Self-sensitized photo-oxidation of platinum(II) complexes of 1,10-phenanthroline with 3,4-dimercaptotoluene and thiosalicylic acid by 1O2 (S. Shukla, S. S. Kamath and T. S. Srivastava, J. Photochem. Photobiol. A: Chem., 50 (1989) 199–207) — a reply

J. Photochem. Photobiol. A: Chem., 56 (1991)

399

399

photo-oxidation of platinum(I1) complexes Self-sensitized of l,lO-phenanthroline with 3,4-dimercaptotoluene and thiosalicylic acid by ‘02 (S. Shukla, S. S. Kamath and T. S. Srivastava, J. Photochem. Photobiol. A: Chem., 50 (1989) 199-207) - a reply A. K. Paul, R. Venkatesan Department of Chemisty,

(Received

In order

and T. S. Srivastavat

Indian Institute of Technology

Powai, Bombay 400076

(India)

July 31, 1990)

to verify

-d[S]ldt),

_ I

I ( - WWWo

1

the applicability

of the equation

-I =k,[Sl+

kd

ko [Ql

(eqn.

(4) of ref. 1)

ko [Ql

we have studied

the photo-oxidation of [Pt(phen)(DMT)] (phen is 1,30-phenananthroline and DMT is 3,4-dimercaptotoluene) quenched by bis(diethyldithiocarbamato)nickel(II) [2]. In these experiments, five different concentrations (2.58 x lo-‘-12.5 x lo-’ M) of [Pt(phen)(DMT)] in saturated molecular-oxygen dimethylformamide were irradiated at 560 nm with a 150 W photo-irradiator with a f/3.4 monochromator (slit width, 35 nm) with a spectral range of 300-1000 nm (Applied Photophysics, London) for different time intervals. The course of photolysis was followed by the decrease in absorption at 570 nm using difference absorption spectroscopy_ The first 5% depletion of [Pt(phen)(DMT)] was used repeated in the presence of bis(diethylfor calculation. These experiments were dithiocarbamato)nickel(II) (1 x lo-’ M) as a physical quencher. These data were plotted and the slopes obtained. The plot of {[( - d[S]ldr)ol( - d[S]/df)o] - 1)-l US. [S] gives a straight line with a slope of 3.7~ lo3 M-’ and a positive intercept of 0.11. Knowing the value of from eqn. (4) kd (equal to 1.4~ lo5 M-’ in DMF), the k, and k. values were calculated of ref. 1 as 4.7 x 10’ M-’ s-l and 12.7 x 10” M-’ s-’ respectively. Since the error is about 10% in the above experimental data, the k. value in DMF must be somewhat higher than its value in CCL,, as reported earlier [2]. In conclusion, the mechanism of photo-oxidation of [Pt(phen)(DMT)] involves singlet molecular oxygen and the mechanism suggested in the ref. 1 is unchanged. 1 S. Shukla,

199. 2 II. Furue ‘Author

S. S. Kamath

and T. S. Srivastava,

and K. E. Russell,

Can. J. Chem.,

to whom correspondence

lOlO-6030/91/$3.50

should

J. Photo&em. 56 (1978)

Photobiol. A: Chem. 50 (1989)

1595.

be addressed.

0 Elsevier

Sequoia/Printed

in The Netherlands