Studies on a New Schiff Baselig and H3 (pte-tsc) synthesized by condensing 7–Acetonyl–xanthopterin [H2 (pte)] with thiosemicarbazide [H(TSC)] and its molybdenum complexes exhibiting reactivity towards Me3N→O, PyN→O and PPh3; crystal structure of 2–pivaloylamino–7–acetonyl–xanthopterin – water (1/1).

Md Afsar Ali^a and Parag S Roy^b*
^aAcharya Jagadish Chandra Bose College, 1/1B, A.J.C. Bose Road, Kolkata – 700020.
^bDepartment of Chemistry, University of North Bengal, Dist. Darjeeling 734 013, India

A B S T R A C T
A new Schiff base ligand,H₃ (pte-tsc) was synthesized by the condensation of  7-acetonyl-xanthopterin [H₂(pte)] and thiosemicarbazide [H(tsc)]. The pterin starting material obtained by modifying a published method was characterized through single crystal X-ray diffraction analysis of its 2-pivaloylamino derivative and other data. Three new Mo(IV,V,VI) complexes synthesized using this ligand and characterized by different physico-chemical methods including elemental analysis, ESIMS, Λ_M data, ¹H NMR, IR, UV-VIS, fluorescence spectroscopy, CV data and CHEM3D representations. Here the H₃(pte-tsc) ligand acts as a reducing agent, reducing the metal centre of the molybdenum starting materials during synthesis in most cases. These complexes show reactivity towards oxygen atom donor agents, e.g., Me₃N→O or PyN→O and their kinetics have been studied. They have negative values for entropy of activation [∆S^# = (–208.29 to –198.63) J mol^–1 deg^{– 1}], suggesting associative type enzyme-substrate reactions. Kinetic data [e.g., k_obs=(3.82×10^{– 3} – 71.00×10^{– 3}) s ^{– 1}] are at par with the available literature.
Keywords: Pterin Schiff base, single crystal X-ray structure, Pterin-Mo (IV,V,VI) complexes, Mo-centred O-transfer redox reaction,  negative ∆S^# value.