Schiff base is a compound with afunctional group that contains acarbon-nitrogen double bond withthe nitrogen atom connected to anaryl or alkyl group.

General formula:

• Schiff base is usually formed bycondensation reaction of a carbonyl withprimary amine.

There are three main approaches toprepare Schiff base ligand systems:

Direct Synthesis Template Effect Conventional Method

UV-Visible IR Spectroscopy

1H and 13C NMR EPR Mass Spectrometry TGA/DTA Elemental Analysis

The Schiff base ligands and their complexes arecharacterized on the basis of following:

It is mainly applied for the detection of functional groups (chromophore),the extent of conjugation , detection of polynuclear Compounds etc.

The radiation in the wavelength range 200-400nmcorresponds to Ultra-violet region while radiationin the wavelength range 400-800nm correspondsto visible region.

The absorption of radiation in the UV-visibleregion causes the excitation of π electron in aconjugation or an non conjugation system.

Thus UV-visible spectrum is quite useful fordetection of conjugation, carbonyl group etc.

APPLICATIONS Identification of an unknown compound Examination of polynuclear hydrocarbons Elucidation of the structure of vitamins A and K Detection of two isomeric formsDetermination of configurations of geometrical

isomers Identification of a compound in different solventsDetermination of strength of hydrogen bondingDistinguishes between equatorials and axial

conformations LIMITATION : UV-visible spectrum does not

provide any information about the remaining partof the molecule.

The formation of Schiff base complexes andbonding modes are inferred from position ofcharacteristic bands in IR spectra andresonance signals in 1H and 13 C-NMR spectra.

A strong intensity band(sharp) 1618-1622cm-1 v(C=N)A medium intensity band 440-460 cm-1 v(M–N)A weak absorption band 2906-2942cm-1 v(–CH3)A broad absorption band 3330cm-1 v(–OH)

Nuclear magnetic resonance (NMR), induces changesin the magnetic properties of certain atomic nuclei,notably that of hydrogen(hydrogen atoms in differentenvironments can be detected, counted and analysedfor structure determination).

In the Nuclear magnetic resonance (NMR), radiationsof longest wavelength range,i.e., Radiowaves areuseful which lie in the frequency range about 60-300MHz.

Electron paramagnetic resonance(EPR) spectroscopy investigate those systems which are organic or inorganic free radicals and ions of transition metals which contain unpaired d or felectrons.

Mass spectrometry is the most accurate methodfor determining molecular mass of the compoundand its elemental composition and deduction ofmolecular structure from fragments.

Mass spectrum of a substance is potted betweenm/z values of ions versus relative abundance

The thermal stabilities of Schiff metal complexes are

investigate using (TGA/DTA) under N2 atmosphere

at a heating rate of 20 ◦C min-1 in the temperature

range 25-800 ◦C

The thermal analysis results are in agreement with

the elemental analysis findings.

Elemental analysis confirms the stoichiometry of ligands and their complexes.

Schiff base nitrogen donar ligands and their complexes show biologically activities i.e. toxicity against bacterial growth, anticancerous, antimalarial antimicrobial, antitubercoluosis and antifungal activities.

Due to their resemblance with natural proteins like hemerythrin enzymes they are also used as biomimic model compounds.

They are potential inorganic and organic cation receptors , electron transfer agents , homogenous catalysts and DNA , RNA interacting agents.

They also employed in hydrometallurgy, material science as luminescence materials and as non linear optical materials.

Schiff base ligands are formed by the condensation reaction between aldehydes/ketones and aliphatic amines.

Their complexes are prepared by the interaction of ligandswith metal salts.

The stoichiometry and the nature of bonding wasascertained on the basis of elemental analysis andconductivity data.

The formation of the proposed compounds is inferred bythe appearance of imine bands in the IR andcorresponding proton resonance signals in the 1H spectra.

Schiff base ligands and their complexes have numerousapplications in the field of pharmacy.

H.Khanmohammadi et al./ SpectrochimicaActa Part A 77 (2010) 342-347

H. Keypour et al./ Polyhedron 51 (2013) 117-122

M.Tyagi et al./ Spectrochimica Acta Part A : Molecular and biomolecular specroscopy118 (2014) 1056-1061

T.A.Khan et al./ Spectroahimica Acta Part A 73 (2009) 622-629