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To the best of my knowledge, the matter contained in the thesis has not been submitted to any other university/institute for the award of any degree or diploma. In the triclinic form, the molecules deviate from the eclipsed conformation (D5d) by 9°, while in the orthorhombic form the rings are completely eclipsed (D5h). Lanthanide ion complexes with ferrocenyl schiff base ligands have proven to be very important in photobiology and ligand to metal energy transfer studies8.

The space between the ferrocene rings is suitable for hydrogen bonding of the attached peptide strands. The arrangement of hydrogen bonding is a key factor in the design of various molecular assemblies due to the directionality and specificity 11. Organometallic chemistry and biochemistry have merged in the last two decades in a new field called bioorganometallic chemistry.

Current research in the medical field is aimed at creating new compounds that work against a wide range of cancers and have fewer side effects. Several reviews focused on ferrocene chemistry, Dyson et al 15 focused their reviews on the properties of organometallic compounds that make them suitable for pharmaceutical applications, Neuse 16,17 devoted their reviews to ferrocene-containing macromolecules in cancer research and Metzler Nolte et al18 and also Fish et al 19 focused their reviews on the bioorganometallic chemistry of ferrocene. Cancer can be treated with several methods, including chemotherapy, which is one of the main weapons in the fight against cancer.

In the last decade a revolution in cancer treatment has been brought about by organometallic chemists.

Figure 1:  Examples of transition metal cyclopentadienyl metallocenes
Figure 1: Examples of transition metal cyclopentadienyl metallocenes

Ferrocenium tetrafluoro borate salt

Ferrocenium tri iodate

NLO Active Ferrocene system

Crystal Engineering based on understanding of physical phenomena such as charge transfer, electrostatic interaction, hydrogen bonding, van der Waals interaction and pi-pi stacking is a powerful technique for producing functionalized solid materials with optimized properties. Flexible pi bonds between metals and ligands produce variable organometallic structures and packing modes depending on the solid state intra and inter-molecular non-bonding interactions. Due to this significant electron donating strength of the ferrocenyl group, it is considered a good donor part of a donor–Π–acceptor system for chromophores with high nonlinear optical (NLO) responses 48 .

To date, most attempts to synthesize nonlinear optical materials have focused on monoacceptor conjugated ferrocenyl compounds. The bis-substituted ferrocenyl molecule with readily available aromatic alcohols such as 1,3-dihydroxybenzene has the NLO active molecular conformation 49. Ferrocene adopts different conformations depending on the size of the rotational barrier, and in a sense is considered as non-rigid molecules that have a variable structure.

Ferrocene based ligands application in Catalysis

Another example of such a ligand is amidoarylferrocenyldiphenylphosphine ligands in the Cu-catalyzed addition of diethylzinc to enones 52, shown in Figure 13.

Introduction

In the present work, a synthetic strategy to attach ferrocenyl moieties by forming schiff bases of salicyloyl hydrazide and anthraniloyl hydrazide was developed and their metal complexes were synthesized and characterized.

Experimental

  • General Procedures
  • Preparation of monoacetyl ferrocene (1)
  • Preparation of 1,1’-Diacetyl ferrocene (2)
  • Reaction of Monoacetyl ferrocene (1) with Salicyloyl hydrazide
  • Reaction of Monoacetyl ferrocene (1) with Anthraniloyl hydrazide
  • Reaction of 1,1’-diacetyl ferrocene (2) with Salicyloyl hydrazide
  • Reaction of 1,1’-diacetyl ferrocene (2) with Anthraniloyl hydrazide
  • Preparation of metal complexes (7-9) of ligand 3 and 4
  • Preparation of metal complexes (10-13) of ligand 5

Purification of compound 1 was performed by column chromatography using pet ether/ethyl acetate as solvent mixture. Purification of compound 2 was performed by column chromatography using pet ether/ethyl acetate as solvent mixture. To 152 mg (1 mm) of salicyloyl hydrazide, 15 ml of ethanol was added, and the solution was stirred under heated conditions for 30 minutes until the salicyloyl hydrazide was completely dissolved in ethanol.

The reaction mixture was then stirred for a further 3 hours at room temperature to give an orange precipitate of the ferrocenyl schiff base ligand, [(-C5H5)Fe(-C5H4) {(CNN(H)C(O) obtained. C6H5(OH)}] (3). The same procedure as used for the preparation of compound 3 was followed for the reaction of monoacetylferrocene, 218 mg (1 mm) with anthraniloyl hydrazide, 151 mg (1 mm) to give the desired to obtain ferrocenyl schiff base ligand, Ethanol solution (25 ml) of compound 3 or 4 was taken in a two-necked round bottom flask and the mixture was stirred in an oil bath under nitrogen atmosphere with a temperature condition of 70°C for about 15 minutes until all the ligand is completely dissolved.

The reaction mixture was then stirred for about 30 minutes under a nitrogen atmosphere at room temperature. The ethanol solution (25 mL) of compound 5 was taken in a two-necked round bottom flask and the mixture was stirred in an oil bath under nitrogen atmosphere maintaining a temperature of 70°C for about 15 minutes until all the ligand dissolve completely. The green isomer was soluble in acetonitrile and the red isomer was soluble in ethanol.

RESULTS AND DISCUSSION

Ferrocenyl Schiff base ligands 3 and 4 were synthesized by mixing salicyloyl hydrazide and anthraniloyl hydrazide, respectively, at room temperature with monoacetylated ferrocene 1 in a 1:1 ratio (Scheme 2). The infrared spectrum of 3 and 4 shows the presence of peaks in the region of 1606 cm-1, 1617 cm-1 due to the νC=N stretching vibrations, which appeared due to the condensation of the NH2 hydrazide end group and the C=O group of the acetyl ferrocene moieties. The spectrum of compound 4 shows peaks at 1636 cm-1 and 3443 cm-1, corresponding to νC=O and νN-H stretching vibrations.

The spectra of 5 and 6 show the presence of peaks at 1608 cm-1, 1618 cm-1 region due to νC=N stretching vibration which arose due to the condensation of the terminal NH2 group of the hydrazide and C= O groups of the acetyl ferrocene moieties. The spectrum of compound 5 also shows peaks at 1637 cm-1 and 3470 cm-1 (broad) due to νC=O and νO-H stretching vibration, respectively. The spectrum of compound 6 shows a sharp peak at 1638 cm-1 and a broad peak at 3448 cm-1 corresponding to νC=O and νN-H stretching vibration respectively.

In all cases, the νC=O and νC=N peaks for the metal complexes shifted to lower frequency compared to the respective ligands suggesting coordination of the carbonyl oxygen and the imine nitrogen to the metal atom. According to the above data, this indicates that the ligands behave in a bidentate manner towards the metal. It was also predicted that in compounds 7 and 8 the metals behave as six coordinated systems forming an octahedral geometry.

The IR data show that complex 9 may consist of a V=O unit, two bidentate ferrocenyl ligands bound to the vanadium metal atom, and a water or ethanol molecule bound to the vanadium atom, forming a six-coordinate neutral complex (Scheme 5). According to the above data, it is suggested that the ligands behave in a tetradentate manner. It has also been predicted that the metals behave as a six-coordinate system, forming an octahedral geometry.

The measured magnetic moment of compound 12 was found to be 3.36 BM, which is due to the two unpaired electrons for the Ni(II) ion in the octahedral geometry. The other band can be assigned to metal-to-ligand and ligand-to-ligand charge transfer absorption.

Magnetic Susceptibility Measurements

Ferrocene containing schiff base ligands has been synthesized and characterized by FTIR and UV spectroscopy. Several metal complexes of cobalt, nickel, copper and vanadium with ferrocene-based schiff base ligands were synthesized and characterized by FTIR, UV spectroscopy and magnetic moment were studied with two of the isomeric complexes. The magnetic susceptibility for [(-C5H4)2Fe{CNN(H)C(O)C6H5(OH)2}Co] and [(- C5H4)2Fe{CNN(H)C(O)C6H5(OH )2}Ni] has been studied and the most likely structure has been predicted based on the number of unpaired electrons present in the system.

Structural confirmation of all the metal complexes can be obtained from single crystal X-ray diffraction study. Antitumor, antibacterial, antiviral, antifungal, antipesticide and antimalarial study with these ferrocene based schiff base metal complexes should be carried out. The electrochemical behavior and properties of the ferrocenyl moiety present in these compounds must be studied using cyclic voltammetry studies to understand the interesting redox properties of these metal complexes.

Figure

Figure 1:  Examples of transition metal cyclopentadienyl metallocenes
Figure 2: Examples of different derivatives of metallocenes
Figure 4:  Complexes of Ferrocenyl based ligands  1.3.1 Ferrocene – Peptide Bioconjugates:
Figure 5: Hydrogen bonding interactions in Ferrocenyl alanine
+7

References

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