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Dr. Labib Ali Mohamed Awin

لبيب عوين هو احد اعضاء هيئة التدريس بقسم الكيمياء بكلية العلوم. يعمل السيد لبيب عوين بجامعة طرابلس كـمحاضر منذ 2014-02-12 وله العديد من المنشورات العلمية في مجال تخصصه

Publications

Some of publications in Department of Chemistry

Dielectric Relaxation and Dipole Moments of Four Hydrogen Bonded Heterocyclic Compounds in Chloroform

Abstract The permittivities and dielectric losses of 2-Piperedone, -Caprolactam, 2-Azacyclooctanone and 2-Azacyclononanone have been studied in chloroform solutions. They have been measured using Q meter at frequency range 150KHz to 15MHz.Both 2-Piperedone and -Caprolactam solutions were studied at concentration range 0.05 to 0.25M and over temperatures range of -10 to 45 and. The dielectric studies of 2-Azacyclooctanone solutions cover a concentration range 0.05 to 0.125M and over temperature range of -10 to 45, while that of 2-Azacyclononanone solutions were studied at concentration range 0.01 to 0.075M and over temperature range of -10 to 45. The permittivities at higher concentrated solutions up to 1.5M of 2-Pipere-done, -Caprolactam and 2-Azacyclononanone were also measured at 2MHz using dipole meter DM01 over the temperature rang -10 to 45.The static permittivities for the four systems were discussed as the affect concentration, temperature and the number of CH2 group in the cyclic amides. All show normal behaviour except that the CH2 does not show clear affect. Single relaxation process were observed for the studied compound in the chloroform solutions ( =10-9 sec). All cases, the presence of a relaxation process was established at frequencies higher than used here. These relaxation processes were discussed in terms of their relation to concentration and the number of CH2 group. The dielectric activation energies were calculated using Eyring equation. The obtained values were discussed also in terms of concentration affect. A dependence of on concentration was observed. The dipole moments for the four studied compounds in solutions were evaluated using of Cole-Cole a semicircle plots, which considered to be associated with the relaxation process and other dipole moments were evaluated using =. This was assigned as an apparent dipole moment. All these dipole moments were discussed in terms of concentration and temperature affect. The obtained dipole moments in all studied case were much larger than those expected for planer dimers association. So they assigned to the presence of dimers and trimer or tetramers association in the studied solutions.Kirkwood correlation factor for the studied systems were calculated and discussed as a function of concentration. All values of g are less than unity and were assigned to a cyclic association form.
لطفية صادق حسن المجدوب (2010)
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Synthesis of Macrocyclic Complexes of Transition Metals and Studies of Their Antibacterial and Electrochemical Behavior

في هذه الدراسة ثم تحضير ثلاث متصلات مختلفة: 1- ذات نظام حلقي كبير (1,4,7,10 tetraaza 2,3,8,9 tetra phenyl tetraocta,1,3,7,9 diene) 2- ذات نظام متبادل ligand tetradentate conjugated benzidine)” acetylacetonato)- bis) - ذات نظام شبه حلقي مفتوح ligand macrocycle open ” ethylendiamin) acetylacetonato))( bis كما تم تحضير المركبات التناسقية MLn لكل من المتصلات السابقة مع 2+M= 2+ Co , 2+ Cu Zn 2+ و المقارنة بينها من حيث التركيب و النشاط الحيوي و السلوك الكهروكيميائي وتبرز أهمية هذه المركبات التناسقية " ذات النظام الحلقي الكبير" من خلال نشاطها الحيوي المشابه لتلك الأنظمة الحيوية الموجودة في جسم الإنسان، ودورها في العديد من المجالات الحيوية و الطبية والصناعية .ولإيجاد الصيغة الأولية و التركيب الهندسي لهذه المركبات التناسقية تمت دراستها بطرق التحليل الفيزيائية و منها : درجة الانصهار m.p0C وتراوحت بين oC300 > 107 والموصلية EC والذوبانية S والتحليل العنصري CHN والتحاليل الطيفية مثل طيف الاشعة تحت الحمراء FT-IR وطيف الرنين المغناطيسي 1H-13C NMR . ومن خلال التحاليل أمكن الوصول إلى النتائج الآتية -تدل قيم درجات الانصهار المتوسطة على أن كل المركبات التي تم تحضيرها يغلب عليها طابع التساهمية و ليست مركبات أيونية -تدل نتائج اختبار الذ وبانية في المذيبات المعروفة منها) (DMSO, DMF, Chloroform,..Methanol على الطبيعة غيرألكتروليتية لها , كما وجد أن معظمها يذوب في DMSO وتقل ذوبا نيتها في المذيبات الأخرى. - ومن خلال القيم المنخفضة لموصلية هذه المواد و التي تتراوح (47-11 Ohm-1cm2.mol-1) ، على أنها غير ألكتروليتية مما يدعم السلوك التساهمي و التناسقي بين الذرات المانحة في المتصلات و ذرة الفلز - ومن خلال دراسة التحليل العنصري للمركبات, أظهرت النتائج تطابقاً كبيراً بين قيم النسبة النظرية والعملية للعناصر C%,H%,N% ، وذلك بما يتوافق مع الصيغ الأولية و التراكيب الهندسية المقترحة للمركبات التي تم تحضيرها.- من نتائج طيف الأشعة تحت الحمراء(4000-600cm-1), ويلاحظ حدوث إزاحة في قيمة الامتصاص عند ارتباط المتصلة بأيون الفلز لتكوين روابط تناسقية (1500-1600cm-1) بالارتباط بذرة النيتروجين لمجموعة الازوميثين((-C=N-, وكذلك (cm-11200-1300) بالارتباط بذرة الأوكسجين لمجموعة -C-O-) ) و يمكن تفسير هذه الإزاحة بسحب للإلكترونات من المتصلة وحدوث الترابط الارجاعي من طرف الفلز مما يسبب ضعفا لبعض الروابط - ومن خلال دراسة نتائج طيف الرنين المغناطيسي NMR ,يتضح الارتباط التساهمي للمتصلات مع أيون الفلز وذلك بالمقارنة بين طيف المتصلة و طيف الفلز. اتضحت إزاحة قمم معينة1H NMR proton ( 7-8ppm); and 13C NMR -C=N ( 150- 170ppm) إلى مواقع أخرى نتيجة لارتباط المتصلة بالفلز. - ولدراسة السلوك الكهروكيميائي للمركبات المحضرة تم استخدام الطريقة الكهروكيميائية CV وذلك لإيجاد جهد الاختزال و الأكسدةRedox Couple و علاقتها بالسلوك الحيوي لهذه المركبات.ويمكن ملاحظة أن جهد الاختزال للفلز يقل عند ارتباطه بالمتصلة المانحة و هذا يزيد من نشاطه الحيوي المتوقع. - وتمت أيضا ًدراسة السلوك الحيوي للمركبات المحضرة وإمكانية استخدامها كمضادات لنمو البكتريا. حيث أظهرت معظمها القدرة علي تثبيط نمو أنواع معينة من البكتريا ومنها Staphylococcus aureus و Escherichia coli حيث بلغت درجة الممانعة "مم 16-10" بالنسبة للمادة القياسية المستعملة الفينول "مم 30-28 " . ومن خلال مقارنة النتائج نلاحظ إن المركب التناسقي يعطي أكثر تثبيطا للبكتيريا مقارنةً بالمتصلة. كما إن النحاس يعطي أفضل درجة ممانعة . ويتدرج النشاط البيولوجي في الزيادة حسب الترتيب الأتي :(+2Cu < < Co2+ +2 Zn). Abstract In this study, three different Schiff bases were prepared: 1- (L1) : macrocycle ligand (1,4,7,10 tetraaza 2,3,8,9 tetra phenyl tetraocta,1,3,7,9 diene macrocycle).2- (H2L2) : conjugated tetradentate ligand (bis(acetylacetonato) 4,4'benzidine(.3- (H2L3) : open macrocycle ligand (bis(acetylacetonato) ethylendiamine(.The metal complexes of these ligands “MLn “ where “M2+= Co+2 ,Cu+2 ,Zn+2 “ were prepared by direct reaction of metal with ligands L1 ,H2L2 ,H2L3. This study is an attempt to prepare macrocycle metal complexes and other ligand metal complexes, which are potentially biologically active similar to those in the biological systems, and to compare these complexes characters with each other and with corresponding molecules in the biological systems. These complexes were synthesized and characterized by several physical methods: melting point (mp .oC ), solubility(S), electric conductivity(EC), elemental analysis (C H N), FT-IR spectroscopy, 1H NMR and 13C NMR spectrometer . - Melting point: the moderate values of the melting points (107 oC< 300 oC ) indicate that all of these compounds have a covalent (coordinative) nature , and are not ionic compounds. -In addition to that the solubility test of these complexes, in suitable solvents ,shows that most of the complexes are slightly soluble in common organic solvents (DMSO,DMF, Chloroform and) methanol.But most of them show maximum solubility in DMSO at room temperature, this indicates that all of these compounds have a covalent nature. -Molar conductance measurements show low molar conductance (11 – 47 S cm2 mol-1) which indicate that the complexes are non electrolytes. These results support the coordination behavior for these complexes. - Elemental analysis (C H N) shows a close coincidence between the experimental values and the theoretical values of %C,%H and %N which were calculated according to the proposed structures. -FT-IR spectra(4000-600cm-1) manifest the coordination of the ligands to the metal ion through the azomethine nitrogen (-C=N-) (1500-1700cm-1) and the oxygen atom of the (-C–O-) (1200-1300) . -1H NMR and 13C NMR spectra showed peaks which are characteristic to the aromatic ligands , ”aromatic” 1H NMR proton ( 7- 8ppm) and 13C NMR -C=N ( 150- 170ppm) are shifted to different field on complexation with metal . This manifests coordination of the ligands to metal ion. -The electrochemical behavior: the complexes were extensively investigated by electrochemical method using cyclic voltammetry (CV) to find a correlation between the redox potential and the antimicrobial activity of these complexes, a lower redox potential enhances higher biological activity. - Antimicrobial screening: the synthesized compounds have been screened against some microorganisms Escherichia coli (gram negative ), Staphylococcus aureus (gram positive), with the help of ‘using cup – cut diffusion method. The inhibition zone range between (11-16mm) against phenol as positive standard(28-30mm) and DMSO as negative control: The activity data show that , the metal complexes to be more potent antibacterial than the parent Schiff base ligand against the tested bacterial species. Also, copper complexes show the best antimicrobial activity against the tested microorganisms, and the biological activity of the complexes increases in this order :( Cu+2 > Co+2 > Zn+2 ).
سهيلة إبراهيم بالقاسم كارة (2013)
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Synthesis and Study of Schiff’s Base Ligands Derivedfrom Reaction of Benzil with Aliphatic and Aromaticamines and Their Metal Complexes with Cu(II), Ni(II),Cd(II), Pb(II), Pd(II), Hg(II), and VO2+.

Abstract Five symmetrical Schiff base ligands[four bi-dentate and one tetradentate(L3- L7)] and two un-symmetrical bi-dentate and tri-dentate (L1-L2) ligands with the Nitrogen and oxygen chromophore were isolated inpure form and good yield. The ligands were fully characterized by elemental analyses, melting point, IR, H1- &13C- NMR, and mass spectra.The Schiff bases L1 and L2 were successfully coordinated to Pd(II) and VO2+ ions respectively and these complexes were characterized using elemental analyses, IR and mass spectra. The interesting result by mass spectrum of VO2+ complex of L2 shows parent peak at 524 confirming that the formula of the complex as [VOL2(ac.ac.)2H2O] in which the complex has an octahedral geometry.The symmetrical Schiff bases (L3-L7) were also successfully coordinated to Nickel (II), Copper (II), Lead (II), Cadmium (II), and Mercury (II) ions to form their corresponding complexes. The total twenty five metal (II) XI Schiff base complexes of (L3-L7) were isolated. These complexes were characterized by elemental analyses, melting points, IR, mass spectra technique. 1H &13C-NMR Spectra in DMSO d6 for Pb, Cd, and Hg complexes show the expected number of peaks with deferent chemical shift comparing with the free ligands in the same solvent. The interesting result by mass spectrum of Ni(L7)2 complex compred with of L7 spectra shows parent peak at 977 confirming that the ligand L7 has lost one proton to give the desire complex in square planar geometry.
حميدة أحمد سالم العباني (2015)
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