55 research outputs found
Iron and cobalt mononitrosyls with schiff base co-ligands / Hadariah Bahron
No full textThe ligand N-4-methoxybenzylsalicylideneimine (MeObsal) is reacted with Fe2+ and Co2+ions separately. Both the systems are then reacted with nitric oxide (NO) to form two different complexes which are bis(N-4-methoxybenzylsalicylideneiminato)nitrosyliron, [Fe(MeObsal)2NO]; and bis(N-4-methoxybenzylsalicylideneiminato)nitrosylcobalt, [Co(MeObsal)2NO]. Both the complexes are microanalysed and subjected to infrared spectroscopy investigation and magnetic measurement. From the infrared investigation, [Fe(MeObsal)2NO] is found to exhibit an NO stretching frequency, VNO, at 1777 cm-I whereas [Co(MeObsal)2NO] shows VNO at 1640 cm-I. These values suggest that the iron nitrosyl complex contains linear Fe-N-O bond and the cobalt nitrosyl complex contains bent Co-N-O bond. The room temperature effective magnetic moment of [Fe(MeObsal)2NO] is measured to be 3.97 B.M. indicative of the presence of 3 unpaired electrons. The value shows that [Fe(MeObsal)2NO] is a high spin {Fe(NO)} system. However, the complex [Co(MeObsal)2NO] gives an effective magnetic moment of 0.91 B.M. indicating that there are no unpaired electrons present in this complex. It can be concluded that [Co(MeObsal)2NO] is a low spin {Co(NO)}
Multidentate azomethine series: complexation and bioactivity studies / Prof Dr Hadariah Bahron, Dr Karimah Kassim and Sharifah Rohaiza Syed Omar
No full textThree Schiff bases namely L1: MPD(ovan)₂, L2: triMe-MPD(ovan)₂ and L3: Cl-MPD(ovan)₂ are obtained from the condensation reaction between derivatives of m-phenylenediamine (MPD) with o-vanillin. Complexation with Co(II), Cu(II) and Zn(II) afford novel dinuclear complexes of dimeric nature. Their structures are elucidated using various physicochemical techniques. The Schiff bases are indicated to act as tetradentate ligands in which both oxygen and nitrogen atoms serve as coordination sites for the metal ions. Antibacterial investigations revealed that the complexes are better bactericides than the parent ligands. The IC50 values against liver cells of the complexes are much lower than those of the parent ligands
Synthesis and characterisation of Mononuclear and Tetranuclear Zinc (II) complexes of Schiff bases derived from Phenylenediamine
No full textA mononuclear and new tetranuclear metal complexes of Zn(II) with Schiff base ligands L1 and L2 respectively, were synthesised. L1 was obtained through the condensation of salicylaldehyde with ortho-phenylenediamine while L2 was the product of reaction between of ortho-vanillin with 2,4,6-trimethyl-m-phenylenediamine. The ligands and complexes were characterised via elemental analysis, melting point, IR and NMR spectroscopy. The shifting of v(C=N), v(C-OH) and v(O-CH3) infrared peaks upon coordination with Zn(II) indicated that these three moieties play a significant role in the complexation. It was found that L1 acted as tetradentate ligand, coordinating with Zn(II) centres through phenolic oxygen and imine nitrogen. The ligand L2 acted as a hexadentate ligand, bonded to metal via phenolic oxygen, imine nitrogen and methoxy oxygen, where four Zn(II) centres formed bridges to connect two ligands
Dinuclear Co(II) and Zn(II) Azomethine complexes: Physicochemical and antibacterial studies
No full textSubstituent effect on catalytic activity of palladium(ii) schiff base complexes for sonogashira reaction
No full textChemical industries are greatly assisted by catalyst
Synthesis and characterization of Pd(II) and Ni(II) complexes of schiff bases and catalytic activity of Pd(II) complexes / Amalina Mohd Tajuddin, Hadariah Bahron and Shahrul Nizam Ahmad
No full textSix new Pd(II) and Ni(II) metal complexes of N, O-bidentate (LI, L2) and ONNO-tetradentate (L3) Schiff base ligands have been synthesized. The compounds were characterized via various physicochemical and spectroscopic techniques namely elemental analysis (CHN), FT-IR, IHand 13C NMR as well as magnetic susceptibility measurement. All complexes showed diamagnetism indicating that they are square planar complexes. Catalytic performance ofPd(Ll)2 andPd(L2)2 were investigated for Heck cross-coupling reaction under optimum operating parameters, monitored using GC-FID for 6 h of reaction time in inert conditions. High catalytic activities of up to 90% were observed in the presence of triethylamine as base and DMA as solvent at 100°C with 1 mmol% catalyst loading. The mechanism of catalyzed Heck reaction is proposed to go through a series of conversion ofPd(0)/Pd(II)
Characterization of New Metal Complexes of Schiff Bases and Macrocyclic Ligands and Some Monitrosyl Derivatives.
No full textWork on iron mononitrosyl complexes of bidentate Schiff base anions derived from salicylaldehyde is described. The complex bis(N-benzylsalicylideneiminato)nitrosyliron and its 4-methyl and 4-methoxy derivatives are the first examples of such compounds to be synthesised. The magnetic properties over the temperature range 293 to 87 K show that they are high spin {FeNO}7 with slightly temperature dependent effective magnetic moments. Infrared investigations suggest that the Fe-N-O groups are linear. Attempts to prepare an iron mononitrosyl with Schiff base derived from 2-hydroxyacetophenone and ethylenediamine resulted in the formation of a binuclear iron(III) oxo-bridged complex, mu-oxo-bis[N,N'-bis(2-hydroxyaceto-phenone)ethylenediiminato]iron(III)], which, when investigated by X-ray crystallography, is shown to contain a bent bridging group with a Fe-O-Fe bond angle of 156.7. This is the first example of au-oxo iron(III) complex with a 2-hydroxyacetophenone-derived Schiff base. A series of cobalt mononitrosyls, mainly with bidentate Schiff base coligands derived from salicylaldehyde has been prepared and characterized by infrared, 1H, 15N and 59Co NMR spectroscopies as well as magnetic measurements. The infrared and 15N NMR indicate that the Co-N-O groups in these complexes are bent. Cobalt(II) complexes of the macrocycle 6,13-diphenyl-1,8-dihydro-2,3:9,10-dibenzo-1,4,8,11-tetraaza-cyclotetradecane-4,6,11,13-tetraene (dptaaH2) and its methyl, methoxy, bromo and nitro derivatives have been prepared. On reaction with nitric oxide, they form mononitrosyls. Similar investigations show that the Co-N-O groups are bent and this has been confirmed by an X-ray investigation carried out on Co(dptaa)NO from which the Co-N-O bond angle is 122.6°. All the mononitrosyls show temperature independent paramagnetism with fractional magnetic moments at room temperature in the range 0.59-1.31 B.M. X-ray investigations carried out on two cobalt(II) Schiff base complexes, bis(N-n-butylsalicylideneiminato)cobalt(II) and bis(N-t-butylsalicylidene-iminato)cobalt(III), suggest that the unreactivity of the t-butyl derivative to nitric oxide and dioxygen in contrast to the n-butyl derivative is due to steric hindrance of the t-butyl group. The reactivity of Co(dptaa) towards chloroform, Br2 and I2 was investigated in attempts to prepare complexes of the type Co(dptaa)X where X = Cl, Br and I. Although reasonable microanalyses were obtained, the magnetic moments of the chloride and bromide were higher than expected for cobalt(III) complexes. Unfortunately, they could not be recrystallised to remove possible paramagnetic impurities. Several chromium(II) complexes of Schiff bases derived from 2-hydroxyacetophenone have been prepared via the sodium and lithium salts of the bases. The instability of the complexes has however, prevented complete characterization. Some miscellaneous investigations, mainly of chromium(ll) complexes are also reported
Effect of hydroxyl group position at imine structure on corrosion inhibition of mild steel in 0.5 m NaCl
No full textEmpowering women in chemistry via a global networking event: IUPAC Breakfast
No full textThe School of Chemistry had organized a breakfast networking event on 12 February 2019 and connected with other groups of women chemists around the world. The event was conducted as a way of strengthening the bonds between women in chemistry. It was initiated by Prof. Datin Dr Rohaya Ahmad and Prof. Dr Nor Hadiani Ismail. The event started with a welcoming remark by the organizer and Head of School of Chemistry, followed by a sharing session. Among the speakers were Assoc. Prof. Dr Sabiha Hanim Saleh, Prof. Ts. Dr Chan Chin Han, Assoc. Prof Dr Zainiharyati Mohd Zain, Prof Dr Hadariah Bahron, Prof. Datin Dr Rohaya Ahmad, Prof. Dr Nor Hadiani Ismail and Prof Dr Norashikin Saim
Homometallic Dinuclear Cu(II) and Zn(II) Complexes Derived from Salophen-type Ligand: Synthesis, Characterization and Anticancer Screening
No full textIntroduction:
A series of salophen-type Cu(II) and Zn(II) dinuclear metal complexes of a Schiff base derived from o-phenylenediamine were successfully synthesized, characterized and screened for their anticancer activity.
Methods and Results:
All compounds were characterized physicochemical and spectral techniques namely elemental analysis (C, H, N), magnetic susceptibility (MSB), molar conductivity, thermal gravimetric analysis (TGA), infrared (IR) and nuclear magnetic resonance (NMR) spectroscopy. The shifting of C=N, C-O phenolic and C-O methoxy peaks and the appearance of new peaks assignable to M-N and M-O in IR spectra of the complexes indicated the coordination of azomethine N, phenolic O and methoxy O donor atoms with metal centers. The disappearance of the hydroxyl peak in 1H NMR spectra of the Zn(II) complex supported the involvement of phenolic O upon formation of the metal complex. The Cu(II) complex was paramagnetic with magnetic moment values of 1.97, close to the theoretical spin only magnetic moment, μso, for Cu(II). The compounds were screened for anticancer activity against human colon cancer cells (HCT116). The Cu(II) complex revealed the highest activity with IC50 value of 21.17 ± 0.76 μM.
Conclusion:
The ligand coordinated as a hexadentate ligand through O and N donor atoms of phenolic, methoxy and azomethine groups. From anticancer screening, it was observed that Cu2(OVanOPD) complex exhibited the highest activity followed by OVanOPD ligand and Zn2(OVanOPD) complex
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