 The  1 H-NMR and IR spectral assignments of the structure RM8 
               
               
                   
               
             
             
               
                   
               
             
          
           
               
                   
                   1 H-NMR spectral data: 
                   
                   
               
               
                   
                 Phenolic —OH 
                 δ 11.0 
                 ppm 
               
               
                   
                 —NH proton of hydrazine side chain 
                 δ 9.5 
                 ppm 
               
               
                   
                 —CH proton of azomethine group 
                 δ 8.2 
                 ppm 
               
               
                   
                 Aromatic protons 
                 δ 6.3-7.9 
                 ppm 
               
               
                   
                 IR spectral data: 
               
               
                   
                 νNH 
                 3430 
                 cm −1   
               
               
                   
                 νOH 
                 3200 
                 cm −1   
               
               
                   
                 νC═N (free) 
                 1641 
                 cm −1   
               
               
                   
                 νC═N (ring) 
                 1581 
                 cm −1   
               
               
                   
                 νC—O (phenolic) 
                 1230 
                 cm −1   
               
               
                   
                   
               
             
          
         
       
     
       2-Furaldehyde-2-(3-chloro-2-quinoxalinyl)hydrazone 
       [0037]    From the analytical data, the molecular formula C 13 H 9 N 4 OCl has been adjudged which agrees well with a product resulting from 1:1 condensation between 2-chloro-3-hydrazinoquinoxaline and 2-furaldehyde with the elimination of water molecule,  FIG. 5 . This is supported by mass,  1 H-NMR and IR spectral data. 
         [0038]    The mass spectrum shows parent peak at m/z 273, Table 4, which corresponds with the molecular formula shown in  FIG. 5  or RM14. 
         [0000]    
       
         
               
             
               
               
               
               
             
           
               
                 TABLE 4 
               
               
                   
               
               
                 The  1 H-NMR and IR spectral assignments of the structure RM14 
               
               
                   
               
             
             
               
                   
               
             
          
           
               
                   
                   1 H-NMR spectral data: 
                   
                   
               
               
                   
                 —NH proton of hydrazine side chain 
                 δ 11.9 
                 ppm 
               
               
                   
                 —CH proton of azomethine group 
                 δ 8.7 
                 ppm 
               
               
                   
                 Aromatic protons 
                 δ 6.6-8.0 
                 ppm 
               
               
                   
                 IR spectral data: 
               
               
                   
                 νNH 
                 3431 
                 cm −1   
               
               
                   
                 νOH 
                 3200 
                 cm −1   
               
               
                   
                 νC═N (free) 
                 1634 
                 cm −1   
               
               
                   
                 νC═N (ring) 
                 1580 
                 cm −1   
               
               
                   
                 νC—O (furan) 
                 886 
                 cm −1   
               
               
                   
                   
               
             
          
         
       
     
       2-Pyridinecarbaldehyde-2-(3-chloro-2-quinoxalinyl)hydrazone 
       [0039]    From the analytical data, the molecular formula C 14 H 10 N 5 Cl for the ligand corresponding to monohydrazone resulting from 1:1 condensation between 2-chloro-3-hydrazinoquinoxaline and 2-pyridinecarbaldehyde has been assigned,  FIG. 6 . 
         [0040]    The mass spectrum shows parent peak at m/z 283, Table 5, which is consistent with the molecular formula shown in  FIG. 6  or RM11. 
         [0000]                                      TABLE 5               The  1 H-NMR and IR spectral assignments of the structure RM11       are shown                                      1 H-NMR spectral data:                   —NH proton of hydrazine side chain   δ 15.3   ppm           —CH proton of azomethine group   δ 8.9   ppm           Aromatic protons   δ 7.2-8.1   ppm           IR spectral data:           νNH   3432   cm −1             νC═N (free)   1634   cm −1             νC═N (ring)   1580   cm −1             νC═N (pyridine ring)   1420   cm −1                          
c. Characterization of the Cu(II) and Ni(II) Complexes:
 
         [0041]    Copper(II) complexes of 2-hydroxybenzaldehyde-1-(3-chloro-2-quinoxalinyl)hydrazone [RM2] ( FIG. 2 ), 2-Hydroxy-3-methoxybenzaldehyde-1-(3-chloro-2-quinoxalinyl)hydrazone [RM5], 2-hydroxy-1-naphthaldehyde-1-(3-chloro-2-quinoxalinyl)hydrazone [RM8], 2-furaldehyde-2-(3-chloro-2-quinoxalinyl)hydrazone [RM14] and 2-pyridinecarbaldehyde-2-(3-chloro-2-quinoxalinyl)hydrazone [RM11] and nickel(II) complexes of 2-hydroxy-1-naphthaldehyde-1-(3-chloro-2-quinoxalinyl)hydrazone [RM7] and 2-pyridinecarbaldehyde-2-(3-chloro-2-quinoxalinyl) hydrazone [RM10] are, as well, stable at room temperature and are non-hygroscopic. Upon heating, the complexes decompose without melting. The complexes are insoluble in water, very slightly soluble in methanol and acetone and fairly soluble in dimethylformamide and dimethylsulphoxide. 
         [0000]    i. Elemental Analysis: 
         [0042]    Analytical data obtained for Cu and Ni complexes are presented in Table 6. 
         [0000]    
       
         
               
             
               
               
               
             
               
               
               
               
               
             
               
               
               
               
               
               
             
           
               
                 TABLE 6 
               
             
             
               
                   
               
               
                 Analytical data of the Cu and Ni complexes 
               
             
          
           
               
                   
                 Percent 
                   
               
             
          
           
               
                   
                 Metal 
                 Carbon 
                 Hydrogen 
                 Nitrogen 
               
               
                   
                   
               
             
          
           
               
                 1 
                 RM2 
                 9.45 
                 54.26 
                 3.19 
                 16.79 
               
               
                   
                   
                 (9.64) 
                 (54.68) 
                 (3.06) 
                 (17.00) 
               
               
                 2 
                 RM5 
                 8.65 
                 53.32 
                 3.33 
                 15.39 
               
               
                   
                   
                 (8.84) 
                 (53.45) 
                 (3.36) 
                 (15.58) 
               
               
                 3 
                 RM8 
                 8.15 
                 59.72 
                 3.07 
                 14.44 
               
               
                   
                   
                 (8.37) 
                 (60.13) 
                 (3.19) 
                 (14.76) 
               
               
                 4 
                 RM14 
                 8.52 
                 49.02 
                 3.28 
                 15.21 
               
               
                   
                   
                 (8.74) 
                 (49.56) 
                 (3.33) 
                 (15.41) 
               
               
                 5 
                 RM11 
                 8.37 
                 51.12 
                 3.42 
                 18.59 
               
               
                   
                   
                 (8.48) 
                 (51.31) 
                 (3.50) 
                 (18.70) 
               
               
                 6 
                 RM7 
                 7.65 
                 60.19 
                 3.10 
                 14.71 
               
               
                   
                   
                 (7.78) 
                 (60.51) 
                 (3.21) 
                 (14.86) 
               
               
                 7 
                 RM10 
                 7.78 
                 51.24 
                 3.49 
                 18.62 
               
               
                   
                   
                 (7.89) 
                 (51.64) 
                 (3.52) 
                 (18.82) 
               
               
                   
               
               
                 The values in parentheses are from calculated data 
               
             
          
         
       
     
         [0043]    The per cent values of the elements: the metal, carbon, hydrogen and nitrogen in the complexes have been calculated as per the composition given in the table. It may be seen from the table that the experimental values are in fair agreement with the calculated ones. The complexes may, thus, be assigned the composition as given. 
         [0000]    ii. Conductance Measurements: 
         [0044]    The molar conductance values observed for the present Cu(II) and Ni complexes in dimethylformamide at 10 −3 M concentration are given in Table 7. 
         [0000]    
       
         
               
             
               
               
               
             
               
               
               
             
           
               
                 TABLE 7 
               
             
             
               
                   
               
               
                 Molar conductance (Ohm −1  · cm 2  · mol −1 ) data of the 
               
               
                 complexes 
               
             
          
           
               
                   
                   
                 Molar 
               
               
                 S. No. 
                 Metal complex 
                 conductance 
               
               
                   
               
             
          
           
               
                 1 
                 RM2 
                 12 
               
               
                 2 
                 RM5 
                 11 
               
               
                 3 
                 RM8 
                 14 
               
               
                 4 
                 RM14 
                 127 
               
               
                 5 
                 RM11 
                 130 
               
               
                 6 
                 RM7 
                 10 
               
               
                 7 
                 RM10 
                 123 
               
               
                   
               
             
          
         
       
     
         [0045]    An examination of the data in Table-2 indicates that the RM2, RM5, RIM8 and RM7 complexes are non-electrolytes while those of RM14, RM11 and RM10 are 1:2 electrolytes. 
         [0000]    iii. IR Spectra: 
         [0046]    The ligands 2-hydroxybenzaldehyde-1-(3-chloro-2-quinoxalinyl)hydrazone, 2-hydroxy-3-methoxybenzaldehyde-1-(3-chloro-2-quinoxalinyl)-hydrazone and 2-hydroxy-1-naphthaldehyde-1-(3-chloro-2-quinoxalinyl)hydrazone show, in their spectra, a medium intensity band in the region 3200-3330 cm −1  that has been assigned to vO—H. This band disappears in the spectra of their complexes indicating that deprotonation of the group has taken place. A small or rnedium intensity band around 1230 cm −1  in the ligands assignable to vC—O is seen to have undergone a positive shift by 30-50 cm −1  in the complexes suggesting coordination through phenolic oxygen 8 . The positive shift observed may be attributed to the drift of electron density from oxygen to the metal ion resulting in greater ionic character of the C—O bond and a consequent increase in its vibration frequency 9 . The ligands record a somewhat broad, medium intensity band around 3430 cm −1  attributable to free vN—H 10 . This band remains either unshifted or higher shifted in the complexes indicating non-participation of nitrogen of this group in coordination. Further, the ligands reveal bands around 1620 cm −1  due to free vC═N and around 1580 cm −1  due to ring vC═N. The bands due to these groups are lower shifted by 20-30 cm −1  in the complexes suggesting that the ligands act as mononegative, tridentate ones bonding through phenolic oxygen and nitrogens of free C═N and ring C═N 11-13 . 
         [0047]    The ligands 2-furaldehyde-2-(3-chloro-2-quinoxalinyl)hydrazone and 2-pyridinecarbaldehyde-2-(3-chloro-2-quinoxalinyl)hydrazone display a strong absorption band around 3430 cm −1  due to free vN—H 10 . This band remains almost unshifted in the spectra of the complexes suggesting non-participation of nitrogen of this group in coordination. A band that appears in the ligands around 1630 cm −1  due to free vC═N and around 1580cm −1  due to quinoxaline ring vC═N are lower shifted by 20-30 cm −1  in their complexes indicating that nitrogens of free vC═N and ring vC═N are involved in coordination. A small intensity band at 886 cm −1  due to vC—O (furan cyclic) and at 1420 cm −1  (pyridine cyclic) have been lower shifted in their complexes indicating that furan oxygen and pyridine nitrogen are involved in coordination respectively in 2-furaldehyde-2-(3-chloro-2-quinoxalinyl)hydrazone and pyridinecarbaldehyde-2-(3-chloro-2-quinoxalinyl)-hydrazone 14,15 . This suggests that the ligands act as neutral, tridentate ones bonding through nitrogens of free C═N and ring C═N and oxygen of furan ring in 2-furaldehyde-2-(3-chloro-2-quinoxalinyl)hydrazone and nitrogen of pyridine ring in pyridinecarbaldehyde-2-(3-chloro-2-quinoxalinyl)-hydrazone. 
         [0000]    iv. Magnetic Data: 
         [0048]    The complexes are found to have μ eff  values in the range 1.81-1.83 B.M. The slight excess over the spin-only value of 1.73 B.M. represents contribution from spin-orbit coupling, which is characteristic of square-planar or tetragonal geometry. However, based on the analytical data observed for the complexes and the ligating behaviour of the ligands, tetragonal geometry may be presumed for the complexes. 
         [0000]    v. Electronic Spectra: 
         [0049]    The Cu-complexes show each two somewhat broad peaks around 15000 and 20000 cm −1  (Table-3) that could be assigned respectively to the transitions:
         2 B 1g    2 B 2g        2 B 1g    2 E g          
 
         [0052]    Tetragonal or square-planar Cu(II) complexes are expected to give three peaks. However, these peaks usually overlap to give one or two peaks 16 , the present complexes thus showing two peaks. 
         [0053]    The Ni(II) complexes each reveal three peaks in their spectra at the frequencies that are usually observed for octahedral Ni(II) complexes. The ν 2 /ν 1  values observed for the complexes corroborate this proposition. The electronic spectral data of the metal complexes is presented in Table 8. 
         [0000]    
       
         
               
             
               
               
               
               
             
               
               
               
               
               
             
           
               
                 TABLE 8 
               
             
             
               
                   
               
               
                 Electronic spectral data of the metal complexes 
               
             
          
           
               
                   
                 Metal 
                   
                   
               
               
                   
                 complex 
                 Frequency (cm −1 ) 
               
               
                   
                   
               
             
          
           
               
                   
                 RM2 
                 15250 
                 20350 
                 — 
               
               
                   
                 RM5 
                 15230 
                 20370 
               
               
                   
                 RM8 
                 15650 
                 19900 
                 — 
               
               
                   
                 RM14 
                 15260 
                 20250 
                 — 
               
               
                   
                 RM11 
                 15280 
                 20310 
                 — 
               
               
                   
                 RM7 
                 9530(ν 1 ) 
                 14200(ν 2 ) 
                 24300(ν 3 ) 
               
               
                   
                 RM10 
                 9510(ν 1 ) 
                 14320(ν 2 ) 
                 24350(ν 3 ) 
               
               
                   
                   
               
             
          
         
       
     
         [0054]    The electronic spectral observations, coupled with the analytical, conductance, infrared and magnetic data obtained, suggest for the present Cu(II) complexes, a tetragonal geometry. 
         [0000]    vi. ESR Spectra: 
         [0055]    The ESR spectral data of the complexes are presented in Table 9. The spectra of all the four complexes are of anisotropic nature in that each of them has two peak envelopes, one of small intensity towards low field and the other of large intensity towards high field. The small intensity envelope towards low field has been resolved into two to four peaks due to hyperfine interaction with copper nucleus (I=3/2). The large intensity peak towards high field has not been resolved. 
         [0000]    
       
         
               
             
               
               
               
               
               
               
               
               
               
             
           
               
                 TABLE 9 
               
             
             
               
                   
               
               
                 ESR parameters of Cu(II) complexes 
               
             
          
           
               
                   
                   
                   
                   
                 A ||  × 
                   
                   
                   
                   
               
               
                   
                   
                   
                   
                 10 4   
                   
                   
                   
                 −λ 
               
               
                 Complex 
                 g ||   
                 g ⊥   
                 g av   
                 (cm −1 ) 
                 α 2   
                 β 2   
                 γ 2   
                 (cm −1 ) 
               
               
                   
               
               
                 RM2 
                 2.24 
                 2.05 
                 2.11 
                 46 
                 0.55 
                 0.93 
                 0.80 
                 453 
               
               
                 RM5 
                 2.25 
                 2.05 
                 2.11 
                 48 
                 0.58 
                 0.94 
                 0.75 
                 471 
               
               
                 RM8 
                 2.24 
                 2.05 
                 2.12 
                 49 
                 0.59 
                 0.92 
                 0.77 
                 465 
               
               
                 RM14 
                 2.24 
                 2.06 
                 2.11 
                 70 
                 0.75 
                 0.86 
                 0.89 
                 452 
               
               
                 RM11 
                 2.25 
                 2.05 
                 2.12 
                 60 
                 0.66 
                 0.93 
                 0.87 
                 507 
               
               
                   
               
             
          
         
       
     
         [0056]    The g tensor values of Cu(II) complexes can be used to derive the ground state. In a square-planar or tetragonally elongated octahedral complex, the unpaired electron lies in d x   2 - y   2  orbital giving  2 B 1g  as the ground state with g ∥ &gt;g ⊥ &gt;2 17 . A comparision of the g ∥  and g ⊥  values obtained for the present complexes indicates that g ∥ &gt;g ⊥ &gt;2 and so the unpaired electron lies predominantly in the d x   2 - y   2  orbital. 
         [0057]    The in-plane σ-bonding parameter, α 2 ; the in-plane π-bonding parameter, β 2  and out-of-plane π-bonding parameter γ 2  for the complexes have been obtained from the following simplified equations 18,19 . 
         [0000]      α 2   =A/PK+g− 2.0023/ K    
         [0000]    where P is the free ion dipole value=0.036 cm −1  and K is the Fermi contact term equal to 0.43. 
         [0000]    
       
         
           
             
               g 
               || 
             
             = 
             
               2.0023 
               - 
               
                 
                   8 
                    
                   
                     λ 
                     0 
                   
                    
                   
                     α 
                     2 
                   
                    
                   
                     β 
                     2 
                   
                 
                 
                   Δ 
                    
                   
                       
                   
                    
                   
                     E 
                      
                     
                       ( 
                       
                         
                           B 
                           
                             1 
                              
                             g 
                           
                             
                             
                             
                           2 
                         
                         → 
                         
                           B 
                           
                             2 
                              
                             g 
                           
                             
                             
                             
                           2 
                         
                       
                       ) 
                     
                   
                 
               
             
           
         
       
       
         
           
             
               g 
               ⊥ 
             
             = 
             
               2.0023 
               - 
               
                 
                   2 
                    
                   
                     λ 
                     0 
                   
                    
                   
                     α 
                     2 
                   
                    
                   
                     γ 
                     2 
                   
                 
                 
                   Δ 
                    
                   
                       
                   
                    
                   
                     E 
                      
                     
                       ( 
                       
                         
                           B 
                           
                             1 
                              
                             g 
                           
                             
                             
                             
                           2 
                         
                         → 
                         
                           E 
                           g 
                             
                             
                             
                           2 
                         
                       
                       ) 
                     
                   
                 
               
             
           
         
       
     
         [0000]    where λ 0  is the spin-orbit coupling constant of the free Cu(II) ion equal to −828 cm −1 . 
         [0058]    α 2  is a measure of the covalency of the in-plane σ-bonding. A value of α 2 =1 indicates complete ionic character while α 2 =0.5 indicates cent per cent covalent nature. The β 2  and γ 2  parameters are, likewise, a measure of covalency in the in-plane and out-of-plane i-bonding respectively. β 2  or γ 2 =1 indicates total ionic character and β 2  or γ 2 =0.5 corresponds to total covalent character. 
         [0059]    The α 2 , β 2  and γ 2  values obtained for the present Cu(II) complexes are in the ranges 0.55-0.75, 0.86-0.93 and 0.77-0.89 suggesting appreciable/weak/moderate in-plane σ-bonding, in-plane π-bonding and out-of-plane π-bonding respectively 20 . 
         [0060]    Further, the spin-orbit coupling constant of Cu(II) ion (X) in the complexes has been evaluated using the equation: 
         [0000]    
       
         
           
             
               g 
               || 
             
             = 
             
               2.0023 
               - 
               
                 
                   8 
                    
                   λ 
                 
                 
                   Δ 
                    
                   
                       
                   
                    
                   
                     E 
                      
                     
                       ( 
                       
                         
                           B 
                           
                             1 
                              
                             g 
                           
                             
                             
                             
                           2 
                         
                         → 
                         
                           B 
                           
                             2 
                              
                             g 
                           
                             
                             
                             
                           2 
                         
                       
                       ) 
                     
                   
                 
               
             
           
         
       
     
         [0061]    The values for the complexes are found to be lower than the free ion value (λ 0 =−828 cm −1 ) indicating considerable mixing of ground and excited terms. 
         [0000]    vii. Anticancer Activity Testing (In Vitro) 
       MTT [3-(4,5-dimethylthiazol-2yl)-2,5-diphenyltetrazolium bromide] method: 
       [0062]    MTT is used to measure the metabolic activity of viable cells. The assay is non-radioactive and can be performed entirely in a micro titer plate (MTP). It is suitable for measuring cell proliferation, cell viability or cytotoxicity. The reaction produces water-insoluble formazan salt that must be solubilized. Procedure involves culturing the cells in a 96-well micro titer plate, and then incubating them with MTT solution for approximately 2 hours. During incubation period, viable cells convert MTT to a water-insoluble formazan dye. The formazan dye in the MTP is solubilized and quantified with an ELISA plate reader. The absorbance directly correlates with the cell number. This can be applicable for adherent cells cultured in MTP. 
         [0063]    Compounds were tested at concentrations of 3 and 30 μg/ml by MTT assay using the ovarian cancer cell line A2780. The results from these studies are shown in table 10 and  FIG. 9 . 
         [0000]    
       
         
               
             
               
               
               
               
               
             
               
               
               
               
               
               
             
           
               
                 TABLE 10 
               
             
             
               
                   
               
               
                 Percent surviving cells of DMSO control (MTT assay, n = 3) 
               
             
          
           
               
                   
                 3 μg/ml (Mean) 
                 SD 
                 30 μg/ml (Mean) 
                 SD 
               
               
                   
                   
               
             
          
           
               
                   
                 TS1 
                 65.7 
                 33.3 
                 25.6 
                 2.2 
               
               
                   
                 TS2 
                 35 
                 5.5 
                 23.8 
                 1.2 
               
               
                   
                 TS3 
                 21.6 
                 21.2 
                 1.9 
                 0.1 
               
               
                   
                 TS4 
                 42.3 
                 8.7 
                 24.6 
                 0.5 
               
               
                   
                 TS5 
                 42.5 
                 12.4 
                 26.5 
                 0.2 
               
               
                   
                 TS6 
                 59.4 
                 27.3 
                 23.8 
                 0.5 
               
               
                   
                 TS7 
                 24.9 
                 6.9 
                 24.1 
                 0.2 
               
               
                   
                 TS8 
                 69.4 
                 9.2 
                 7.4 
                 0.8 
               
               
                   
                 TS9 
                 58.9 
                 0.4 
                 2.5 
                 0.1 
               
               
                   
                 TS10 
                 65.1 
                 11.5 
                 26 
                 0.9 
               
               
                   
                 RM1 
                 86.3 
                 18 
                 13.4 
                 1.5 
               
               
                   
                 RM2 
                 0.4 
                 0.1 
                 0.4 
                 0.6 
               
               
                   
                 RM3 
                 102.1 
                 5.2 
                 1 
                 0.2 
               
               
                   
                 RM4 
                 103.6 
                 3 
                 54.3 
                 1.6 
               
               
                   
                 RM5 
                 0.6 
                 0.1 
                 0.2 
                 0.2 
               
               
                   
                 RM6 
                 92.1 
                 7 
                 104.8* 
                 5 
               
               
                   
                 RM7 
                 6.6 
                 0.1 
                 0.9 
                 0.1 
               
               
                   
                 RM8 
                 0.3 
                 0.1 
                 0.1 
                 0.1 
               
               
                   
                 RM9 
                 92.9 
                 9.7 
                 2 
                 0.3 
               
               
                   
                 RM10 
                 4.6 
                 0.4 
                 1 
                 0.4 
               
               
                   
                 RM11 
                 0.4 
                 0.1 
                 0.7 
                 0.2 
               
               
                   
                 RM12 
                 84 
                 7.5 
                 1.7 
                 0.2 
               
               
                   
                 RM13 
                 89.7 
                 13.5 
                 1.7 
                 0.3 
               
               
                   
                 RM14 
                 13.2 
                 7.9 
                 0.7 
                 0.2 
               
               
                   
                 RM15 
                 78.6 
                 6.4 
                 2.2 
                 0.1 
               
               
                   
                   
               
               
                   
                 *The compound was precipitated in the NaCl solution 
               
             
          
         
       
     
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