New palladium (II) complexes with 1‐phenyl‐1H‐tetrazole‐5‐thiol and diphosphine Synthesis, characterization, biological, theoretical calculations and molecular docking studies

This paper reports the syntheses and spectral investigations of the new complexes [Pd( k 1 ‐S‐ptt) 2 ( k 2 ‐dppmS 2 )] ( 1 ), [Pd( k 1 ‐S‐ptt) 2 ( k 2 ‐dppp)] ( 2a ), [Pd( k 1 ‐N‐ptt) 2 ( k 2 ‐dppp)] ( 2b ) , [Pd( k 1 ‐S‐ptt) 2 ( k 2 ‐dpppS 2 )] ( 3 ) , [Pd( k 1 ‐S‐ptt) 2 ( k 2 ‐dppb)] ( 4 ), [Pd( k 1 ‐S‐ptt) 2 ( k 2 ‐dppf)] ( 5a ) and [Pd( k 1 ‐N‐ptt) 2 ( k 2 ‐dppf)] ( 5b ) , derived from 1‐phenyl‐5‐thiol‐1H‐tetrazole (Hptt) and diphosphine (dppmS 2 , dppp, dpppS 2 , dppb and dppf) as co‐ligand. The Hptt ligand acts as monodentate through the thiolato sulfur atom in complexes 1 , 3 and 4 . While in complexes 2 and 5 , the Hptt ligand also acts as monodentate through the nitrogen of heterocyclic ring, or sulfur of thiol group after deprotonation, as two linkage isomers. Theoretical calculations on the all complexes were performed, isomers based on 2a, 2b and 5a, 5b reveal that each pair of isomers is isoenergetic. For the 2a and 2b complexes the energy difference was 19.92 kcal mol −1 , while for the 5a and 5b complexes the difference was 11.78 kcal mol −1 . These differences are relatively small and suggest that the linkage isomers may be in equilibrium in solution. The reasons for the adoption of these different coordination modes are not clear but steric factors are likely to be a major contributory factor. Further, in vitro anti‐bacterial activity and molecular docking analysis has been carried out to study the activity of the compound.