The newly synthesized ligand, dihydro bis(salicylidene)
2,2′ aminobenzothiazolyl borate (2), was derived from the reaction
of Schiff base of 2-aminobenzothiazole and salicylaldehyde with
KBH4. (3) and (4) complexes of
(2) were synthesized and further metallated with
dimethyltindichloride to yield heterobimetallic complexes (5) and
(6). All complexes have been thoroughly characterized by
elemental analysis, and IR, NMR, EPR, and UV-Vis spectroscopy
and conductance measurements. The spectroscopic data support
square planar environment around the atom, while the
atom acquires pentacoordinate geometry. The
interaction of complex (5) with guanine, adenine, and calf thymus
DNA was studied by spectrophotometric, electrochemical, and kinetic
methods. The absorption spectra of complex (5) exhibit a
remarkable “hyperchromic effect” in the presence of guanine and calf
thymus DNA. Indicative of strong binding of the complex to calf
thymus DNA preferentially binds through position of
guanine base, while the adenine shows binding to a lesser extent.
The kinetic data were obtained from the rate constants, kobs,
values under pseudo-first-order conditions. Cyclic voltammetry was
employed to study the interaction of complex (5) with guanine,
adenine, and calf thymus DNA. The CV of complex (5) in the
absence and in the presence of guanine and calf thymus DNA altered
drastically, with a positive shift in formal peak potential
Epa and Epc values and a significant increase in peak
current. The positive shift in formal potentials with increase in
peak current favours strong interaction of complex (5) with calf
thymus DNA. The net shift in E
1/2 has been used to estimate
the ratio of equilibrium constants for the binding of
and complexes to calf thymus DNA.
A new oxamide ligand 2,2'-(oxalydimino)bis(diacetic acid)[C10H11O10N2],[L] has been synthesized by the
condensation reaction of Iminodiacetic acid and Diethyloxalate. This ligand [L] was further allowed to
interact with triethylene-tetraamine metal complexes [C16H26N6O8M]Cl2 (where M=Co11, Ni11 and Cu11) to
yield the new N4 macrocyclic complexes 3, 3', 6, 6' tetraazadodeca 1-1' diimino N N tetraacetic acid M)
chloride ([C16H26N6O8Co]Cl2, [C16H26N6O8Ni]Cl2 and [C16H26N6O8Cu]Cl2). These complexes were
characterized by elemental analyses, i.r., n.m.r., e.p.r, and u.v.-vis spectroscopy. All the complexes show
square planar geometry and are ionic in nature. The kinetic studies of the Cu(lI) complex were ascertained
spectrophotometrically by observing the absorbance changes in presence of protein Human Serum Albumin
(HSA) in phosphate buffer at different pH's at 300C. The absorbance changes were monitored at 278 nm
(λmax of HSA) with respect to time and pseudo-first-order rate constants, kobs, were obtained from the slope of
the straight line using the least squares regression method. The electrochemical behaviour of the Cu(ll)
complex was monitored by cyclic voltammetry in a phosphate buffer. The Ep values-0.730 and-0.560 V
respectively, were obtained at the scan rate of 0.1 Vs-1. The interaction of the Cu(II) complex with the HSA
was studied at the same scan rate, which reveals weak binding as the E0 values do not shift considerably. The
cyclic voltammogram of the Cu(II) complex bound to HSA was recorded at different pH's also (6.5 to 7.4).
The pH-rate profile data reveals that the reactions are pH dependent.
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